Recent advances in PLGA-based biomaterials for bone tissue regeneration

Degradable poly-lactic-co-glycolic acid and non-degradable polymer implants result in similar fracture healing at early timepoints

BACKGROUND

Although rigid interfragmentary fixation is required for fracture repair, overly stiff implants are known to cause stress shielding which ultimately inhibits healing. While gradual dynamization of the fracture site both accelerates and improves osteogenesis, this approach requires external fixators or secondary surgeries. This study leverages biodegradable implants as mechanisms of gradual, passive dynamization during fracture healing.

METHODS

Using a rat femoral osteotomy model, additively manufactured poly-lactic-co-glycolic acid implants were compared to geometrically matched non-degradable biocompatible resin devices. Bone healing was assessed at 3 and 6 weeks via micro-computed tomography, histology, and mechanical testing. Implant degradation kinetics were assessed through testing of plates that were used in the rat model and with an unloaded in vitro degradation model.

FINDINGS

Quantitative bone measures made with micro-computed tomography, histology, and mechanical testing of the healing femora revealed no differences between degradable and non-degradable implants at 3 or 6 weeks. Degradable implants caused significant increases in bone volume to total volume mean density (p < 0.0001) and callus to cortical volume (p < 0.05) ratios between 3 and 6 weeks. Poly-lactic-co-glycolic acid devices were significantly stiffer than resin at week 0, but the two groups were equivalent by week 6 due to in vivo degradation. In vivo ambulatory loading caused significant losses of degradable implant stiffness at both 3 (p < 0.05) and 6 (p < 0.01) weeks, but this was not observed in the unloaded in vitro model.

INTERPRETATION

The results from this early timepoint study demonstrate the feasibility of passive, internal fracture dynamization driven by implant material mechanics.

Insulin for oral bone tissue engineering: a review on innovations in targeted insulin-loaded nanocarrier scaffold

The occurrence of oral bone tissue degeneration and bone defects by osteoporosis, tooth extraction, obesity, trauma, and periodontitis are major challenges for clinicians. Traditional bone regeneration methods often come with limitations such as donor site morbidity, limitation of special shape, inflammation, and resorption of the implanted bone. The treatment oriented with biomimetic bone materials has achieved significant attention recently. In the oral bone tissue engineering arena, insulin has gained considerable attention among all the known biomaterials for osteogenesis and angiogenesis. It also exhibits osteogenic and angiogenic properties by interacting with insulin receptors on osteoblasts. Insulin influences bone remodelling both directly and indirectly. It acts directly through the PI3K/Akt and MAPK signalling pathways and indirectly by modulating the RANK/RANKL/OPG pathway, which helps reduce bone resorption. The current review reports the role of insulin in bone remodelling and bone tissue regeneration in the oral cavity in the form of scaffolds and nanomaterials. Different insulin delivery systems, utilising nanomaterials and scaffolds functionalised with polymeric biomaterials have been explored for oral bone tissue regeneration. The review put forward a theoretical basis for future research in insulin delivery in the form of scaffolds and composite materials for oral bone tissue regeneration.

Enhanced osteogenic and angiogenic capabilities of adipose-derived stem cells in fish collagen scaffolds for treatment of femoral head osteonecrosis

Osteonecrosis of the femoral head (ONFH) is a debilitating condition that often leads to femoral head collapse due to insufficient blood supply and impaired bone regeneration. However, effective treatment options for this condition are limited. This study explored a novel fish collagen (FC) scaffold combined with adipose-derived stem cells (ADSCs) to enhance osteogenesis and angiogenesis in ONFH. ADSCs were isolated and cultured on FC scaffolds to evaluate their biocompatibility and differentiation capacity. Osteogenic and angiogenic differentiation potentials were assessed in vitro, and the FC/ADSC combination was further evaluated in vivo using a rat model of ONFH. The molecular mechanisms were investigated via gene expression profiling and Hippo signaling pathway analysis. The FC scaffolds promoted ADSCs adhesion, proliferation, and migration without cytotoxicity. In vitro, FC/ADSCs significantly enhanced mineralization and capillary-like structure formation compared to the controls. FC/ADSCs improved bone regeneration and neovascularization in the femoral head in vivo, as confirmed by histological and immunohistochemical analyses. Mechanistically, the Hippo pathway is activated, increasing HIF-1α expression, which enhances osteogenic and angiogenic differentiation. FC scaffolds combined with ADSCs provide a promising therapeutic strategy for ONFH by facilitating bone regeneration and vascularization through the p-YAP/HIF-1α/VEGF axis. This scaffold-cell approach represents a potential advancement in ONFH treatment.

Genetic and bioactive functionalization of bioinks for 3D bioprinting

3D bioprinting is revolutionizing tissue engineering and regenerative medicine by enabling the precise fabrication of biologically functional constructs. At its core, the success of 3D bioprinting hinges on the development of bioinks, hydrogel-based materials that support cellular viability, proliferation, and differentiation. However, conventional bioinks face limitations in mechanical strength, biological activity, and customization. Recent advancements in genetic engineering have addressed these challenges by enhancing the properties of bioinks through genetic modifications. These innovations allow the integration of stimuli-responsive elements, bioactive molecules, and extracellular matrix (ECM) components, significantly improving the mechanical integrity, biocompatibility, and functional adaptability of bioinks. This review explores the state-of-the-art genetic approaches to bioink development, emphasizing microbial engineering, genetic functionalization, and the encapsulation of growth factors. It highlights the transformative potential of genetically modified bioinks in various applications, including bone and cartilage regeneration, cardiac and liver tissue engineering, neural tissue reconstruction, and vascularization. While these advances hold promise for personalized and adaptive therapeutic solutions, challenges in scalability, reproducibility, and integration with multi-material systems persist. By bridging genetics and bioprinting, this interdisciplinary field paves the way for sophisticated constructs and innovative therapies in tissue engineering and regenerative medicine.

A stiff bioink for hybrid bioprinting of vascularized bone tissue with enhanced mechanical properties

3D bioprinting is an emerging technique in tissue engineering that is advantageous for fabricating intricate tissues. However, challenges arise in bioprinting functional, implantable tissues. Commonly utilized hydrogel bioinks, while offering desirable printability and a cell-friendly environment, often lack the mechanical robustness necessary for post-printing maturation, handling, and implantation. These limitations are particularly relevant for bone tissue. Treatment of bone loss resulting from trauma or infection poses a significant clinical challenge. While surgical interventions exist, they frequently lead to complications and limited outcomes. Thus, a strategy to enhance the mechanical integrity of bioprinted constructs compatible with cells is needed. This study presents a novel hybrid bioprinting approach to create mechanically robust, vascularized bone tissue. A reinforcing bioink composed of a poly(lactic-co-glycolic) acid (PLGA), hydroxyapatite (HA), and polyethylene-glycol microparticles blend, which is thermosensitive due to a reduced glass transition temperature (∼36 °C), enabling sintering at physiological conditions is co-printed with a cell-laden, ECM-based hydrogel. The microparticles sinter at 37 °C, forming a porous, stiff scaffold. The hybrid bioprinted constructs demonstrate high cell viability, vascular network formation, and osteogenic differentiation. In vivo implantation in a rat femoral defect reveals superior bone regeneration compared to acellular controls. This study highlights the potential of hybrid bioprinting for creating tissues exhibiting high cell viability and enhanced mechanical properties, allowing for their handling and implantation.

Advances in harnessing biological macromolecules for periodontal tissue regeneration: A review

Periodontitis is a chronic multifactorial inflammatory oral disease that can lead to gingival recession, destruction of the periodontal ligament, alveolar bone loss, and tooth loss. Solutions for periodontal tissue regeneration utilize biological macromolecules, including natural ones (such as collagen (COL), alginate (ALG), chitosan (CS), silk fibroin (SF), hyaluronic acid (HA), etc.), inorganic ones (such as hydroxyapatite (HAp), β-tricalcium phosphate (β-TCP), bioactive glass (BG), etc.), synthetic, composite, and nanomaterials. Carrier materials, including hydrogels, nanofibers, nanoparticles, microneedles, and thin films, are used to effectively deliver therapeutic agents and biological factors such as stem cells, bioactive molecules, and genes, so as to promote the elimination of bacteria and tissue regeneration at the damaged periodontal sites. This review mainly focuses on the latest progress of biological macromolecules and tissue engineering technologies in periodontal regeneration in recent years. It aims to inspire the design and development of innovative biomaterials and delivery systems for novel regenerative periodontal treatments.

Engineered protein-based materials for tissue repair: A review

The human body may suffer multiple injuries and losses due to various external factors, such as tumors, diseases, traffic accidents, and war conflicts. Under such circumstances, engineered protein-based materials, as an innovative adjunctive material, can not only effectively promote the natural repair process of tissues, but also greatly circumvent the negative effects and complications that may be associated with conventional surgery. In this review, we first trace the definition and development of engineered protein-based materials and explain in detail their mechanism of action in promoting tissue repair. Subsequently, the advantages and disadvantages of various engineered protein-based materials in tissue repair are analyzed by comparison. In addition, the present review reveals in depth how material properties can be optimized by scientific means to meet different tissue repair needs. In addition, we present in detail specific application cases of engineered protein-based materials in the field of tissue repair. Finally, we summarize current challenges in engineered protein-based materials and provide an outlook for the future. This review not only provides theoretical support for the further exploration and development of engineered protein-based materials in the field of tissue repair, but also provides valuable references and inspiration for research in related fields.

The application of tissue engineering strategies for uterine regeneration

Uterine injuries, particularly damages to endometrium, are usually associated with abnormal menstruation, recurrent miscarriage, pregnancy complications, and infertility. Tissue engineering using cell-based, biomolecule-based, or biomaterial and scaffold-based strategies has emerged as a novel and promising approach for uterine regeneration. Stem cells, biomolecules, and porous scaffolds used alone or, very often, used in combination as a more effective treatment means have shown great potential in promoting uterine regeneration. The reported preclinical studies have indicated that appropriate tissue engineering strategies could safely and effectively reconstruct not only endometrium but also partial or even the whole uterine structure. However, the progress in the uterine regeneration area is slow in comparison to that of regenerating many other body tissues and hence it still remains a great challenge to apply uterine tissue engineering for clinical applications. In this review, conventional treatments for uterine-related diseases are briefly reviewed and discussed first. Subsequently, tissue engineering strategies (cell-based, biomolecule-based, biomaterial and scaffold-based, or their combinations) for uterine repair in preclinical studies and clinical trials are presented and analyzed. Finally, the challenges and perspectives in uterine regeneration are pointed and discussed. Despite various limitations and obstacles, the tissue engineering approach is viable and holds high promise for uterine regeneration.

Enhanced healing of critical-sized bone defects using degradable scaffolds with tailored composition through immunomodulation and angiogenesis

The impact of orthopedic scaffolds on bone defect healing, particularly the late-stage bone remodeling process, is pivotal for the therapeutic outcome. This study applies fadditively manufactured scaffolds composed of hydroxyapatite-doped poly(lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (HA-PELGA) with varying properties to treat rat calvarial defects, elucidating their significant role in bone remodeling by modulating physiological responses. We engineered two scaffolds with different polylactic acid (PLA) to polyglycolic acid (PGA) ratio (9/1 and 18/1) to vary in hydrophobicity, degradation rate, mechanical properties, and structural stability. These variations influenced physiological responses, including osteogenesis, angiogenesis, and immune reactions, thereby guiding bone remodeling. Our findings show that the HA-PELGA(18/1) scaffold, with a slower degradation rate, supported bulk bone formation due to a stable microenvironment. Conversely, the HA-PELGA(9/1) scaffold, with a faster degradation rate and more active interfaces, facilitated the formation of a thin bone layer and higher bone infiltration. This study demonstrates these degradable scaffolds help to promote bone healing and reveals how scaffold properties influence the bone remodeling process, offering a potential strategy to optimize scaffold design aiming at late-stage bone defect healing.

Advances in the application and research of biomaterials in promoting bone repair and regeneration through immune modulation

With the ongoing development of osteoimmunology, increasing evidence indicates that the local immune microenvironment plays a critical role in various stages of bone formation. Consequently, modulating the immune inflammatory response triggered by biomaterials to foster a more favorable immune microenvironment for bone regeneration has emerged as a novel strategy in bone tissue engineering. This review first examines the roles of various immune cells in bone tissue injury and repair. Then, the contributions of different biomaterials, including metals, bioceramics, and polymers, in promoting osteogenesis through immune regulation, as well as their future development directions, are discussed. Finally, various design strategies, such as modifying the physicochemical properties of biomaterials and integrating bioactive substances, to optimize material design and create an immune environment conducive to bone formation, are explored. In summary, this review comprehensively covers strategies and approaches for promoting bone tissue regeneration through immune modulation. It offers a thorough understanding of current research trends in biomaterial-based immune regulation, serving as a theoretical reference for the further development and clinical application of biomaterials in bone tissue engineering.

Optimizing solvent systems for electrospun PLGA scaffolds: effects on microstructure and mechanical properties for biomedical applications

Electrospun scaffolds fabricated from poly(lactic-co-glycolic acid) (PLGA) have garnered widespread interest in biomedical applications due to their ability to mimic the extracellular matrix (ECM) structure with a tunable degradability profile. The properties of electrospun scaffolds are meticulously tailored for specific applications through the adjustment of polymer properties, solution parameters, and processing conditions. Solvent selection is crucial, influencing polymer spinnability and scaffold topographical, physical and mechanical features. Hansen solubility theory aids in predicting suitable solvent systems. The absence of specific data prompted a solubility experiment to determine Hansen solubility parameters for PLGA. Subsequently, various solvent systems were investigated for their impact on the microstructure of electrospun PLGA scaffolds. Optimizing the electrospinning process resulted in fibrous scaffolds with consistent average fibre diameter from different solvent systems, allowing a focused examination of the solvent's isolated influence on mechanical properties. PLGA samples electrospun using hexafluoro isopropanol (HFIP) displayed lower Young's modulus and ultimate tensile strength but higher failure strains than those created using binary solvent systems composed of tetrahydrofuran (THF), dichloromethane (DCM), and dimethylformamide (DMF). This research advances the understanding and optimization of electrospun PLGA scaffolds, enhancing their potential for biomedical applications.

Development of silk fibroin/collagen film containing GI-20 peptide-loaded PLGA nanoparticles against corneal herpes simplex virus-1

Herpes simplex virus-1 (HSV-1) is the primary cause of infectious blindness. Despite impressive therapeutic outcomes of conventional treatments, HSV-1 drug resistance can be easily developed. Thus, more constructive strategies should be implemented. Led by this inspiration, this work describes the potential utility of a biodegradable silk fibroin/collagen (SF/Col) film combined with GI-20-loaded poly lactic-co-glycolic acid (PLGA) nanoparticle to provide efficient and sustained delivery platform for synthetic GI-20 peptide against HSV-1. A non-irritant film containing 90 % SF and 10 % Col incorporated with mentioned nanodrug showed some optimum physicochemical properties including loading efficiency (74.15 % ± 1.12), tensile strength (3.16 ± 0.67 MPa), water uptake ability (∼73 %), cytocompatibility (viable up to 35 µg/mL of GI-20), and sustained release paradigm (∼90 % within 14 days). Also, GI-20 peptide at concentration of 35 µg/mL could prophylactically attenuate viral titration by 5 log10 units. In addition, the corneal uptake was improved without vascular irritation. In accordance with in vitro results, no hallmarks of keratitis and significant neovascularization along with ignorable inflammatory responses were obtained. Taken together, these results could guarantee the potential of mentioned multifunctional biomaterial in the healing of infected corneal tissue.

Engineering the interfaces of 3D-printed polylactic acid scaffolds with bioactive molecules for bone tissue engineering

3D-printed tissue engineering scaffolds have emerged as a substitute to overcome the challenges faced in the reconstruction of bone. The prime objective of the study is to explore the feasibility of plasma-coated 3D-printed PLA scaffolds for bone tissue engineering. By engineering interfaces of these scaffolds with functional molecules, the surface properties can be controlled to ensure better interactions with the cells. To pursue this goal, the surface of these scaffolds was initially coated with polyoxazoline and then functionalized using L-Tryptophan. Hierarchical porous structures composed of meticulously ordered and well-connected pores were evident from the morphological analysis. The surface chemical characterisation revealed successful immobilisation of L-tryptophan on coated samples. The wettability of these scaffolds was favourable for cell adhesion and migration. They exhibited good mechanical properties, cytocompatibility and promoted the proliferation of osteosarcoma bone cells (MG-63). These results show the potential of bio-interface engineering in tailoring the surface properties of scaffolds in bone tissue engineering.

Engineering the Ratios of Nanoparticles Dispersed in Triphasic Nanocomposites for Biomedical Applications

Polymer/ceramic nanocomposites integrated the advantages of both polymers and ceramics for a wide range of biomedical applications, such as bone tissue repair. Here, we reported triphasic poly(lactic-co-glycolic acid) (PLGA, LA/GA = 90:10) nanocomposites with improved dispersion of hydroxyapatite (HA) and magnesium oxide (MgO) nanoparticles using a process that integrated the benefits of ultrasonic energy and dual asymmetric centrifugal mixing. We characterized the microstructure and composition of the nanocomposites and evaluated the effects of the HA/MgO ratios on degradation behavior and cell-material interactions. The PLGA/HA/MgO nanocomposites were composed of 70 wt % PLGA and 30 wt % nanoparticles made of 20:10, 25:5, and 29:1% by weight of HA and MgO, respectively. The results showed that the nanocomposites had a homogeneous nanoparticle distribution and as-designed elemental composition. The cell study indicated that reducing the MgO content in the triphasic nanocomposite increased the BMSC adhesion density under both direct and indirect contact conditions. Specifically, after the 24 and 48 h of culture, the PLGA/HA/MgO group with a weight ratio of 70:29:1 (P70/H29/M1) exhibited the greatest average cell adhesion density under direct and indirect contact conditions among triphasic nanocomposites. During a 28-day degradation study, the mass loss of triphasic nanocomposites was 18 ± 2% for P70/H20/M10, 9 ± 2% for P70/H25/M5, and 7 ± 1% for P70/H29/M1, demonstrating that MgO nanoparticles accelerated the degradation of the nanocomposites. Postculture analysis showed that the pH values and Mg2+ ion concentrations in the media increased with increasing MgO content in the nanocomposites. Triphasic nanocomposites provided different degradation profiles that can be tuned for different biomedical applications, especially when a shorter or longer period of degradation would be desirable for optimal bone tissue regeneration. The concentration and ratio of nanoparticles should be adjusted and optimized when other polymers with different degradation modes and rates are used in the nanocomposites.

β-ecdysone/PLGA composite scaffolds promote skull defect healing in diabetic rat

Introduction

Diabetes mellitus often leads to bone metabolism disorders, hindering bone regeneration and delaying the healing of bone defects. β-Ecdysone, a plant-derived hormone known for its wide range of physiological activities, possesses hypoglycemic effects and promotes osteogenic differentiation. This study developed a composite PLGA slow-release scaffold loaded with β-ecdysone to enhance its bioavailability through topical administration and to investigate its potential to heal diabetic bone defects.

Methods

The composite scaffolds were fabricated using solution casting/particle leaching and freeze-drying techniques. Then a series of characterizations were subjected to test the performance of composite scaffolds, and in vitro safety of the composite scaffolds was tested by CCK8 assay and live/dead cell staining. Further, micro-CT and histology to evaluate the effect of β-E/PLGA composite scaffolds on healing of skull defects in diabetic rats at 4 and 8 weeks after implantation. Simultaneously, the safety of the scaffolds in vivo was also evaluated.

Results

The material characterization results indicated that, in comparison to the single-pore size scaffold, the composite scaffold exhibited superior porosity, swelling ratio, drug loading capacity, and mechanical properties. Additionally, the composite scaffolds showed appropriate degradation performance and sustained drug release profiles. The CCK8 cytotoxicity assay and live/dead cell staining demonstrated that BMSCs survived and proliferated on the composite scaffold under both low-glucose and high-glucose conditions. Micro-CT and histological investigation demonstrated that β-E/PLGA composite scaffolds promoted new bone growth in the skull defect region of diabetic rats.

Conclusion

Overall, these findings suggest that the β-E/PLGA composite scaffolds promote the healing of bone defects in diabetic rats. The combination of β-ecdysone and tissue-engineered scaffolds presents a promising approach for treating diabetes-related bone defects.

Radical Ring-Opening Polymerization: Unlocking the Potential of Vinyl Polymers for Drug Delivery, Tissue Engineering, and More

Synthetic vinyl polymers have long been recognized for their potential to be utilized in drug delivery, tissue engineering, and other biomedical applications. The synthetic control that chemists have over their structure and properties is unmatched, allowing vinyl polymer-based materials to be precisely engineered for a range of therapeutic applications. Yet, their lack of biodegradability compromises the biocompatibility of vinyl polymers and has held back their translation into clinically used treatments for disease thus far. In recent years, radical ring-opening polymerization (rROP) has emerged as a promising strategy to render synthetic vinyl polymers biodegradable and bioresorbable. While rROP has long been touted as a strategy for preparing biodegradable vinyl polymers for biomedical applications, the translation of rROP into clinically approved treatments for disease has not yet been realized. This review highlights the opportunities for leveraging rROP to render vinyl polymers biodegradable and unlock their potential for use in biomedical applications.

Preparation and osteogenesis of a multiple crosslinking silk fibroin/carboxymethyl chitosan/sodium alginate composite scaffold loading with mesoporous silica/poly (lactic acid-glycolic acid) microspheres

Large bone defect repair is a striking challenge in orthopedics. Currently, inorganic-organic composite scaffolds are considered as a promising approach to these bone regeneration. Silicon ions (Si4+) are bioactive and beneficial to bone regeneration and Si4+-containing inorganic mesoporous silica (MS) can effectively load drugs for bone repair. To better control the release of drug, we prepared biodegradable MS/PLGA (MP) microspheres. MP loaded organic silk fibroin/carboxymethyl chitosan/sodium alginate (MP/SF/CMCS/SA) composite scaffolds were further constructed by genipin and Ca2+ crosslinking. All MP/SF/CMCS/SA scaffolds had good swelling ability, degradation rate and high porosity. The incorporation of 1% MP significantly enhanced the compressive strength of composite scaffolds. Besides, MP loaded scaffold showed a sustained release of Si4+ and Ca2+. Moreover, the release rate of rhodamine (a model drug) of MP/SF/CMCS/SA scaffolds was obviously lower than that of MP. When culturing with rat bone marrow mesenchymal stem cells, scaffolds with 1% MP displayed good proliferation, adhesion and enhanced osteogenic differentiation ability. Based on the results above, the addition of 1% MP in SF/CMCS/SA scaffolds is a prospective way for drug release in bone regeneration and is promising for further in vivo bone repair applications.

Recent advances in bioactive wound dressings

Traditional wound dressings, despite their widespread use, face limitations, such as poor infection control and insufficient healing promotion. To address these challenges, bioactive materials have emerged as a promising solution in wound care. This comprehensive review explores the latest developments in wound healing technologies, starting with an overview of the importance of effective wound management, emphasising the need for advanced bioactive wound dressings. The review further explores various bioactive materials, defining their characteristics. It covers a wide range of natural and synthetic biopolymers used to develop bioactive wound dressings. Next, the paper discusses the incorporation of bioactive agents into wound dressings, including antimicrobial and anti-inflammatory agents, alongside regenerative components like growth factors, platelet-rich plasma, platelet-rich fibrin and stem cells. The review also covers fabrication techniques for bioactive wound dressings, highlighting techniques like electrospinning, which facilitated the production of nanofibre-based dressings with controlled porosity, the sol-gel method for developing bioactive glass-based dressings, and 3D bioprinting for customised, patient-specific dressings. The review concludes by addressing the challenges and future perspectives in bioactive wound dressing development. It includes regulatory considerations, clinical efficacy, patient care protocol integration and wound healing progress monitoring. Furthermore, the review considers emerging trends such as smart materials, sensors and personalised medicine approaches, offering insights into the future direction of bioactive wound dressing research.

Nanostructured polymer composites for bone and tissue regeneration

Nanostructured polymer composites have gained significant attention in recent years for their remarkable potential in bone and tissue regeneration. Moreover, with the integration of 3D printing technology, these composites hold promise for use in personalized medicine, where patient-specific scaffolds can be tailored to enhance therapeutic outcomes. Therefore, this review article aims to provide a comprehensive overview of the latest advancements in the development and application of nanostructured polymeric composites within the field of tissue engineering and bone regeneration. Here, the potential of biopolymers, natural polymers, and 3D-printed polymers to craft biocompatible, non-toxic, and mechanically robust composites is discussed in brief. Further, the fabrication techniques for 3D scaffolds and various forms of nanocomposites, including nanoparticles, nanocapsules, nanofibers, nanogels, and micelles for bone and tissue regeneration, are listed. Also, particular emphasis is placed on the role of nano-scaffolds and in situ hydrogels in bone and tissue regeneration. Overall, this review provides a concise and authoritative summary of the current state-of-the-art in nanostructured polymer composites for regenerative medicine, highlighting future directions and potential clinical applications.

An Updated Review Summarizing the Anticancer Potential of Poly(Lactic-co-Glycolic Acid) (PLGA) Based Curcumin, Epigallocatechin Gallate, and Resveratrol Nanocarriers

The utilization of nanoformulations derived from natural products for the treatment of many human diseases, including cancer, is a rapidly developing field. Conventional therapies used for cancer treatment have limited efficacy and a greater number of adverse effects. Hence, it is imperative to develop innovative anticancer drugs with superior effectiveness. Among the diverse array of natural anticancer compounds, resveratrol, curcumin, and epigallocatechin gallate (EGCG) have gained considerable attention in recent years. Despite their strong anticancer properties, medicinally significant phytochemicals such as resveratrol, curcumin, and EGCG have certain disadvantages, such as limited solubility in water, stability, and bioavailability problems. Encapsulating these phytochemicals in poly(lactic-co-glycolic acid) (PLGA), a polymer that is nontoxic, biodegradable, and biocompatible, is an effective method for delivering medication to the tumor location. In addition, PLGA nanoparticles can be modified with targeting molecules to specifically target cancer cells, thereby improving the effectiveness of phytochemicals in fighting tumors. Combining plant-based medicine (phytotherapy) with nanotechnology in a clinical environment has the potential to enhance the effectiveness of drugs and improve the overall health outcomes of patients. Therefore, it is crucial to have a comprehensive understanding of the different aspects and recent advancements in using PLGA-based nanocarriers for delivering anticancer phytochemicals. This review addresses the most recent advancements in PLGA-based delivery systems for resveratrol, EGCG, and curcumin, emphasizing the possibility of resolving issues related to the therapeutic efficacy and bioavailability of these compounds.

Penetration of Microplastics and Nanoparticles Through Skin: Effects of Size, Shape, and Surface Chemistry

Skin represents an effective barrier against the penetration of external agents into the human body. Nevertheless, recent research has shown that small particles, especially in the nanosized range, can not only penetrate through the skin but also work as vectors to transport active molecules such as contrast agents or drugs. This knowledge has opened new perspectives on nanomedicine and controlled drug delivery. On the other hand, micro- and nanoplastics represent a form of emerging pollutants, and their concentration in the environment has been reported to drastically increase in the last years. The possible penetration of these particles through the skin has become a major concern for human health. If the actual primary toxicity of these materials is still debated, their possible role in the transport of toxic molecules through the skin, originating as secondary toxicity, is surely alarming. In this review paper, we analyze and critically discuss the most recent scientific publications to underline how these two processes, (i) the controlled delivery of bioactive molecules by micro- and nano-structures and (ii) the unwanted and uncontrolled penetration of toxic species through the skin mediated by micro- and nanoparticles, are deeply related and their efficiency is strongly affected by the nature, size, and shape of the particles.

Concrete-Inspired Bionic Bone Glue Repairs Osteoporotic Bone Defects by Gluing and Remodeling Aging Macrophages

Osteoporotic fractures are characterized by abnormal inflammation, deterioration of the bone microenvironment, weakened mechanical properties, and difficulties in osteogenic differentiation. The chronic inflammatory state characterized by aging macrophages leads to delayed or non-healing of the fracture or even the formation of bone defects. The current bottleneck in clinical treatment is to achieve strong fixation of the comminuted bone fragments and effective regulation of the complex microenvironment of aging macrophages. Inspired by cement and gravel in concrete infrastructure, a biomimetic bone glue with poly(lactic-co-glycolic acid) microspheres is developed and levodopa/oxidized chitosan hydrogel stabilized on an organic-inorganic framework of nanohydroxyapatite, named DOPM. DOPM is characterized via morphological and mechanical characterization techniques, in vitro experiments with bone marrow mesenchymal stromal cells, and in vivo experiments with an aged SD rat model exhibiting osteoporotic bone defects. DOPM exhibited excellent adhesion properties, good biocompatibility, and significant osteogenic differentiation. Transcriptomic analysis revealed that DOPM improved the inflammatory microenvironment by inhibiting the NF-κB signaling pathway and promoting aging macrophage polarization toward M2 macrophages, thus significantly accelerating bone defect repair and regeneration. This biomimetic bone glue, which enhances osteointegration and reestablishes the homeostasis of aging macrophages, has potential applications in the treatment of osteoporotic bone defects.

Advances and Challenges in Polymer-Based Scaffolds for Bone Tissue Engineering: A Path Towards Personalized Regenerative Medicine

Polymers have become essential in advancing bone tissue engineering, providing adaptable bone healing and regeneration solutions. Their biocompatibility and biodegradability make them ideal candidates for creating scaffolds that mimic the body's natural extracellular matrix (ECM). However, significant challenges remain, including degradation by-products, insufficient mechanical strength, and suboptimal cellular interactions. This article addresses these challenges by evaluating the performance of polymers like poly(lactic-co-glycolic acid) (PLGA), polycaprolactone (PCL), and polylactic acid (PLA) in scaffold development. It also explores recent innovations, such as intelligent polymers, bioprinting, and the integration of bioactive molecules to enhance scaffold efficacy. We propose that overcoming current limitations requires a combination of novel biomaterials, advanced fabrication techniques, and tailored regulatory strategies. The future potential of polymer-based scaffolds in personalised regenerative medicine is discussed, focusing on their clinical applicability.

Poly(Lactic Acid): Recent Stereochemical Advances and New Materials Engineering

Poly(lactic acid) (PLA) is a representative biobased and biodegradable aliphatic polyester and a front-runner among sustainable materials. As a semicrystalline thermoplastic, PLA exhibits excellent mechanical and physical properties, attracting considerable attention in commodity and medical fields. Stereochemistry is a key factor affecting PLA's properties, and to this end, the engineering of PLA's microstructure for tailored material properties has been an active area of research over the decade. This Review first covers the basic structural variety of PLA. A perspective on the current states of stereocontrolled synthesis as well as the relationships between the structures and properties of PLA stereosequences are included, with an emphasis on record regularity and properties. At last, state-of-the-art examples of high-performance PLA-based materials within an array of applications are given, including packaging, fibers, and textiles, healthcare and electronic devices. Among various stereo-regular sequences of PLA, poly(L-lactic acid) (PLLA) is the most prominent category and has myriad unique properties and applications. In this regard, cutting-edge applications of PLLA are mainly overviewed in this review. At the same time, new materials developed based on other PLA stereosequences are highlighted, which holds the potential to a wide variety of PLA-based sustainable materials.

Recent Advances in Degradable Biomedical Polymers for Prevention, Diagnosis and Treatment of Diseases

Biomedical polymers play a key role in preventing, diagnosing, and treating diseases, showcasing a wide range of applications. Their unique advantages, such as rich source, good biocompatibility, and excellent modifiability, make them ideal biomaterials for drug delivery, biomedical imaging, and tissue engineering. However, conventional biomedical polymers suffer from poor degradation in vivo, increasing the risks of bioaccumulation and potential toxicity. To address these issues, degradable biomedical polymers can serve as an alternative strategy in biomedicine. Degradable biomedical polymers can efficiently relieve bioaccumulation in vivo and effectively reduce patient burden in disease management. This review comprehensively introduces the classification and properties of biomedical polymers and the recent research progress of degradable biomedical polymers in various diseases. Through an in-depth analysis of their classification, properties, and applications, we aim to provide strong guidance for promoting basic research and clinical translation of degradable biomedical polymers.

Engineered Protein Hydrogels as Biomimetic Cellular Scaffolds

The biochemical and biophysical properties of the extracellular matrix (ECM) play a pivotal role in regulating cellular behaviors such as proliferation, migration, and differentiation. Engineered protein-based hydrogels, with highly tunable multifunctional properties, have the potential to replicate key features of the native ECM. Formed by self-assembly or crosslinking, engineered protein-based hydrogels can induce a range of cell behaviors through bioactive and functional domains incorporated into the polymer backbone. Using recombinant techniques, the amino acid sequence of the protein backbone can be designed with precise control over the chain-length, folded structure, and cell-interaction sites. In this review, the modular design of engineered protein-based hydrogels from both a molecular- and network-level perspective are discussed, and summarize recent progress and case studies to highlight the diverse strategies used to construct biomimetic scaffolds. This review focuses on amino acid sequences that form structural blocks, bioactive blocks, and stimuli-responsive blocks designed into the protein backbone for highly precise and tunable control of scaffold properties. Both physical and chemical methods to stabilize dynamic protein networks with defined structure and bioactivity for cell culture applications are discussed. Finally, a discussion of future directions of engineered protein-based hydrogels as biomimetic cellular scaffolds is concluded.

Biodegradable magnesium and zinc composite microspheres with synergistic osteogenic effect for enhanced bone regeneration

Biodegradable polymer microspheres in bone tissue engineering have become appealing as their non-invasive advantages in irregular damage bone repair. However, current microspheres used in BTE still lack sufficient osteogenic capacity to induce effective bone regeneration. In this study, we developed osteogenic composite microspheres concurrently loaded with magnesium oxide (MgO) and zinc oxide (ZnO), both of which are osteogenic active substances, using a facile and scalable emulsification method. The osteogenic composite microspheres exhibited a sequential yet complementary release profile characterized by a rapid release of Mg2+ and a gradual release of Zn2+ in a physiological environment, thereby maintaining the concentration of bioactive ions at a sustained high level. As a result, the combination of Mg2+ and Zn2+ in the composite microspheres led to a synergistic enhancement in biomimetic mineralization and the upregulation in the expression of osteogenic-related genes and proteins at the cellular level. Through a critical-sized calvarial rate defect model, the osteogenic composite microspheres were demonstrated to have strong osteogenic ability to promote new bone formation via ultrasonic imaging, histological and immunohistochemical evaluations. In sum, these osteogenic composite microspheres as microcarriers of Mg2+ and Zn2+ have great potential in the delivery of therapeutic ions for treating bone defects.

Anti-aging Metabolite-Based Polymeric Microparticles for Intracellular Drug Delivery and Bone Regeneration

Alpha-ketoglutarate (AKG), a key component of the tricarboxylic acid (TCA) cycle, has attracted attention for its anti-aging properties. Our recent study indicates that locally delivered cell-permeable AKG significantly promotes osteogenic differentiation and mouse bone regeneration. However, the cytotoxicity and rapid hydrolysis of the metabolite limit its application. In this study, we synthesize novel AKG-based polymeric microparticles (PAKG MPs) for sustained release. In vitro data suggest that the chemical components, hydrophilicity, and size of the MPs can significantly affect their cytotoxicity and pro-osteogenic activity. Excitingly, these biodegradable PAKG MPs are highly phagocytosable for nonphagocytic pre-osteoblasts MC3T3-E1 and primary bone marrow mesenchymal stem cells (BMSCs), significantly promoting their osteoblastic differentiation. RNAseq data suggest that PAKG MPs strongly activate Wnt/β-catenin and PI3K-Akt pathways for osteogenic differentiation. Moreover, PAKG enables poly (L-lactic acid) and poly (lactic-co-glycolic acid) MPs (PLLA & PLGA MPs) for efficient phagocytosis. Our data indicate that PLGA-PAKG MPs-mediated intracellular drug delivery can significantly promote stronger osteoblastic differentiation compared to PLGA MPs-delivered phenamil. Notably, PAKG MPs significantly improve large bone regeneration in a mouse cranial bone defect model. Thus, the novel PAKG-based MPs show great promise to improve osteogenic differentiation, bone regeneration, and enable efficient intracellular drug delivery for broad regenerative medicine.

Biomaterials Mimicking Mechanobiology: A Specific Design for a Specific Biological Application

Mechanosensing and mechanotransduction pathways between the Extracellular Matrix (ECM) and cells form the essential crosstalk that regulates cell homeostasis, tissue development, morphology, maintenance, and function. Understanding these mechanisms involves creating an appropriate cell support that elicits signals to guide cellular functions. In this context, polymers can serve as ideal molecules for producing biomaterials designed to mimic the characteristics of the ECM, thereby triggering responsive mechanisms that closely resemble those induced by a natural physiological system. The generated specific stimuli depend on the different natural or synthetic origins of the polymers, the chemical composition, the assembly structure, and the physical and surface properties of biomaterials. This review discusses the most widely used polymers and their customization to develop biomaterials with tailored properties. It examines how the characteristics of biomaterials-based polymers can be harnessed to replicate the functions of biological cells, making them suitable for biomedical and biotechnological applications.

Recent Applications of PLGA in Drug Delivery Systems

Poly(lactic-co-glycolic acid) (PLGA) is a widely used biodegradable and biocompatible copolymer in drug delivery systems (DDSs). In this article, we highlight the critical physicochemical properties of PLGA, including its molecular weight, intrinsic viscosity, monomer ratio, blockiness, and end caps, that significantly influence drug release profiles and degradation times. This review also covers the extensive literature on the application of PLGA in delivering small-molecule drugs, proteins, peptides, antibiotics, and antiviral drugs. Furthermore, we discuss the role of PLGA-based DDSs in the treating various diseases, including cancer, neurological disorders, pain, and inflammation. The incorporation of drugs into PLGA nanoparticles and microspheres has been shown to enhance their therapeutic efficacy, reduce toxicity, and improve patient compliance. Overall, PLGA-based DDSs holds great promise for the advancement of the treatment and management of multiple chronic conditions.

Carrier cascade target delivery of 5-aminolevulinic acid nanoplatform to enhance antitumor efficiency of photodynamic therapy against lung cancer

5-Aminolevulinic acid (5-ALA) is a prodrug of porphyrin IX (PpIX). Disadvantages of 5-ALA include poor stability, rapid elimination, poor bioavailability, and weak cell penetration, which greatly reduce the clinical effect of 5-ALA based photodynamic therapy (PDT). Presently, a novel targeting nanosystem was constructed using gold nanoparticles (AuNPs) as carriers loaded with a CSNIDARAC (CC9)-targeting peptide and 5-ALA via Au-sulphur and ionic bonds, respectively, and then wrapped in polylactic glycolic acid (PLGA) NPs via self-assembly to improve the antitumor effects and reduce the side effect. The successful preparation of ALA/CC9@ AuNPs-PLGA NPs was verified using ultraviolet-visible, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The analyses revealed good sphericity with a particle size of approximately140 nm, Zeta potential of 10.11 mV, and slow-controlled release characteristic in a weak acid environment. Confocal microscopy revealed targeting of NCL-H460 cells by NPs by actively internalising CC9 and avoiding the phagocytic action of RAW264.7 cells, and live fluorescence imaging revealed targeting of tumours in tumour-bearing mice. Compared to free 5-ALA, the nanosystem displayed amplified anticancer activity by increasing production of PpIX and reactive oxygen species to induce mitochondrial pathway apoptosis. Antitumor efficacy was consistently observed in three-dimensionally cultured cells as the loss of integrity of tumour balls. More potent anti-tumour efficacy was demonstrated in xenograft tumour models by decreased growth rate and increased tumour apoptosis. Histological analysis showed that this system was not toxic, with lowered liver toxicity of 5-ALA. Thus, ALA/CC9@AuNPs-PLGA NPs deliver 5-ALA via a carrier cascade, with excellent effects on tumour accumulation and PDT through passive enhanced permeability and retention action and active targeting. This innovative strategy for cancer therapy requires more clinical trials before being implemented.

Development and Applications of PLGA Hydrogels for Sustained Delivery of Therapeutic Agents

Poly(lactic-co-glycolic acid) (PLGA) hydrogels are highly utilized in biomedical research due to their biocompatibility, biodegradability, and other versatile properties. This review comprehensively explores their synthesis, properties, sustained release mechanisms, and applications in drug delivery. The introduction underscores the significance of PLGA hydrogels in addressing challenges like short half-lives and systemic toxicity in conventional drug formulations. Synthesis methods, including emulsion solvent evaporation, solvent casting, electrospinning, thermal gelation, and photopolymerization, are described in detail and their role in tailoring hydrogel properties for specific applications is highlighted. Sustained release mechanisms-such as diffusion-controlled, degradation-controlled, swelling-controlled, and combined systems-are analyzed alongside key kinetic models (zero-order, first-order, Higuchi, and Peppas models) for designing controlled drug delivery systems. Applications of PLGA hydrogels in drug delivery are discussed, highlighting their effectiveness in localized and sustained chemotherapy for cancer, as well as in the delivery of antibiotics and antimicrobials to combat infections. Challenges and future prospects in PLGA hydrogel research are discussed, with a focus on improving drug loading efficiency, improving release control mechanisms, and promoting clinical translation. In summary, PLGA hydrogels provide a promising platform for the sustained delivery of therapeutic agents and meet diverse biomedical requirements. Future advancements in materials science and biomedical engineering are anticipated to further optimize their efficacy and applicability in clinical settings. This review consolidates the current understanding and outlines future research directions for PLGA hydrogels, emphasizing their potential to revolutionize therapeutic delivery and improve patient outcomes.

Cutting-Edge Biomaterials in Intervertebral Disc Degeneration Tissue Engineering

Intervertebral disc degeneration (IVDD) stands as the foremost contributor to low back pain (LBP), imposing a substantial weight on the world economy. Traditional treatment modalities encompass both conservative approaches and surgical interventions; however, the former falls short in halting IVDD progression, while the latter carries inherent risks. Hence, the quest for an efficacious method to reverse IVDD onset is paramount. Biomaterial delivery systems, exemplified by hydrogels, microspheres, and microneedles, renowned for their exceptional biocompatibility, biodegradability, biological efficacy, and mechanical attributes, have found widespread application in bone, cartilage, and various tissue engineering endeavors. Consequently, IVD tissue engineering has emerged as a burgeoning field of interest. This paper succinctly introduces the intervertebral disc (IVD) structure and the pathophysiology of IVDD, meticulously classifies biomaterials for IVD repair, and reviews recent advances in the field. Particularly, the strengths and weaknesses of biomaterials in IVD tissue engineering are emphasized, and potential avenues for future research are suggested.

Osteointegration of functionalised high-performance oxide ceramics: imaging from micro-computed tomography

BACKGROUND

This study evaluated the osseointegration potential of functionalised high-performance oxide ceramics (HPOC) in isolation or coated with BMP-2 or RGD peptides in 36 New Zeeland female rabbits using micro-computed tomography (micro CT). The primary outcomes of interest were to assess the amount of ossification evaluating the improvement in the bone volume/ total volume (BV/TV) ratio and trabecular thickness at 6 and 12 weeks. The second outcome of interest was to investigate possible differences in osteointegration between the functionalised silanised HPOC in isolation or coated with Bone Morphogenetic Protein 2 (BMP-2) or RGD peptides.

METHODS

36 adult female New Zealand white rabbits with a minimum weight of three kg were used. One-third of HPOCs were functionalised with silicon suboxide (SiOx), a third with BMP-2 (sHPOC-BMP2), and another third with RGD (sHPOC-RGD). All samples were scanned with a high-resolution micro CT (U-CTHR, MILabs B.V., Houten, The Netherlands) with a reconstructed voxel resolution of 10 µm. MicroCT scans were reconstructed in three planes and processed using Imalytics Preclinical version 2.1 (Gremse-IT GmbH, Aachen, Germany) software. The total volume (TV), bone volume (BV) and ratio BV/TV were calculated within the coating area.

RESULTS

BV/TV increased significantly from 6 to 12 weeks in all HPOCs: silanised (P = 0.01), BMP-2 (P < 0.0001), and RGD (P < 0.0001) groups. At 12 weeks, the BMP-2 groups demonstrated greater ossification in the RGD (P < 0.0001) and silanised (P = 0.008) groups. Trabecular thickness increased significantly from 6 to 12 weeks (P < 0.0001). At 12 weeks, BMP-2 promoted greater trabecular thickness compared to the silanised group (P = 0.07), although no difference was found with the RGD (P = 0.1) group.

CONCLUSION

Sinalised HPOC in isolation or functionalised with BMP-2 or RGD promotes in vivo osteointegration. The sinalised HOPC functionalised with BMP-2 demonstrated the greatest osseointegration.

Nanofibrous Microspheres: A Biomimetic Platform for Bone Tissue Regeneration

Bone, a fundamental constituent of the human body, is a vital scaffold for support, protection, and locomotion, underscoring its pivotal role in maintaining skeletal integrity and overall functionality. However, factors such as trauma, disease, or aging can compromise bone structure, necessitating effective strategies for regeneration. Traditional approaches often lack biomimetic environments conducive to efficient tissue repair. Nanofibrous microspheres (NFMS) present a promising biomimetic platform for bone regeneration by mimicking the native extracellular matrix architecture. Through optimized fabrication techniques and the incorporation of active biomolecular components, NFMS can precisely replicate the nanostructure and biochemical cues essential for osteogenesis promotion. Furthermore, NFMS exhibit versatile properties, including tunable morphology, mechanical strength, and controlled release kinetics, augmenting their suitability for tailored bone tissue engineering applications. NFMS enhance cell recruitment, attachment, and proliferation, while promoting osteogenic differentiation and mineralization, thereby accelerating bone healing. This review highlights the pivotal role of NFMS in bone tissue engineering, elucidating their design principles and key attributes. By examining recent preclinical applications, we assess their current clinical status and discuss critical considerations for potential clinical translation. This review offers crucial insights for researchers at the intersection of biomaterials and tissue engineering, highlighting developments in this expanding field.

Application and Development of Electrospun Nanofiber Scaffolds for Bone Tissue Engineering

Nanofiber scaffolds have gained significant attention in the field of bone tissue engineering. Electrospinning, a straightforward and efficient technique for producing nanofibers, has been extensively researched. When used in bone tissue engineering scaffolds, electrospun nanofibers with suitable surface properties promote new bone tissue growth and enhance cell adhesion. Recent advancements in electrospinning technology have provided innovative approaches for scaffold fabrication in bone tissue engineering. This review comprehensively examines the utilization of electrospun nanofibers in bone tissue engineering scaffolds and evaluates the relevant literature. The review begins by presenting the fundamental principles and methodologies of electrospinning. It then discusses various materials used in the production of electrospun nanofiber scaffolds for bone tissue engineering, including natural and synthetic polymers, as well as certain inorganic materials. The challenges associated with these materials are also described. The review focuses on novel electrospinning techniques for scaffold construction in bone tissue engineering, such as multilayer nanofibers, multifluid electrospinning, and the integration of electrospinning with other methods. Recent advancements in electrospinning technology have enabled the fabrication of precisely aligned nanofiber scaffolds with nanoscale architectures. These innovative methods also facilitate the fabrication of biomimetic structures, wherein bioactive substances can be incorporated and released in a controlled manner for drug delivery purposes. Moreover, they address issues encountered with traditional electrospun nanofibers, such as mechanical characteristics and biocompatibility. Consequently, the development and implementation of novel electrospinning technologies have revolutionized scaffold fabrication for bone tissue engineering.

Chitosan-PLGA mucoadhesive nanoparticles for gemcitabine repurposing for glioblastoma therapy

Glioblastoma (GBM) is a highly deadly brain tumor that does not respond satisfactorily to conventional treatment. The non-alkylating agent gemcitabine (GEM) has been proposed for treating GBM. It can overcome MGMT protein-mediated resistance, a major limitation of conventional therapy with the alkylating agent temozolomide (TMZ). However, GEM's high systemic toxicity and poor permeability across the blood-brain barrier (BBB) pose significant challenges for its delivery to the brain. Thus, mucoadhesive poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) coated with chitosan (CH), suitable for intranasal GEM delivery, were proposed in this work. A central composite design (CCD) was implemented for NPs optimization, and NPs with appropriate characteristics for intranasal administration were obtained. in vitro studies revealed that the NPs possess excellent mucoadhesive properties and the ability to selectively release GEM in the simulated tumor tissue environment. in vitro studies using two human GBM cell lines (U215 and T98G) revealed the NPs' ability to promote GEM's antiproliferative activity to sensitize cells to the effect of TMZ. The findings of this work demonstrate that the developed CH-GEM-NPs are suitable delivery systems for GEM, both as a single therapy and as a chemosensitizer to the GBM gold standard therapy.

Directed Assembly of Elastic Fibers via Coacervate Droplet Deposition on Electrospun Templates

Elastic fibers provide critical elasticity to the arteries, lungs, and other organs. Elastic fiber assembly is a process where soluble tropoelastin is coacervated into liquid droplets, cross-linked, and deposited onto and into microfibrils. While much progress has been made in understanding the biology of this process, questions remain regarding the timing of interactions during assembly. Furthermore, it is unclear to what extent fibrous templates are needed to guide coacervate droplets into the correct architecture. The organization and shaping of coacervate droplets onto a fiber template have never been previously modeled or employed as a strategy for shaping elastin fiber materials. Using an in vitro system consisting of elastin-like polypeptides (ELPs), genipin cross-linker, electrospun polylactic-co-glycolic acid (PLGA) fibers, and tannic acid surface coatings for fibers, we explored ELP coacervation, cross-linking, and deposition onto fiber templates. We demonstrate that integration of coacervate droplets into a fibrous template is primarily influenced by two factors: (1) the balance of coacervation and cross-linking and (2) the surface energy of the fiber templates. The success of this integration affects the mechanical properties of the final fiber network. Our resulting membrane materials exhibit highly tunable morphologies and a range of elastic moduli (0.8-1.6 MPa) comparable to native elastic fibers.

Antitumoral-Embedded Biopolymeric Spheres for Implantable Devices

The bioactive surface modification of implantable devices paves the way towards the personalized healthcare practice by providing a versatile and tunable approach that increase the patient outcome, facilitate the medical procedure, and reduce the indirect or secondary effects. The purpose of our study was to assess the performance of composite coatings based on biopolymeric spheres of poly(lactide-co-glycolide) embedded with hydroxyapatite (HA) and methotrexate (MTX). Bio-simulated tests performed for up to one week evidenced the gradual release of the antitumor drug and the biomineralization potential of PLGA/HA-MTX sphere coatings. The composite materials proved superior biocompatibility and promoted enhanced cell adhesion and proliferation with respect to human preosteoblast and osteosarcoma cell lines when compared to pristine titanium.

Fabrication of atelocollagen-coated bioabsorbable suture and the evaluation of its regenerative efficacy in Achilles tendon healing using a rat experimental model

Recently, the incidence of Achilles tendon ruptures (ATRs) has become more common, and repair surgery using a bioabsorbable suture is generally preferred, particularly in the case of healthy patients. Sutures composed of poly(lactic-co-glycolic acid) (PLGA) are commonly used in ATR surgeries. Nevertheless, owing to the inherent limitations of PLGA, novel bioabsorbable sutures that can accelerate Achilles tendon healing are sought. Recently, several studies have demonstrated the beneficial effects of atelocollagen on tendon healing. In this study, poly(3,4-dihydroxy-L-phenylalanine) (pDOPA), a hydrophilic biomimetic material, was used to modify the hydrophobic surface of a PLGA suture (Vicryl, VC) for the stable coating of atelocollagen on its surface. The main objective was to fabricate an atelocollagen-coated VC suture and evaluate its performance in the healing of Achilles tendon using a rat model of open repair for ATR. Structural analyses of the surface-modified suture indicated that the collagen was successfully coated on the VC/pDOPA suture. Postoperative in vivo biomechanical analysis, histological evaluation, ultrastructural/morphological analyses, and western blotting confirmed that the tendons in the VC/pDOPA/Col group exhibit superior healing than those in the VC and VC/pDOPA groups after 1 and 6 weeks following the surgery. The this study suggests that atelocollagen-coated PLGA/pDOPA sutures are preferable for future medical applications, especially in the repair of ATR.

Recent Advancements in Bone Tissue Engineering: Integrating Smart Scaffold Technologies and Bio-Responsive Systems for Enhanced Regeneration

In exploring the challenges of bone repair and regeneration, this review evaluates the potential of bone tissue engineering (BTE) as a viable alternative to traditional methods, such as autografts and allografts. Key developments in biomaterials and scaffold fabrication techniques, such as additive manufacturing and cell and bioactive molecule-laden scaffolds, are discussed, along with the integration of bio-responsive scaffolds, which can respond to physical and chemical stimuli. These advancements collectively aim to mimic the natural microenvironment of bone, thereby enhancing osteogenesis and facilitating the formation of new tissue. Through a comprehensive combination of in vitro and in vivo studies, we scrutinize the biocompatibility, osteoinductivity, and osteoconductivity of these engineered scaffolds, as well as their interactions with critical cellular players in bone healing processes. Findings from scaffold fabrication techniques and bio-responsive scaffolds indicate that incorporating nanostructured materials and bioactive compounds is particularly effective in promoting the recruitment and differentiation of osteoprogenitor cells. The therapeutic potential of these advanced biomaterials in clinical settings is widely recognized and the paper advocates continued research into multi-responsive scaffold systems.

Towards Stem Cell Therapy for Critical-Sized Segmental Bone Defects: Current Trends and Challenges on the Path to Clinical Translation

The management and reconstruction of critical-sized segmental bone defects remain a major clinical challenge for orthopaedic clinicians and surgeons. In particular, regenerative medicine approaches that involve incorporating stem cells within tissue engineering scaffolds have great promise for fracture management. This narrative review focuses on the primary components of bone tissue engineering-stem cells, scaffolds, the microenvironment, and vascularisation-addressing current advances and translational and regulatory challenges in the current landscape of stem cell therapy for critical-sized bone defects. To comprehensively explore this research area and offer insights for future treatment options in orthopaedic surgery, we have examined the latest developments and advancements in bone tissue engineering, focusing on those of clinical relevance in recent years. Finally, we present a forward-looking perspective on using stem cells in bone tissue engineering for critical-sized segmental bone defects.

Optimizing Process Parameters for Controlled Drug Delivery: A Quality by Design (QbD) Approach in Naltrexone Microspheres

The formulation of microspheres involves a complex manufacturing process with multiple steps. Identifying the appropriate process parameters to achieve the desired quality attributes poses a significant challenge. This study aims to optimize the critical process parameters (CPPs) involved in the preparation of naltrexone microspheres using a Quality by Design (QbD) methodology. Additionally, the research aims to assess the drug release profiles of these microspheres under both in vivo and in vitro conditions. Critical process parameters (CPPs) and critical quality attributes (CQAs) were identified, and a Box-Behnken design was utilized to delineate the design space, ensuring alignment with the desired Quality Target Product Profile (QTPP). The investigated CPPs comprised polymer concentration, aqueous phase ratio to organic phase ratio, and quench volume. The microspheres were fabricated using the oil-in-water emulsion solvent extraction technique. Analysis revealed that increased polymer concentration was correlated with decreased particle size, reduced quench volume resulted in decreased burst release, and a heightened aqueous phase ratio to organic phase ratio improved drug entrapment. Upon analyzing the results, an optimal formulation was determined. In conclusion, the study conducted in vivo drug release testing on both the commercially available innovator product and the optimized test product utilizing an animal model. The integration of in vitro dissolution data with in vivo assessments presents a holistic understanding of drug release dynamics. The QbD approach-based optimization of CPPs furnishes informed guidance for the development of generic pharmaceutical formulations.

Hydrogel-Based Systems in Neuro-Vascularized Bone Regeneration: A Promising Therapeutic Strategy

Blood vessels and nerve fibers are distributed throughout the skeletal tissue, which enhance the development and function of each other and have an irreplaceable role in bone formation and remodeling. Despite significant progress in bone tissue engineering, the inadequacy of nerve-vascular network reconstruction remains a major limitation. This is partly due to the difficulty of integrating and regulating multiple tissue types with artificial materials. Thus, understanding the anatomy and underlying coupling mechanisms of blood vessels and nerve fibers within bone to further develop neuro-vascularized bone implant biomaterials is an extremely critical aspect in the field of bone regeneration. Hydrogels have good biocompatibility, controllable mechanical characteristics, and osteoconductive and osteoinductive properties, making them important candidates for research related to neuro-vascularized bone regeneration. This review reports the classification and physicochemical properties of hydrogels, with a focus on the application advantages and status of hydrogels for bone regeneration. The authors also highlight the effect of neurovascular coupling on bone repair and regeneration and the necessity of achieving neuro-vascularized bone regeneration. Finally, the recent progress and design strategies of hydrogel-based biomaterials for neuro-vascularized bone regeneration are discussed.

Injectable microspheres adhering to the cartilage matrix promote rapid reconstruction of partial-thickness cartilage defects

An effective treatment for the irregular partial-thickness cartilage defect in the early stages of osteoarthritis (OA) is lacking. Cartilage tissue engineering is effective for treating full-thickness cartilage defects with limited area. In this study, we designed an injectable multifunctional poly(lactic-co-glycolic acid) (PLGA) microsphere to repair partial-thickness cartilage defects. The microsphere was grafted with an E7 peptide after loading the microsphere with kartogenin (KGN) and modifying the outer layer through dopamine self-polymerization. The microsphere could adhere to the cartilage defect, recruit synovial mesenchymal stem cells (SMSCs) in situ, and stimulate their differentiation into chondrocytes after injection into the articular cavity. Through in vivo and in vitro experiments, we demonstrated the ability of multifunctional microspheres to adhere to cartilage matrix, recruit SMSCs, and promote their differentiation into cartilage. Following treatment, the cartilage surface of the model group with partial-thickness cartilage defect showed smooth recovery, and the glycosaminoglycan content remained normal; the untreated control group showed significant progression of OA. The microsphere, a framework for cartilage tissue engineering, promoted the expression of SMSCs involved in cartilage repair while adapting to cell migration and growth. Thus, for treating partial-thickness cartilage defects in OA, this innovative carrier system based on stem cell therapy can potentially improve therapeutic outcomes. STATEMENT OF SIGNIFICANCE: Mesenchymal stem cells (MSCs) therapy is effective in the repair of cartilage injury. However, because of the particularity of partial-thickness cartilage injury, it is difficult to recruit enough seed cells in situ, and there is a lack of suitable scaffolds for cell migration and growth. Here, we developed polydopamine surface-modified PLGA microspheres (PMS) containing KGN and E7 peptides. The adhesion ability of the microspheres is facilitated by the polydopamine layer wrapped in them; thus, the microspheres can adhere to the injured cartilage and recruit MSCs, thereby promoting their differentiation into chondrocytes and accomplishing cartilage repair. The multifunctional microspheres can be used as a safe and potential method to treat partial-thickness cartilage defects in OA.

Nanofunctionalized Microparticles for Glucose Delivery in Three-Dimensional Cell Assemblies

Three-dimensional (3D) cell assemblies, such as multicellular spheroids, can be powerful biological tools to closely mimic the complexity of cell-cell and cell-matrix interactions in a native-like microenvironment. However, potential applications of large spheroids are limited by the insufficient diffusion of oxygen and nutrients through the spheroids and, thus, result in the formation of a necrotic core. To overcome this drawback, we present a new strategy based on nanoparticle-coated microparticles. In this study, microparticles function as synthetic centers to regulate the diffusion of small molecules, such as oxygen and nutrients, within human mesenchymal stem cell (hMSC) spheroids. The nanoparticle coating on the microparticle surface acts as a nutrient reservoir to release glucose locally within the spheroids. We first coated the surface of the poly(lactic-co-glycolic acid) (PLGA) microparticles with mesoporous silica nanoparticles (MSNs) based on electrostatic interactions and then formed cell-nanofunctionalized microparticle spheroids. Next, we investigated the stability of the MSN coating on the microparticles' surface during 14 days of incubation in cell culture medium at 37 °C. Then, we evaluated the influence of MSN-coated PLGA microparticles on spheroid aggregation and cell viability. Our results showed the formation of homogeneous spheroids with good cell viability. As a proof of concept, fluorescently labeled glucose (2-NBD glucose) was loaded into the MSNs at different concentrations, and the release behavior was monitored. For cell culture studies, glucose was loaded into the MSNs coated onto the PLGA microparticles to sustain local nutrient release within the hMSC spheroids. In vitro results demonstrated that the local delivery of glucose from MSNs enhanced the cell viability in spheroids during a short-term hypoxic culture. Taken together, the newly developed nanofunctionalized microparticle-based delivery system may offer a versatile platform for local delivery of small molecules within 3D cellular assemblies and, thus, improve cell viability in spheroids.