Medical textiles in orthopedics: An overview

Toward the Improvement of the Mechanical and Tribological Properties of Braided Ligament for ACL Reconstruction: A "Carrot and Stick" Strategy

Bone tunnel enlargement has been troubling the clinical adoption of braided artificial ligaments for decades, to which mechanical and tribological performance promotion shall be an effective and promising approach. Herein, a "carrot and stick" strategy has been introduced with two types of polyethylene terephthalate (PET) fibers to fabricate hybrid textures, which is expected to advance fatigue and tribological performance without yielding essential mechanical strength and biocompatibility. Owing to advancements in such a "carrot and stick" strategy, the obtained grafts present three promising properties: i) enhancement of mechanical strength; ii) coefficient of friction (COF) reduction of 25% at the greatest extent, thus lowering the risk of bone tunnel enlargement; iii) final displacement shrinkage of graft length after cyclic loadings, favored in the clinic for isometric reconstruction. The results obtained in this study show that the "carrot and stick" strategy can be a creative and convenient method to optimize the service life, saving the complication rate of artificial ligaments for clinical applications.

Fabrication and Characterization of a Bioscaffold Using Hydroxyapatite and Unsaturated Polyester Resin

Outstanding biodegradability and biocompatibility are attributes associated with particular polyester substances that make this group useful in specific biomedical fields. To assess the potential as a biomaterial, a novel composite consisting of hydroxyapatite (HAp) and unsaturated polyester resin (UPR) was developed in this work. Using a hand-lay-up technique, various percentages (50, 40, 30, 20, and 10%) of HAp were reinforced into the UPR matrix to fabricate composite materials out of glass sheets. Prior to processing of the composite samples, hydroxyapatite was chemically synthesized in a wet chemical manner. Using a universal testing machine (UTM), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA), the fabricated samples were characterized. The crystallographic parameters of synthesized hydroxyapatite (HAp) were also estimated through a range of formulas. The optimal amount for hydroxyapatite was 40% according to the findings of the tensile strength (TS), tensile modulus (TM), percentage of elongation at break (EB), bending strength (BS), and bending modulus (BM). Improvements in TS, TM, BS, and BM for the ideal combination were 39.39, 9.21, 912.05, and 259.96%, in each case, over the controlled one. Thermogravimetric analysis (TGA) has been implemented to determine the degradation temperature of the fabricated composites up to 600 °C.

Review: Application of chitosan and its derivatives in medical materials

Chitin is a natural polymeric polysaccharide extracted from marine crustaceans, and chitosan is obtained by removing part of the acetyl group (usually more than 60 %) in chitin's structure. Chitosan has attracted wide attention from researchers worldwide due to its good biodegradability, biocompatibility, hypoallergenic and biological activities (antibacterial, immune and antitumor activities). However, research has shown that chitosan does not melt or dissolve in water, alkaline solutions and general organic solvents, which greatly limits its application range. Therefore, researchers have carried out extensive and in-depth chemical modification of chitosan and prepared a variety of chitosan derivatives, which have expanded the application field of chitosan. Among them, the most extensive research has been conducted in the pharmaceutical field. This paper summarizes the application of chitosan and chitosan derivatives in medical materials over the past five years.

Surface modifications to promote the osteoconductivity of ultra-high-molecular-weight-polyethylene fabrics for a novel biomimetic artificial disc prosthesis: An in vitro study

A novel biomimetic artificial intervertebral disc (bioAID) for the cervical spine was developed, containing a hydrogel core representing the nucleus pulposus, an UHMWPE fiber jacket as annulus fibrosis, and titanium endplates with pins for mechanical fixation. Osseointegration of the UHMWPE fibers to adjacent bone structures is required to achieve proper biomimetic behavior and to provide long-term stability. Therefore, the aim of this study was to assess the osteoconductivity of several surface modifications of UHMWPE fabrics, 2D weft-knitted, using non-treated UHMWPE fibers (N), plasma treated UHMWPE fibers (PT), 10% hydroxy apatite (HA) loaded UHMWPE fibers (10%HA), plasma treated 10%HA UHMWPE fibers (PT-10%HA), 15%HA loaded UHMWPE fibers (15%HA) and plasma treated 15%HA UHMWPE fibers (PT-15%HA). Scanning electron microscopy (SEM) was used for surface characterization. Biological effects were assessed by evaluating initial cell attachment (SEM, DNA content), metabolic activity (PrestoBlue assay), proliferation, differentiation (alkaline phosphatase activity) and mineralization (energy dispersive x-ray, EDX analysis) using human bone marrow stromal cells. Plasma treated samples showed increased initial cell attachment, indicating the importance of hydrophilicity for cell attachment. However, incorporation only of HA or plasma treatment alone was not sufficient to result in upregulated alkaline phosphatase activity (ALP) activity. Combining HA loaded fibers with plasma treatment showed a combined effect, leading to increased cell attachment and upregulated ALP activity. Based on these results, combination of HA loaded UHMWPE fibers and plasma treatment provided the most promising fabric surface for facilitating bone ingrowth.

State-of-the-art review of advanced electrospun nanofiber yarn-based textiles for biomedical applications

The pandemic of the coronavirus disease 2019 (COVID-19) has made biotextiles, including face masks and protective clothing, quite familiar in our daily lives. Biotextiles are one broad category of textile products that are beyond our imagination. Currently, biotextiles have been routinely utilized in various biomedical fields, like daily protection, wound healing, tissue regeneration, drug delivery, and sensing, to improve the health and medical conditions of individuals. However, these biotextiles are commonly manufactured with fibers with diameters on the micrometer scale (> 10 μm). Recently, nanofibrous materials have aroused extensive attention in the fields of fiber science and textile engineering because the fibers with nanoscale diameters exhibited obviously superior performances, such as size and surface/interface effects as well as optical, electrical, mechanical, and biological properties, compared to microfibers. A combination of innovative electrospinning techniques and traditional textile-forming strategies opens a new window for the generation of nanofibrous biotextiles to renew and update traditional microfibrous biotextiles. In the last two decades, the conventional electrospinning device has been widely modified to generate nanofiber yarns (NYs) with the fiber diameters less than 1000 nm. The electrospun NYs can be further employed as the primary processing unit for manufacturing a new generation of nano-textiles using various textile-forming strategies. In this review, starting from the basic information of conventional electrospinning techniques, we summarize the innovative electrospinning strategies for NY fabrication and critically discuss their advantages and limitations. This review further covers the progress in the construction of electrospun NY-based nanotextiles and their recent applications in biomedical fields, mainly including surgical sutures, various scaffolds and implants for tissue engineering, smart wearable bioelectronics, and their current and potential applications in the COVID-19 pandemic. At the end, this review highlights and identifies the future needs and opportunities of electrospun NYs and NY-based nanotextiles for clinical use.

Optimization of the Mechanical Properties and the Cytocompatibility for the PMMA Nanocomposites Reinforced with the Hydroxyapatite Nanofibers and the Magnesium Phosphate Nanosheets

Commercial poly methyl methacrylate (PMMA)-based cement is currently used in the field of orthopedics. However, it suffers from lack of bioactivity, mechanical weakness, and monomer toxicity. In this study, a PMMA-based cement nanocomposite reinforced with hydroxyapatite (HA) nanofibers and two-dimensional (2D) magnesium phosphate MgP nanosheets was synthesized and optimized in terms of mechanical property and cytocompatibility. The HA nanofibers and the MgP nanosheets were synthesized using a hydrothermal homogeneous precipitation method and tuning the crystallization of the sodium-magnesium-phosphate ternary system, respectively. Compressive strength and MTT assay tests were conducted to evaluate the mechanical property and the cytocompatibility of the PMMA-HA-MgP nanocomposites prepared at different ratios of HA and MgP. To optimize the developed nanocomposites, the standard response surface methodology (RSM) design known as the central composite design (CCD) was employed. Two regression models generated by CCD were analyzed and compared with the experimental results, and good agreement was observed. Statistical analysis revealed the significance of both factors, namely, the HA nanofibers and the MgP nanosheets, in improving the compressive strength and cell viability of the PMMA-MgP-HA nanocomposite. Finally, it was demonstrated that the HA nanofibers of 7.5% wt and the MgP nanosheets of 6.12% wt result in the PMMA-HA-MgP nanocomposite with the optimum compressive strength and cell viability.

Triboelectric Nanogenerators for Self-Powered Wound Healing

Wound healing, one of the most complex processes in the human body, involves the spatial and temporal synchronization of a variety of cell types with distinct roles. Slow or nonhealing skin wounds have potentially life-threatening consequences, ranging from infection to scar, clot, and hemorrhage. Recently, the advent of triboelectric nanogenerators (TENGs) has brought about a plethora of self-powered wound healing opportunities, owing to their pertinent features, including wide range choices of constitutive biocompatible materials, simple fabrication, portable size, high output power, and low cost. Herein, a comprehensive review of TENGs as an emerging biotechnology for wound healing applications is presented and covered from three unique aspects: electrical stimulation, antibacterial activity, and drug delivery. To provide a broader context of TENGs applicable to wound healing applications, state-of-the-art designs are presented and discussed in each section. Although some challenges remain, TENGs are proving to be a promising platform for human-centric therapeutics in the era of Internet of Things. Consequently, TENGs for wound healing are expected to provide a new solution in wound management and play an essential role in the future of point-of-care interventions.

Combining electrospinning with hot drawing process to fabricate high performance poly (L-lactic acid) nanofiber yarns for advanced nanostructured bio-textiles

Fiber constructed yarns are the elementary building blocks for the generation of implantable biotextiles, and there are always needs for designing and developing new types of yarns to improve the properties of biotextile implants. In the present study, we aim to develop novel nanofiber yarns (NYs) by combining nanostructure that more closely mimic the extracellular matrix fibrils of native tissues with biodegradability, strong mechanical properties and great textile processibility. A novel electrospinning system which integrates yarn formation with hot drawing process was developed to fabricate poly(L-lactic acid) (PLLA) NYs. Compared to the PLLA NYs without hot drawing, the thermally drawn PLLA NYs presented superbly-orientated fibrous structure and notably enhanced crystallinity. Importantly, they possessed admirable mechanical performances, which matched and even exceeded the commercial PLLA microfiber yarns (MYs). The thermally drawn PLLA NYs were also demonstrated to notably promote the adhesion, alignment, proliferation, and tenogenic differentiation of human adipose derived mesenchymal stem cells (hADMSCs) compared to the PLLA NYs without hot drawing. The thermally drawn PLLA NYs were further processed into various nanofibrous tissue scaffolds with defined structures and adjustable mechanical and biological properties using textile braiding and weaving technologies, demonstrating the feasibility and versatility of thermally drawn PLLA NYs for textile-forming utilization. The hADMSCs cultured on PLLA NY-based textiles presented enhanced attachment and proliferation capacities than those cultured on PLLA MY-based textiles. This work presents a facile technique to manufacture high performance PLLA NYs, which opens up opportunities to generate advanced nanostructured biotextiles for surgical implant applications.

Analysis of Surface Properties of Ag and Ti Ion-Treated Medical Textiles by Metal Vapor Vacuum Arc Ion Implantation

The study focuses on the effects of Ag (silver) and Ti (titanium) ions on textiles by MEVVA (metal vapor vacuum arc) ion implantation. In order to comprehend this, the research was executed in three parts. In the first part, the antibacterial efficiencies of Ag and TiO2 were investigated in detail since the antibacterial capabilities of Ag and TiO2 are well known. A group of polyester- and cotton-based medical textiles were modified by Ag and TiO2 ions, with doses ranging from 5 × 1015 to 5 × 1016 ion/cm2. To determine the adhesion capabilities of the implanted ions on surfaces, after the first round of antibacterial tests, these medical textiles were washed 30 times, and then antibacterial tests were performed for the second time. The results were also compared with nanoparticle-treated medical textiles. In the second part, the corrosion and friction capabilities of Ag and Ti ion-implanted polyester textiles, with a dose of 5 × 1015 ion/cm2, were investigated. Finally, the UV protection capabilities of Ag and Ti ion-implanted polyester textiles, with a dose of 5 × 1015 ion/cm2, were investigated. The experiments showed that even after 30 washes, the TiO2 ion-implanted polyester textile had almost 85% antibacterial efficiency. In addition, Ti ion implantation reduced the friction coefficiency of a polyester textile by almost 50% when compared with an untreated textile. Finally, the Ag-ion-implanted polyester textile provided a UV protection factor of 30, which is classified as very good protection.

Preclinical evaluation of a mini-arthroplasty implant based on polyetheretherketone and Ti6AI4V for treatment of a focal osteochondral defect in the femoral head of the hip

A mini or partial arthroplasty may offer the advantages of reduced pain, shorter hospital stay, and increased range of motion, which are beneficial for the treatment of large-sized focal osteochondral defects. We aimed to evaluate the in vivo histologic response and function of our nonresorbable, composite structure implant, developed using polyetheretherketone (PEEK) and Ti6AI4V alloy, as a treatment for full-thickness osteochondral defects in the femoral head of the hip using a goat model. The gross and imaging appearance and histologic results were compared to those of a similar size cobalt-chromium-molybdenum (CoCrMo) alloy implant placed in a defect in the femoral head and evaluated up to 12 weeks. The X radiographs showed that there was no evidence of loosening of the implants for both the PEEK-Ti6AI4V and CoCrMo groups. Magnetic resonance imaging results showed no inflammatory signal findings in both PEEK-Ti6AI4V and CoCrMo implants. Macroscopically and histologically, there was lesser cartilage degeneration in the PEEK-Ti6AI4V implant than in the CoCrMo implant. The modified macroscopic articular evaluation score was lower in the PEEK-Ti6AI4V group than in the CoCrMo group (p < 0.05), and the histological score of the periprosthetic and acetabular cartilage was lower in the PEEK-Ti6AI4V group than in the CoCrMo group (P < 0.05). The micro-computed tomography results showed that the uncemented PEEK-Ti6AI4V implant has better osseointegration and higher bone-implant contact than the cemented CoCrMo implant. The peri-implant bone mass was higher in the PEEK-Ti6AI4V implant(p < 0.05). Meanwhile, the optical profile analytical results showed that the surface roughness of the cartilage in the acetabulum was higher in the CoCrMo group. In conclusion, the mini-arthroplasty implant based on PEEK-Ti6AI4V was superior to an identical CoCrMo alloy implant as a treatment for local osteochondral defect in the femoral head, owing to its in vivo cartilage protection and better osseointegration.

Electrospun thymosin Beta-4 loaded PLGA/PLA nanofiber/ microfiber hybrid yarns for tendon tissue engineering application

Microfiber yarns (MY) have been widely employed to construct tendon tissue grafts. However, suboptimal ultrastructure and inappropriate environments for cell interactions limit their clinical application. Herein, we designed a modified electrospinning device to coat poly(lactic-co-glycolic acid) PLGA nanofibers onto polylactic acid (PLA) MY to generate PLGA/PLA hybrid yarns (HY), which had a well-aligned nanofibrous structure, resembling the ultrastructure of native tendon tissues and showed enhanced failure load compared to PLA MY. PLGA/PLA HY significantly improved the growth, proliferation, and tendon-specific gene expressions of human adipose derived mesenchymal stem cells (HADMSC) compared to PLA MY. Moreover, thymosin beta-4 (Tβ4) loaded PLGA/PLA HY presented a sustained drug release manner for 28 days and showed an additive effect on promoting HADMSC migration, proliferation, and tenogenic differentiation. Collectively, the combination of Tβ4 with the nano-topography of PLGA/PLA HY might be an efficient strategy to promote tenogenesis of adult stem cells for tendon tissue engineering.

In-situ green myco-synthesis of silver nanoparticles onto cotton fabrics for broad spectrum antimicrobial activity

In the realm of green synthesis of metals nanoparticles for medical textile application, silver nanoparticles (AgNPs) were biosynthesized in situ cotton fabrics for the first time by using fungi for rendering cotton fabrics antimicrobial activity with abroad range towards different pathogenic organisms. Herein, five different isolated fungi from medicinal plants were identified and optimized their growth media prior examined their ability to reduce Ag⁺ ions to AgNPs in-situ cotton fabrics along with ex-situ method. Synthesis of AgNPs were characterized by making use of instruments e.g. UV-vis spectroscopy, Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared (FTIR). Whereas antimicrobial activities of the resultant cotton fabrics were investigated against Gram positive (S. aureus ATCC29213), Gram negative (E. coli ATCC 25922), Yeast (C. albicans ATCC10321) and, fungi (A. niger NRC 53). Results revealed the successful biosynthesis of AgNPs using different fungus strains whether in-situ cotton fabrics or ex-situ manner. The size of the resultant AgNPs by ex-situ method were varied (5-20 nm). The antimicrobial activity of the in-situ treated cotton samples exhibited different behaviors towards both pathogenic bacteria and fungi. This manner opens up a new way to discover the ability of nanobiotechnology to provide world with substitutional aids mimic to synthetic materials.