Biology:3D cell culture

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Short description: Free-floating three-dimensional culture of cells

A 3D cell culture is an artificially created environment in which biological cells are permitted to grow or interact with their surroundings in all three dimensions. Unlike 2D environments (e.g. a Petri dish), a 3D cell culture allows cells in vitro to grow in all directions, similar to how they would in vivo.[1] These three-dimensional cultures are usually grown in bioreactors, small capsules in which the cells can grow into spheroids, or 3D cell colonies. Approximately 300 spheroids are usually cultured per bioreactor.[1]

Background

3D cell cultures have been used in research for several decades.[2] One of the first recorded approaches for their development was at the beginning of the 20th century, with the efforts of Alexis Carrel to develop methods for prolonged in vitro tissue cultures.[3] Early studies in the 80's, led by Mina Bissell from the Lawrence Berkeley National Laboratory, highlighted the importance of 3D techniques for creating accurate in vitro culturing models. This work focused on the importance of the extracellular matrix and the ability of cultures in artificial 3D matrices to produce physiologically relevant multicellular structures, such as acinar structures in healthy and cancerous breast tissue models. These techniques have been applied to in vitro disease models used to evaluate cellular responses to pharmaceutical compounds.[4]

Eric Simon, in a 1988 NIH SBIR grant report, showed that electrospinning could be used to produce nano- and submicron-scale polystyrene and polycarbonate fibrous mats (now known as scaffolds) specifically intended for use as in vitro cell substrates. This early use of electrospun fibrous lattices for cell culture and tissue engineering showed that various cell types including Human Foreskin Fibroblasts (HFF), transformed Human Carcinoma (HEp-2), and Mink Lung Epithelium (MLE) would adhere to and proliferate upon the fibers. It was noted that as opposed to the flattened morphology typically seen in 2D culture, cells grown on the electrospun fibers exhibited a more histotypic rounded 3-dimensional morphology generally observed in vivo.[5]

3D cell culture, by emulating essential aspects of the in vivo environment, including interactions between cells and the extracellular matrix, allows for the faithful recreation of structural architecture and specialized functions in normal tissues or tumors in a laboratory setting. This approach authentically models the conditions and processes of living tissues, producing responses akin to those observed in vivo. Since its inception in the 1970s, 3D cell culture has provided significant insights into the mechanisms regulating tissue homeostasis and cancer.[6] Moreover, it has expedited translational research in the realms of cancer biology and tissue engineering.[7] To date a major limiting factor in the size of constructs has been unprogrammed cell death called necrosis.[8]

Properties

In living tissue, cells exist in 3D microenvironments with intricate cell-cell and cell-matrix interactions and complex transport dynamics for nutrients and cells.[9][10][11][12][13][14][15][16][17] Standard 2D, or monolayer, cell cultures are inadequate representations of this environment, which often makes them unreliable predictors of in vivo drug efficacy and toxicity.[18][15] 3D spheroids more closely resemble in vivo tissue in terms of cellular communication and the development of extracellular matrices.[1] These matrices help the cells to be able to move within their spheroid similar to the way cells would move in living tissue.[11] The spheroids are thus improved models for cell migration, differentiation, survival, and growth.[16] Furthermore, 3D cell cultures provide more accurate depiction of cell polarization, since in 2D, the cells can only be partially polarized.[11] Moreover, cells grown in 3D exhibit different gene expression than those grown in 2D.[11]

The third dimension of cell growth provides more contact space for mechanical inputs and for cell adhesion, which is necessary for integrin ligation, cell contraction and even intracellular signalling.[19][20] Normal solute diffusion and binding to effector proteins (like growth factors and enzymes) is also reliant on the 3D cellular matrix, so it is critical for the establishment of tissue scale solute concentration gradients[21][22]

For the purposes of drug toxicology screening, it is much more useful to test gene expression of in vitro cells grown in 3D than 2D, since the gene expression of the 3D spheroids will more closely resemble gene expression in vivo. Lastly, 3D cell cultures have greater stability and longer lifespans than cell cultures in 2D.[23] This means that they are more suitable for long-term studies and for demonstrating long-term effects of the drug. 3D environments also allow the cells to grow undisturbed. In 2D, the cells must undergo regular trypsinization to provide them with sufficient nutrients for normal cell growth.[24] 3D spheroids have been cultured in a lab setting for up to 302 days while still maintaining healthy, non-cancerous growth.[23]

In the interdisciplinary research of biology and aerospace, the 3D printed-scaffolds are also being used for protecting cells from the effect of gravity during the launching.[25]

Classification of 3D culture methods

There are a large number of commercially available culturing tools that claim to provide the advantages of 3D cell culture. In general, the platforms can be classified in two types of 3D culturing methods: scaffold techniques and scaffold-free techniques.

A model showing three examples of techniques used for culturing cells in a 3D environment.

Scaffold techniques

Scaffold techniques include the use of solid scaffolds, hydrogels and other materials. In a recent study potentiality of human CD34+ stem cells explored by generating in vitro agarose gel 3D model to understand the bone ossification process.[26] Scaffolds can be used to generate microtissue 3D model by culturing fibroblasts outside of tumour cells, mimicking the tumor stroma interaction.[27]

The effectiveness of scaffolds in various applications, particularly in tissue engineering, is significantly impacted by factors such as pore distribution, exposed surface area, and porosity. The quantity and arrangement of these elements influence both the depth and rate at which cells penetrate the scaffold volume, the structure of the resulting extracellular matrix, and ultimately, the success of the regenerative process.[28] Scaffolds can be produced with diverse architectures depending on the manufacturing method, leading to either random or precisely designed pore distribution.[29] Recently, advanced computer-controlled rapid prototyping techniques have been employed to create scaffolds with well-organized geometries.[30]

Hydrogels

As the natural extracellular matrix (ECM) is important in the survival, proliferation, differentiation and migration of the cells, different hydrogel matrices mimicking natural ECM structure are considered as potential approaches towards in vivo –like cell culturing.[31][32][33] Hydrogels are composed of interconnected pores with high water retention, which enables efficient transport of e.g. nutrients and gases. Several different types of hydrogels from natural and synthetic materials are available for 3D cell culture, including e.g. animal ECM extract hydrogels, protein hydrogels, peptide hydrogels, polymer hydrogels, and wood-based nanocellulose hydrogel.

The approach to crafting the optimal ECM replica relies on the specific characteristics of the culture in question and typically involves employing diverse and independent chemical processes.[34] For example, the utilization of photolabile chemistries can lead to the erosion of specific regions within a gel, and subsequently exposing these areas allows for the application of adhesive ligands, promoting cell adhesion and migration.[35] The development of more intricate frameworks is anticipated, comprising interwoven networks of chemistries under the control of both cells and users. In essence, there is no singular network capable of faithfully emulating the intricate ECM of every tissue type. However, a thoughtful integration of bioinspired cues into synthetic gels holds the potential to yield resilient and versatile scaffolds applicable across various cell culture systems.[36]

Scaffold-free techniques

Scaffold free techniques employ another approach independent from the use scaffold. Scaffold-free methods include e.g. the use of low adhesion plates, hanging drop plates, micropatterned surfaces, and rotating bioreactors, magnetic levitation, and magnetic 3D bioprinting.

Spheroids

File:Electron microscopy (Ho).tif Spheroids are a type of three-dimensional cell modeling that better simulate a live cell's environmental conditions compared to a two-dimensional cell model, specifically with the reactions between cells and the reactions between cells and the matrix.[38] Due to the strong interactions between the cells and the extracellular matrix in the spheroid, the permeability is limited, generating physiologically relevant gradients of e.g. nutrients and oxygen through the spheroid.[39] Spheroids are useful in the study of changing physiological characteristics of cells,[40] the difference in the structure of healthy cells and tumor cells, and the changes cells undergo when forming a tumor.[41] Spheroids co-cultured with tumor and healthy cells were used to simulate how cancerous cells interact with normal cells.[42] Spheroids can also be co-cultured with fibroblasts to mimic tumor-stroma interaction.[43] Spheroids can be grown with a few different methods. One common method is to use low cell adhesion plates, typically a 96 well plate, to mass-produce spheroid cultures, where the aggregates form in the rounded bottom of the cell plates.[37][44] Spheroids can also be cultured using the hanging drop method[45] involving forming cell aggregates in drops that hang from the surface of a cell plate.[38] Other methods under investigation include the use of rotating wall vessel bioreactors, which spins and cultures the cells when they are constantly in free fall and forms aggregates in layers[46] Recently, some protocols have been standardized to produce uniform and reliable spheroids.[47] Researchers had also explored standardized, economical and reproducible methods for 3D cell culture.[48] To improve reproducibility and transparency in spheroid experiments, an international consortium developed MISpheroID (Minimal Information in Spheroid Identity).[49]

Clusteroids

clusteroids are a type of three-dimensional cell modeling similar to spheroids but are distinguished by their creation method; grown as clusters of cells in an aqueous two-phase system of water-in-water Pickering emulsion using interfacial tension and osmotic shrinkage to pack the cells into dense clusters which are then cultured in a hydrogel into tissues or organoids.[50][51]

In the absence of blood vessels, oxygen permeability is impaired during necrotic nucleus formation and this prevents the ex vivo use of 3D cell culture. There is an emulsion template that can overcome this problem. This approach allowed researchers to adjust the cell composition to attain the ideal conditions for promoting the synthesis of diverse angiogenic protein markers within the co-cultured clusteroids.[51] HUVEC cells exhibit a reaction to the presence of Hep-G2 cells and their derivatives by generating endothelial cell sprouts in Matrigel, all without the external introduction of vascular endothelial growth factor (VEGF) or other agents that induce angiogenesis.[52][53] The replication of this cultivation technique is straightforward for generating various cell co-culture spheroids.[54] The w/w Pickering emulsion template greatly aids in constructing 3D co-culture models, offering significant potential for applications in drug testing and tissue engineering.[55]

Bioreactors

The bioreactors used for 3D cell cultures are small plastic cylindrical chambers that are specifically engineered for the purpose of growing cells in three dimensions. The bioreactor uses bioactive synthetic materials such as polyethylene terephthalate membranes to surround the spheroid cells in an environment that maintains high levels of nutrients.[56][57] They are easy to open and close, so that cell spheroids can be removed for testing, yet the chamber is able to maintain 100% humidity throughout.[1] This humidity is important to achieve maximum cell growth and function. The bioreactor chamber is part of a larger device that rotates to ensure equal cell growth in each direction across three dimensions.[1]
MC2 Biotek has developed a bioreactor to incubate proto-tissue that uses gas exchange to maintain high oxygen levels within the cell chamber.[58] This is an improvement over previous bioreactors because the higher oxygen levels help the cell grow and undergo normal cell respiration.[16]

Collaborative efforts between tissue engineering (TE) firms, academic institutions, and industrial partners can enhance the transformation of research-oriented bioreactors into efficient commercial manufacturing systems.[59] Academic collaborators contribute foundational aspects, while industrial partners provide essential automation elements, ensuring compliance with regulatory standards and user-friendliness.[60] Established consortia in Europe, such as REMEDI, AUTOBONE, and STEPS, focus on developing automated systems to streamline the engineering of autologous cell-based grafts.[61] The aim is to meet regulatory criteria and ensure cost-effectiveness, making tissue-engineered products more clinically accessible and advancing the translational paradigm of TE from research to a competitive commercial field.[62]

Microfluidics

The utilization of microfluidic technology facilitates the generation of intricate micro-scale structures and the precise manipulation of parameters, thereby emulating the in vivo cellular milieu. The integration of microfluidic technology with 3D cell culture holds considerable potential for applications that seek to replicate in vivo tissue characteristics, notably exemplified by the evolving organ-on-a-chip system.[63] The various cell structures in the human body must be vascularized to receive the nutrients and gas exchange in order to survive. Similarly, 3D cell cultures in vitro require certain levels of fluid circulation, which can be problematic for dense, 3D cultures where cells may not all have adequate exposure to nutrients. This is particularly important in hepatocyte cultures because the liver is a highly vascularized organ. One study cultured hepatocytes and vascular cells together on a collagen gel scaffold between microfluidic channels, and compared growth of cells in static and flowing environments, and showed the need for models with tissues and a microvascular network.[64] Another study showed that hanging-drop based spheroid co-culture device can be useful, generating two different cell spheroids on adjacent channels of microfluidic hanging drop device, and co-culturing spheroids with merging droplets, to monitor tumor-induced angiogenesis.[65]

Microfluidic 3D cell culture, with its potential applications in biomedical research and tissue engineering, is an area of growing interest. However, its advancement is accompanied by several formidable challenges.[66] One such challenge pertains to the difficulty in accessing cultured cells within microsystems, coupled with the intricate nature of sample extraction for subsequent assays.[67] Additionally, the development of methodologies and devices dedicated to in vivo-like cell metabolism and functions study, as well as drug discovery, represents a significant hurdle for microfluidic 3D cell culture devices.[68] Another noteworthy impediment is the limited availability of microfabrication instrumentation in conventional biology laboratories. Moreover, the commercialization of mature and user-friendly microfluidic devices poses a substantial challenge, hindering their accessibility to biologists.[69] Lastly, while biologists often seek high-throughput assay tools with optimal reproducibility, microfluidics encounters technical limitations in meeting these demands, despite the potential feasibility of parallel assays.[70]

High-throughput screening

Advanced development of 3D models for high-throughput screening in high density formats has recently been achievable due to technological achievements related to increased microplate density. These can be found in 384 and 1536-well formats that are cell repellent, cost effective, and amenable to fully automated screening platforms.[71] Two options that afford 1536-well formats are available from either Greiner Bio-One using the m3D Magnetic 3D bioprinting[72] and Corning Life Sciences which incorporates an ultra-low attachment surface coating, along with a microcavity geometry and gravity to create 3D models.[73][74] Due to the rapid and affordable methods and technologies that have been developed for 3D screening, parallel high-throughput screening approaches to test isogenic pairs of oncogene related mutants versus wildtype have been enabled.[75] Moreover, High-throughput screening techniques play a pivotal role in connecting the realms of pharmacology and toxicology within the framework of 3D cell culture.

Pharmacology and toxicology

A primary purpose of growing cells in 3D scaffolds and as 3D cell spheroids in vitro is to test pharmacokinetic and pharmacodynamic effects of drugs and nanomaterials in preclinical trials.[16][76][77][78][79] Toxicology studies have shown 3D cell cultures to be nearly on par with in vivo studies for the purposes of testing toxicity of drug compounds. When comparing -1">50 values for 6 common drugs: acetaminophen, amiodarone, diclofenac, metformin, phenformin, and valproic acid, the 3D spheroid values correlated directly with those from in vivo studies.[80] Although 2D cell cultures have previously been used to test for toxicity along with in vivo studies, the 3D spheroids are better at testing chronic exposure toxicity because of their longer life spans.[81] The matrix in 3D Spheroids causes cells to maintain actin filaments and is more relevant physiologically in cytoskeletal organization and cell polarity and shape of human cells.[82] The three-dimensional arrangement allows the cultures to provide a model that more accurately resembles human tissue in vivo without using animal test subjects.[83]

The current protocols for evaluating drug candidates and assessing toxicity heavily depend on outcomes derived from early-stage in vitro cell-based assays, with the expectation that these assays faithfully capture critical aspects of in vivo pharmacology and toxicology.[84] Various in vitro designs have been fine-tuned for high throughput to enhance screening efficiency, allowing exhaustive libraries of potential pharmacologically relevant or potentially toxic molecules to undergo scrutiny for cell signals indicative of tissue damage or aligned with therapeutic objectives.[85] Innovative approaches to multiplexed cell-based assay designs, involving the selection of specific cell types, signaling pathways, and reporters, have become standard practice.[86]

Despite these advancements, a considerable percentage of new chemical and biological entities (NCEs/NBEs) encounter setbacks in late-stage human drug testing. Some receive regulatory "black box" warnings, while others are withdrawn from the market due to safety concerns post-regulatory approval.[87] This recurrent pattern underscores the inadequacy of in vitro cell-based assays and subsequent preclinical in vivo studies in furnishing comprehensive pharmacological and toxicity data or reliable predictive capacity for comprehending the in vivo performance of drug candidates.[88]

The absence of a dependable translational assay toolkit for pharmacology and toxicology contributes to the high cost and inefficiency of transitioning from initial in vitro cell-based screens to in vivo testing and subsequent clinical approvals.[89] Particular emphasis is placed on their capacity to retain essential cell and molecular interactions, as well as physiological parameters influencing cell phenotypes and responses to bioactive agents. The distinctive advantages and challenges associated with these models are scrutinized, with a specific focus on their suitability for cell-based assays and their predictive capabilities, crucial for establishing accurate correlations with in vivo mechanisms of drug toxicity.[90]

While assessing safety and efficacy, these models are well equipped to model a wide range of disease states. Each of these models has advantages and limitations that require model development and data interpretation. Public-private partnerships are critical to advance and stimulate research in this area.[91]

Criticisms

Existing 3D methods are not without limitations, including scalability, reproducibility, sensitivity, and compatibility with high-throughput screening (HTS) instruments. Cell-based HTS relies on rapid determination of cellular response to drug interaction, such as dose dependent cell viability, cell-cell/cell-matrix interaction, and/or cell migration, but the available assays are not optimized for 3D cell culturing. Another challenge faced by 3D cell culturing is the limited amount of data and publications that address mechanisms and correlations of drug interaction, cell differentiation, and cell-signalling in these 3D environments. None of the 3D methods have yet replaced 2D culturing on a large scale, including in the drug development process; although the number of 3D cell culturing publications is increasing rapidly, the current limited biochemical characterization of 3D tissue diminishes the adoption of new methods.

There are also problems using spheroids as a model for cancerous tissue. Although beneficial for 3D tissue culture, tumor spheroids have been criticized for being challenging or impossible to "manipulate gradients of soluble molecules in [3D spheroid] constructs, and to characterize cells in these complex gradients", unlike the paper-supported 3D cell culture for tissue-based bioassays explored by Ratmir et al.[57] Further challenges associated with complex 3D cell culture techniques include: imaging due to large scaffold sizes and incompatibility with many fluorescence microscopes, flow cytometry because it requires the dissociation of spheroids into a single-cell suspension, and the automation of liquid handling.[92]

Tissue engineering requires 3D cellular scaffolds. As biomaterials, various natural and synthetic polymer hydrogels have been used by scientists to design 3D scaffolds. Since this barrier is a structure that mimics the natural ECM microenvironment, synthetic scaffolds may be more useful for studying specific tumorigenic steps.[36] Finally, it is suggested that the most suitable three-dimensional models should be carefully selected according to specific targets.[93]

See also

References

  1. 1.0 1.1 1.2 1.3 1.4 Fey, Stephen; Wrzesinski, Krzysztof (2013). "Determination of Acute Lethal and Chronic Lethal Thresholds of Valproic Acid Using 3D Spheroids Constructed From the Immortal Human Hepatocyte Cell Line HEPG2/C3A". Valproic Acid. Nova Science Publishers, Inc.. pp. 141–165. ISBN 978-1-62417-952-5. http://www.mc2biotek.com/media/7655/fey_wrzesinski_2013_valproic_acid_978-1-62417-952-5_ch5.pdf. 
  2. Mapanao, Ana Katrina; Voliani, Valerio (June 2020). "Three-dimensional tumor models: Promoting breakthroughs in nanotheranostics translational research". Applied Materials Today 19. doi:10.1016/j.apmt.2019.100552. 
  3. "On the Permanent Life of Tissues Outside of the Organisms". The Journal of Experimental Medicine 15 (5): 516–28. May 1912. doi:10.1084/jem.15.5.516. PMID 19867545. 
  4. MERIT Award Recipient: Mina J. Bissell, Ph.D. (n.d.). Retrieved 16 June 2016, from http://www.cancer.gov/research/nci-role/spotlight/merit/Bissell
  5. Simon, Eric M. (1988). "NIH Phase I Final Report: Fibrous Substrates for Cell Culture (R3RR03544A) (PDF Download Available)" (in en). https://www.researchgate.net/publication/317053872. 
  6. "3D-Autologous Culture Method for Precision Oncology". Cancer Systems and Integrative Biology. Methods Mol Biol. 2660. 2023. pp. 61–68. doi:10.1007/978-1-0716-3163-8_5. ISBN 978-1-0716-3162-1. 
  7. "3D Cell Culture: An Introduction". 3D Cell Culture. Methods Mol Biol. 1612. 2017. pp. 1–11. doi:10.1007/978-1-4939-7021-6_1. ISBN 978-1-4939-7019-3. 
  8. Kern, Carina; Bonventre, Joseph V.; Justin, Alexander W.; Kashani, Kianoush; Reynolds, Elizabeth; Siew, Keith; Davis, Bill; Karakoy, Halime et al. (2025-05-29). "Necrosis as a fundamental driver of loss of resilience and biological decline: what if we could intervene?" (in en). Oncogene 44 (24): 1893–1904. doi:10.1038/s41388-025-03431-y. ISSN 1476-5594. PMID 40437182. https://www.nature.com/articles/s41388-025-03431-y. 
  9. Marx, Vivien (11 April 2013). "A Better Brew". Nature. https://brown.edu/academics/molecular-pharmacology-physiology-and-biotechnology/sites/brown.edu.academics.molecular-pharmacology-physiology-and-biotechnology/files/uploads/Nature%20apr%2011%20a%20better%20brew.pdf. 
  10. "Three-dimensional tissue culture based on magnetic cell levitation". Nature Nanotechnology 5 (4): 291–6. April 2010. doi:10.1038/nnano.2010.23. PMID 20228788. Bibcode2010NatNa...5..291S. 
  11. 11.0 11.1 11.2 11.3 "The third dimension bridges the gap between cell culture and live tissue". Nature Reviews Molecular Cell Biology 8 (10): 839–45. October 2007. doi:10.1038/nrm2236. PMID 17684528. 
  12. "A pericellular collagenase directs the 3-dimensional development of white adipose tissue". Cell 125 (3): 577–91. May 2006. doi:10.1016/j.cell.2006.02.050. PMID 16678100. 
  13. "Modeling tissue morphogenesis and cancer in 3D". Cell 130 (4): 601–10. August 2007. doi:10.1016/j.cell.2007.08.006. PMID 17719539. 
  14. "Spheroid-based drug screen: considerations and practical approach". Nature Protocols 4 (3): 309–24. 12 February 2009. doi:10.1038/nprot.2008.226. PMID 19214182. 
  15. 15.0 15.1 "Simplifying the extracellular matrix for 3-D cell culture and tissue engineering: a pragmatic approach". Journal of Cellular Biochemistry 101 (6): 1370–83. August 2007. doi:10.1002/jcb.21386. PMID 17492655. 
  16. 16.0 16.1 16.2 16.3 "Capturing complex 3D tissue physiology in vitro". Nature Reviews Molecular Cell Biology 7 (3): 211–24. March 2006. doi:10.1038/nrm1858. PMID 16496023. https://infoscience.epfl.ch/handle/20.500.14299/232799. 
  17. "Three-dimensional cell culture matrices: state of the art". Tissue Engineering. Part B, Reviews 14 (1): 61–86. March 2008. doi:10.1089/teb.2007.0150. PMID 18454635. https://deepblue.lib.umich.edu/bitstream/2027.42/63369/1/teb.2007.0150.pdf. 
  18. "3D Cell Culture: A Review of Current Approaches and Techniques". 3D Cell Culture. Methods in Molecular Biology. 695. 2011. pp. 1–15. doi:10.1007/978-1-60761-984-0_1. ISBN 978-1-60761-983-3. 
  19. "Building in vitro models of organs". A Survey of Cell Biology. International Review of Cytology. 244. 2005. pp. 137–73. doi:10.1016/s0074-7696(05)44004-8. ISBN 978-0-12-364648-4. 
  20. "Status and prospects of in vitro tests in risk assessment". Alternatives to Laboratory Animals 32 (4): 431–5. October 2004. doi:10.1177/026119290403200416. PMID 15651929. 
  21. "Visualizing muscle cell migration in situ". Current Biology 10 (10): 576–85. May 2000. doi:10.1016/s0960-9822(00)00486-3. PMID 10837222. Bibcode2000CBio...10..576K. 
  22. "Extracellular matrix-dependent tissue-specific gene expression in mammary epithelial cells requires both physical and biochemical signal transduction". Proceedings of the National Academy of Sciences of the United States of America 91 (26): 12378–82. December 1994. doi:10.1073/pnas.91.26.12378. PMID 7528920. Bibcode1994PNAS...9112378R. 
  23. 23.0 23.1 "HepG2/C3A spheroids exhibit stable physiological functionality for at least 24 days after recovering from trypsinisation". Toxicol. Res. 2 (3): 163–172. 2013. doi:10.1039/C3TX20086H. http://findresearcher.sdu.dk/portal/da/publications/hepg2c3a-3d-spheroids-exhibit-stable-physiological-functionality-for-at-least-24-days-after-recovering-from-trypsination(57ab9c9e-1777-41e7-9247-47b9abeb56aa).html. 
  24. "After trypsinisation, 3D spheroids of C3A hepatocytes need 18 days to re-establish similar levels of key physiological functions to those seen in the liver". http://www.mc2biotek.com/media/7075/121217_toxres_published_manus_c2tx20060k.pdf. 
  25. Han, Y; Zeger, L; Tripathi, R; Egli, M; Ille, F; Lockowandt, C; Florin, G; Atic, E et al. (October 2021). "Molecular genetic analysis of neural stem cells after space flight and simulated microgravity on earth.". Biotechnology and Bioengineering 118 (10): 3832–46. doi:10.1002/bit.27858. PMID 34125436. Bibcode2021BiotB.118.3832H. 
  26. "+ stem cells". Molecular Biology Reports 43 (11): 1233–42. November 2016. doi:10.1007/s11033-016-4053-4. PMID 27497820. 
  27. Pednekar, Kunal P.; Heinrich, Marcel A.; van Baarlen, Joop; Prakash, Jai (2021-10-06). "Novel 3D µtissues Mimicking the Fibrotic Stroma in Pancreatic Cancer to Study Cellular Interactions and Stroma-Modulating Therapeutics" (in en). Cancers 13 (19): 5006. doi:10.3390/cancers13195006. PMID 34638490. 
  28. "The role of three-dimensional polymeric scaffold configuration on the uniformity of connective tissue formation by adipose stromal cells". Biomaterials 31 (15): 4322–9. May 2010. doi:10.1016/j.biomaterials.2010.02.008. PMID 20199809. 
  29. "Effects of the architecture of tissue engineering scaffolds on cell seeding and culturing". Acta Biomater 6 (11): 4208–17. November 2010. doi:10.1016/j.actbio.2010.06.012. PMID 20561602. https://eprints.qut.edu.au/38848/1/c38848.pdf. 
  30. "Scaffolds for tissue engineering and 3D cell culture". 3D Cell Culture. Methods Mol Biol. 695. 2011. pp. 17–39. doi:10.1007/978-1-60761-984-0_2. ISBN 978-1-60761-983-3. 
  31. "Controlled pattern of cell growth in modulated protein nanocomplexes: Regulating cells spreading in three dimensions". Materials Today 21 (6): 686–8. 2018. doi:10.1016/j.mattod.2018.06.003. 
  32. "Hydrogels as extracellular matrix mimics for 3D cell culture". Biotechnology and Bioengineering 103 (4): 655–63. July 2009. doi:10.1002/bit.22361. PMID 19472329. Bibcode2009BiotB.103..655T. 
  33. "Engineering hydrogels as extracellular matrix mimics". Nanomedicine (London, England) 5 (3): 469–84. April 2010. doi:10.2217/nnm.10.12. PMID 20394538. 
  34. "Gene expression perturbation in vitro—a growing case for three-dimensional (3D) culture systems". Semin Cancer Biol 15 (5): 405–12. October 2005. doi:10.1016/j.semcancer.2005.06.009. PMID 16055341. 
  35. "Comparison of bone marrow cell growth on 2D and 3D alginate hydrogels". J Mater Sci Mater Med 16 (6): 515–9. June 2005. doi:10.1007/s10856-005-0526-z. PMID 15928866. 
  36. 36.0 36.1 "Hydrogels as extracellular matrix mimics for 3D cell culture". Biotechnology and Bioengineering 103 (4): 655–63. July 2009. doi:10.1002/bit.22361. PMID 19472329. Bibcode2009BiotB.103..655T. 
  37. 37.0 37.1 "The development and characterization of a human mesothelioma in vitro 3D model to investigate immunotoxin therapy". PLOS ONE 6 (1). January 2011. doi:10.1371/journal.pone.0014640. PMID 21305058. Bibcode2011PLoSO...614640X. 
  38. 38.0 38.1 "Spheroid culture as a tool for creating 3D complex tissues". Trends in Biotechnology 31 (2): 108–15. February 2013. doi:10.1016/j.tibtech.2012.12.003. PMID 23336996. https://ris.utwente.nl/ws/files/6892518/2013-02-01_Fennema.pdf. 
  39. Moshksayan, Khashayar; Kashaninejad, Navid; Warkiani, Majid Ebrahimi; Lock, John G.; Moghadas, Hajar; Firoozabadi, Bahar; Saidi, Mohammad Said; Nguyen, Nam-Trung (2018-06-15). "Spheroids-on-a-chip: Recent advances and design considerations in microfluidic platforms for spheroid formation and culture". Sensors and Actuators B: Chemical 263: 151–176. doi:10.1016/j.snb.2018.01.223. ISSN 0925-4005. Bibcode2018SeAcB.263..151M. https://linkinghub.elsevier.com/retrieve/pii/S092540051830248X. 
  40. "A multiscale model for avascular tumor growth". Biophysical Journal 89 (6): 3884–94. December 2005. doi:10.1529/biophysj.105.060640. PMID 16199495. Bibcode2005BpJ....89.3884J. 
  41. "Prolonged mammosphere culture of MCF-7 cells induces an EMT and repression of the estrogen receptor by microRNAs". Breast Cancer Research and Treatment 132 (1): 75–85. February 2012. doi:10.1007/s10549-011-1534-y. PMID 21553120. 
  42. "A heterologous 3-D coculture model of breast tumor cells and fibroblasts to study tumor-associated fibroblast differentiation". Experimental Cell Research 266 (1): 74–86. May 2001. doi:10.1006/excr.2001.5210. PMID 11339826. 
  43. Priwitaningrum, Dwi L.; Blondé, Jean-Baptiste G.; Sridhar, Adithya; van Baarlen, Joop; Hennink, Wim E.; Storm, Gert; Le Gac, Séverine; Prakash, Jai (December 2016). "Tumor stroma-containing 3D spheroid arrays: A tool to study nanoparticle penetration" (in en). Journal of Controlled Release 244 (Pt B): 257–268. doi:10.1016/j.jconrel.2016.09.004. PMID 27616660. https://linkinghub.elsevier.com/retrieve/pii/S0168365916306903. 
  44. "Rapid generation of in vitro multicellular spheroids for the study of monoclonal antibody therapy". Journal of Cancer 2: 507–14. 2011. doi:10.7150/jca.2.507. PMID 22043235. 
  45. "High-throughput 3D spheroid culture and drug testing using a 384 hanging drop array". The Analyst 136 (3): 473–8. February 2011. doi:10.1039/c0an00609b. PMID 20967331. Bibcode2011Ana...136..473T. 
  46. "Three-dimensional in vitro tumor models for cancer research and drug evaluation". Biotechnology Advances 32 (7): 1256–68. November 2014. doi:10.1016/j.biotechadv.2014.07.009. PMID 25116894. 
  47. Santi, Melissa; Mapanao, Ana Katrina; Cappello, Valentina; Voliani, Valerio (1 July 2020). "Production of 3D tumor models of head and neck squamous cell carcinomas for nanotheranostics assessment" (in en). ACS Biomaterials Science & Engineering 6 (9): 4862–9. doi:10.1021/acsbiomaterials.0c00617. PMID 33395269. 
  48. Tan, Loh Teng Hern; Low, Liang Ee; Tang, Siah Ying; Yap, Wei Hsum; Chuah, Lay Hong; Chan, Chim Kei; Lee, Learn Han; Goh, Bey Hing (2019). "A reliable and affordable 3D tumor spheroid model for natural product drug discovery: A case study of curcumin". Progress in Drug Discovery & Biomedical Science 2. doi:10.36877/pddbs.a0000017. 
  49. Peirsman, Arne; Blondeel, Eva; Ahmed, Tasdiq; Anckaert, Jasper; Audenaert, Dominique; Boterberg, Tom; Buzas, Krisztina; Carragher, Neil et al. (2021-11-01). "MISpheroID: a knowledgebase and transparency tool for minimum information in spheroid identity" (in en). Nature Methods 18 (11): 1294–1303. doi:10.1038/s41592-021-01291-4. PMID 34725485. 
  50. Celik; Dominici; Filby; Das; Madden; Paunov (2019-07-11). "Fabrication of Human Keratinocyte Cell Clusters for Skin Graft Applications by Templating Water-in-Water Pickering Emulsions" (in en). Biomimetics 4 (3): 50. doi:10.3390/biomimetics4030050. PMID 31336810. 
  51. 51.0 51.1 "High-throughput fabrication of hepatic cell clusteroids with enhanced growth and functionality for tissue engineering applications". Mater. Adv. 1 (8): 3022–32. 2020. doi:10.1039/D0MA00635A. 
  52. "Physical supports from liver cancer cells are essential for differentiation and remodeling of endothelial cells in a HepG2-HUVEC co-culture model". Sci. Rep. 5 (1). 2015. doi:10.1038/srep10801. PMID 26053957. Bibcode2015NatSR...510801C. 
  53. "A Human Liver-on-a-Chip Platform for Modeling Nonalcoholic Fatty Liver Disease". Advanced Biosystems 3 (8). August 2019. doi:10.1002/adbi.201900104. PMID 32648699. 
  54. "Biofilm-Infected Human Clusteroid Three-Dimensional Coculture Platform to Replace Animal Models in Testing Antimicrobial Nanotechnologies". ACS Appl Mater Interfaces 13 (19): 22182–22194. May 2021. doi:10.1021/acsami.1c02679. PMID 33956425. Bibcode2021AAMI...1322182W. https://hull-repository.worktribe.com/output/3760262. 
  55. "Vascularized Co-Culture Clusteroids of Primary Endothelial and Hep-G2 Cells Based on Aqueous Two-Phase Pickering Emulsions". Bioengineering 9 (3): 126. March 2022. doi:10.3390/bioengineering9030126. PMID 35324815. 
  56. "Synthetic sandwich culture of 3D hepatocyte monolayer". Biomaterials 29 (3): 290–301. January 2008. doi:10.1016/j.biomaterials.2007.09.016. PMID 17964646. http://scholarbank.nus.edu.sg/handle/10635/25174. 
  57. 57.0 57.1 "Paper-supported 3D cell culture for tissue-based bioassays". Proceedings of the National Academy of Sciences of the United States of America 106 (44): 18457–62. November 2009. doi:10.1073/pnas.0910666106. PMID 19846768. Bibcode2009PNAS..10618457D. 
  58. Fey, Stephen J. "WO2012022351". European Patent Register.
  59. "Spaceflight bioreactor studies of cells and tissues". Adv Space Biol Med. Advances in Space Biology and Medicine 8: 177–95. 2002. doi:10.1016/s1569-2574(02)08019-x. ISBN 978-0-444-50735-8. PMID 12951697. 
  60. "Bioreactors in tissue engineering: scientific challenges and clinical perspectives". Bioreactor Systems for Tissue Engineering. Advances in Biochemical Engineering/Biotechnology. 112. 2009. pp. 1–27. doi:10.1007/978-3-540-69357-4_1. ISBN 978-3-540-69356-7. Bibcode2009bste.book....1W. 
  61. "A Perfusion Bioreactor System for Cell Seeding and Oxygen-Controlled Cultivation of Three-Dimensional Cell Cultures". Tissue Eng Part C Methods 24 (10): 585–595. October 2018. doi:10.1089/ten.TEC.2018.0204. PMID 30234443. 
  62. "Potential and bottlenecks of bioreactors in 3D cell culture and tissue manufacturing". Advanced Materials 21 (32–33): 3352–67. September 2009. doi:10.1002/adma.200802748. PMID 20882502. Bibcode2009AdM....21.3352W. 
  63. "Microfluidic 3D cell culture: potential application for tissue-based bioassays". Bioanalysis 4 (12): 1509–25. June 2012. doi:10.4155/bio.12.133. PMID 22793034. 
  64. "Transport-mediated angiogenesis in 3D epithelial coculture". FASEB Journal 23 (7): 2155–64. July 2009. doi:10.1096/fj.08-122820. PMID 19246488. 
  65. Rodoplu, Didem; Matahum, Jefunnie Sierra; Hsu, Chia-Hsien (2022-03-29). "A microfluidic hanging drop-based spheroid co-culture platform for probing tumor angiogenesis" (in en). Lab on a Chip 22 (7): 1275–85. doi:10.1039/D1LC01177D. PMID 35191460. https://pubs.rsc.org/en/content/articlelanding/2022/lc/d1lc01177d. 
  66. "Microfluidic cell coculture methods for understanding cell biology, analyzing bio/pharmaceuticals, and developing tissue constructs". Anal Biochem 413 (2): 81–9. June 2011. doi:10.1016/j.ab.2011.02.027. PMID 21354094. 
  67. "A review of three-dimensional in vitro tissue models for drug discovery and transport studies". Journal of Pharmaceutical Sciences 100 (1): 59–74. January 2011. doi:10.1002/jps.22257. PMID 20533556. Bibcode2011JPhmS.100...59E. 
  68. "Microfluidic array for three-dimensional perfusion culture of human mammary epithelial cells". Biomed Microdevices 13 (4): 753–8. August 2011. doi:10.1007/s10544-011-9545-3. PMID 21556741. 
  69. "Three-dimensional micro-electrode array for recording dissociated neuronal cultures". Lab Chip 9 (14): 2036–42. July 2009. doi:10.1039/b820596e. PMID 19568672. 
  70. "Critical Considerations for the Design of Multi-Organ Microphysiological Systems (MPS)". Front Cell Dev Biol 9. 2021. doi:10.3389/fcell.2021.721338. PMID 34568333. 
  71. Baillargeon, P et al. (2019). "Automating a Magnetic 3D Spheroid Model Technology for High-Throughput Screening.". SLAS Technol 24 (4): 420–8. doi:10.1177/2472630319854337. PMID 31225974. 
  72. Hou, S et al. (2018). "Advanced Development of Primary Pancreatic Organoid Tumor Models for High-Throughput Phenotypic Drug Screening.". SLAS Discov 23 (6): 574–584. doi:10.1177/2472555218766842. PMID 29673279. 
  73. Madoux, F et al. (2017). "A 1536-Well 3D Viability Assay to Assess the Cytotoxic Effect of Drugs on Spheroids.". SLAS Discov 22 (5): 516–524. doi:10.1177/2472555216686308. PMID 28346088. 
  74. Quereda, V; Hou, S; Madoux, F; Scampavia, L; Spicer, TP; Duckett, D (2018). "A Cytotoxic Three-Dimensional-Spheroid, High-Throughput Assay Using Patient-Derived Glioma Stem Cells.". SLAS Discov 23 (8): 842–9. doi:10.1177/2472555218775055. PMID 29750582. 
  75. Kota, S et al. (2018). "A novel three-dimensional high-throughput screening approach identifies inducers of a mutant KRAS selective lethal phenotype.". Oncogene 37 (32): 4372–84. doi:10.1038/s41388-018-0257-5. PMID 29743592. 
  76. "Photothermal effect by NIR-responsive excretable ultrasmall-in-nano architectures" (in en). Materials Horizons 6 (3): 531–7. 2019. doi:10.1039/C9MH00096H. 
  77. "Endogenously Triggerable Ultrasmall-in-Nano Architectures: Targeting Assessment on 3D Pancreatic Carcinoma Spheroids". ACS Omega 3 (9): 11796–801. September 2018. doi:10.1021/acsomega.8b01719. PMID 30320273. 
  78. Zustiak, Silviya Petrova; Dadhwal, Smritee; Medina, Carlos; Steczina, Sonette; Chehreghanianzabi, Yasaman; Ashraf, Anisa; Asuri, Prashanth (February 2016). "Three-dimensional matrix stiffness and adhesive ligands affect cancer cell response to toxins". Biotechnology and Bioengineering 113 (2): 443–452. doi:10.1002/bit.25709. PMID 26184715. Bibcode2016BiotB.113..443Z. 
  79. Otieno, Monicah A.; Gan, Jinping; Proctor, William (2018), Chen, Minjun; Will, Yvonne, eds., "Status and Future of 3D Cell Culture in Toxicity Testing" (in en), Drug-Induced Liver Toxicity, Methods in Pharmacology and Toxicology (New York, NY: Springer): pp. 249–261, doi:10.1007/978-1-4939-7677-5_12, ISBN 978-1-4939-7677-5 
  80. "Determination of drug toxicity using 3D spheroids constructed from an immortal human hepatocyte cell line". Toxicological Sciences 127 (2): 403–11. June 2012. doi:10.1093/toxsci/kfs122. PMID 22454432. 
  81. "Multi-cell type human liver microtissues for hepatotoxicity testing". Archives of Toxicology 87 (1): 209–13. January 2013. doi:10.1007/s00204-012-0968-2. PMID 23143619. Bibcode2013ArTox..87..209M. 
  82. "Human embryonic stem cell technologies and drug discovery". Journal of Cellular Physiology 219 (3): 513–9. June 2009. doi:10.1002/jcp.21732. PMID 19277978. 
  83. "A novel lab-on-a-chip platform for spheroid metabolism monitoring". Cytotechnology 70 (1): 375–386. February 2018. doi:10.1007/s10616-017-0152-x. PMID 29032507. 
  84. "The discovery and development of proteomic safety biomarkers for the detection of drug-induced liver toxicity". Toxicol Appl Pharmacol 245 (1): 134–42. May 2010. doi:10.1016/j.taap.2010.02.011. PMID 20219512. Bibcode2010ToxAP.245..134A. 
  85. "Is toxicogenomics a more reliable and sensitive biomarker than conventional indicators from rats to predict drug-induced liver injury in humans?". Chem Res Toxicol 25 (1): 122–9. January 2012. doi:10.1021/tx200320e. PMID 22122743. 
  86. "Future of toxicology—mechanisms of toxicity and drug safety: where do we go from here?". Chem Res Toxicol 19 (11): 1393–1401. November 2006. doi:10.1021/tx060213n. PMID 17112225. 
  87. "High-throughput human metabolism and toxicity analysis". Curr Opin Biotechnol 17 (6): 619–27. December 2006. doi:10.1016/j.copbio.2006.09.003. PMID 17046235. 
  88. "Understanding mechanisms of toxicity: insights from drug discovery research". Toxicol Appl Pharmacol 227 (2): 163–78. March 2008. doi:10.1016/j.taap.2007.10.022. PMID 18063003. Bibcode2008ToxAP.227..163H. 
  89. "Evaluating drug efficacy and toxicology in three dimensions: using synthetic extracellular matrices in drug discovery". Acc Chem Res 41 (1): 139–48. January 2008. doi:10.1021/ar7000827. PMID 17655274. 
  90. "A critical evaluation of in vitro cell culture models for high-throughput drug screening and toxicity". Pharmacol Ther 134 (1): 82–106. April 2012. doi:10.1016/j.pharmthera.2012.01.001. PMID 22252140. 
  91. "3D cell culture models: Drug pharmacokinetics, safety assessment, and regulatory consideration". Clin Transl Sci 14 (5): 1659–80. September 2021. doi:10.1111/cts.13066. PMID 33982436. 
  92. "Is It Time to Start Transitioning From 2D to 3D Cell Culture?" (in en). Frontiers in Molecular Biosciences 7. 2020. doi:10.3389/fmolb.2020.00033. PMID 32211418. 
  93. "3D Cell Culture Systems: Tumor Application, Advantages, and Disadvantages". International Journal of Molecular Sciences 22 (22). November 2021. doi:10.3390/ijms222212200. PMID 34830082.