Dual-crosslinked in-situ forming alginate/silk fibroin hydrogel with potential for bone tissue engineering

Osteoimmunomodulation by bone implant materials: harnessing physicochemical properties and chemical composition

Chronic inflammation at bone defect sites can impede regenerative processes, but local immune responses can be adjusted to promote healing. Regulating the osteoimmune microenvironment, particularly through macrophage polarization, has become a key focus in bone regeneration research. While bone implants are crucial for addressing significant bone defects, they are often recognized by the immune system as foreign, triggering inflammation that leads to bone resorption and implant issues like fibrous encapsulation and aseptic loosening. Developing osteoimmunomodulatory implants offers a promising approach to transforming destructive inflammation into healing processes, enhancing implant integration and bone regeneration. This review explores strategies based on tuning the physicochemical attributes and chemical composition of materials in engineering osteoimmunomodulatory and pro-regenerative bone implants.

Neem gum and its derivatives as potential polymeric scaffold for diverse applications: a review

Naturally occurring polymers, particularly polysaccharides, are gaining significant attention for their eco-friendly, non-toxic nature and abundant availability. Neem Gum (NEG), a natural exudate from the neem tree (Azadirachta indica), is secreted as a defense mechanism to protect against microbial invasion and physical damage. Unlike common polysaccharides, NEG exhibits a distinct composition rich in bioactive constituents, including heteropolysaccharides and secondary metabolites, contributing to its diverse functional and therapeutic potential. These unique characteristics make NEG a promising biopolymer for applications in pharmaceuticals, food, cosmetics, and environmental industries, where it serves as a binding, emulsifying, gelling, and stabilizing agent. Recent advancements have focused on developing NEG composites and derivatives with enhanced properties and broader applications. Structural modifications like grafting and carboxymethylation have improved its utility in drug delivery, wound healing, and biodegradable materials. Modified NEG derivatives exhibit superior antimicrobial, anti-inflammatory, and antioxidant effects, expanding their biomedical potential in tissue engineering and controlled drug release. NEG-based hydrogels and films show promise in eco-friendly packaging and self-healing biomaterials. This review compiles NEG's diverse applications, highlighting its role in sustainable technologies and emerging fields like self-healing materials and smart polymers. It addresses challenges in scaling production, regulatory compliance, and technical constraints.

Composite cryogel of gelatin/nanofibrillated cellulose/partially demineralized chitin with potential for bone tissue engineering

Fabrication of macroporous scaffolds with favorable mechanical and biological properties based on natural polysaccharides embedding inorganic components has emerged as a promising alternative for bone regeneration. We hypothesized that partially demineralized chitin containing natural calcium phosphate with suitable mechanical strength as the inorganic component is more favorable for this purpose than commonly used nano-hydroxyapatite (nHA). Therefore, a macroporous cryogel scaffold composed of gelatin (G), nanofibrillated cellulose (NFC), and partially demineralized chitin (PDCh), chemically crosslinked with oxidized dextran (ODex), was developed in this study. The scaffold exhibited suitable aqueous solvent absorption, with a controlled degradation and proper calcium phosphate concentration and a 50-500 μm pore size distribution that promoted cell growth and osteogenesis. Incorporating PDCh provided a high surface-to-volume ratio and significantly enhanced the scaffold's mechanical properties with a compressive strength of 315.4 kPa, suitable for cancellous bone regeneration. Moreover, the presence of natural calcium phosphate in PDCh led to superior biocompatibility and bone differentiation in human mesenchymal stem cells (hMSCs), as evidenced by an increase in calcium deposition, higher alkaline phosphatase (ALP) activity, and an increase in collagen-type 1 and osteocalcin gene expression compared to scaffold containing nHA. These results demonstrated the promising potential of gelatin/nanofibrillated cellulose/PDCh cryogel scaffolds for bone tissue engineering applications.

N-(3-trimethoxysilylpropyl)ethylenediamine-crosslinked sodium alginate hydrogel: applications in angiogenesis and wound healing across avian and murine models

Managing wounds remains a significant challenge in modern medicine. Biopolymer hydrogels provide a moist environment conducive to tissue healing. In this study, N-(3-trimethoxysilylpropyl)ethylenediamine (N-3-TMSPED) crosslinked sodium alginate hydrogels were synthesized via lyophilization, with varying concentrations of polyethylene glycol (PEG 600) to evaluate their role in angiogenesis and wound healing. Scanning electron microscopy confirmed porous structures essential for angiogenesis. The hydrogels showed maximum swelling at neutral and basic pH, and enhanced thermal stability with increasing PEG content. In vivo CAM assay results showed significantly increased blood vessels in PEG-containing hydrogels, with ANP2 exhibiting the highest vessel count (25.05 ± 0.0513) compared to control (13.02 ± 0.3600, p ≤ 0.05). PEG also ensured high embryo viability (94.6 %). Biochemical markers remained within normal physiological ranges, confirming hydrogel safety. All PEG-containing hydrogels displayed a significantly improved wound healing, affirming their therapeutic potential. Wound contraction analysis in mice showed ANP2 (loaded with XLC) achieved 72 % contraction by day 7 and 99.8 % by day 14, compared to untreated (57 %) and experimental controls (61 %) (p ≤ 0.05). Histology confirmed enhanced re-epithelialization and increased collagen deposition. These findings demonstrate that ANP hydrogels promote angiogenesis, accelerate wound healing, and exhibit excellent biocompatibility, highlighting their potential for tissue regeneration applications.

Alginate gels: Chemistry, gelation mechanisms, and therapeutic applications with a focus on GERD treatment

Alginate, a natural polysaccharide derived primarily from marine algae, has become popular in biomedical research due to its versatile gelation properties and biocompatibility. This review explores the chemistry, gelation mechanisms, and therapeutic applications of alginate gels, with a particular focus on their role in gastroesophageal reflux disease (GERD) management. Alginate's structure, comprised of guluronic and mannuronic acid blocks, allows for gel formation by ionic cross-linking with divalent cations like calcium ions, generating a stable "egg-box" structure. The effects of pH, temperature, and ion concentration on gelation are explored, as well as other gel forms such as in situ and heat-sensitive gels. Alginate is widely used in the medical and pharmaceutical areas to promote tissue engineering through cell encapsulation and scaffolding, as well as in drug delivery systems for controlled and targeted release. In GERD therapy, alginate produces a gel raft that inhibits acid reflux, providing an effective alternative to proton pump inhibitors. Alginate-based products have demonstrated clinical success, strengthening alginate's medicinal promise. The review also discusses alginate-related issues, such as source variability and stability, as well as innovative modifications to improve treatment effects. These improvements establish alginate as a potential material for customized medication and tailored delivery systems.

In Situ Forming Hydrogel Reinforced with Antibiotic-Loaded Mesoporous Silica Nanoparticles for the Treatment of Bacterial Keratitis

Bacterial keratitis (BK) is a serious ocular infection that can lead to vision impairment or blindness if not treated promptly. Herein, we report the development of a versatile composite hydrogel consisting of silk fibroin and sodium alginate, reinforced by antibiotic-loaded mesoporous silica nanoparticles (MSNs) for the treatment of BK. The drug delivery system is constructed by incorporating vancomycin- and ceftazidime-loaded MSNs into the hydrogel network. The synthesized MSNs were found to be spherical in shape with an average size of about 95 nm. The loading capacities of both drugs were approximately 45% and 43%, for vancomycin and ceftazidime respectively. Moreover, the formulation exhibited a sustained release profile, with 92% of vancomycin and 90% of ceftazidime released over a 24 h period. The cytocompatibility of the drug carrier was also confirmed by MTT assay results. In addition, we performed molecular dynamics (MD) simulations to better reflect the drug-drug and drug-MSN interactions. The results obtained from RMSD, number of contacts, and MSD analyses perfectly corroborated the experimental findings. In brief, the designed drug-MSN@hydrogel could mark an intriguing new chapter in the treatment of BK.

Bioactive silk fibroin hydrogels: Unraveling the potential for biomedical engineering

Silk fibroin (SF) has received special attention from the scientific community due to its noteworthy properties. Its unique chemical structure results in an uncommon combination of macroscopically useful properties, yielding a strong, fine and flexible material which, in addition, presents good biodegradability and better biocompatibility. Therefore, silk fibroin in various formats, appears as an ideal candidate for supporting biomedical applications. In this review, we will focus on the hydrogels obtained from silk fibroin or in combination with it, paying special attention to the synthesis procedures, characterization methodologies and biomedical applications. Tissue engineering and drug-delivery systems are, undoubtedly, the two main areas where silk fibroin hydrogels find their place.

Methods to achieve tissue-mimetic physicochemical properties in hydrogels for regenerative medicine and tissue engineering

Hydrogels are water-swollen polymeric matrices with properties that are remarkably similar in function to the extracellular matrix. For example, the polymer matrix provides structural support and adhesion sites for cells in much of the same way as the fibers of the extracellular matrix. In addition, depending on the polymer used, bioactive sites on the polymer may provide signals to initiate certain cell behavior. However, despite their potential as biomaterials for tissue engineering and regenerative medicine applications, fabricating hydrogels that truly mimic the physicochemical properties of the extracellular matrix to physiologically-relevant values is a challenge. Recent efforts in the field have sought to improve the physicochemical properties of hydrogels using advanced materials science and engineering methods. In this review, we highlight some of the most promising methods, including crosslinking strategies and manufacturing approaches such as 3D bioprinting and granular hydrogels. We also provide a brief perspective on the future outlook of this field and how these methods may lead to the clinical translation of hydrogel biomaterials for tissue engineering and regenerative medicine applications.

Dexamethasone Long-Term Controlled Release from Injectable Dual-Network Hydrogels with Porous Microspheres Immunomodulation Promotes Bone Regeneration

Long-lasting, controlled-release, and minimally invasive injectable platforms that provide a stable blood concentration to promote bone regeneration are less well developed. Using hexagonal mesoporous silica (HMS) loaded with dexamethasone (DEX) and poly(lactic-co-glycolic acid) (PLGA), we prepared porous DEX/HMS/PLGA microspheres (PDHP). In contrast to HMS/PLGA microspheres (HP), porous HMS/PLGA microspheres (PHP), DEX/PLGA microspheres (DP), and DEX/HMS/PLGA microspheres (DHP), PDHP showed notable immuno-coordinated osteogenic capabilities and were best at promoting bone mesenchymal stem cell proliferation and osteogenic differentiation. PDHP were combined with methacrylated silk (SilMA) and sodium alginate (SA) to form an injectable photocurable dual-network hydrogel platform that could continuously release the drug for more than 4 months. By adjusting the content of the microspheres in the hydrogel, a zero-order release hydrogel platform was obtained in vitro for 48 days. When the microsphere content was 1%, the hydrogel platform exhibited the best biocompatibility and osteogenic effects. The expression levels of the osteogenic gene alkaline phosphatases, BMP-2 and OPN were 10 to 15 times higher in the 1% group than in the 0% group, respectively. In addition, the 1% microsphere hydrogel strongly stimulated macrophage polarization to the M2 phenotype, establishing an immunological milieu that supports bone regrowth. The aforementioned outcomes were also observed in vivo. The most successful method for correcting cranial bone abnormalities in SD rats was to use a hydrogel called SilMA/SA containing 1% drug-loaded porous microspheres (PDHP/SS). The angiogenic and osteogenic effects of this treatment were also noticeably greater in the PDHP/SS group than in the control and blank groups. In addition, PDHP/SS polarized M2 macrophages and suppressed M1 macrophages in vivo, which reduced the local immune-inflammatory response, promoted angiogenesis, and cooperatively aided in situ bone healing. This work highlights the potential application of an advanced hydrogel platform for long-term, on-demand, controlled release for bone tissue engineering.

Triple-Hybrid BioScaffold Based on Silk Fibroin, Chitosan, and nano-Biphasic Calcium Phosphates: Preparation, Characterization of Physiochemical and Biopharmaceutical Properties

Bioscaffolds, which promote cell regeneration and restore tissues' functions, have emerged as significant need in clinic. The hybrid of several biomaterials in a bioscaffold renders clinically advanced and relevant properties for applications yet add challenges in cost efficiency, production, and clinical investigation. This study proposes a facile and sustainable method to formulate a triple-hybrid bioscaffold based on Vietnamese cocoon origin Silk Fibroin, Chitosan, and nano-Biphasic Calcium Phosphates (nano-BCP) that can be easily molded, has high porosity (55-80%), and swelling capacity that facilitates cell proliferation and nutrient diffusion. Notably, their mechanical properties, in particular compressive strength, can easily be tuned in a range from 50 - 200 kPa by changing the amount of nano-BCP addition, which is comparable to the successful precedents for productive cell regeneration. The latter parts investigate the biopharmaceutical properties of a representative bioscaffold, including drug loading and release studies with two kinds of active compounds, salmon calcitonin and methylprednisolone. Furthermore, the bioscaffold is highly biocompatible as the results of hemocompatibility and hemostasis tests, as well as ovo chick chorioallantoic membrane investigation. The findings of the study suggest the triple-hybrid scaffold as a promising platform for multi-functional drug delivery and bone defect repair.

Propelling Minimally Invasive Tissue Regeneration With Next-Era Injectable Pre-Formed Scaffolds

The growing aging population, with its associated chronic diseases, underscores the urgency for effective tissue regeneration strategies. Biomaterials play a pivotal role in the realm of tissue reconstruction and regeneration, with a distinct shift toward minimally invasive (MI) treatments. This transition, fueled by engineered biomaterials, steers away from invasive surgical procedures to embrace approaches offering reduced trauma, accelerated recovery, and cost-effectiveness. In the realm of MI tissue repair and cargo delivery, various techniques are explored. While in situ polymerization is prominent, it is not without its challenges. This narrative review explores diverse biomaterials, fabrication methods, and biofunctionalization for injectable pre-formed scaffolds, focusing on their unique advantages. The injectable pre-formed scaffolds, exhibiting compressibility, controlled injection, and maintained mechanical integrity, emerge as promising alternative solutions to in situ polymerization challenges. The conclusion of this review emphasizes the importance of interdisciplinary design facilitated by synergizing fields of materials science, advanced 3D biomanufacturing, mechanobiological studies, and innovative approaches for effective MI tissue regeneration.

Genipin-Cross-Linked Silk Fibroin/Alginate Dialdehyde Hydrogel with Tunable Gelation Kinetics, Degradability, and Mechanical Properties: A Potential Candidate for Tissue Regeneration

Genipin-cross-linked silk fibroin (SF) hydrogel is considered to be biocompatible and mechanically robust. However, its use remains a challenge for in situ forming applications due to its prolonged gelation process. In our attempt to facilitate the in situ fabrication of a genipin-mediated SF hydrogel, alginate dialdehyde (ADA) was utilized as a reinforcement template. Here, SF/ADA-based hydrogels with different compositions were synthesized covalently and ionically. Incorporating ADA into the SF hydrogel increased pore size (44.66-174.66 μm), porosity (61.59-80.40%), and the equilibrium swelling degree (7.60-30.17). Moreover, a wide range of storage modulus and compressive modulus were obtained by adjusting the proportions of SF and ADA networks within the hydrogel. The in vitro cell analysis using preosteoblast cells (MC3T3-E1) demonstrated the cytocompatibility of all hydrogels. Overall, the covalently and ionically cross-linked SF/ADA hydrogel represents a promising solution for in situ forming hydrogels for applications in tissue regeneration.

Pectin based hydrogel with covalent coupled doxorubicin and limonin loading for lung tumor therapy

Self-healing hydrogels have shown great application potential in drug delivery for anti-tumor therapy and tissue engineering. In this research, Doxorubicin (DOX) was coupled onto the oxidized pectin (pec-Ald) to prepare DOX grafted pec-AD and used to fabricate self-healing hydrogel for lung cancer therapy combined with novel herbal medicine extract limonin targeting lung cancer cells. The hydrogel was prepared with P(NIPAM195-co-AH54) cross-linking and the hydrazone bond cross-linked hydrogel showed good mechanical property and self-healing behavior. With pectin composition, the hydrogel was still biodegradable catalyzed by enzyme and in vivo. The hydrogel formed fast fit for injectable application and the hydrogel itself showed moderate lung cancer inhibition activity. With limonin loading, the hydrogel showed synergistic lung cancer therapy with the tumor growth greatly inhibited. The covalent coupling of DOX and loaded limonin in the hydrogel decreased in vivo toxicity and the hydrogel degraded on time. With biodegradability and improved lung cancer therapy efficiency, this DOX grafted self-healing hydrogel could find great potential application in cancer therapy in near future.

Structure-activity relationships of bioactive polysaccharides extracted from macroalgae towards biomedical application: A review

Macroalgae are valuable and structurally diverse sources of bioactive compounds among marine resources. The cell walls of macroalgae are rich in polysaccharides which exhibit a wide range of biological activities, such as anticoagulant, antioxidant, antiviral, anti-inflammatory, immunomodulatory, and antitumor activities. Macroalgae polysaccharides (MPs) have been recognized as one of the most promising candidates in the biomedical field. However, the structure-activity relationships of bioactive polysaccharides extracted from macroalgae are complex and influenced by various factors. A clear understanding of these relationships is indeed critical in developing effective biomedical applications with MPs. In line with these challenges and knowledge gaps, this paper summarized the structural characteristics of marine MPs from different sources and relevant functional and bioactive properties and particularly highlighted those essential effects of the structure-bioactivity relationships presented in biomedical applications. This review not only focused on elucidating a particular action mechanism of MPs, but also intended to identify a novel or potential application of these valued compounds in the biomedical field in terms of their structural characteristics. In the last, the challenges and prospects of MPs in structure-bioactivity elucidation were further discussed and predicted, where they were emphasized on exploring modern biotechnology approaches potentially applied to expand their promising biomedical applications.