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Peptide Hydrogels - Versatile Matrices for 3D Cell Culture in Cancer Medicine.

Worthington P, Pochan DJ, Langhans SA - Front Oncol (2015)

Bottom Line: Traditional two-dimensional (2D) cell culture systems have contributed tremendously to our understanding of cancer biology but have significant limitations in mimicking in vivo conditions such as the tumor microenvironment.In addition, 3D cultures allow for the development of concentration gradients, including oxygen, metabolites, and growth factors, with chemical gradients playing an integral role in many cellular functions ranging from development to signaling in normal epithelia and cancer environments in vivo.One important area of synthetic materials currently available for 3D cell culture is short sequence, self-assembling peptide hydrogels.

View Article: PubMed Central - PubMed

Affiliation: Nemours Center for Childhood Cancer Research, Alfred I. duPont Hospital for Children , Wilmington, DE , USA ; Department of Biomedical Engineering, Delaware Biotechnology Institute, University of Delaware , Newark, DE , USA.

ABSTRACT
Traditional two-dimensional (2D) cell culture systems have contributed tremendously to our understanding of cancer biology but have significant limitations in mimicking in vivo conditions such as the tumor microenvironment. In vitro, three-dimensional (3D) cell culture models represent a more accurate, intermediate platform between simplified 2D culture models and complex and expensive in vivo models. 3D in vitro models can overcome 2D in vitro limitations caused by the oversupply of nutrients, and unphysiological cell-cell and cell-material interactions, and allow for dynamic interactions between cells, stroma, and extracellular matrix. In addition, 3D cultures allow for the development of concentration gradients, including oxygen, metabolites, and growth factors, with chemical gradients playing an integral role in many cellular functions ranging from development to signaling in normal epithelia and cancer environments in vivo. Currently, the most common matrices used for 3D culture are biologically derived materials such as matrigel and collagen. However, in recent years, more defined, synthetic materials have become available as scaffolds for 3D culture with the advantage of forming well-defined, designed, tunable materials to control matrix charge, stiffness, porosity, nanostructure, degradability, and adhesion properties, in addition to other material and biological properties. One important area of synthetic materials currently available for 3D cell culture is short sequence, self-assembling peptide hydrogels. In addition to the review of recent work toward the control of material, structure, and mechanical properties, we will also discuss the biochemical functionalization of peptide hydrogels and how this functionalization, coupled with desired hydrogel material characteristics, affects tumor cell behavior in 3D culture.

No MeSH data available.


Related in: MedlinePlus

The fibrillar structure of Fmoc-FF and Fmoc-RGD. Reprinted with permission from Ref. (84). Copyright 2009 Elsevier Ltd.
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Figure 2: The fibrillar structure of Fmoc-FF and Fmoc-RGD. Reprinted with permission from Ref. (84). Copyright 2009 Elsevier Ltd.

Mentions: Fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF) and fluorenylmethoxycarbonyl arginine–glycine–aspartic acid (Fmoc-RDG) form hydrogels based on aromatic interactions (82–84) and have been successful as a scaffold for cell culture (85, 86). The hydrogel is a relatively simple gelator relying on a few peptides and Fmoc groups and is formed by pi–pi staking between the Fmoc groups, thereby forming 3 nm fibrils which interact laterally to create “flat ribbons.” RGD groups were added to increase cell attachment (Figure 2, in red) and these gels produce a viable 3D encapsulated cell culture with HDFa cells. As such, the scaffolds are suitable for assessment by various methods including fluorescence microscopy and the MTS assay (84). The cell gel constructs are formed by dissolving the peptide in DMSO followed by dilution in an aqueous solution at pH 10 (Fmoc-FF) or pH 3 (Fmoc-RGD), followed by adjustment of the pH to physiological conditions. The solutions can then be mixed with cells in culture medium (87). The gel forms quickly <1 min and has a G′ of around 780 Pa with the final stiffness of the gel being primarily dependent on the final pH (88). Within this system, addition of amino acids other than RGD were tested as well resulting in hydrogel constructs that were more suitable for some cell lines than others. For example, Fmoc-Lysine, Fmoc-Glutamic acid, or Fmoc-Serine constructs were able to grow human dermal fibroblasts but only Fmoc-Serine allowed for the growth of chondrocytes and 3T3 cells (89). Other stacking groups, naphthalene and benzyloxycarbonyl, in place of the Fmoc group have been shown to create fibrils that support chondrocyte growth (90). Changes to the sequence included different combinations of phenylalanine and RGD in order to avoid mixing of different peptides (91). Recently, work has been done to improve the biocompatibility of the gelation process by using glutathione to cleave a sulfide bond on the pregelator that would allow the peptide to gel avoiding the use of DMSO (92). Another group altered and improved gelation by halogenating the phenyl ring on phenylalanine, a scaffold that could be used to culture 3T3 cells after adding RGD to the system (72). Yet, other groups have added different amino acids to improve cell attachment and confirmed the importance of the RGD group (93). While Fmoc groups are not normally found in the ECM, these gels exhibit decent stiffness and appropriate rheology and have proven suitable as 3D cell culture scaffold.


Peptide Hydrogels - Versatile Matrices for 3D Cell Culture in Cancer Medicine.

Worthington P, Pochan DJ, Langhans SA - Front Oncol (2015)

The fibrillar structure of Fmoc-FF and Fmoc-RGD. Reprinted with permission from Ref. (84). Copyright 2009 Elsevier Ltd.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4403249&req=5

Figure 2: The fibrillar structure of Fmoc-FF and Fmoc-RGD. Reprinted with permission from Ref. (84). Copyright 2009 Elsevier Ltd.
Mentions: Fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF) and fluorenylmethoxycarbonyl arginine–glycine–aspartic acid (Fmoc-RDG) form hydrogels based on aromatic interactions (82–84) and have been successful as a scaffold for cell culture (85, 86). The hydrogel is a relatively simple gelator relying on a few peptides and Fmoc groups and is formed by pi–pi staking between the Fmoc groups, thereby forming 3 nm fibrils which interact laterally to create “flat ribbons.” RGD groups were added to increase cell attachment (Figure 2, in red) and these gels produce a viable 3D encapsulated cell culture with HDFa cells. As such, the scaffolds are suitable for assessment by various methods including fluorescence microscopy and the MTS assay (84). The cell gel constructs are formed by dissolving the peptide in DMSO followed by dilution in an aqueous solution at pH 10 (Fmoc-FF) or pH 3 (Fmoc-RGD), followed by adjustment of the pH to physiological conditions. The solutions can then be mixed with cells in culture medium (87). The gel forms quickly <1 min and has a G′ of around 780 Pa with the final stiffness of the gel being primarily dependent on the final pH (88). Within this system, addition of amino acids other than RGD were tested as well resulting in hydrogel constructs that were more suitable for some cell lines than others. For example, Fmoc-Lysine, Fmoc-Glutamic acid, or Fmoc-Serine constructs were able to grow human dermal fibroblasts but only Fmoc-Serine allowed for the growth of chondrocytes and 3T3 cells (89). Other stacking groups, naphthalene and benzyloxycarbonyl, in place of the Fmoc group have been shown to create fibrils that support chondrocyte growth (90). Changes to the sequence included different combinations of phenylalanine and RGD in order to avoid mixing of different peptides (91). Recently, work has been done to improve the biocompatibility of the gelation process by using glutathione to cleave a sulfide bond on the pregelator that would allow the peptide to gel avoiding the use of DMSO (92). Another group altered and improved gelation by halogenating the phenyl ring on phenylalanine, a scaffold that could be used to culture 3T3 cells after adding RGD to the system (72). Yet, other groups have added different amino acids to improve cell attachment and confirmed the importance of the RGD group (93). While Fmoc groups are not normally found in the ECM, these gels exhibit decent stiffness and appropriate rheology and have proven suitable as 3D cell culture scaffold.

Bottom Line: Traditional two-dimensional (2D) cell culture systems have contributed tremendously to our understanding of cancer biology but have significant limitations in mimicking in vivo conditions such as the tumor microenvironment.In addition, 3D cultures allow for the development of concentration gradients, including oxygen, metabolites, and growth factors, with chemical gradients playing an integral role in many cellular functions ranging from development to signaling in normal epithelia and cancer environments in vivo.One important area of synthetic materials currently available for 3D cell culture is short sequence, self-assembling peptide hydrogels.

View Article: PubMed Central - PubMed

Affiliation: Nemours Center for Childhood Cancer Research, Alfred I. duPont Hospital for Children , Wilmington, DE , USA ; Department of Biomedical Engineering, Delaware Biotechnology Institute, University of Delaware , Newark, DE , USA.

ABSTRACT
Traditional two-dimensional (2D) cell culture systems have contributed tremendously to our understanding of cancer biology but have significant limitations in mimicking in vivo conditions such as the tumor microenvironment. In vitro, three-dimensional (3D) cell culture models represent a more accurate, intermediate platform between simplified 2D culture models and complex and expensive in vivo models. 3D in vitro models can overcome 2D in vitro limitations caused by the oversupply of nutrients, and unphysiological cell-cell and cell-material interactions, and allow for dynamic interactions between cells, stroma, and extracellular matrix. In addition, 3D cultures allow for the development of concentration gradients, including oxygen, metabolites, and growth factors, with chemical gradients playing an integral role in many cellular functions ranging from development to signaling in normal epithelia and cancer environments in vivo. Currently, the most common matrices used for 3D culture are biologically derived materials such as matrigel and collagen. However, in recent years, more defined, synthetic materials have become available as scaffolds for 3D culture with the advantage of forming well-defined, designed, tunable materials to control matrix charge, stiffness, porosity, nanostructure, degradability, and adhesion properties, in addition to other material and biological properties. One important area of synthetic materials currently available for 3D cell culture is short sequence, self-assembling peptide hydrogels. In addition to the review of recent work toward the control of material, structure, and mechanical properties, we will also discuss the biochemical functionalization of peptide hydrogels and how this functionalization, coupled with desired hydrogel material characteristics, affects tumor cell behavior in 3D culture.

No MeSH data available.


Related in: MedlinePlus