Substrate-anchored and degradation-sensitive anti-inflammatory coatings for implant materials

Wound Healing Promotion via Release of Therapeutic Metallic Ions from Phosphate Glass Fibers: An In Vitro and Ex Vivo Study

Biomaterials capable of promoting wound healing and preventing infections remain in great demand to address the global unmet need for the treatment of chronic wounds. Phosphate-based glasses (PG) have shown potential as bioresorbable materials capable of inducing tissue regeneration, while being replaced by regenerated tissue and releasing therapeutic species. In this work, phosphate-glass-based fibers (PGF) in the system P2O5-CaO-Na2O added with 1, 2, 4, 6, and 10 mol % of the therapeutic metallic ions (TMI) Ag+, Zn2+, and Fe3+ were manufactured via electrospinning of coacervate gels. Coacervation is a sustainable, cost-effective, water-based method to produce PG. All TMI are effective in promoting wound closure (re-epithelialization) in living human skin ex vivo, where the best-performing system is PGF containing Ag+. In particular, PGF with ≥4 mol % of Ag+ is capable of promoting 84% wound closure over 48 h. These results are confirmed by scratch test migration assays, with the PGF-Ag systems containing ≥6 mol % of Ag+, demonstrating significant wound closure enhancement (up to 72%) after 24 h. The PGF-Ag systems are also the most effective in terms of antibacterial activity against both the Gram-positive Staphylococcus aureus and the Gram-negative Escherichia coli. PGF doped with Zn2+ shows antibacterial activity only against S. aureus in the systems containing Zn2+ ≥ 10 mol %. In addition, PGF doped with Fe3+ rapidly accelerates ex vivo healing in patient chronic wound skin (>30% in 48 h), demonstrating the utility of doped PGF as a potential therapeutic strategy to treat chronic wounds.

Implantable Neural Microelectrodes: How to Reduce Immune Response

Implantable neural microelectrodes exhibit the great ability to accurately capture the electrophysiological signals from individual neurons with exceptional submillisecond precision, holding tremendous potential for advancing brain science research, as well as offering promising avenues for neurological disease therapy. Although significant advancements have been made in the channel and density of implantable neural microelectrodes, challenges persist in extending the stable recording duration of these microelectrodes. The enduring stability of implanted electrode signals is primarily influenced by the chronic immune response triggered by the slight movement of the electrode within the neural tissue. The intensity of this immune response increases with a higher bending stiffness of the electrode. This Review thoroughly analyzes the sequential reactions evoked by implanted electrodes in the brain and highlights strategies aimed at mitigating chronic immune responses. Minimizing immune response mainly includes designing the microelectrode structure, selecting flexible materials, surface modification, and controlling drug release. The purpose of this paper is to provide valuable references and ideas for reducing the immune response of implantable neural microelectrodes and stimulate their further exploration in the field of brain science.

Recent Development of Neural Microelectrodes with Dual-Mode Detection

Neurons communicate through complex chemical and electrophysiological signal patterns to develop a tight information network. A physiological or pathological event cannot be explained by signal communication mode. Therefore, dual-mode electrodes can simultaneously monitor the chemical and electrophysiological signals in the brain. They have been invented as an essential tool for brain science research and brain-computer interface (BCI) to obtain more important information and capture the characteristics of the neural network. Electrochemical sensors are the most popular methods for monitoring neurochemical levels in vivo. They are combined with neural microelectrodes to record neural electrical activity. They simultaneously detect the neurochemical and electrical activity of neurons in vivo using high spatial and temporal resolutions. This paper systematically reviews the latest development of neural microelectrodes depending on electrode materials for simultaneous in vivo electrochemical sensing and electrophysiological signal recording. This includes carbon-based microelectrodes, silicon-based microelectrode arrays (MEAs), and ceramic-based MEAs, focusing on the latest progress since 2018. In addition, the structure and interface design of various types of neural microelectrodes have been comprehensively described and compared. This could be the key to simultaneously detecting electrochemical and electrophysiological signals.

A collagen/PLA hybrid scaffold supports tendon-derived cell growth for tendon repair and regeneration

A rotator cuff tendon tear is a common shoulder injury with a relatively high rate of recurrence after surgical repair. In order to reinforce the repair and reduce the risk of clinical complications, a patch scaffold is typically sutured over the tendon tear to provide post-surgical mechanical support. However, despite considerable research effort in this area, a patch scaffold that provides both superior initial mechanical properties and supports cell proliferation at the same time has not yet been achieved. In this study, we engineered a collagen/poly(lactic acid) (COL/PLA) hybrid yarn to leverage mechanical strength of PLA yarn and the bioactivity of collagen. The COL/PLA yarns were used to fabricate a tissue engineering scaffold using textile weaving technology. This hybrid scaffold had a tensile strength of 354.0 ± 36.0 N under dry conditions and 267.2 ± 15.9 N under wet conditions, which was satisfactory to maintain normal tendon function. By introducing COL yarns into the hybrid scaffold, the proliferation of tendon-derived cells was significantly improved on the scaffold. Cell coverage after 28-days of in vitro cell culture was noticeably higher on the COL yarns compared to the PLA yarns as a result of a larger number of cells and more spread cell morphology on collagen. Cells spread in multiple directions on COL yarns, which resembled a more natural cell attachment on extracellular matrix. On the contrary, the cells attached to the PLA filaments presented an elongated morphology along the fiber's axial direction. Combining the mechanical robustness of PLA and the biological activity of collagen, the woven COL/PLA hybrid scaffold has shown its potential to be a promising candidate for tendon repair applications.

Heterogenous hydrogel mimicking the osteochondral ECM applied to tissue regeneration

Inspired by the intricate extracellular matrix (ECM) of natural cartilage and subchondral bone, a heterogenous bilayer hydrogel scaffold is fabricated. Gelatin methacrylate (GelMA) and acryloyl glucosamine (AGA) serve as the main components in the upper layer, mimicking the chondral ECM. Meanwhile, vinylphosphonic acid (VPA) as a non-collagen protein analogue is incorporated into the bottom layer to induce the in situ biomineralization of calcium phosphate. The two heterogenous layers are effectively sutured together by the inter-diffusion between the upper and bottom layer hydrogels, together with chelation between the calcium ions and alginate added to separate layers. The interfacial bonding between the two different layers was thoroughly investigated via rheological measurements. The incorporation of AGA promotes chondrocytes to produce collagen type II and glycosaminoglycans and upregulates the expression of chondrogenesis-related genes. In addition, the minerals induced by VPA facilitate the osteogenesis of bone marrow mesenchymal stem cells (BMSCs). In vivo evaluation confirms the biocompatibility of the scaffold with minor inflammation and confirms the best repair ability of the bilayer hydrogel. This cell-free, cost-effective and efficient hydrogel shows great potential for osteochondral repair and inspires the design of other tissue-engineering scaffolds.

Thermoplastic polyurethane with controllable degradation and critical anti-fouling properties

Bioresorbable polymers, including polyesters and polypeptides, are being widely used in the medical field. However, these materials still suffer from some long-standing challenges, such as material-induced blood coagulation, foreign body response, non-adjustable degradation rate, and absence of elastic properties. In this work, we explored a new approach to address these challenges by incorporating critical anti-fouling, improved mechanical and controllable degradation properties into the existing bioresorbable polymers. We synthesized a set of zwitterionic thermoplastic polyurethanes, which consist of degradable polycaprolactone diols as soft segments and faster hydrolyzable carboxybetaine (CB) diols as chain extenders. Differential scanning calorimetry and temperature sweep rheology revealed thermal transition performance and thermoplastic behavior of the polymers. The calorimetric study observed that CB-based chain extender played a critical role in the crystallization process by affecting the structure and crystallization temperature. Cell attachment study demonstrated that the degradable zwitterionic polyurethane surfaces highly resist cell attachment even after being submerged in 100% fetal bovine serum for two weeks. The gold standard PEG-based degradable polyurethane showed the initial resistance to the cell attachment for one day and then failed after three days. This work clearly shows that the adaption of existing materials with slightly better anti-fouling properties is unlikely to solve these long-lasting challenges. Our design approach and the material platform with critical anti-fouling properties and other desired tunable properties show the potential to address these complications associated with existing bioresorbable polymers. This method can be adapted to design customized bioresorbable polymers for a wide range of applications, including implantable biomedical devices and drug delivery.

Strategies for Enhancing Polyester-Based Materials for Bone Fixation Applications

Polyester-based materials are established options, regarding the manufacturing of bone fixation devices and devices in routine clinical use. This paper reviews the approaches researchers have taken to develop these materials to improve their mechanical and biological performances. Polymer blending, copolymerisation, and the use of particulates and fibre bioceramic materials to make composite materials and surface modifications have all been studied. Polymer blending, copolymerisation, and particulate composite approaches have been adopted commercially, with the primary focus on influencing the in vivo degradation rate. There are emerging opportunities in novel polymer blends and nanoscale particulate systems, to tune bulk properties, and, in terms of surface functionalisation, to optimise the initial interaction of devices with the implanted environment, offering the potential to improve the clinical performances of fracture fixation devices.

Recent Advances in Antiinflammatory Material Design

Implants and prostheses are widely used to replace damaged tissues or to treat various diseases. However, besides the risk of bacterial or fungal infection, an inflammatory response usually occurs. Here, recent progress in the field of anti-inflammatory biomaterials is described. Different materials and approaches are used to decrease the inflammatory response, including hydrogels, nanoparticles, implant surface coating by polymers, and a variety of systems for anti-inflammatory drug delivery. Complex multifunctional systems dealing with inflammation, microbial infection, bone regeneration, or angiogenesis are also described. New promising stimuli-responsive systems, such as pH- and temperature-responsive materials, are also being developed that would enable an "intelligent" antiinflammatory response when the inflammation occurs. Together, different approaches hold promise for creation of novel multifunctional smart materials allowing better implant integration and tissue regeneration.

An osteoconductive PLGA scaffold with bioactive β-TCP and anti-inflammatory Mg(OH)2 to improve in vivo bone regeneration

Poly(lactic-co-glycolic acid) (PLGA) has been widely used as a biomaterial for pharmaceutical and medical applications. However, the decomposition products of PLGA are known to acidify the surrounding tissue of the implanted site, causing an inflammatory response. Previously, we developed PLGA/inorganic nanocomposites and optimized the amounts of inorganic compounds, β-tricalcium phosphate (β-TCP) and magnesium hydroxide [Mg(OH)2], in terms of osteogenesis of normal human osteoblasts and anti-inflammatory responses of preosteoclastic cells in vitro. In this study, the potential of the optimized PLGA/β-TCP/Mg(OH)2 nanocomposite (TCP/MH) to promote bone repair through osteoinductive, osteoconductive, and anti-inflammatory abilities was assessed using a bone defect in a rat humeral defect model. PLGA nanocomposites with or without inorganic compounds, PLGA, β-TCP, MH, and TCP/MH were prepared through one-step bulk modification using a twin-screw extruder. The resulting TCP/MH nanocomposite successfully enhanced the bone regeneration rate for allowing complete bone defect healing with significantly suppressed inflammatory responses. Taken together, the organic and inorganic bioactive nanocomposite developed in this study, TCP/MH, is a promising material in orthopedic implantation.

A femtosecond Bessel laser for preparing a nontoxic slippery liquid-infused porous surface (SLIPS) for improving the hemocompatibility of NiTi alloys

A nontoxic slippery liquid-infused porous surface prepared by femtosecond Bessel laser ablation to improve the hemocompatibility of NiTi alloys.

Adipose-Derived Stem Cells in Bone Tissue Engineering: Useful Tools with New Applications

Adipose stem cells (ASCs) are a crucial element in bone tissue engineering (BTE). They are easy to harvest and isolate, and they are available in significative quantities, thus offering a feasible and valid alternative to other sources of mesenchymal stem cells (MSCs), like bone marrow. Together with an advantageous proliferative and differentiative profile, they also offer a high paracrine activity through the secretion of several bioactive molecules (such as growth factors and miRNAs) via a sustained exosomal release which can exert efficient conditioning on the surrounding microenvironment. BTE relies on three key elements: (1) scaffold, (2) osteoprogenitor cells, and (3) bioactive factors. These elements have been thoroughly investigated over the years. The use of ASCs has offered significative new advancements in the efficacy of each of these elements. Notably, the phenotypic study of ASCs allowed discovering cell subpopulations, which have enhanced osteogenic and vasculogenic capacity. ASCs favored a better vascularization and integration of the scaffolds, while improvements in scaffolds' materials and design tried to exploit the osteogenic features of ASCs, thus reducing the need for external bioactive factors. At the same time, ASCs proved to be an incredible source of bioactive, proosteogenic factors that are released through their abundant exosome secretion. ASC exosomes can exert significant paracrine effects in the surroundings, even in the absence of the primary cells. These paracrine signals recruit progenitor cells from the host tissues and enhance regeneration. In this review, we will focus on the recent discoveries which have involved the use of ASCs in BTE. In particular, we are going to analyze the different ASCs' subpopulations, the interaction between ASCs and scaffolds, and the bioactive factors which are secreted by ASCs or can induce their osteogenic commitment. All these advancements are ultimately intended for a faster translational and clinical application of BTE.

A Bioinspired Scaffold with Anti-Inflammatory Magnesium Hydroxide and Decellularized Extracellular Matrix for Renal Tissue Regeneration

Kidney diseases are a worldwide public health issue. Renal tissue regeneration using functional scaffolds with biomaterials has attracted a great deal of attention due to limited donor organ availability. Here, we developed a bioinspired scaffold that can efficiently induce renal tissue regeneration. The bioinspired scaffold was designed with poly(lactide-co-glycolide) (PLGA), magnesium hydroxide (Mg(OH)2), and decellularized renal extracellular matrix (ECM). The Mg(OH)2 inhibited materials-induced inflammatory reactions by neutralizing the acidic microenvironment formed by degradation products of PLGA, and the acellular ECM helped restore the biological function of kidney tissues. When the PLGA/ECM/Mg(OH)2 scaffold was implanted in a partially nephrectomized mouse model, it led to the regeneration of renal glomerular tissue with a low inflammatory response. Finally, the PLGA/ECM/Mg(OH)2 scaffold was able to restore renal function more effectively than the control groups. These results suggest that the bioinspired scaffold can be used as an advanced scaffold platform for renal disease treatment.

Anti-inflammatory drug-eluting implant model system to prevent wear particle-induced periprosthetic osteolysis

BACKGROUND

Aseptic loosening, as a consequence of an extended inflammatory reaction induced by wear particles, has been classified as one of the most common complications of total joint replacement (TJR). Despite its high incidence, no therapeutical approach has yet been found to prevent aseptic loosening, leaving revision as only effective treatment. The local delivery of anti-inflammatory drugs to modulate wear-induced inflammation has been regarded as a potential therapeutical approach to prevent aseptic-loosening.

METHODS

In this context, we developed and characterized anti-inflammatory drug-eluting TiO2 surfaces, using nanoparticles as a model for larger surfaces. The eluting surfaces were obtained by conjugating dexamethasone to carboxyl-functionalized TiO2 particles, obtained by using either silane agents with amino or mercapto moieties.

RESULTS

Zeta potential measurements, thermogravimetric analysis (TGA) and drug release results suggest that dexamethasone was successfully loaded onto the TiO2 particles. Release was pH dependent and greater amounts of drug were observed from amino route functionalized surfaces. The model-system was then tested for its cytotoxic and anti-inflammatory properties in LPS-stimulated macrophages. Dexamethasone released from amino route functionalized surfaces TiO2 particles was able to decrease LPS-induced nitric oxide (NO) and TNF-a production similarly to pure DEX at the same concentration; DEX released from mercapto route functionalized surfaces was at a too low concentration to be effective.

CONCLUSION

Dexamethasone released from amino functionalized titanium can offer the possibility of preventing asepting loosening of joint replacement devices.

One-step phosphorylated poly(amide-amine) dendrimer loaded with apigenin for simultaneous remineralization and antibacterial of dentine

Dental caries, starting from demineralization of enamel and dentine, is closely related with acid-producing bacteria in oral cavity, for example, Streptococcus mutans. Remineralization is an efficient way to prevent the disease progression and facilitate the therapy of incipient caries. Therefore, for the purpose of effective dentine repair, remineralization and antibacterial should be combined simultaneously. However, most of the literatures only focus on one single aspect, while combing remineralization and antibacteria for dentine repair in one system is rarely reported. Here in this work, phosphoryl-terminated poly(amide-amine) dendrimers were loaded with apigenin, a water-nonsoluble drug antibacterial agains Streptococcus mutans. The apigenin-loaded dendrimers bind strongly with dentine, which further induce dentine tubules occlusion through mineralization in artificial saliva, and the release of apigenin can prevent further erosion of dentine by bacteria. Meanwhile, the phosphorylated dendrimers are easily prepared by one-step modification of poly(amide-amine) and exhibit good cytocompatibility. This strategy developed here can provide reference for the design of effective anti-caries materials.

Endogenous pH-responsive nanoparticles with programmable size changes for targeted tumor therapy and imaging applications

Nanotechnology-based antitumor drug delivery systems, known as nanocarriers, have demonstrated their efficacy in recent years. Typically, the size of the nanocarriers is around 100 nm. It is imperative to achieve an optimum size of these nanocarriers which must be designed uniquely for each type of delivery process. For pH-responsive nanocarriers with programmable size, changes in pH (~6.5 for tumor tissue, ~5.5 for endosomes, and ~5.0 for lysosomes) may serve as an endogenous stimulus improving the safety and therapeutic efficacy of antitumor drugs. This review focuses on current advanced pH-responsive nanocarriers with programmable size changes for anticancer drug delivery. In particular, pH-responsive mechanisms for nanocarrier retention at tumor sites, size reduction for penetrating into tumor parenchyma, escaping from endo/lysosomes, and swelling or disassembly for drug release will be highlighted. Additional trends and challenges of employing these nanocarriers in future clinical applications are also addressed.

Bio-inspired peptide decorated dendrimers for a robust antibacterial coating on hydroxyapatite

SSP-PAMAM-NH₂ inspired by the salivary statherin protein can tightly adsorb on the HA surface to achieve long-term antibacterial activity.

Liquid-Infused Poly(styrene-b-isobutylene-b-styrene) Microfiber Coating Prevents Bacterial Attachment and Thrombosis

Infection and thrombosis associated with medical implants cause significant morbidity and mortality worldwide. As we know, current technologies to prevent infection and thrombosis may cause severe side effects. To overcome these complications without using antimicrobial and anticoagulant drugs, we attempt to prepare a liquid-infused poly(styrene-b-isobutylene-b-styrene) (SIBS) microfiber coating, which can be directly coated onto medical devices. Notably, the SIBS microfiber was fabricated through solution blow spinning. Compared to electrospinning, the solution blow spinning method is faster and less expensive, and it is easy to spray fibers onto different targets. The lubricating liquids then wick into and strongly adhere the microfiber coating. These slippery coatings can effectively suppress blood cell adhesion, reduce hemolysis, and inhibit blood coagulation in vitro. In addition, Pseudomonas aeruginosa (P. aeruginosa) on the lubricant infused coatings slides readily, and no visible residue is left after tilting. We furthermore confirm that the lubricants have no effects on bacterial growth. The slippery coatings are also not cytotoxic to L929 cells. This liquid-infused SIBS microfiber coating could reduce the infection and thrombosis of medical devices, thus benefiting human health.

Layer-by-layer assembled PMMA-SH/CdSe–Au nanocomposite thin films and the optical limiting property

We demonstrate layer-by-layer assembly of PMMA-SH/CdSe–Au nanocomposite thin films with good transparency, thermal stability and optical liming property, which provide potential uses in laser protective devices.

Facile Fabrication of Lubricant-Infused Wrinkling Surface for Preventing Thrombus Formation and Infection

Despite the advanced modern biotechniques, thrombosis and bacterial infection of biomedical devices remain common complications that are associated with morbidity and mortality. Most antifouling surfaces are in solid form and cannot simultaneously fulfill the requirements for antithrombosis and antibacterial efficacy. In this work, we present a facile strategy to fabricate a slippery surface. This surface is created by combining photografting polymerization with osmotically driven wrinkling that can generate a coarse morphology, and followed by infusing with fluorocarbon liquid. The lubricant-infused wrinkling slippery surface can greatly prevent protein attachment, reduce platelet adhesion, and suppress thrombus formation in vitro. Furthermore, E. coli and S. aureus attachment on the slippery surfaces is reduced by ∼98.8% and ∼96.9% after 24 h incubation, relative to poly(styrene-b-isobutylene-b-styrene) (SIBS) references. This slippery surface is biocompatible and has no toxicity to L929 cells. This surface-coating strategy that effectively reduces thrombosis and the incidence of infection will greatly decrease healthcare costs.