Microgels with tunable affinity-controlled protein release via desolvation of self-assembled peptide nanofibers

Microgel delivery systems of functional substances for precision nutrition

Microgels delivery system have great potential in functional substances encapsulation, protection, release, precise delivery and nutritional intervention. Microgel is a three-dimensional network structure formed by physical or chemical crosslinking of biopolymers, whose characteristics include dispersion and swelling, stable structure, small volume and high specific surface area, and is a special kind of colloid. In this chapter, the common wall materials for preparing food grade microgels, and the main preparation principles, methods, advantages and disadvantages of microgels loaded with functional substances were firstly reviewed. Then the main characteristics of microgel as delivery system, such as deformability, high encapsulation, stimulus-responsive release and targeted delivery, and its potential benefits in intervening chronic diseases were summarized. Finally, the applications of microgel delivery system for functional substance in the field of precision nutrition were discussed. This chapter will help to design of next-generation advanced targeting microgel delivery system, and realize precision nutrition intervention of food functional substances on body health.

Mechanisms and influencing factors of peptide hydrogel formation and biomedicine applications of hydrogels

Self-assembled peptide-based hydrogels have shown great potential in bio-related applications due to their porous structure, strong mechanical stability, high biocompatibility, and easy functionalization. Herein, the structure and characteristics of hydrogels and the mechanism of action of several regular secondary structures during gelation are investigated. The factors influencing the formation of peptide hydrogels, especially the pH responsiveness and salt ion induction are analyzed and summarized. Finally, the biomedical applications of peptide hydrogels, such as bone tissue engineering, cell culture, antigen presentation, antibacterial materials, and drug delivery are reviewed.

Hybrid Self-Assembled Gel Beads for Tuneable pH-Controlled Rosuvastatin Delivery

This article describes the fabrication of new pH-responsive hybrid gel beads combining the polymer gelator calcium alginate with two different low-molecular-weight gelators (LMWGs) based on 1,3 : 2,4-dibenzylidene-d-sorbitol: pH-responsive DBS-COOH and thermally responsive DBS-CONHNH2 , thus clearly demonstrating that different classes of LMWG can be fabricated into gel beads by using this approach. We also demonstrate that self-assembled multicomponent gel beads can be formed by using different combinations of these gelators. The different gel bead formulations exhibit different responsiveness - the DBS-COOH network can disassemble within those beads in which it is present upon raising the pH. To exemplify preliminary data for a potential application for these hybrid gel beads, we explored aspects of the delivery of the lipid-lowering active pharmaceutical ingredient (API) rosuvastatin. The release profile of this statin from the hybrid gel beads is pH-dependent, with greater release at pH 7.4 than at pH 4.0 - primary control of this process results from the pKa of the API. The extent of pH-mediated API release is also significantly further modified according to gel bead composition. The DBS-COOH/alginate beads show rapid, highly effective drug release at pH 7.4, whereas the three-component DBS-COOH/DBS-CONHNH2 /alginate system shows controlled slow release of the API under the same conditions. These initial results indicate that such gel beads constitute a promising, versatile and easily tuned platform suitable for further development for controlled drug-delivery applications.

Self-assembled low-molecular-weight gelator injectable microgel beads for delivery of bioactive agents

We report the preparation of hybrid self-assembled microgel beads by combining the low molecular weight gelator (LMWG) DBS-CONHNH2 and the natural polysaccharide calcium alginate polymer gelator (PG). Microgel formulations based on LMWGs are extremely rare due to the fragility of the self-assembled networks and the difficulty of retaining any imposed shape. Our hybrid beads contain interpenetrated LMWG and PG networks, and are obtained by an emulsion method, allowing the preparation of spherical gel particles of controllable sizes with diameters in the mm or μm range. Microgels based on LMWG/alginate can be easily prepared with reproducible diameters <1 μm (ca. 800 nm). They are stable in water at room temperature for many months, and survive injection through a syringe. The rapid assembly of the LMWG on cooling plays an active role in helping control the diameter of the microgel beads. These LMWG microbeads retained the ability of the parent gel to deliver the bioactive molecule heparin, and in cell culture medium this enhanced the growth of human mesenchymal stem cells. Such microgels may therefore have future applications in tissue repair. This approach to fabricating LMWG microgels is a platform technology, which could potentially be applied to a variety of different functional LMWGs, and hence has wide-ranging potential.

Electrostatically Driven Guanidinium Interaction Domains that Control Hydrogel-Mediated Protein Delivery In Vivo

Protein biologics are an important class of drugs, but the necessity for frequent parenteral administration is a major limitation. Drug-delivery materials offer a potential solution, but protein-material adsorption can cause denaturation, which reduces their effectiveness. Here, we describe a new protein delivery platform that limits direct contact between globular protein domains and material matrix, yet from a single subcutaneous administration can be tuned for long-term drug release. The strategy utilizes complementary electrostatic interactions made between a suite of designed interaction domains (IDs), installed onto the terminus of a protein of interest, and a negatively charged self-assembled fibrillar hydrogel. These intermolecular interactions can be easily modulated by choice of ID to control material interaction and desorption energies, which allows regulation of protein release kinetics to fit desired release profiles. Molecular dynamics studies provided a molecular-level understanding of the mechanisms that govern release and identified optimal binding zones on the gel fibrils that facilitate strong ID-material interactions, which are crucial for sustained release of protein. This delivery platform can be easily loaded with cargo, is shear-thin syringe implantable, provides improved protein stability, is capable of a diverse range of in vitro release rates, and most importantly, can accomplish long-term control over in vivo protein delivery.

Protein Microgels from Amyloid Fibril Networks

Nanofibrillar forms of amyloidogenic proteins were initially discovered in the context of protein misfolding and disease but have more recently been found at the origin of key biological functionality in many naturally occurring functional materials, such as adhesives and biofilm coatings. Their physiological roles in nature reflect their great strength and stability, which has led to the exploration of their use as the basis of artificial protein-based functional materials. Particularly for biomedical applications, they represent attractive building blocks for the development of, for instance, drug carrier agents due to their inherent biocompatibility and biodegradability. Furthermore, the propensity of proteins to self-assemble into amyloid fibrils can be exploited under microconfinement, afforded by droplet microfluidic techniques. This approach allows the generation of multi-scale functional microgels that can host biological additives and can be designed to incorporate additional functionality, such as to aid targeted drug delivery.

Using Self-Assembling Peptides to Integrate Biomolecules into Functional Supramolecular Biomaterials

Throughout nature, self-assembly gives rise to functional supramolecular biomaterials that can perform complex tasks with extraordinary efficiency and specificity. Inspired by these examples, self-assembly is increasingly used to fabricate synthetic supramolecular biomaterials for diverse applications in biomedicine and biotechnology. Peptides are particularly attractive as building blocks for these materials because they are based on naturally derived amino acids that are biocompatible and biodegradable; they can be synthesized using scalable and cost-effective methods, and their sequence can be tailored to encode formation of diverse architectures. To endow synthetic supramolecular biomaterials with functional capabilities, it is now commonplace to conjugate self-assembling building blocks to molecules having a desired functional property, such as selective recognition of a cell surface receptor or soluble protein, antigenicity, or enzymatic activity. This review surveys recent advances in using self-assembling peptides as handles to incorporate biologically active molecules into supramolecular biomaterials. Particular emphasis is placed on examples of functional nanofibers, nanovesicles, and other nano-scale structures that are fabricated by linking self-assembling peptides to proteins and carbohydrates. Collectively, this review highlights the enormous potential of these approaches to create supramolecular biomaterials with sophisticated functional capabilities that can be finely tuned to meet the needs of downstream applications.

Functional Microgels: Recent Advances in Their Biomedical Applications

Here, a spotlight is shown on aqueous microgel particles which exhibit a great potential for various biomedical applications such as drug delivery, cell imaging, and tissue engineering. Herein, different synthetic methods to develop microgels with desirable functionality and properties along with degradable strategies to ensure their renal clearance are briefly presented. A special focus is given on the ability of microgels to respond to various stimuli such as temperature, pH, redox potential, magnetic field, light, etc., which helps not only to adjust their physical and chemical properties, and degradability on demand, but also the release of encapsulated bioactive molecules and thus making them suitable for drug delivery. Furthermore, recent developments in using the functional microgels for cell imaging and tissue regeneration are reviewed. The results reviewed here encourage the development of a new class of microgels which are able to intelligently perform in a complex biological environment. Finally, various challenges and possibilities are discussed in order to achieve their successful clinical use in future.

Stimuli-Responsive Microgels and Microgel-Based Systems: Advances in the Exploitation of Microgel Colloidal Properties and Their Interfacial Activity

In this paper, recent developments in the chemical design of functional microgels are summarized. A wide range of available synthetic methods allows the incorporation of various reactive groups, charges, or biological markers inside the microgel network, thus controlling the deformation and swelling degree of the resulting smart microgels. These microgels can respond to various stimuli, such as temperature, pH, light, electric field, etc. and can show unique deformation behavior at the interface. Due to their switchability and interfacial properties, these smart microgels are being extensively explored for various applications, such as antifouling coatings, cell encapsulation, catalysis, controlled drug delivery, and tissue engineering.

Tailor-Making Fluorescent Hyaluronic Acid Microgels via Combining Microfluidics and Photoclick Chemistry for Sustained and Localized Delivery of Herceptin in Tumors

Antibody therapeutics, though representing a most used biomedicine, suffers from poor in vivo stability, rapid degradation, and frequent injections. Here, we report that fluorescent hyaluronic acid microgels (HMGs) tailor-made by combining microfluidics and "tetrazole-alkene" photoclick chemistry enable sustained and localized delivery of Herceptin in ovarian tumors. HMGs were obtained with a defined size (25-50 μm), narrow size distribution, high stability, and strong green fluorescence. Notably, HMGs exhibited a remarkably high loading of proteins such as Herceptin and IgG with a loading efficiency exceeding 90% at a theoretical protein-loading content of 30 wt %. In vitro protein release experiments revealed a sustained and hyaluronidase (HAase)-dependent release of Herceptin from HMGs, in which 80.6% of Herceptin was released at 1 U/mL HAase in 10 days. The released Herceptin maintained its secondary structure and antitumor activity. In vivo imaging results demonstrated obviously better tumoral retention for Cy5-labeled Herceptin-loaded HMGs following subcutaneous (sc) injection than for the free-protein counterpart. Interestingly, sc injection of the Herceptin-loaded HMGs into SKOV-3 human ovarian tumor-bearing nude mice at a dose of 30 mg Herceptin equiv/kg induced nearly complete tumor suppression, which was significantly more effective than the sc or systemic injection of free Herceptin. These tailor-made fluorescent HMGs appeared as a robust injectable platform for sustained and localized delivery of therapeutic proteins.

Release of small bioactive molecules from physical gels

Pharmaceutical drugs with low water solubility have always received great attention within the scientific community. The reduced bioavailability and the need of frequent administrations have motivated the investigation of new drug delivery systems. Within this context, drug carriers that release their payload in a sustained way and hence reduce the administration rate are highly demanded. One interesting strategy to meet these requirements is the entrapment of the drugs into gels. So far, the most investigated materials for such drug-loaded gels are derived from polymers and based on covalent linkages. However, over the last decade the use of physical (or supramolecular) gels derived from low molecular weight compounds has experienced strong growth in this field, mainly due to important properties such as injectability, stimuli responsiveness and ease of synthesis. This review summarizes the use of supramolecular gels for the encapsulation and controlled release of small therapeutic molecules.

Tuning carbohydrate density enhances protein binding and inhibition by glycosylated β-sheet peptide nanofibers

The efficacy of glycosylated β-sheet peptide nanofibers for inhibiting carbohydrate-binding proteins can be increased by tuning carbohydrate density to maximize protein binding affinity.

Engineering galectin-glycan interactions for immunotherapy and immunomodulation

Galectins, a 15-member family of soluble carbohydrate-binding proteins, are receiving increasing interest as therapeutic targets for immunotherapy and immunomodulation due to their role as extracellular signals that regulate innate and adaptive immune cell phenotype and function. However, different galectins can have redundant, synergistic, or antagonistic signaling activity in normal immunological responses, such as resolution of inflammation and induction of antigen-specific tolerance. In addition, certain galectins can be hijacked to promote progression of immunopathologies, such as tumor immune privilege, metastasis, and viral infection, while others can inhibit these processes. Thus, eliciting a desired immunological outcome will likely necessitate therapeutics that can precisely enhance or inhibit particular galectin-glycan interactions. Multivalency is an important determinant of the affinity and specificity of natural galectin-glycan interactions, and is emerging as a key design element for therapeutics that can effectively manipulate galectin bioactivity. This minireview surveys current molecular and biomaterial engineering approaches to create therapeutics that can stabilize galectin multivalency or recapitulate natural glycan multivalency (i.e. "the glycocluster effect"). In particular, we highlight examples of using natural and engineered multivalent galectins for immunosuppression and immune tolerance, with a particular emphasis on treating autoimmune diseases or avoiding transplant rejection. In addition, we present examples of multivalent inhibitors of galectin-glycan interactions to maintain or restore T-cell function, with a particular emphasis on promoting antitumor immunity. Finally, we discuss emerging opportunities to further engineer galectin-glycan interactions for immunotherapy and immunomodulation.

Synthesis and properties of poly(DEX-GMA/AAc) microgel particle as a hemostatic agent

Poly(DEX-GMA/AAc) microgel particles were designed for the staunching of bleeding through absorption of water in blood and forming a gelled film as a barrier.

A phenomenological order approach to the volume phase transition in microgel particles

A phenomenological insight into the volume transition of microgel particles via nematic-like ordering behavior through solvation processes of a polymer matrix.