CELL CULTURE

3. 2D and 3D Cell Culture Approaches

2D and 3D Cell Culture: Structural and Functional Differences

2D cell culture refers to monolayer systems, in which cells are grown on a flat, rigid surface and primarily interact with the underlying substrate. These systems are widely used for routine applications such as cell expansion and microscopy. They also support standard assays, including viability, proliferation, cytotoxicity, and compound screening under controlled and reproducible conditions. Cells are typically cultured on plastic or coated surfaces and experience a defined, simplified environment.

 3D cell culture systems are structurally more complex. Cells are embedded in or interact with a three-dimensional matrix, enabling cell–cell and cell–matrix interactions in all directions. This configuration supports tissue-like organization and allows, depending on the system, the inclusion of multiple cell types. It more closely reflects in vivo-like conditions, including spatial organization, matrix interactions, and dynamic remodeling processes.

Key characteristics of 3D cell culture include:

  • Physiological cell morphology and polarity
  • Multi-directional cell–cell and cell–matrix interactions
  • Tissue-like structural organization
  • Formation of nutrient, oxygen, and signaling gradients
  • More physiologically relevant cellular responses in drug and toxicity studies
  • Suitability for migration, invasion, and differentiation assays

Types of 3D Culture Models

Matrix-Embedded 3D Cultures

Cells can be embedded in biomaterials such as Collagen Hydrogels, a common scaffold-based 3D culture approach. Collagen-based hydrogels are widely used for primary human cells due to their biologically relevant composition. They are compatible with a broad range of assay formats, including migration, invasion, and advanced 3D cell culture applications (see PureCol® Collagen Type I assay overview).

Layered and full-thickness 3D Models

Not all 3D cell culture systems rely on full matrix embedding. In layered or interface-based models, cells are cultured on permeable supports, at air–liquid interfaces (ALI), or in defined multicellular layers to recreate tissue structure and barrier function.

These systems are commonly used for epithelial and barrier tissues, including skin, airway, cornea, and gut. Typical applications include barrier integrity, permeability, wound healing, irritation testing, and co-culture studies.

More advanced formats extend this concept into full-thickness tissue models, where multiple cell types and compartments are combined to better reflect native tissue organization. A common example is a full-thickness skin model consisting of a dermal compartment and an epidermal layer.

For these applications, Bio-Spun™ Scaffolds for 3D Cell Culture Applications provide an animal-free, electrospun nanofibrous scaffold suitable for layered, interface-based, and full-thickness 3D culture models. For a format and application overview, see the Bio-Spun™ Scaffold Overview.

Frequently Asked Questions

In 2D culture, cells grow on a flat surface and interact either with the underlying plastic or, if coated, with the extracellular matrix (ECM), predominantly from one side. In 3D culture, cells are embedded within a matrix and interact with the extracellular matrix (ECM), establish direct cell–cell contacts with neighboring cells, and communicate through soluble signaling factors in all spatial directions.

This results in more physiologically relevant morphology, gene expression, differentiation, migration, and functional responses. As a result, 3D models often generate more predictive and biologically meaningful data compared to conventional 2D systems.

They can improve the translational value of in vitro experiments, enable more informative screening approaches, and help reduce experimental simplification. In many applications, advanced 3D models also contribute to reducing reliance on animal experiments.

Depending on the application, 3D environments can be created using collagen-based matrices, tunable hydrogels, or structured collagen-based or synthetic scaffolds.

The choice of medium for co-culture systems depends on the specific requirements and compatibility of the different cell types involved. In many cases, a compromise medium is used that supports the viability and function of all cell populations.

Common approaches include:

  • Using a base medium compatible with multiple cell types, supplemented as needed
  • Combining media (e.g., defined ratios of individual culture media)
  • Prioritizing the requirements of the most sensitive or functionally critical cell type

It is important to verify that the selected conditions maintain the phenotype and functionality of each cell type, as well as their interactions within the co-culture system. In more complex systems, medium composition can significantly influence cell–cell signaling, spatial organization, and overall experimental outcomes.

If you would like to discuss your co-culture setup and identify the most suitable medium strategy, please contact us.

A coating creates a thin layer of extracellular matrix (ECM) or adhesion molecules on the culture surface and is typically used to improve cell attachment, spreading, and survival in 2D culture. It does not create a true 3D environment.

In contrast, a hydrogel forms a three-dimensional matrix that surrounds cells and allows them to interact with the ECM in all directions, making it a much more physiologically relevant system for many 3D cell culture applications.

In practical terms, coatings are usually simpler and faster to use, while hydrogels require more control during preparation. Important parameters include pH, temperature, gelation timing, and the desired matrix stiffness, which should be matched to the needs of the cell type and the intended assay. For example, coatings may use materials such as collagen, fibronectin, or poly-D-lysine, whereas true 3D systems can be created using Collagen Hydrogels, Thiol-Modified Hyaluronan (HyStem®), or Methacrylated Matrices.

If you are unsure whether a coating or a hydrogel is the better choice for your workflow, feel free to contact us.

pH is a critical factor during hydrogel preparation because it directly affects gel formation, matrix structure, and cell viability. In collagen hydrogels, for example, the pH must be carefully adjusted to 7.0–7.4 to allow proper fibril formation and consistent polymerization. Small deviations can lead to incomplete gelation, irregular fibril assembly, uneven matrix structure, poor reproducibility, or reduced cell viability.

A typical preparation involves gently mixing chilled collagen with buffer or media, carefully adjusting the pH with sterile 0.1 M NaOH, and maintaining the mixture at 2–10 °C to prevent premature gelation. Ensure thorough mixing and avoid collagen ‘hold-up’ in pipette tips to prevent even slight alterations to the collagen-to-neutralization solution ratio. Once the pH and temperature are correct, the hydrogel can be incubated at 37 °C to form a stable, firm 3D matrix. While collagen is the most common example, other hydrogels such as Thiol-Modified Hyaluronan (HyStem®) or Methacrylated Matrices also require controlled preparation conditions to ensure consistent mechanical and biological properties.

If you need support selecting or preparing a 3D matrix, feel free to contact us.

Keeping a hydrogel mixture cold (2–10 °C) before gelation is crucial to prevent premature polymerization and to ensure uniform mixing and even cell distribution. For collagen hydrogels, temperature directly affects fibril assembly: if the solution warms too early, the gel may start forming unevenly, leading to inhomogeneous matrix structure, air inclusions (air bubbles), or uneven cell distribution (cell sedimentation).

Maintaining the hydrogel at a low temperature until casting or seeding ensures a uniform 3D architecture and reproducible mechanical properties. Once prepared, the mixture should be transitioned to an incubator; while 37 °C is the optimal temperature for firm gelation, precise control is vital. Avoid exceeding 38.5 °C, as the collagen fibers will begin to denature, compromising the structural integrity of the matrix.

This principle applies not only to collagen hydrogels but also to other systems such as Thiol-Modified Hyaluronan (HyStem®)
or Methacrylated Matrices, where controlled conditions before crosslinking are critical for reproducibility. If you are unsure about handling temperatures or timing for your hydrogel, please contact us for guidance.

Failure of gel formation is typically caused by incorrect ionic conditions, insufficient collagen concentration, or improper handling during preparation.

A critical factor is ionic strength (~300 mOsm). Collagen fibrillogenesis requires physiological salt conditions, which are usually achieved by adding 1 part of 10X PBS or culture medium. Deviations in salt concentration—often caused by inaccurate mixing or pipetting losses—can prevent proper fiber assembly and result in no gel formation.

In addition, low collagen concentrations (<1.5 mg/mL) may not provide sufficient material for stable network formation. Mechanical factors also play an important role. Vortexing, excessive mixing, or disturbance during gelation can disrupt fibril formation and prevent the development of a continuous matrix. Other potential causes include:

  • use of degraded or improperly stored collagen (e.g., freeze–thaw cycles)
  • very small or unconfined volumes, which impair structural stability
  • incomplete or inhomogeneous mixing of components

Changes in hydrogel stability over time are a common observation in cell culture and are not inherently negative. In many 3D systems, controlled matrix remodeling is required for cell migration, differentiation, and tissue-like organization. The optimal level of hydrogel stability therefore depends on the experimental objective.

When hydrogels lose stability, this is typically driven by a combination of cell-mediated contraction, enzymatic matrix degradation, and culture-related factors.

Key drivers include:

  • Cell-generated forces: Contractile cells such as fibroblasts, mesenchymal stromal cells (MSCs), or smooth muscle cells generate traction forces via the actin cytoskeleton, leading to matrix compaction and gel shrinkage.
  • Matrix degradation: Cells secrete enzymes such as matrix metalloproteinases (MMPs) that degrade natural extracellular matrix components including collagen and fibrin.
  • Hydrogel properties: Low polymer concentration or insufficient crosslinking reduces mechanical stability and increases susceptibility to remodeling.
  • Culture conditions: Serum and certain growth factors (for example TGF-β, PDGF, or EGF) can increase cell activity and matrix remodeling depending on cell type and context.
  • Cell density: Higher seeding densities amplify both mechanical forces and enzymatic degradation.

To improve stability, hydrogel composition, crosslinking density, cell density, and medium formulation can be optimized. In addition, specific medium supplements and culture conditions can help reduce excessive matrix degradation or contraction, including MMP inhibitors, ROCK pathway inhibitors (to reduce actomyosin-driven contraction), as well as reduced serum conditions or defined (serum-free) media.

Hydrogel contraction or detachment from the well edges is a common challenge in 3D cell culture. It occurs when cells pull on or remodel the surrounding matrix, which can lead to shrinkage, uneven surfaces, or altered cell distribution. Certain cell types, particularly fibroblasts or other mesenchymal cells, actively reorganize the ECM and secrete enzymes such as matrix metalloproteinases (MMPs) that modify the hydrogel.

To reduce unwanted contraction:

  • Increase matrix stiffness by using highly crosslinked or chemically reinforced hydrogels, such as HyStem®, or methacrylated matrices, and by optimizing polymer concentration.  A stiffer hydrogel better resists cell-generated forces, preserving its 3D structure.
  • Use structural scaffolds such as Bio-Spun® electrospun matrices, which provide spatial support for layered tissue models like Skin Models. Cells may still deposit their own ECM, but the scaffold maintains the overall architecture independently of hydrogel contraction.

By selecting the appropriate matrix or scaffold, contraction can be minimized while supporting physiologically relevant 3D cell culture.

If you are experiencing hydrogel contraction or need guidance on selecting the right system, please contact us for support.

Engineering the 3D Microenvironment: Matrix Stiffness and Mechanical Control

3D cell culture systems can be tuned by adjusting matrix stiffness and mechanical properties. These parameters influence key cellular processes, including proliferation, differentiation, lineage specification, gene expression, morphology, self-renewal, pluripotency, and migration.

Matrix mechanics therefore represent an important design parameter for controlling the cellular microenvironment in 3D culture systems.

Approaches for tuning matrix stiffness

Different material strategies are used to achieve defined mechanical properties in 3D hydrogels:

Methacrylated Matrices feature photocrosslinkable functional groups (e.g., OH, COOH, NH2) that form covalent networks under light, enabling controlled adjustment of gel rigidity.
Thiol-Modified Hyaluronan (HyStem®) uses chemical thio-reactive crosslinking to generate hydrogels with tunable mechanical properties without light exposure.

Biomaterials used in tunable hydrogels

Matrix stiffness can be adjusted using a wide range of biomaterials, including Hyaluronic Acid, Alginate, Chitosan, Dextran, Gelatin, Collagen, and Sericin.

These materials allow modulation of both mechanical and biochemical properties to match specific cell types and experimental applications.

Tunable hydrogels are commonly used in applications such as stem cell maintenance, differentiation studies, and functional tissue models.

Frequently Asked Questions

The stiffness of a 3D hydrogel is mainly determined by its polymer concentration, crosslinking density, and chemical composition. In general, higher polymer content and stronger crosslinking produce a firmer matrix, while lower concentrations or weaker crosslinking result in a softer, more compliant hydrogel.

This is especially important because hydrogel stiffness directly affects both cell behavior and mechanical stability. A stiffer hydrogel can better resist cell-generated traction forces, which helps reduce contraction, detachment, or structural collapse in 3D culture.

Examples of tunable systems include:

Choosing the right stiffness is therefore not only important for proliferation, migration, differentiation, and gene expression, but also for maintaining a stable and reproducible 3D culture environment.

If you are unsure which stiffness range is suitable for your cells or assay, please contact us for guidance.

Chemical and photo-crosslinking are two common strategies used to form and tune 3D hydrogel networks, differing mainly in how the crosslinking reaction is initiated and controlled.

Chemical crosslinking occurs through reactive functional groups that form covalent bonds under defined conditions without the need for external stimuli. For example, thiol-reactive systems such as thiol-modified hyaluronan (HyStem®) enable gel formation under mild conditions and are typically easy to handle, making them suitable for a wide range of cell culture applications.

Photo-crosslinking, in contrast, is initiated by light in the presence of a photoinitiator. Common photoinitiators include LAP (Lithium phenyl-2,4,6-trimethylbenzoylphosphinate), which is widely used due to its high cytocompatibility and activation with visible light (e.g., 405 nm), as well as Irgacure®, which is typically activated by UV light. Ruthenium-based systems are also used in specific applications, enabling crosslinking under visible light conditions in combination with suitable co-initiators.

This approach allows precise temporal and spatial control over gelation, as the crosslinking process can be triggered on demand. Systems such as methacrylated matrices enable fine-tuning of mechanical properties by adjusting light exposure, intensity, and formulation.

Both approaches allow the generation of tunable hydrogels, but differ in their level of control, handling requirements, and experimental flexibility. The choice depends on the specific application, required precision, and compatibility with the cells used.

If you are unsure which crosslinking strategy is best suited for your system, please contact us for guidance.

Methacrylated hydrogels are typically provided as lyophilized powders and allow precise adjustment of mechanical properties through both material composition and photocrosslinking conditions.

Key parameters include:

  • ECM concentration
  • Photocrosslinking time
  • Photocrosslinking intensity
  • Choice of photoinitiator
  • Photoinitiator concentration

By varying these factors, hydrogels can be tuned across a wide range of stiffness, from very soft matrices similar to brain tissue to firmer structures resembling cartilage or muscle. This enables adaptation to specific cell types and experimental applications.

If you would like to discuss your project and identify the most suitable 3D cell culture system, please feel free to contact us.

Yes. Cells can be recovered from HyStem® hydrogels using enzymatic digestion. A collagenase/hyaluronidase mixture is typically recommended to efficiently degrade the matrix and release embedded cells while maintaining cell viability.

HyStem® hydrogels (including HyStem-C and HyStem-HP) have an average pore size of approximately 17 nm, with reported values of <15.9 nm in the literature. This pore structure typically allows the diffusion of small globular proteins and molecules below ~75 kDa, depending on hydrogel composition and crosslinking density. [/av_toggle] [av_toggle title=' What is the difference between scaffold-based and self-organizing 3D cell culture?' title_open='' tags='' title_pos='' slide_speed='' custom_id='' aria_collapsed='' aria_expanded='' av_uid='av-13oo99k' sc_version='1.0'] 3D cell culture systems can be broadly divided into scaffold-based and self-organizing approaches, depending on the extent to which an external matrix defines or supports cell organization. Scaffold-based systems use defined materials such as hydrogels (e.g., collagen-based matrices, HyStem®, or methacrylated matrices), collagen sponges, or Bio-Spun® electrospun matrices to provide structural support and control the cellular microenvironment. These systems allow researchers to control the cellular microenvironment, including stiffness, architecture, and biochemical cues.

In contrast, self-organizing systems are based on the intrinsic ability of cells to form 3D structures through cell–cell interactions and endogenous organization processes without a predefined scaffold. This category includes spheroids and organoids, which differ in complexity but share the same fundamental principle of self-assembly.

Both approaches have distinct advantages:

  • Scaffold-based systems offer high control and reproducibility, making them well suited for defined assays and mechanistic studies.
  • Self-organizing systems can better capture intrinsic tissue organization and emergent behavior, which is valuable for modeling complex biological processes.

Both approaches may involve interactions with extracellular matrix (ECM), but they differ in how the 3D architecture is established and controlled. The choice depends on the specific research question, required level of control, and desired physiological relevance.

A more detailed overview of spheroids and organoids is provided in the following chapter.

Advanced Scaffold Materials: Silk Fibroin

In addition to commonly used hydrogel systems, Silk Fibroin is increasingly recognized as a versatile scaffold material in 3D cell culture and tissue engineering.

Silk fibroin is a fibrous protein primarily derived from silkworms and is characterized by excellent biocompatibility, tunable biodegradability, and remarkable mechanical strength. It can be processed into a wide range of scaffold formats, combined with other biomaterials, and chemically modified to further tailor its properties.

Due to these features, silk fibroin supports a broad spectrum of applications, including bone, cartilage, skin, nerve, and soft tissue models, and has shown particular potential in guiding stem cell differentiation, for example along osteogenic lineages.

Frequently Asked Questions

Yes. This Silk Fibroin used for scaffold preparation is sericin-free. The silk solution is produced from degummed (de-sericinized) silk fibers, and the sericin coating is removed during the extraction process to isolate the purified fibroin protein.

No. The silk fibroin solution is prepared from degummed (de-sericinized) silk fibers, and sericin is removed during the extraction process to obtain purified fibroin.

Yes. Silk fibroin can be processed into aqueous solutions, making it suitable for use in water-based environments such as cell culture and biomaterial applications.

Yes. Silk fibroin scaffolds can be enzymatically degraded. The silk protein backbone is susceptible to proteolytic digestion, and efficient degradation can typically be achieved using a high-concentration Proteinase K solution or similar protease-based enzyme cocktails, depending on scaffold density and structure.

Beyond Scaffold-Based 3D Culture

In addition to matrix-based and layered 3D models, cells can also self-organize into multicellular structures such as spheroids and organoids. These systems represent a distinct category of 3D cell culture and will be covered in upcoming sections.

Browse Related Topics

1. Introduction to Cell Culture

2. Best Practices for Successful Primary Cell Culture

3. 2D and 3D Cell Culture Approaches

Coming soon:

4. Spheroids and Organoids

5. Vascularization of Spheroids

Published: 6 May 2026