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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

MAX1 and MAX8 fibril formation. Reprinted with permission from Ref. (114). Copyright 2007 National Academy of Sciences.
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Figure 5: MAX1 and MAX8 fibril formation. Reprinted with permission from Ref. (114). Copyright 2007 National Academy of Sciences.

Mentions: MAX1 is an amphiphilic peptide with the sequence VKVKVKVK-VDPPT-KVEVKVKV (54) (Figure 5). Gelation is triggered by a combination of salt concentration, pH, and temperature (114). These factors lead to charge screening which causes the peptide to fold into a beta hairpin, the hairpins then associate into fibrils forming the network through physical bonds (115). MAX1 gelation takes approximately 30 min to complete, which results in a heterogeneous cell distribution because the cells are able to sink through the gel. In order to ensure a homogenous cell distribution MAX8 was created by substituting a glutamic acid for a lysine, speeding up the gelation time to 1 min (114). To form a cell–gel construct, cells in serum-free medium are added to peptide dissolved in Hepes buffer and the construct is allowed to gelate before serum-containing medium is added to the culture. Using such a construct, mesenchymal stem cells, DAOY, Panc-1, and MG63 cells have been successfully cultured encapsulated within the gel (116, 117) (and our unpublished observations). The cell–hydrogel constructs can be assessed by fluorescence microscopy and MTT assays have been successfully performed. The fibrils have a 3.2 nm × 2 nm cross section (115) and the stiffness is around 1000 Pa, which can be controlled by changing the weight percent of the peptide and the speed of gelation which controls the number of branch points (118). MAX1 and MAX8 are shear thinning material allowing for gel injection while protecting its cargo (119). Thus, MAX8 can be used to deliver cells for therapy via syringe injecting while at the same time protecting the cells from shear forces (117). Furthermore, these hydrogels can be used for sustained delivery of active compounds including drugs. Studies have shown that encapsulated compounds may be protected from inactivation resulting in a consistent drug release over increased periods of time (119, 120) and in vivo biocompatibility has been demonstrated (116) (and our unpublished observations). The result is a highly customizable physical gel that shear thins and reheals. Gelation is triggered by physiological conditions allowing for easy culture setup without requiring the addition of harmful chemicals or organic reagents. It is mechanically robust with control over the storage modulus and a range of 500–10,000 Pa, thereby providing a very versatile 3D culture scaffold.


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

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

MAX1 and MAX8 fibril formation. Reprinted with permission from Ref. (114). Copyright 2007 National Academy of Sciences.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: MAX1 and MAX8 fibril formation. Reprinted with permission from Ref. (114). Copyright 2007 National Academy of Sciences.
Mentions: MAX1 is an amphiphilic peptide with the sequence VKVKVKVK-VDPPT-KVEVKVKV (54) (Figure 5). Gelation is triggered by a combination of salt concentration, pH, and temperature (114). These factors lead to charge screening which causes the peptide to fold into a beta hairpin, the hairpins then associate into fibrils forming the network through physical bonds (115). MAX1 gelation takes approximately 30 min to complete, which results in a heterogeneous cell distribution because the cells are able to sink through the gel. In order to ensure a homogenous cell distribution MAX8 was created by substituting a glutamic acid for a lysine, speeding up the gelation time to 1 min (114). To form a cell–gel construct, cells in serum-free medium are added to peptide dissolved in Hepes buffer and the construct is allowed to gelate before serum-containing medium is added to the culture. Using such a construct, mesenchymal stem cells, DAOY, Panc-1, and MG63 cells have been successfully cultured encapsulated within the gel (116, 117) (and our unpublished observations). The cell–hydrogel constructs can be assessed by fluorescence microscopy and MTT assays have been successfully performed. The fibrils have a 3.2 nm × 2 nm cross section (115) and the stiffness is around 1000 Pa, which can be controlled by changing the weight percent of the peptide and the speed of gelation which controls the number of branch points (118). MAX1 and MAX8 are shear thinning material allowing for gel injection while protecting its cargo (119). Thus, MAX8 can be used to deliver cells for therapy via syringe injecting while at the same time protecting the cells from shear forces (117). Furthermore, these hydrogels can be used for sustained delivery of active compounds including drugs. Studies have shown that encapsulated compounds may be protected from inactivation resulting in a consistent drug release over increased periods of time (119, 120) and in vivo biocompatibility has been demonstrated (116) (and our unpublished observations). The result is a highly customizable physical gel that shear thins and reheals. Gelation is triggered by physiological conditions allowing for easy culture setup without requiring the addition of harmful chemicals or organic reagents. It is mechanically robust with control over the storage modulus and a range of 500–10,000 Pa, thereby providing a very versatile 3D 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