Protein Hydrogels as Tissue Engineering Scaffolds (original) (raw)
Related papers
Thermoreversible lysozyme hydrogels: properties and an insight into the gelation pathway
Soft Matter, 2008
The gelation behaviour of aqueous solutions of hen egg white lysozyme (HEWL) in the presence of 20 mM DTT in the concentration range 0.7 to 4.0 mM has been investigated using microDSC, FTIR, cryoTEM, SANS and oscillatory rheology. The macroscopic critical gelation concentration, C gel , was found to be $ 3.0 mM. The disruption of the disulfide bonds by the DTT and the destabilisation of the protein were found to be a prerequisite for the formation of b-sheet rich fibrils under the mild conditions used in this work. Using our methodology the hydrogels obtained have a pH of 7, hence are suitable for cell culture, and are also thermoreversible. The hydrogel melting temperature was found to increase with increasing concentration and a similar structure was observed across the concentration range investigated. Our results suggest these systems are composed of a well defined regular network where single b-sheet rich fibrils ($ 3 nm diameter) form initially, then two of these fibrils associate two-by-two to form junctions ($ 6 nm diameter) and then on cooling further aggregate to form larger bundles of fibres. The network mesh size was found to decrease with increasing concentration. Our results suggest that below C gel small unconnected gel-like aggregates exist that have a similar structure to the hydrogels obtained above C gel. Using our data we propose a model for the denaturation and gelation behaviour of our system. During the first heating an a-helix to b-sheet molecular transition for the protein conformation occurs resulting in b-sheet rich fibrils forming through the self-assembly of b-sheet rich denaturated proteins. At high temperature the solution contains b-sheet rich fibrils with dissolved protein. On cooling an increase in the amount of b-sheet was observed via FTIR suggesting that as the temperature is decreased more and more protein forms b-sheet rich fibrils. At the gelation temperature these fibrils associate two-by-two to form the network junctions resulting in the macroscopic gelation of the sample. Our results suggest the network junctions are formed via specific hydrophobic interactions. The hydrogels elastic modulus was found to scale as C 2.45 for C > C gel .
An intrinsically shielded hydrogel for the adsorptive recovery of lysozyme
Biotechnology and Applied Biochemistry, 2006
The present paper addresses the selective recovery of lysozyme from egg white using CM-dextran (carboxymethyldextran)-based hydrogels containing Cibacron Blue as an affinity ligand and co-immobilized BSA intended to act as a shielding agent to reduce non-specific adsorption. Initial studies using pure lysozyme were conducted that indicated that the adsorption capacity increased with ligand density and that adsorption was well described by a Langmuir-type isotherm. The inclusion of BSA as a putative shielding agent did not decrease the adsorption capacity for lysozyme in singleadsorbate experiments. To assess the effectiveness of the shielding strategy, subsequent experiments were conducted with both defined lysozyme/ovalbumin mixtures and hen's-egg white. From these studies, the optimal operating conditions for lysozyme recovery have been determined. These include: optimal initial eggwhite concentration [a 10 % (v/v) solution of native egg white in the chosen buffer], affinity-ligand density (1.86 mM) and ligand-to-shielding-agent ratio (4:1). The purity of lysozyme obtained from egg white was improved from 69 % with a non-shielded hydrogel to 94 % with an intrinsically shielded hydrogel. Finally, the possibility of using a protein, rather than dextran-backbone-based, hydrogel was investigated. It was found that BSA could take the place of CM-dextran as the gel backbone in a simplified synthesis, producing a gel which also proved effective for lysozyme recovery with a 30 % lysozyme in egg-white solution purified to approx. 92 % in a single adsorption-desorption cycle.
2021
Hydrogel scaffolds have attracted much interest in the last few years for applications in the field of bone and cartilage tissue engineering. These scaffolds serve as a convenient three-dimensional structure on which cells can grow while sensing the native environment. Natural polymer-based hydrogels are an interesting choice for such purposes, but they lack the required mechanical properties. In contrast, composite hydrogels formed by biopolymers and short peptide hydrogelators possess mechanical characteristics suitable for osteogenesis. Here, we describe how combining the short peptide hydrogelator, Pyrene-Lysine-Cysteine (PyKC), with other biopolymers, can produce materials that are suitable for tissue engineering purposes. The presence of PyKC considerably enhances the strength and water content of the composite hydrogels, and confers thixotropic behavior. The hyaluronic acid-PyKC composite hydrogels were shown to be biocompatible, with the ability to support osteogenesis, sinc...
Pharmaceutics, 2018
Hydrogels evolved as an outstanding carrier material for local and controlled drug delivery that tend to overcome the shortcomings of old conventional dosage forms for small drugs (NSAIDS) and large peptides and proteins. The aqueous swellable and crosslinked polymeric network structure of hydrogels is composed of various natural, synthetic and semisynthetic biodegradable polymers. Hydrogels have remarkable properties of functionality, reversibility, sterilizability, and biocompatibility. All these dynamic properties of hydrogels have increased the interest in their use as a carrier for peptides and proteins to be released slowly in a sustained manner. Peptide and proteins are remarkable therapeutic agents in today's world that allow the treatment of severe, chronic and life-threatening diseases, such as diabetes, rheumatoid arthritis, hepatitis. Despite few limitations, hydrogels provide fine tuning of proteins and peptides delivery with enormous impact in clinical medicine. Novels drug delivery systems composed of smart peptides and molecules have the ability to drive self-assembly and form hydrogels at physiological pH. These hydrogels are significantly important for biological and medical fields. The primary objective of this article is to review current issues concerned with the therapeutic peptides and proteins and impact of remarkable properties of hydrogels on these therapeutic agents. Different routes for pharmaceutical peptides and proteins and superiority over other drugs candidates are presented. Recent advances based on various approaches like self-assembly of peptides and small molecules to form novel hydrogels are also discussed. The article will also review the literature concerning the classification of hydrogels on a different basis, polymers used, "release mechanisms" their physical and chemical characteristics and diverse applications.
2011
The terms gels and hydrogels are used interchangeably by food and biomaterials scientists to describe polymeric cross-linked network structures. Gels are defined as a substantially dilute cross-linked system, and are categorised principally as weak or strong depending on their flow behaviour in steady-state (Ferry, 1980). Edible gels are used widely in the food industry and mainly refer to gelling polysaccharides (i.e. hydrocolloids) (Phillips & Williams, 2000). The term hydrogel describes three-dimensional network structures obtained from a class of synthetic and/or natural polymers which can absorb and retain significant amount of water (Rosiak & Yoshii, 1999). The hydrogel structure is created by the hydrophilic groups or domains present in a polymeric network upon the hydration in an aqueous environment. This chapter reviews the preparation methods of hydrogels from hydrophilic polymers of synthetic and natural origin with emphasis on water soluble natural biopolymers (hydrocolloids). Recent advances in radiation cross-linking methods for the preparation of hydrogel are particularly addressed. Additionally, methods to characterise these hydrogels and their proposed applications are also reviewed. 1.1 Mechanism of network formation Gelation refers to the linking of macromolecular chains together which initially leads to progressively larger branched yet soluble polymers depending on the structure and conformation of the starting material. The mixture of such polydisperse soluble branched polymer is called 'sol'. Continuation of the linking process results in increasing the size of the branched polymer with decreasing solubility. This 'infinite polymer' is called the 'gel' or 'network' and is permeated with finite branched polymers. The transition from a system with finite branched polymer to infinite molecules is called 'sol-gel transition' (or 'gelation') and the critical point where gel first appears is called the 'gel point' (Rubinstein & Colby, 2003). Different types of gelation mechanism are summarised in Figure 1. Gelation can take place either by physical linking (physical gelation) or by chemical linking (chemical gelation). Physical gels can be sub categorised as strong physical gels and weak gels. Strong physical gel has strong physical bonds between polymer chains and is effectively permanent
Protein-Based Hydrogels and Their Biomedical Applications
Molecules
Hydrogels made from proteins are attractive materials for diverse medical applications, as they are biocompatible, biodegradable, and amenable to chemical and biological modifications. Recent advances in protein engineering, synthetic biology, and material science have enabled the fine-tuning of protein sequences, hydrogel structures, and hydrogel mechanical properties, allowing for a broad range of biomedical applications using protein hydrogels. This article reviews recent progresses on protein hydrogels with special focus on those made of microbially produced proteins. We discuss different hydrogel formation strategies and their associated hydrogel properties. We also review various biomedical applications, categorized by the origin of protein sequences. Lastly, current challenges and future opportunities in engineering protein-based hydrogels are discussed. We hope this review will inspire new ideas in material innovation, leading to advanced protein hydrogels with desirable pro...
Journal of Applied Polymer Science
Hydrogels have attracted considerable attention due to numerous applications, in particular as contact lenses and carriers for sustained drug delivery. The aim of the present work is to characterize the interactions of copolymer hydrogels consisted of 2-hydroxyethylmethacrylate (HEMA) and 2hydroxyethylacrylate (HEA) with a small protein (lysozyme) and to assess the potential applications of these hydrogels as a drug delivery system for sustained release of protein-based therapeutics. Physicochemical properties of protein-loaded hydrogels, as well as lysozyme in vitro loading and release and the conformation of the protein released from hydrogels were studied. The effect of copolymer composition on the protein deposition on hydrogels and protein aggregation in the presence of hydrogels was also assessed. The results show that introduction of HEA into the copolymeric hydrogels enhances their suitability as a delivery system for proteins. Copolymerisation of HEMA and HEA allows controlling the physicochemical properties of hydrogels and the protein release rate.
Rational design and application of responsive α-helical peptide hydrogels
Nature Materials, 2009
Biocompatible hydrogels have a wide variety of potential applications in biotechnology and medicine, such as the controlled delivery and release of cells, cosmetics and drugs, and as supports for cell growth and tissue engineering 1 . Rational peptide design and engineering are emerging as promising new routes to such functional biomaterials 2-4 . Here, we present the first examples of rationally designed and fully characterized self-assembling hydrogels based on standard linear peptides with purely α-helical structures, which we call hydrogelating self-assembling fibres (hSAFs). These form spanning networks of α-helical fibrils that interact to give self-supporting physical hydrogels of >99% water content. The peptide sequences can be engineered to alter the underlying mechanism of gelation and, consequently, the hydrogel properties. Interestingly, for example, those with hydrogen-bonded networks of fibrils melt on heating, whereas those formed through hydrophobic fibril-fibril interactions strengthen when warmed. The hSAFs are dual-peptide systems that gel only on mixing, which gives tight control over assembly 5 . These properties raise possibilities for using the hSAFs as substrates in cell culture. We have tested this in comparison with the widely used Matrigel substrate, and demonstrate that, like Matrigel, hSAFs support both growth and differentiation of rat adrenal pheochromocytoma cells for sustained periods in culture.