Transglutaminase Cross-Linked Gelatin-Alginate-Antibacterial Hydrogel as the Drug Delivery-Coatings for Implant-Related Infections

A 3D-printable gelatin/alginate/ε-poly-l-lysine hydrogel scaffold to enable porcine muscle stem cells expansion and differentiation for cultured meat development

The mass proliferation of seed cells and imitation of meat structures remain challenging for cell-cultured meat production. With excellent biocompatibility, high water content and porosity, hydrogels are frequently-studied materials for anchorage-dependent cell scaffolds in biotechnology applications. Herein, a scaffold based on gelatin/alginate/ε-Poly-l-lysine (GAL) hydrogel is developed for skeletal muscle cells, which has a great prospect in cell-cultured meat production. In this work, the hydrogel GAL-4:1, composed of gelatin (5 %, w/v), alginate (5 %, w/v) and ε-Poly-l-lysine (molar ratio vs. alginate: 4:1) is selected as cell scaffold based on Young's modulus of 11.29 ± 1.94 kPa, satisfactory shear-thinning property and suitable porous organized structure. The commercially available C2C12 mouse skeletal myoblasts and porcine muscle stem cells (PMuSCs), are cultured in the 3D-printed scaffold. The cells show strong ability of attachment, proliferation and differentiation after induction, showing high biocompatibility. Furthermore, the cellular bioprinting is performed with GAL-4:1 hydrogel and freshly extracted PMuSCs. The extracted PMuSCs exhibit high viability and display early myogenesis (desmin) on the 3D scaffold, suggesting the great potential of GAL hydrogel as 3D cellular constructs scaffolds. Overall, we develop a novel GAL hydrogel as a 3D-printed bioactive platform for cultured meat research.

Research progress on biodegradable polymeric platforms for targeting antibiotics to the bone

The treatment of bone infections still involves systemic or local antibiotic therapy in high doses for prolonged periods. Current research focuses on the application of different drug delivery systems to the bone, aiming at a targeted local administration that will decrease the number of drugs used and their toxicity, compared to the systemic route. The gold standard in clinical practice is currently poly(methyl methacrylate) (PMMA) cement. The main drawback of PMMA, however, is that it is non-biodegradable, requiring a second follow-up surgery to remove the implant. Biodegradable delivery systems, on the other hand, are easily resorbable within the organism, and less invasive alternative with better patient compliance. Among biodegradable materials, natural and synthetic polymers are being studied as local drug delivery systems due to their excellent biocompatibility, sustained effect, and antibiotic release with high penetrability to infected bone and soft tissue. In this review, we focus on biodegradable polymeric platforms, such as micro- and nanoparticles, scaffolds, and hydrogels, as well as multi-delivery systems for targeting antibiotics to the bone. Additionally, we discuss the reported drug release profiles that provide important information about the systems' functionality.

Fabrication of triple-crosslinked gelatin/alginate hydrogels for controlled release applications

Hydrogels have been demonstrated as smart drug carriers to recognize the tumor microenvironment for cancer treatment, where the dynamic crosslinks in the hydrogel network contribute to the stimuli-responsive features but also result in poor stability and weak mechanical property of the hydrogels. Here, phenylboronic acid-grafted polyethyleneimine (PBA-PEI)-modified gelatin (PPG) was synthesized to crosslink alginate dialdehyde (ADA) through imine bonds and boronate ester bonds, and then calcium ions (Ca2+) were added to introduce the third calcium-carboxylate crosslinking in the network to form the triple-crosslinked PPG/ADA-Ca2+ hydrogels. Given the three types of dynamic bonds in the network, PPG/ADA-Ca2+ hydrogels possessed a self-healing manner, stimuli-responsiveness, and better mechanical properties compared to single- or double-crosslinked hydrogels. The controlled release capability of PPG/ADA-Ca2+ hydrogels was also demonstrated, showing the encapsulated molecules can be rapidly released from the hydrogel network in the presence of hydrogen peroxide while the release rate can be slowed down at acidic pH. Furthermore, PPG/ADA-Ca2+ hydrogels presented selected cytotoxicity and drug delivery to cancer cells due to the regulated degradation by the cellular microenvironment. Taken together, PPG/ADA-Ca2+ hydrogels have been demonstrated as promising biomaterials with multiple desirable properties and dynamic features to perform controlled molecule release for biomedical applications.

Concentration Selection of Biofriendly Enzyme-Modified Gelatin Hydrogels for Periodontal Bone Regeneration

Periodontitis is challenging to cure radically due to its complex periodontal structure and particular microenvironment of dysbiosis and inflammation. However, with the assistance of various materials, cell osteogenic differentiation could be improved, and the ability of hard tissue regeneration could be enhanced. This study aimed to explore the appropriate concentration ratio of biofriendly transglutaminase-modified gelatin hydrogels for promoting periodontal alveolar bone regeneration. Through a series of characterization and cell experiments, we found that all the hydrogels possessed multi-space network structures and demonstrated their biocompatibility. In vivo and in vitro osteogenic differentiation experiments also confirmed that the group 40-5 (transglutaminase-gelatin concentration ratio) possessed a favorable osteogenic potential. In summary, we conclude that such hydrogel with a 40-5 concentration is most conducive to promoting periodontal bone reconstruction, which might be a new route to deal with the dilemma of clinical periodontal treatment.

Progress in Surface Modification of Titanium Implants by Hydrogel Coatings

Although titanium and titanium alloys have become the preferred materials for various medical implants, surface modification technology still needs to be strengthened in order to adapt to the complex physiological environment of the human body. Compared with physical or chemical modification methods, biochemical modification, such as the introduction of functional hydrogel coating on implants, can fix biomolecules such as proteins, peptides, growth factors, polysaccharides, or nucleotides on the surface of the implants, so that they can directly participate in biological processes; regulate cell adhesion, proliferation, migration, and differentiation; and improve the biological activity on the surface of the implants. This review begins with a look at common substrate materials for hydrogel coatings on implant surfaces, including natural polymers such as collagen, gelatin, chitosan, and alginate, and synthetic materials such as polyvinyl alcohol, polyacrylamide, polyethylene glycol, and polyacrylic acid. Then, the common construction methods of hydrogel coating (electrochemical method, sol-gel method and layer-by-layer self-assembly method) are introduced. Finally, five aspects of the enhancement effect of hydrogel coating on the surface bioactivity of titanium and titanium alloy implants are described: osseointegration, angiogenesis, macrophage polarization, antibacterial effects, and drug delivery. In this paper, we also summarize the latest research progress and point out the future research direction. After searching, no previous relevant literature reporting this information was found.

Laccase-mediated formation of hydrogels based on silk-elastin-like protein polymers with ultra-high molecular weight

As artificial extracellular matrix-like materials, silk-elastin-like protein (SELP) hydrogels, with excellent mechanical properties, high tunability, favorable biocompatibility, and controlled degradability, have become an important candidate in biomedical materials. In this study, SELP is composed of silk-like (GAGAGS) and elastin-like (GXGVP) tandem repeats, in which X residues are set as tyrosine and lysine. Furthermore, SELP polymers are prepared via SpyTag/SpyCatcher. To explore a gentler and more efficient enzymatic crosslinking method, an innovative method was invented to apply laccase to catalyze the formation of SELP hydrogels. Gelation could be successfully achieved in 2-5 min . SELP hydrogels mediated by laccase had the characteristic of low swelling rate, which could maintain a relatively stable shape even when immersed in water, and hence had the potential to be further developed into injectable biomaterials. Additionally, SELP hydrogels cross-linked by laccase showed excellent biocompatibility verified by L929 and HEK 293 T cells with cell viability >93.8 %. SELP hydrogels also exhibit good properties in sustained drug release and cell encapsulation in vitro. This study demonstrates a novel method to construct SELP hydrogels with excellent biocompatibility and expands the possibility of SELP-based material applications in biomedical fields.

Inorganic/Biopolymers Hybrid Hydrogels Dual Cross-Linked for Bone Tissue Regeneration

In tissue engineering, the potential of re-growing new tissue has been considered, however, developments towards such clinical and commercial outcomes have been modest. One of the most important elements here is the selection of a biomaterial that serves as a "scaffold" for the regeneration process. Herein, we designed hydrogels composed of two biocompatible natural polymers, namely gelatin with photopolymerizable functionalities and a pectin derivative amenable to direct protein conjugation. Aiming to design biomimetic hydrogels for bone regeneration, this study proposes double-reinforcement by way of inorganic/biopolymer hybrid filling composed of Si-based compounds and cellulose nanofibers. To attain networks with high flexibility and elastic modulus, a double-crosslinking strategy was envisioned-photochemical and enzyme-mediated conjugation reactions. The dual cross-linked procedure will generate intra- and intermolecular interactions between the protein and polysaccharide and might be a resourceful strategy to develop innovative scaffolding materials.

Enzyme-Triggered Crosslinked Hybrid Hydrogels for Bone Tissue Engineering

The quest to develop state-of-the-art hydrogels for bone tissue engineering has accompanied substantial innovation and significant progression in the field of bioactive hydrogels. Still, there is scope for advancement in this cell-friendly and biocompatible scaffold system. The crosslinking approaches used for hydrogel synthesis plays a decisive role in guiding and regulating the mechanical stability, network framework, macroscopic architect, immunological behaviors, and cellular responses. Until recently, enzyme-based crosslinking strategies were considered as the pinnacle in designing efficient hybrid hydrogel systems. A variety of enzymes have been explored for manufacturing hydrogels while taking the advantage of the biocompatible nature, specificity, ability to produce nontoxic by products and high efficiency of enzymes. The current review focuses on the utility of different enzymes as crosslinking agents for hydrogel formation with their application in bone tissue engineering. The field of enzyme crosslinked hydrogel synthesis is rapidly maturing with a lot of opportunities to be explored in bone tissue engineering. Enzyme-based in situ and externally crosslinked hydrogels for bone regeneration is an attractive field, and with innovation in using engineered enzymes this field will continue to flourish with clinical orientation.

Recent Advances in Multifunctional Hydrogels for the Treatment of Osteomyelitis

Osteomyelitis (OM), a devastating disease caused by microbial infection of bones, remains a major challenge for orthopedic surgeons. Conventional approaches for prevention and treatment of OM are unsatisfactory. Various alternative strategies have been proposed, among which, hydrogel-based strategies have demonstrated potential due to their unique properties, including loadable, implantable, injectable, printable, degradable, and responsive to stimuli. Several protocols, including different hydrogel designs, selection of antimicrobial agent, co-administration of bone morphogenetic protein 2 (BMP 2), and nanoparticles, have been shown to improve the biological properties, including antimicrobial effects, osteo-induction, and controlled drug delivery. In this review, we describe the current and future directions for designing hydrogels and their applications to improve the biological response to OM in vivo.

Advances in Nanostructures for Antimicrobial Therapy

Microbial infections caused by a variety of drug-resistant microorganisms are more common, but there are fewer and fewer approved new antimicrobial chemotherapeutics for systemic administration capable of acting against these resistant infectious pathogens. Formulation innovations of existing drugs are gaining prominence, while the application of nanotechnologies is a useful alternative for improving/increasing the effect of existing antimicrobial drugs. Nanomaterials represent one of the possible strategies to address this unfortunate situation. This review aims to summarize the most current results of nanoformulations of antibiotics and antibacterial active nanomaterials. Nanoformulations of antimicrobial peptides, synergistic combinations of antimicrobial-active agents with nitric oxide donors or combinations of small organic molecules or polymers with metals, metal oxides or metalloids are discussed as well. The mechanisms of actions of selected nanoformulations, including systems with magnetic, photothermal or photodynamic effects, are briefly described.

Transglutaminase-Catalyzed Bottom-Up Synthesis of Polymer Hydrogel

Enzyme catalysis has attracted increasing attention for application in the synthesis of polymer hydrogel due to the eco-friendly process and the devisable catalytic reaction. Moreover, bottom-up approaches combining enzyme catalysts and molecular self-assembly have been explored for synthesizing hydrogel with complex architectures. An enzyme widely distributed in nature, transglutaminase (TGase) has been confirmed to catalyze the formation of isopeptide bonds between proteins, which can effectively improve the gelation of proteins. In this mini-review, TGase-catalyzed synthesis of polymer hydrogels, including fibrin hydrogels, polyethylene glycol hydrogels, soy protein hydrogels, collagen hydrogels, gelatin hydrogels and hyaluronan hydrogels, has been reviewed in detail. The catalytic process and gel formation mechanism by TGase have also been considered. Furthermore, future perspectives and challenges in the preparation of polymer hydrogels by TGase are also highlighted.

Bioactive Coatings on Titanium: A Review on Hydroxylation, Self-Assembled Monolayers (SAMs) and Surface Modification Strategies

Titanium (Ti) and its alloys have been demonstrated over the last decades to play an important role as inert materials in the field of orthopedic and dental implants. Nevertheless, with the widespread use of Ti, implant-associated rejection issues have arisen. To overcome these problems, antibacterial properties, fast and adequate osseointegration and long-term stability are essential features. Indeed, surface modification is currently presented as a versatile strategy for developing Ti coatings with all these challenging requirements and achieve a successful performance of the implant. Numerous approaches have been investigated to obtain stable and well-organized Ti coatings that promote the tailoring of surface chemical functionalization regardless of the geometry and shape of the implant. However, among all the approaches available in the literature to functionalize the Ti surface, a promising strategy is the combination of surface pre-activation treatments typically followed by the development of intermediate anchoring layers (self-assembled monolayers, SAMs) that serve as the supporting linkage of a final active layer. Therefore, this paper aims to review the latest approaches in the biomedical area to obtain bioactive coatings onto Ti surfaces with a special focus on (i) the most employed methods for Ti surface hydroxylation, (ii) SAMs-mediated active coatings development, and (iii) the latest advances in active agent immobilization and polymeric coatings for controlled release on Ti surfaces.

Recent Advances in Functional Polymer Materials for Energy, Water, and Biomedical Applications: A Review

Academic research regarding polymeric materials has been of great interest. Likewise, polymer industries are considered as the most familiar petrochemical industries. Despite the valuable and continuous advancements in various polymeric material technologies over the last century, many varieties and advances related to the field of polymer science and engineering still promise a great potential for exciting new applications. Research, development, and industrial support have been the key factors behind the great progress in the field of polymer applications. This work provides insight into the recent energy applications of polymers, including energy storage and production. The study of polymeric materials in the field of enhanced oil recovery and water treatment technologies will be presented and evaluated. In addition, in this review, we wish to emphasize the great importance of various functional polymers as effective adsorbents of organic pollutants from industrial wastewater. Furthermore, recent advances in biomedical applications are reviewed and discussed.

Modern Wound Dressings: Hydrogel Dressings

Chronic wounds do not progress through the wound healing process in a timely manner and are considered a burden for healthcare system; they are also the most common reason for decrease in patient quality of life. Traditional wound dressings e.g., bandages and gauzes, although highly absorbent and effective for dry to mild, exudating wounds, require regular application, which therefore can cause pain upon dressing change. In addition, they have poor adhesional properties and cannot provide enough drainage for the wound. In this regard, the normalization of the healing process in chronic wounds is an extremely urgent task of public health and requires the creation and implementation of affordable dressings for patients with chronic wounds. Modern wound dressings (WDs) are aimed to solve these issues. At the same time, hydrogels, unlike other types of modern WDs (foam, films, hydrocolloids), have positive degradation properties that makes them the perfect choice in applications where a targeted delivery of bioactive substances to the wound is required. This mini review is focused on different types of traditional and modern WDs with an emphasis on hydrogels. Advantages and disadvantages of traditional and modern WDs as well as their applicability to different chronic wounds are elucidated. Furthermore, an effectiveness comparison between hydrogel WDs and the some of the frequently used biotechnologies in the field of regenerative medicine (adipose-derived mesenchymal stem cells (ADMSCs), mesenchymal stem cells, conditioned media, platelet-rich plasma (PRP)) is provided.