Investigation of the antimicrobial activity and biocompatibility of magnesium alloy coated with HA and antimicrobial peptide.

Implant-associated infection is one of the biggest problems in orthopedic surgery. Antimicrobial peptides (AMPs) are well-known components of the innate immunity and less susceptible to the development of pathogen resistance compared to conventional antibiotics. Magnesium alloys as potential biodegradable bone implants have been received much attention in biomaterials field. This study investigated the deposition of calcium phosphate (CaP) coatings and loading of AMPs on the magnesium alloy surface by a biomimetic method. Scanning electron microscope (SEM) results presented that a microporous and plate-like CaP coating was processed on the magnesium alloy surface. X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis showed the main component of coating was hydroxyapatite (HA). Degradation assay in vitro showed that the HA coating deposited onto the magnesium alloy was corroded more slowly than the bare one. The amount of AMP loaded in the HA coating was 11.16±1.99 µg/cm2. The AMP loaded onto HA coatings had slow release for 7 days. The AMP-loaded coating showed antimicrobial activity against Staphylococcus aureus. Its bacterial inhibition rate exceeded 50% after 4 days and the antibacterial effect was sustained for 7 days. The coated magnesium alloys loaded with AMP could improve rat bone marrow mesenchymal stem cells (rBMMSCs) proliferation. Furthermore, it could also promote alkaline phosphatase (ALP) activity of rBMMSCs. Both radiographic evaluation and histopathology analysis demonstrated that implantation of the coated magnesium alloy into the rabbit femoral condyle had promoted bone repair and showed anti-inflammatory effect. The results showed that the AMP loaded onto HA coatings on the magnesium alloy surface could be considered an ideal orthopedic implant against S. aureus infection.

3D light-curing printing to construct versatile octopus-bionic patches.

Reliable, fast and switchable gluing modes are critically important in medical adhesives and intelligent climbing robot applications. The octopus-bionic patch has attracted the attention of many scholars. The suction cup structure of the octopus achieves adhesion through differential pressure, showing strong adhesion in both dry and wet environments. However, the construction of the octopus-bionic patch remains limited in terms of adaptability, personalization and mass production. Herein, a composite hydrogel consisting of gelatin methacryloyl (GelMA), polyethylene glycol diacrylate (PEGDA) and acrylamide (AAM) was developed, and a structure mimicking the octopus sucker was constructed by digital light processing (DLP). The obtained octopus-bionic patch has strong adhesion, good biocompatibility and multi-functionality. Compared with the template method in most studies, the octopus-bionic patch constructed by the DLP printing method has the advantages of customizability and low cost. In addition, the DLP printing method endows the patch surface with an octopus-like groove structure for a better bionic effect.

[Preparation of chitosan/hydroxyapatite membrane and its effect on cell culture].

Compound membranes of chitosan/hydroxyapatite were prepared by blending. The physical performance showed that the air-water contact angles decreased from chitosan's 103 degrees to chitosan/hydroxyapatite's 57 and the water adsorption rate increased slightly. When immersed into culture medium, the materials adsorbed Ca2+, and low crystalline hydroxyapatite deposited on the surface of the membranes. Chitosan/hydroxyapatite compound membranes could enhance the attachment and proliferation of mescenchymal stem cells (MSCs). After 12 days' induction on the materials, the alkaline phosphatase (ALP) activity value of MSCs on the compound membrane was 10.1, being much higher than 1.6 on chitosan membrane (P<0.01). All these results indicate that chitosan does not have very good affinity for MSCs, but the biocompatibility of chitosan can be apparently enhanced after mixing with hydroxyapatite. The compound membrane stimulates MSCs to differentiate into osteoblasts and it may be a good potential material for bone substitution.

Antibacterial poly (ethylene glycol) diacrylate/chitosan hydrogels enhance mechanical adhesiveness and promote skin regeneration.

Various functional active hydrogels have been widely applied in tissue regeneration, especially in fields of wound repair as they are similar to the natural extracellular matrix (ECM) and can maintain moist at the wound site. However, preparing a hydrogel with multifunctional properties including high mechanical properties, excellent biocompatibility and long-term antibacterial activity is still a challenge. Herein, we developed a series of double network hydrogels based on poly (ethylene glycol) diacrylate (PEGDA) and chitosan (CS) or thiolated chitosan (TCS). The hydrogels presented in situ forming properties, good mechanical strength, adhesiveness, antibacterial activity and biocompatibility. The sample with the optimal formula of 15 wt% of PEGDA and 2 wt% of CS or TCS showed excellent mechanical adhesiveness, sustained release of antibacterial peptide and plasmid DNA, and it significantly accelerated in vivo wound healing process in a full-thickness skin defect model by reducing the inflammation and promoting the angiogenesis, meaning that the prepared hydrogels are excellent candidates for wound dressing.

Fabrication, antibacterial activity and cytocompatibility of quaternary ammonium chitooligosaccharide functionalized polyurethane membrane via polydopamine adhesive layer.

In this study, to enhance the antibacterial activity and cytocompatibility of the electrospinning polyurethane (PU) fibrous membrane, quaternary ammonium chitooligosaccharide (G-COS) was immobilized on the fibrous membrane surface via an intermediate layer of polydopamine (PDOPA) to obtain the G-COS functionalized PU (G-C-D-PU), as a control, chitooligosaccharide (COS) functionalized PU fibrous membrane (C-D-PU) was prepared, too. Surface composition, morphology, hydrophilicity and surface energy of the original and modified PU fibrous membranes were characterized, which revealed that the surface roughness and hydrophilicity of the PU fibrous membrane were obviously increased by modified with COS and G-COS, respectively. Antibacterial experiment against E. coli and S. aureus indicated that antibacterial activity of the G-C-D-PU fibrous membrane was markedly superior to that of pure PU and C-D-PU fibrous membranes. In vitro cells culture experiments revealed that the adhesion and proliferation of NIH-3T3 cells on the PU fibrous membrane were improved by successively immobilized with PDOPA and COS as well as G-COS with the concentration of 2 g/L and 6 g/L. Moreover, the G-C-D-PU fibrous membranes with relative high G-COS content were more beneficial to the enhancement of antibacterial activity, but on the contrary, those with relative low G-COS content were more in favor of cell attachment and proliferation.

Dual drug loaded coaxial electrospun PLGA/PVP fiber for guided tissue regeneration under control of infection.

Electrospinning promisingly fabricate mats for Guided Tissue Regeneration (GTR). Due to a chronic inflammatory pathology in periodontal, it is highly desirable to develop a novel GTR mats to realize tissue regeneration under control of infection. In the study, coaxial electrospinning was firstly conducted to fabricate dual drug loaded fiber mats with core/shell structure. Naringin-loaded polyvinylpyrrolidone was designed as core fiber to enrich tissue regeneration and metronidazole-loaded poly(lactic-co-glycolic acid) as shell fiber to inhibit bacterial. TEM revealed that the fibers with distinct core/shell structure were in an outer diameter of 1.5-1.7 µm with an inner diameter of <1.0 µm. The loading of dual drug decreased the tensile strength and elongation of the coaxial fiber mats. On in vitro assessment, metronidazole had a short-term release while naringin had a long-term release behavior in all the coaxial mats. The colonization of anaerobic bacteria on the mats effectively were inhibited over 21 days. Furthermore, the dual drug loaded coaxial fiber mats were observed to positively supported the adhesion and proliferation of MC3T3-E1 and was conductive to high alkaline phosphatase express. Thus, a simple and effective coaxial electrospinning approach was demonstrated for the fabrication of anti-infective GTR mats with promoting tissue regeneration.

Antibacterial activity and cytocompatibility of chitooligosaccharide-modified polyurethane membrane via polydopamine adhesive layer.

The aim of this study was to provide a convenient surface modification method for polyurethane (PU) membrane and evaluate its influence on hydrophilicity, antibacterial activity and cell functions, which are the most important factors for wound dressings. For this purpose, chitooligosaccharide (COS) was modified onto the surface of PU membrane based on the self-polymerization of dopamine (DOPA). Surface composition, morphology, hydrophilicity and surface energy of the original and modified PU membranes were characterized. Surface roughness and hydrophilicity of the PU membrane were obviously increased by modified with polydopamine (PDOPA) and COS. Antibacterial experiment against Escherichia coli and Staphylococcus aureus indicated that antibacterial activity of PU membrane increased only slightly by modified with PDOPA, but increased significantly by further modified with COS. Cells culture results revealed that COS-functionalized PU membrane is more beneficial to the adhesion and proliferation of NIH-3T3 cells compared to the original and PDOPA-modified PU membranes.

Osteodifferentiation of mesenchymal stem cells on chitosan/hydroxyapatite composite films.

Chitosan (Ch) is one of the most commonly used natural biomaterials. Osteodifferentiation of mesenchymal stem cells (MSCs) on Ch has drawn extensive interest. Hydroxyapatite (HA) is a component of skeleton and teeth with good biocompatibility. Combination with HA may be a good method to modify Ch to facilitate cellular behaviors and functions on it. In this study, Ch/HA film was prepared and characterized. Its potential to benefit cellular behaviors and osteodifferentiation of MSCs was evaluated. Resultantly, physical properties of composite Ch/HA, including water-in-air contact angle, tensile strength, elastic modulus, and breaking elongation were favorably modified. In cellular culture medium, Ch/HA films absorbed more Ca(2+) than Ch films, and more HA crystalline growths on Ch/HA films. 3-(4,5-Dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and morphological features showed better proliferation and adhesion of MSCs on Ch/HA films. Osteodifferentiation of MSCs on Ch/HA was promoted, indicated by modified transcription level of osteocalcin, osteopontin, collagen I, alkaline phosphatase (ALP), and induced ALP activity. These data suggest biocompatibility of Ch is modified after being blended with HA, which promotes osteodifferentiation of MSCs. This can be a promising approach to modify Ch for its applications in bone tissue engineering.