Preparation of antibacterial degummed silk fiber/nano-hydroxyapatite/polylactic acid composite scaffold by degummed silk fiber loaded silver nanoparticles

Osteoconductive composite membranes produced by rotary jet spinning bioresorbable PLGA for bone regeneration

Bone defects and injuries are common, and better solutions are needed for improved regeneration and osseointegration. Bioresorbable membranes hold great potential in bone tissue engineering due to their high surface area and versatility. In this context, polymers such as poly(lactic-co-glycolic acid) (PLGA) can be combined with osteoconductive materials like hydroxyapatite (HA) nanoparticles (NPs) to create membranes with enhanced bioactivity and bone regeneration. Rotary Jet spinning (RJS) is a powerful technique to produce these composite membranes. This study presents an innovative and efficient method to obtain PLGA-HA(NPs) membranes with continuous fibers containing homogeneous HA(NPs) distribution. The membranes demonstrated stable thermal degradation, allowing HA(NPs) quantification. In addition, the PLGA-HA(NPs) presented osteoconductivity, were not cytotoxic, and had high cell adhesion when cultured with pre-osteoblastic cells. These findings demonstrate the potential of RJS to produce PLGA-HA(NPs) membranes for easy and effective application in bone regeneration.

Silk Fibroin and Its Nanocomposites for Wound Care: A Comprehensive Review

For most individuals, wound healing is a highly organized, straightforward process, wherein the body transitions through different phases in a timely manner. However, there are instances where external intervention becomes necessary to support and facilitate different phases of the body's innate healing mechanism. Furthermore, in developing countries, the cost of the intervention significantly impacts access to treatment options as affordability becomes a determining factor. This is particularly true in cases of long-term wound treatment and management, such as chronic wounds and infections. Silk fibroin (SF) and its nanocomposites have emerged as promising biomaterials with potent wound-healing activity. Driven by this motivation, this Review presents a critical overview of the recent advancements in different aspects of wound care using SF and SF-based nanocomposites. In this context, we explore various formats of hemostats and assess their suitability for different bleeding situations. The subsequent sections discuss the primary causes of nonhealing wounds, i.e., prolonged inflammation and infections. Herein, different treatment strategies to achieve immunomodulatory and antibacterial properties in a wound dressing were reviewed. Despite exhibiting excellent pro-healing properties, few silk-based products reach the market. This Review concludes by highlighting the bottlenecks in translating silk-based products into the market and the prospects for the future.

Tough and antibacterial poly(l-lactic acid) composites prepared via blending with the bifunctional macromolecular ionomer

In order to expand the application of PLLA in the packaging field, improving its toughness and antibacterial activity has been widely concerned. However, seldom researches can simultaneously efficiently improve the toughness and antibacterial activity of PLLA by adding one kind of additions. To address above problems, the bifunctional branched poly(butylene adipate) ionomer additive (b-PBAUi) was synthesized. For b-PBAUi, its branched structure not only increased the plasticizing effect of additive, but also acted as reaction sites to introduce more antibacterial ionic salt. Due to the special structure of b-PBAUi, PLLA/b-PBAUi blends achieved excellent toughness and antibacterial efficiency. The elongation of blend reached 125 % even by adding 5 wt% b-PBAUi, which was 10 times higher than that of PLLA. From the analysis of phase morphology, it could be found that the microvoids promoting tensile yielding was the main tensile toughening mechanism for PLLA/b-PBAUi blends. In addition, the antibacterial activity of PLLA was significantly improved by adding b-PBAUi. For PLLA/b-PBAUi10 and PLLA/b-PBAUi15, the antibacterial efficiency against E. coli and S. aureus bacteria exceeded 99.0 %. By comprehensive consideration, the optimal blend ratio was achieved by PLLA/b-PBAUi10 due to its excellent toughness and antibacterial efficiency.

A Review on Antibacterial Silk Fibroin-based Biomaterials: Current State and Prospects

Bacterial contamination of biomaterials is a common problem and a serious threat to human health worldwide. Therefore, the development of multifunctional biomaterials that possess antibacterial properties and can resist infection is a continual goal for biomedical applications. Silk fibroin (SF), approved by U.S. Food and Drug Administration (FDA) as a biomaterial, is one of the most widely studied natural polymers for biomedical applications due to its unique mechanical properties, biocompatibility, tunable biodegradation, and versatile material formats. In the last decade, many methods have been employed for the development of antibacterial SF-based biomaterials (SFBs) such as physical loading or chemical functionalization of SFBs with different antibacterial agents and bio-inspired surface modifications. In this review, we first describe the current understanding of the composition and structure-properties relationship of SF as a leading-edge biomaterial. Then we demonstrate the different antibacterial agents and methods implemented for the development of bactericidal SFBs, their mechanisms of action, and different applications. We briefly address their fabrication methods, advantages, and limitations, and finally discuss the emerging technologies and future trends in this research area.

The Use of Fibers in Bone Tissue Engineering

Bone tissue engineering aims to restore and maintain the function of bone by means of biomaterial-based scaffolds. This review specifically focuses on the use of fibers in biomaterials used for bone tissue engineering as suitable environment for bone tissue repair and regeneration. We present a bioinspired rationale behind the use of fibers in bone tissue engineering and provide an overview of the most common fiber fabrication methods, including solution, melt, and microfluidic spinning. Subsequently, we provide a brief overview of the composition of fibers that are used in bone tissue engineering, including fibers composed of (i) natural polymers (e.g., cellulose, collagen, gelatin, alginate, chitosan, and silk, (ii) synthetic polymers (e.g., polylactic acid [PLA], polycaprolactone, polyglycolic acid [PGA], polyethylene glycol, and polymer blends of PLA and PGA), (iii) ceramic fibers (e.g., aluminium oxide, titanium oxide, and zinc oxide), (iv) metallic fibers (e.g., titanium and its alloys, copper and magnesium), and (v) composite fibers. In addition, we review the most relevant fiber modification strategies that are used to enhance the (bio)functionality of these fibers. Finally, we provide an overview of the applicability of fibers in biomaterials for bone tissue engineering, with a specific focus on mechanical, pharmaceutical, and biological properties of fiber-functionalized biomaterials for bone tissue engineering. Impact statement Natural bone is a complex composite material composed of an extracellular matrix of mineralized fibers containing living cells and bioactive molecules. Consequently, the use of fibers in biomaterial-based scaffolds offers a wide variety of opportunities to replicate the functional performance of bone. This review provides an overview of the use of fibers in biomaterials for bone tissue engineering, thereby contributing to the design of novel fiber-functionalized bone-substituting biomaterials of improved functionality regarding their mechanical, pharmaceutical, and biological properties.

Enwrapping Polydopamine on Doxorubicin-Loaded Lamellar Hydroxyapatite/Poly(lactic-co-glycolic acid) Composite Fibers for Inhibiting Bone Tumor Recurrence and Enhancing Bone Regeneration

Simultaneous prevention of bone tumor recurrence and promotion of repairing bone defects resulting from tumorectomy remain a challenge. Herein, we report a polydopamine (PDA)-coated composite scaffold consisting of doxorubicin (DOX)-loaded lamellar hydroxyapatite (LHAp) and poly(lactic-co-glycolic acid) (PLGA) in an attempt to reach dual functions of tumor inhibition and bone repair. The DOX was intercalated into LHAp, and the DOX-loaded LHAp was incorporated into PLGA solution to prepare a DOX-intercalated LHAp/PLGA (labeled as DH/PLGA) scaffold that was coated with PDA to obtain a PDA@DH/PLGA scaffold. The morphology, structure, wettability, mechanical properties, drug release, biocompatibility, and in vitro and in vivo bioactivities of the PDA@DH/PLGA scaffold were evaluated. It is found that PDA coating not only improves hydrophilicity and mechanical properties, but also leads to more sustainable drug release. More importantly, the PDA@DH/PLGA scaffold shows significantly inhibited growth of tumor cells initially and subsequent improved adhesion and proliferation of osteoblasts. In addition, the PDA coating improves the bioactivity of the DH/PLGA scaffold as suggested by the in vitro biomineralization. Further in vivo study demonstrates the improved bone growth around PDA@DH/PLGA over DH/PLGA after 20 days of drug release. The dual functional PDA@DH/PLGA scaffold shows great promise in the treatment of bone tumor.

Application of nanoparticles in bone tissue engineering; a review on the molecular mechanisms driving osteogenesis

The introduction of nanoparticles into bone tissue engineering strategies is beneficial to govern cell fate into osteogenesis and the regeneration of large bone defects. The present study explored the role of nanoparticles to advance osteogenesis with a focus on the cellular and molecular pathways involved. Pubmed, Pubmed Central, Embase, Scopus, and Science Direct databases were explored for those published articles relevant to the involvement of nanoparticles in osteogenic cellular pathways. As multifunctional compounds, nanoparticles contribute to scaffold-free and scaffold-based tissue engineering strategies to progress osteogenesis and bone regeneration. They regulate inflammatory responses and osteo/angio/osteoclastic signaling pathways to generate an osteogenic niche. Besides, nanoparticles interact with biomolecules, enhance their half-life and bioavailability. Nanoparticles are promising candidates to promote osteogenesis. However, the interaction of nanoparticles with the biological milieu is somewhat complicated, and more considerations are recommended on the employment of nanoparticles in clinical applications because of NP-induced toxicities.

Polymeric Materials with Antibacterial Activity: A Review

Infections caused by bacteria are one of the main causes of mortality in hospitals all over the world. Bacteria can grow on many different surfaces and when this occurs, and bacteria colonize a surface, biofilms are formed. In this context, one of the main concerns is biofilm formation on medical devices such as urinary catheters, cardiac valves, pacemakers or prothesis. The development of bacteria also occurs on materials used for food packaging, wearable electronics or the textile industry. In all these applications polymeric materials are usually present. Research and development of polymer-based antibacterial materials is crucial to avoid the proliferation of bacteria. In this paper, we present a review about polymeric materials with antibacterial materials. The main strategies to produce materials with antibacterial properties are presented, for instance, the incorporation of inorganic particles, micro or nanostructuration of the surfaces and antifouling strategies are considered. The antibacterial mechanism exerted in each case is discussed. Methods of materials preparation are examined, presenting the main advantages or disadvantages of each one based on their potential uses. Finally, a review of the main characterization techniques and methods used to study polymer based antibacterial materials is carried out, including the use of single force cell spectroscopy, contact angle measurements and surface roughness to evaluate the role of the physicochemical properties and the micro or nanostructure in antibacterial behavior of the materials.

A new Ag-nanostructured hydroxyapatite porous scaffold: Antibacterial effect and cytotoxicity study

We report a new chemical method for the functionalization of Mg-hydroxyapatite (Mg-HA) scaffold with Ag nanoparticles (Ag NPs) integrating in one step both the synthesis of the Ag NPs and their nano-structuring into the HA matrix (Ag-Mg-HA scaffold). This method exploits a green photochemical synthesis and allows the direct growth of Ag NPs on the Mg-HA surface. The surface structure of Ag-Mg-HA scaffold, investigated by scanning electron microscopy, shows no significant changes in the morphology upon Ag NPs incorporation. The presence of Ag was confirmed by EDX analysis. TEM and spectroscopic investigations show Ag NPs spherical shaped with a mean diameter of about 20 nm exhibiting the typical plasmon absorption band with maximum at 420 nm. The antibacterial properties of Ag-Mg-HA scaffolds were tested against two bacterial strains, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The results show excellent antibacterial properties achieving up to 99% and 100% reduction of colonies for both bacteria cultures after 24 h of incubation and 100% of reduction after 48 h of incubation. The cytotoxicity of Ag-Mg-HA was also in deep investigated assessing both cell proliferation and differentiation using hADSCs (human Adipose Derived Stem Cells) and testing data point at 0, 7, 14 and 24 days. The results show cytotoxic effect with cell proliferation decreasing up to 90% at 24 days and osteogenic differentiation inhibition. The observed cytotoxicity can be probable ascribed to the oxidative stress by ROS. Indeed, considering the effectiveness of the nanofunctionalization method and the excellent antibacterial properties showed by the Ag-Mg-HA scaffold, future works will be devoted to create nanofunctionalized scaffold satisfying both antimicrobial and osteo-regenerative properties.

Mechanical properties and toughening mechanisms of natural silkworm silks and their composites

There is an emerging interest in natural silkworm silks as alternative reinforcement for engineering composites. Here, we summarize the research on two common silkworm silks and silk fibre reinforced plastics (SFRPs) from the authors over the past few years in the context of related research. Silk fibres from silkworms display good strength and toughness under ambient and cryogenic conditions owing to their elastic-plastic deformation mechanism. In particular, the wild Antheraea pernyi (A. pernyi) silk also displays micro- and nano-fibrillation as an important mechanism for toughness and impact resistance. For SFRP composites, we found: (i) it is critical to achieve silk fibre volume fraction to above 50% for an optimal reinforcement and toughening effect; (ii) the tougher A. pernyi silks present a better reinforcement and toughening agent than B. mori silks; (iii) impact and toughness properties are advantageous properties of SFRPs; (iv) hybridization of natural silk with other fibres can further improve the mechanical performance and economics of SFRPs for engineering applications; and (v) the lightweight structure designs can improve the service efficiency of SFRPs for energy absorption. The understanding on the comprehensive mechanical properties and the toughening mechanisms of silks and silk fibre-reinforced polymer composites (SFRPs) could provide key insights into material design and applications.