Bilayer nanostructure coated AZ31 magnesium alloy implants: in vivo reconstruction of critical-sized rabbit femoral segmental bone defect.

Healing or reconstruction of critical-sized bone defects is still challenging in orthopaedic practice. In this study, we developed a new approach to control the degradation and improve the bone regeneration of the AZ31 magnesium substrate, fabricated as mesh cage implants. Subsequently, bilayer nanocomposite coating was carried out using polycaprolactone (PCL) and nano-hydroxyapatite (nHA) by dip-coating and electrospinning. Lastly, the healing capacity of the implants was studied in New Zealand White (NZW) rabbit critical-sized femur bone defects. X-ray analysis showed the coated implant group bridged and healed the critical defects 100% during four weeks of post-implantation. Micro-computed tomography (Micro-CT) study showed higher total bone volume (21.10%), trabecular thickness (0.73), and total porosity (85.71%) with bilayer coated implants than uncoated. Our results showed that nanocomposite coated implants controlled the in vivo degradation and improved bioactivity. Hence, the coated implants can be used as a promising bioresorbable implant for critical segmental bone defect repair applications.

Synthesis of magnesium phosphate nanoflakes and its PCL composite electrospun nanofiber scaffolds for bone tissue regeneration.

This study describes the preparation of nano-magnesium phosphate (nMP) flakes by one step microwave irradiation method. The synthesized nMP was incorporated with polycaprolactone (PCL), hyperbranched polyglycerol (HPG) and nano-hydroxyapatite (nHA) to fabricate as composite electrospun nanofibrous scaffold for bone tissue engineering applications. The electrospun nanofibers were analyzed by scanning electron microscope, XRD, FTIR, DSC, TGA, and wettability measurement. The nanofibers were smooth, randomly oriented, and surface decorated with nMP. The water contact angle was 32 ± 1° (initial contact angle), which reduces to 0° after 1 min for HPG and nMP containing nanocomposites, while the contact angle of PCL is 104 ± 5°. The nanocomposite scaffolds exhibited higher swelling, biomineralization, and breakages during PBS immersion. The scaffolds were non-cytotoxic to MG63 osteosarcoma cells and hMSCs with higher viability after 72 h. They allowed good adhesion and spreading of these cells when compared to PCL and PCL/nHA electrospun nanofibers. These results indicated that HPG with surface decorated nMP electrospun nanocomposite scaffold can be a promising material for bone tissue engineering applications.

Influence of magnesium particles and Pluronic F127 on compressive strength and cytocompatibility of nanocomposite injectable and moldable beads for bone regeneration.

A novel one-step preparation of magnesium particles and Pluronic F127 incorporated with calcium sulfate hemihydrate (CSH) and nano-hydroxyapatite (nHA) ready to use injectable or moldable beads was developed for bone tissue regeneration applications. The nanocomposite showed setting time less than 15 min, very good injectability (75-85%) and good mechanical strength (52-80 MPa). Samples immersed in SBF showed controlled degradation (40-45% reduction in weight) in 28 days. The nanocomposite bone graft was cytocompatible against MG63 osteosarcoma cells and increased the osteogenic gene expression by 2-3 folds. These results indicate that it can be a potential defect filling biomaterial for bone tissue regeneration at the fracture site.

Synthesis and characterization of curcumin loaded PLA-Hyperbranched polyglycerol electrospun blend for wound dressing applications.

This study is aimed to develop curcumin (Cur) incorporated electrospun nanofibers of a blend of poly (lactic acid) (PLA) and hyperbranched polyglycerol (HPG) for wound healing applications. Both the polymers are synthesized and fabricated by electrospinning technique. The produced nanofibers were characterized by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Colorimetry (DSC) and Thermogravimetric Analysis (TGA). Electrospun scaffolds (PLA/HPG/Cur) exhibits very high hydrophilicity, high swelling and drug uptake and promotes better cell viability, adhesion and proliferation when compared to PLA/Cur electrospun nanofibers. Biodegradation study revealed that the morphology of the nanofibers were unaffected even after 14days immersion in Phosphate Buffered Saline. In vitro scratch assay indicates that migration of the cells in the scratch treated with PLA/HPG/Cur is complete within 36h. These results suggest that PLA/HPG/Cur nanofibers can be a potential wound patch dressing for acute and chronic wound applications.

Differential Adhesive and Bioactive Properties of the Polymeric Surface Coated with Graphene Oxide Thin Film.

Surface engineering of implantable devices involving polymeric biomaterials has become an essential aspect for medical implants. A surface enhancement technique can provide an array of unique surface properties that improve its biocompatibility and functionality as an implant. Polyurethane-based implants that have found extensively acclaimed usage as an implant in biomedical applications, especially in the area of cardiovascular devices, still lack any mechanism to ward off bacterial or platelet adhesion. To bring out such a defense mechanism we are proposing a surface modification technique. Graphene oxide (GO) in very thin film form was wrapped onto the electrospun fibroporous polycarbonate urethane (PCU) membrane (GOPCU) by a simple method of electrospraying. In the present study, we have developed a simple single-step method for coating a polymeric substrate with a thin GO film and evaluated the novel antiadhesive activity of these films. SEM micrographs after coating showed the presence of very thin GO films over the PCU membrane. On the GOPCU surface, the contact angle was shifted by ∼30°, making the hydrophobic PCU surface slightly hydrophilic, while Raman spectral characterization and mapping showed the presence and distribution of GO over 75% of the membrane. A reduced platelet adhesion on the GOPCU surface was observed; meanwhile, bacterial adhesion also got reduced by 85% for Staphylococcus aureus (Gram positive, cocci) and 64% for Pseudomonas aeruginosa (Gram negative, bacilli). A cell adhesion study conducted using mammalian fibroblast cells projected its proliferation percentage in a MTT assay, with 82% cell survival on PCU and 86% on GOPCU after 24 h culture, while a study for an extended period of 72 h showed 87% of survival on PCU and 88% on GOPCU. This plethora of functionalities by a simple modification technique makes thin GO films a self-sufficient surface engineering material for future biomedical applications.

Effect of tobacco extract on surfactant synthesis and its reversal by retinoic acid-role of cell-cell interactions in vitro.

Tobacco induces oxidative stress in the alveolar epithelium and causes its damage. Retinoic acid (RA) has a cardinal role in alveolar cell growth, differentiation, and maturation. The aim of the study was to investigate the role of cell-cell interactions and whether RA could reverse the effect of tobacco extract on epithelial function as expressed by surfactant synthesis. For this, an in vitro model, which provides multiple cell type interactions, as seen in vivo, was used. We had used the major lung cell types, alveolar epithelial and mesenchymal cells represented by the cell lines A549 (human lung adenocarcinoma cell line), and human fetal lung fibroblast-1 (HFL-1) for developing the monoculture and co-culture systems and studied the effect of tobacco extract and retinoic acid. The effect of tobacco and retinoic acid both singly and in combination on proliferation and surfactant synthesis was analyzed. Retinoic acid induced proliferation and upregulated surfactant synthesis in monocultures and co-cultures. Tobacco extract at 100 µg/ml concentration decreased A549 proliferation and upregulated surfactant protein mRNA expression. In co-cultures treated with tobacco extract (100 µg/ml), retinoic acid (1 µM), regulated cell proliferation, and surfactant protein mRNA expression vis-à-vis the monoculture system. This clearly points to the fact that cell-cell interactions modulate the effect of additives or stimulants and help in assessing the in vivo combinatorial responses in vitro and that the retinoic acid effect is regenerative.

Multiple drug resistant bacterial biofilms on implanted catheters - a reservoir of infection.

BACKGROUND: Medical devices are an essential part of modern health-care, but its usage has led to the emergence of medical device associated infections otherwise known as Foreign-Body related infections (FBRIs). This is caused by bacterial adhesion and biofilm formation on their surfaces which act as a nidus of infection. These biofilms are resistant to antibacterial agents and host immune response. The antibiotics which are useful in treating planktonic forms cannot clear the biofilm and the device must usually be removed to resolve the infection. OBJECTIVE: The main objective of the study was to identify the prevalence of bacterial biofilms on retrieved catheters which included vascular catheters (141) and Foley catheters (86) from patients and understand the nature of antibiotic resistant strains in these biofilms. MATERIALS USED :227 numbers of retrieved catheters which included vascular catheters (141nos) and Foley catheters (86 nos) were used in the study.These retrieved implants were from patients from neurosurgery ward of SCTIMST who had undergone selective neurosurgical procedures. Patients with pre-existing infections including brain abscess were not included in the study.These patients had no clinical infection or pyrexia. Skin swabs were taken from patients using intravascular devices after retrieval of catheter. RESULTS AND CONCLUSIONS: Among vascular catheters Staphylococcus species were the major isolate and among the isolates many of the strains were Methicillin and some were Vancomycin resistant. Among the Foley catheter isolates E. faecalis was the major isolate followed by E. coli, Staphylococcus species, Klebsiella species, Pseudomonas species, Citrobacter etc. Most of the strains were resistant to multiple antibiotics. Although the patients selected did not have any clinical symptoms of infection, the presence of multiple-drug resistant organisms as biofilm points to this niche which can constitute a threat for HAls and its resultant complications. This suggests that catheters should be removed as early as possible to prevent Biofilm development on them.

Distribution of glutathione S-transferase T1 and M1 genes polymorphisms in North East Indians: a potential report.

BACKGROUND: Detoxifying glutathione S-transferase (GST) gene polymorphisms show variation in different ethnic populations. GST detoxifies and metabolizes carcinogens, including oxygen free radicals. GST polymorphisms have been associated with susceptibility to different diseases. In the current study, allelic polymorphisms of GSTM1 and GSTT1 were analyzed in three ethnic groups of North East (NE) India where a high prevalence of various cancers and other diseases such as hypertension, tuberculosis, and asthma have been reported. METHODS: We compared the prevalence of GSTT1 and GSTM1 deletion genotypes, which were determined by multiplex polymerase chain reaction, in 422 voluntary, healthy NE Indians with those of other populations. The data was statistically analyzed. RESULTS: The GSTT1-null genotype was found in 51%, 34.3%, and 15.7% of individuals (from Mizoram, Sikkim, and Assam regions of NE India, respectively), whereas the GSTM1-null genotype was found in 46.9%, 46%, and 35% of individuals from the same areas. CONCLUSIONS: The NE Indians differ from the rest of the Indian population with reference to genotypic distribution of GST polymorphisms but the frequency was found to be similar to that which has been reported from China. This may explain the hypothesis of the common ancestral origin of both the NE Indians and the Chinese and a higher frequency of cancers such as gastric, esophageal, and oral cancers, which has been reported from these regions. This study establishes baseline frequency data for GST polymorphisms for future case control studies on the role these polymorphisms play with regard to diseases. The results presented here provide the first report on GST polymorphisms in the NE Indian population.