Genetically Engineered Elastin-based Biomaterials for Biomedical Applications

A Versatile Elastin-Like Carrier for Bioactive Antimicrobial Peptide Production and Delivery

Elastin-like polypeptides are biotechnological protein and peptide carriers that offer a vast scope of applicability. This work aims to build a model for the expression of antimicrobial peptides (AMPs) by genetically engineering the Human Elastin-like Polypeptide platform developed in the lab. The well-characterized AMP indolicidin is selected as an example of an antimicrobial domain for the recombinant fusion at the C-terminus of the carrier. The fusion construct has been designed to allow the release of the antimicrobial domain. The expression product has been purified and its physicochemical and antimicrobial properties has been characterized. Taking advantage of the self-assembling and matrix-forming properties of the recombinant biopolymer, the materials that are obtained have been evaluated for antimicrobial activity toward bacterial-strain models. This approach represents a cost-effective strategy for the production of smart components and materials endowed with antimicrobial capacity triggered by external stimuli.

Trends in biopolymer science applied to cosmetics

The term biopolymer refers to materials obtained by chemically modifying natural biological substances or producing them through biotechnological processes. They are biodegradable, biocompatible and non-toxic. Due to these advantages, biopolymers have wide applications in conventional cosmetics and new trends and have emerged as essential ingredients that function as rheological modifiers, emulsifiers, film-formers, moisturizers, hydrators, antimicrobials and, more recently, materials with metabolic activity on skin. Developing approaches that exploit these features is a challenge for formulating skin, hair and oral care products and dermatological formulations. This article presents an overview of the use of the principal biopolymers used in cosmetic formulations and describes their sources, recently derived structures, novel applications and safety aspects of the use of these molecules.

Silk-Elastin-like Polymers for Acute Intraparenchymal Treatment of the Traumatically Injured Spinal Cord: A First Systematic Experimental Approach

Despite the promising potential of hydrogel-based therapeutic approaches for spinal cord injury (SCI), the need for new biomaterials to design effective strategies for SCI treatment and the outstanding properties of silk-elastin-like polymers (SELP), the potential use of SELPs in SCI is currently unknown. In this context, we assessed the effects elicited by the in vivo acute intraparenchymal injection of an SELP named (EIS)₂-RGD6 in a clinically relevant model of SCI. After optimization of the injection system, the distribution, structure, biodegradability, and cell infiltration capacity of (EIS)₂-RGD6 were assessed. Finally, the effects exerted by the (EIS)₂-RGD6 injection-in terms of motor function, myelin preservation, astroglial and microglia/macrophage reactivity, and fibrosis-were evaluated. We found that (EIS)₂-RGD6 can be acutely injected in the lesioned spinal cord without inducing further damage, showing a widespread distribution covering all lesioned areas with a single injection and facilitating the formation of a slow-degrading porous scaffold at the lesion site that allows for the infiltration and/or proliferation of endogenous cells with no signs of collapse and without inducing further microglial and astroglial reactivity, as well as even reducing SCI-associated fibrosis. Altogether, these observations suggest that (EIS)₂-RGD6-and, by extension, SELPs-could be promising polymers for the design of therapeutic strategies for SCI treatment.

Protein-based nanomaterials: a new tool for targeted drug delivery

Protein nanomaterials are well-defined, hollow protein nanoparticles comprised of virus capsids, virus-like particles, ferritin, heat shock proteins, chaperonins and many more. Protein-based nanomaterials are formed by the self-assembly of protein subunits and have numerous desired properties as drug-delivery vehicles, including being optimally sized for endocytosis, nontoxic, biocompatible, biodegradable and functionalized at three separate interfaces (external, internal and intersubunit). As a result, protein nanomaterials have been intensively investigated as functional entities in bionanotechnology, including drug delivery, nanoreactors and templates for organic and inorganic nanomaterials. Several variables influence efficient administration, particularly active targeting, cellular uptake, the kinetics of the release and systemic elimination. This review examines the wide range of medicines, loading/release processes, targeted therapies and treatment effectiveness.

Improving the cell-membrane-penetrating activity of globins by introducing positive charges on protein surface: A case study of sperm whale myoglobin

Globins are heme proteins such as hemoglobin (Hb), myoglobin (Mb) and neuroglobin (Ngb), playing important roles in biological system. In addition to normal functions, zebrafish Ngb was able to penetrate cell membranes, whereas less was known for other globin members. In this study, to improve the cell-membrane-penetrating activity of globins, we used sperm whale Mb as a model protein and constructed a quadruple mutant of G5K/Q8K/A19K/V21K Mb (termed 4K Mb), by introduction of four positive charges on the protein surface, which was designed according to the amino acid alignment with that of zebrafish Ngb. Spectroscopic and crystallographic studies showed that the four positively charged Lys residues did not affect the protein structure. Cell-membrane-penetrating essay further showed that 4K Mb exhibited enhanced activity compared to that of native Mb. This study provides valuable information for the effect of distribution of charged residues on the protein structure and the cell-membrane-penetrating activity of globins. Therefore, it will guide the design of protein-based biomaterials for biological applications.

Smart Nanoparticles as Advanced Anti-Akt Kinase Delivery Systems for Pancreatic Cancer Therapy

Pancreatic cancer is one of the deadliest cancers partly due to late diagnosis, poor drug delivery to the target site, and acquired resistance to therapy. Therefore, more effective therapies are urgently needed to improve the outcome of patients. In this work, we have tested self-assembling genetically engineered polymeric nanoparticles formed by elastin-like recombinamers (ELRs), carrying a small peptide inhibitor of the protein kinase Akt, in both PANC-1 and patient-derived pancreatic cancer cells (PDX models). Nanoparticle cell uptake was measured by flow cytometry, and subcellular localization was determined by confocal microscopy, which showed a lysosomal localization of these nanoparticles. Furthermore, metabolic activity and cell viability were significantly reduced after incubation with nanoparticles carrying the Akt inhibitor in a time- and dose-dependent fashion. Self-assembling 73 ± 3.2 nm size nanoparticles inhibited phosphorylation and consequent activation of Akt protein, blocked the NF-κB signaling pathway, and triggered caspase 3-mediated apoptosis. Furthermore, in vivo assays showed that ELR-based nanoparticles were suitable devices for drug delivery purposes with long circulating time and minimum toxicity. Hence, the use of these smart nanoparticles could lead to the development of more effective treatment options for pancreatic cancer based on the inhibition of Akt.

Structure of Elastin

As the extracellular matrix protein, elastin is a crucial component of connective tissue in life. It is responsible for the structural integrity and function of tissues undergoing reversible extensibility or deformability, even though it may make up only a small percentage of a tissue. The structure stability, elastic resilience, bioactivity, and ability of self-assembly make elastin a highly desirable candidate for the fabrication of biomaterials. Elastin's properties mainly depend on their special structure. As elastin can be obtained by the assembly and cross-linking of its soluble precursor, tropoelastin. This chapter centers on introducing the structure of those two materials.

Recombination and Purification of Elastin-Like Polypeptides

Elastin, as an extracellular matrix protein, has inherent advantages for biomedical applications. For example, it is highly extensible and biocompatible, biodegradable, and has no immunogenicity. However, directly extracting elastin from biological tissues remains challenging because they usually coexist with other proteins such as collagen. Therefore, an effective strategy to produce elastin is to transfer the elastin's target gene into other expression hosts and synthesize the resultant polypeptides using chemical biology methods. The polypeptides and proteins produced using these methods are usually referred to as elastin-like peptides (ELPs), which have received intensive interests in drug delivery and release, tissue engineering, implanted devices, and so on. Therefore, this chapter introduces the detailed protocol for the preparation of ELPs using genetic recombination, including DNA recombination, expression, and purification. The methods presented here are expected to provide methodological guidance for preparation and application of ELP materials.

Designed protein- and peptide-based hydrogels for biomedical sciences

Proteins are fundamentally the most important macromolecules for biochemical, mechanical, and structural functions in living organisms. Therefore, they provide us with diverse structural building blocks for constructing various types of biomaterials, including an important class of such materials, hydrogels. Since natural peptides and proteins are biocompatible and biodegradable, they have features advantageous for their use as the building blocks of hydrogels for biomedical applications. They display constitutional and mechanical similarities with the native extracellular matrix (ECM), and can be easily bio-functionalized via genetic and chemical engineering with features such as bio-recognition, specific stimulus-reactivity, and controlled degradation. This review aims to give an overview of hydrogels made up of recombinant proteins or synthetic peptides as the structural elements building the polymer network. A wide variety of hydrogels composed of protein or peptide building blocks with different origins and compositions - including β-hairpin peptides, α-helical coiled coil peptides, elastin-like peptides, silk fibroin, and resilin - have been designed to date. In this review, the structures and characteristics of these natural proteins and peptides, with each of their gelation mechanisms, and the physical, chemical, and mechanical properties as well as biocompatibility of the resulting hydrogels are described. In addition, this review discusses the potential of using protein- or peptide-based hydrogels in the field of biomedical sciences, especially tissue engineering.

Engineered Matrices Enable the Culture of Human Patient-Derived Intestinal Organoids

Human intestinal organoids from primary human tissues have the potential to revolutionize personalized medicine and preclinical gastrointestinal disease models. A tunable, fully defined, designer matrix, termed hyaluronan elastin-like protein (HELP) is reported, which enables the formation, differentiation, and passaging of adult primary tissue-derived, epithelial-only intestinal organoids. HELP enables the encapsulation of dissociated patient-derived cells, which then undergo proliferation and formation of enteroids, spherical structures with polarized internal lumens. After 12 rounds of passaging, enteroid growth in HELP materials is found to be statistically similar to that in animal-derived matrices. HELP materials also support the differentiation of human enteroids into mature intestinal cell subtypes. HELP matrices allow stiffness, stress relaxation rate, and integrin-ligand concentration to be independently and quantitatively specified, enabling fundamental studies of organoid-matrix interactions and potential patient-specific optimization. Organoid formation in HELP materials is most robust in gels with stiffer moduli (G' ≈ 1 kPa), slower stress relaxation rate (t1/2 ≈ 18 h), and higher integrin ligand concentration (0.5 × 10-3-1 × 10-3 m RGD peptide). This material provides a promising in vitro model for further understanding intestinal development and disease in humans and a reproducible, biodegradable, minimal matrix with no animal-derived products or synthetic polyethylene glycol for potential clinical translation.

Functional characterization of an enzymatically degradable multi-bioactive elastin-like recombinamer

One of the main goals in both tissue engineering and regenerative medicine is to design innovative synthetic scaffolds that can simulate and control the communication pathways between cells and the extracellular matrix (ECM). In this context, we describe herein the characterization of protein polymer, a recombinant elastin-like recombinamer (ELR) designed for developing tissue-engineered devices for use in vascular regeneration. This ELR is composed of an elastin-like backbone that contains a fibronectin domain, which provides specific, endothelial cell adhesion, and a protease target domain directed towards specific proteases involved in ECM remodeling. We also compare the specific response of endothelial and fibroblast cells to ELR scaffolds and show that cell adhesion and spreading on this ELR is significantly higher for endothelial cells than for fibroblasts. The reactivity of this polymer and its hydrogels to specific enzymatic degradation is demonstrated in vitro. As with natural elastin, enzymatic hydrolysis of the ELR produces elastin-derived peptides, or "matrikines", which, in turn, are potentially able to regulate important cell activities.

Development and Characterization of Calmodulin-Based Copolymeric Hydrogels

Recently, there has been growing interest in harnessing genetically engineered polymers to develop responsive biomaterials, such as hydrogels. Unlike their synthetic counterparts, genetically engineered polymers are produced without the use of toxic reagents and can easily be programmed to incorporate desirable hydrogel properties, including bioactivity, biodegradability, and monodispersity. Herein, we report the development of a copolymeric hydrogel that is based on the calcium-dependent protein, calmodulin (CaM). For our system, CaM and M13, a CaM-binding peptide, were incorporated into genetically engineered polymers with intervening linkers containing cleavable sequences. Spectroscopic and multiple-particle tracking (MPT) studies demonstrate that these polymers self-assemble through calcium-stabilized, noncovalent crosslinking to form a soft viscoelastic material. MPT further revealed that gelation is concentration-dependent. Collagenase digests show that the protein polymers are selectively degraded through specific cleavage. The modularity and stimuli-responsiveness of this system suggest its potential as a flexible scaffold for biomedical applications.

A DNA Vaccine Delivery Platform Based on Elastin-Like Recombinamer Nanosystems for Rift Valley Fever Virus

This work analyzes the immunogenicity of six genetically engineered constructs based on elastin-like recombinamers (ELRs) fused to the Gn glycoprotein from Rift Valley fever virus (RVFV). Upon transfection, all constructs showed no effect on cell viability. While fusion constructs including ELR blocks containing hydrophobic amino acids (alanine or isoleucine) did not increase the expression of viral Gn in eukaryotic cells, glutamic acid- or valine-rich fusion proteins showed enhanced expression levels compared with the constructs encoding the viral antigen alone. However, in vivo DNA plasmid immunization assays determined that the more hydrophobic constructs reduced viremia levels after RVFV challenge to a higher extent than glutamic- or valine-rich encoding plasmids and were better inducers of cellular immunity as judged by in vitro restimulation experiments. Although the Gn-ELR fusion constructs did not surpass the protective efficacy of a plasmid vaccine expressing nonfused Gn, our results warrant further experiments directed to take advantage of the immunomodulatory potential of ELR biomaterials for improving vaccines against infectious diseases.