Mussel-Inspired Adhesive Hydrogels Based on Laponite-Confined Dopamine Polymerization as a Transdermal Patch.

Transdermal patch for local drug delivery has attained huge attention as an attractive alternative to existing drug delivery techniques as it is painless and user-friendly. However, most adhesive hydrogels either do not have adequate adhesion with the skin or cause discomfort while being removed from the skin surface due to excessive adhesion. To address this challenge, we developed an adhesive hydrogel based on laponite-confined dopamine polymerization as a transdermal patch. Laponite RDS nanoclay was used to control the hydrogel's viscous behavior and dopamine polymerization. The laponite polymerized polydopamine (l-PDA) was incorporated into poly(vinyl alcohol) (PVA) to make the PVA-l-PDA hydrogel. The laponite-confined polymerization improved the hydrogels' water contact angle and adhesion strength. The adhesion strength of the PVA-l-PDA hydrogel was adequate to adhere to the evaluated goat skin, glass, and polypropylene surfaces. Notably, the PVA-l-PDA hydrogel was easy to peel off from the skin. Further, we evaluated the drug release profile in goat skin using lidocaine as a model drug. We observed the controlled release of lidocaine from the PVA-l-PDA hydrogel compared to the PVA-PDA hydrogel. In addition, the nanoclay-confined adhesive hydrogel did not show any cytotoxic effect in fibroblasts. Altogether, PVA-l-PDA hydrogels offer appropriate adhesive strength, toughness, and biocompatibility. Thus, the PVA-l-PDA hydrogel has the potential to be an efficient transdermal patch.

Gelatin grafted poly(D,L-lactide) as an inhibitor of protein aggregation: An in vitro case study.

Amyloids are a group of proteins that are capable of forming aggregated amyloid fibrils, which is responsible for many neurodegenerative diseases including Alzheimer's disease (AD). In our previous study, synthesis and characterization of star-shaped poly(D,L-lactide)-b-gelatin (ss-pLG) have been reported. In the present work, we have extended our work to study ss-pLG against protein aggregation. To the best of our knowledge, this is the first report on the inhibition of amyloid fibrillation by protein grafted poly(D,L-lactide). Bovine serum albumin (BSA) was chosen as the model protein, which readily forms fibril under high temperature. We found that ss-pLG efficiently suppressed the fibril formation of BSA compared with gelatin (Gel), which was supported by Thioflavin T assay, circular dichroism (CD) spectroscopy and atomic force microscopy (AFM). In addition, ss-pLG significantly curtailed amyloid-induced hemolysis. We also found that incubation of ss-pLG with neuroblastoma cells (MC65) protected the cells from fibril-induced toxicity. The rescuing efficiency of ss-pLG was better than Gel, which could be attributed to the reduced lamella thickness in branched ss-pLG. These results suggest the significance of gelatin grafting, which probably allows gelatin to interact with the key residues of the amyloidogenic core of BSA effectively.

l-Arginine-Loaded Oxidized Isabgol/Chitosan-Based Biomimetic Composite Scaffold Accelerates Collagen Synthesis, Vascularization, and Re-epithelialization during Wound Healing in Diabetic Rats.

Impaired wound healing in diabetic wounds is common due to infection, inflammation, less collagen synthesis, and vascularization. Diabetic wound healing in patients is still a challenge and needs an ideal wound dressing to treat and manage diabetic wounds. Herein, an efficacious wound dressing biomaterial was fabricated by cross-linking oxidized isabgol (Oisab) and chitosan (Cs) via trisodium trimetaphosphate and Schiff base bonds. l-Arginine (l-Arg) was incorporated as a bioactive substance in the Oisab + Cs scaffold to promote cell adhesion, cell proliferation, collagen synthesis, and vascularization. The fabricated scaffolds showed microporous networks in the scanning electron microscopy analysis. The scaffold also possessed excellent hemocompatibility. In vitro studies using fibroblasts (L929 and human dermal fibroblast cells) confirmed the cytocompatibility of these scaffolds. The results of the in vivo chicken chorioallantoic membrane assay confirmed the proangiogenic activity of the Oisab + Cs + l-Arg scaffolds. The wound-healing potential of these scaffolds was studied in streptozotocin-induced diabetic rats. This in vivo study showed that the period of epithelialization in the Oisab + Cs + l-Arg scaffold-treated wounds was 21.67 ± 1.6 days, which was significantly faster than the control (30.33 ± 2.5 days). Histological and immunohistochemical studies showed that the Oisab + Cs + l-Arg scaffolds significantly accelerated the rate of wound contraction by reducing inflammation, improving collagen synthesis, and promoting neovascularization. These findings suggest that the Oisab + Cs + l-Arg scaffolds could be beneficial in treating diabetic wounds in clinical applications.

Iron oxide nanoparticle-stabilized Pickering emulsion-templated porous scaffolds loaded with polyunsaturated fatty acids (PUFAs) for bone tissue engineering.

Dietary intake of ω-3-polyunsaturated fatty acids (PUFAs) can significantly improve the expression levels of alkaline phosphatase (ALP) and osteocalcin. However, PUFAs are hydrophobic and highly sensitive to temperature, oxygen concentration, pH, and ionic strength. Hence, it is challenging to use PUFAs as bioactive compounds for bone tissue engineering. Here, we encapsulated PUFAs in liposomes to improve their stability. The hydrodynamic size of the PUFA-loaded liposomes was found to be 121.3 ± 35 nm. GC-MS analysis showed that the encapsulation efficiency of the PUFAs was 19.9 ± 3.4%. These PUFA-loaded liposomes were loaded into porous scaffolds that were prepared by polymerizing glycidyl methacrylate and trimethylolpropane triacrylate monomers using the Pickering emulsion polymerization technique. Oleic acid-coated iron oxide nanoparticles were used as the stabilizing agent to prepare these acrylate-based scaffolds containing PUFA-loaded liposomes (P-Lipo-IO(GMA-TMPTA)). SEM micrographs confirmed the porous nature of the scaffolds and the presence of well-adhered liposomes. An in vitro cytotoxicity study conducted using MG63 cells confirmed that these scaffolds showed desirable cytocompatibility. Cell adhesion study showed a well-spread morphology, indicating firm adhesion of the cells. The alizarin red staining of P-Lipo-IO(GMA-TMPTA) scaffolds showed 3- and 2-fold higher calcium deposition compared to the control on days 7 and 14, respectively. ALP activity was also 2-fold higher than that of the control on day 14. RT-PCR analysis of cells exposed to P-Lipo-IO(GMA-TMPTA) scaffolds showed significantly higher expression of osteogenic markers compared to the control. An antibacterial study conducted on Staphylococcus aureus showed a higher percentage inhibition and reactive oxygen species generation in samples treated with P-Lipo-IO(GMA-TMPTA) scaffolds. These desirable biological properties indicate that the developed scaffolds are suitable for bone tissue engineering.

Preparation and characterization of a jelly fig (Ficus awkeotsang Makino) polysaccharide-based bioactive 3D scaffold for improved vascularization and skin tissue engineering applications.

Jelly fig polysaccharides (JFP) were extracted from Ficus awkeotsang Makino achenes. The yield of JFP was approximately 10-15 %. FT-IR spectrum of the extracted JFP confirmed that it was made of low methoxyl pectin (LMP). 3D scaffolds of JFP (JFP scaffold) were fabricated using ionic crosslinking of 2 % (w/v) JFP solution with Ca2+ ions and freeze-drying. The JFP scaffold showed 73.46 ± 1.97 % porosity and a 12-fold swelling capacity. The porous morphology was also observed in SEM micrographs. JFP scaffolds were completely degraded in 14 days when incubated in 1 mg/mL lysozyme solution, compared to the 50 % degradation observed in PBS alone. The antioxidant activity of the JFP and JFP scaffold was approximately 40 %. The hemolytic assay of the JFP scaffold showed <5 % (3.0 ± 0.4) RBC lysis. The cytocompatibility of the JFP scaffold was evaluated using L929 mouse fibroblasts and human dermal fibroblasts (HDF). The in vitro studies using L929 cells showed that the JFP scaffold is cytocompatible. HDF cells cultured in the presence of JFP scaffolds show a higher fold cell viability, proliferation, and migration. Collagen expression and deposition were also studied, and no significant changes occurred with JFP scaffold treatment. In vivo CAM assay showed an increase in the number and thickness of blood vessels by 1.185-fold and 1.19-fold, respectively. These results confirm the angiogenic property of the JFP scaffold. These biocompatible and bioactive properties of the JFP scaffold could be beneficial for tissue engineering and regenerative medicine applications.

Enhancing bone repair through improved angiogenesis and osteogenesis using mesoporous silica nanoparticle-loaded Konjac glucomannan-based interpenetrating network scaffolds.

We have fabricated and characterized novel bioactive nanocomposite interpenetrating polymer network (IPN) scaffolds to treat bone defects by loading mesoporous silica nanoparticles (MSNs) into blends of Konjac glucomannan, polyvinyl alcohol, and polycaprolactone. By loading MSNs, we developed a porous nanocomposite scaffold with mechanical strengths comparable to cancellous bone. In vitro cell culture studies proved the cytocompatibility of the nanocomposite scaffolds. RT-PCR studies confirmed that these scaffolds significantly upregulated major osteogenic markers. The in vivo chick chorioallantoic membrane (CAM) assay confirmed the proangiogenic activity of the nanocomposite IPN scaffolds. In vivo studies were performed using Wistar rats to evaluate the scaffolds' compatibility, osteogenic activity, and proangiogenic properties. Liver and renal function tests confirmed that these scaffolds were nontoxic. X-ray and µ-CT results show that the bone defects treated with the nanocomposite scaffolds healed at a much faster rate compared to the untreated control and those treated with IPN scaffolds. H&E and Masson's trichrome staining showed angiogenesis near the newly formed bone and the presence of early-stage connective tissues, fibroblasts, and osteoblasts in the defect region at 8 weeks after surgery. Hence, these advantageous physicochemical and biological properties confirm that the nanocomposite IPN scaffolds are ideal for treating bone defects.

Edge-functionalized coal-derived graphene oxide in bacterial nanocellulose hydrogel for active wound healing.

This work presents a comparison of physicochemical and in vitro active wound healing properties of two distinct Graphene Oxides (GOs) from graphite and coal. These GOs are incorporated in Bacterial Nanocellulose (BNC) to form hydrogels. The performance and limitations of the loading fraction of both GOs in BNC are controlled by the processing technology and the source materials from which GOs are derived. Edge functionalization with C-GO offers the advantage of facilitating face-to-edge assembly in the hydrogel leading to better dispersion than the face-to-face assembly of basal functionalized G-GO. The latter leads to more aggregation of G-GO, resulting in a lower optimal loading fraction. Our investigation into the antibacterial properties of the BNC and BNC/GO hydrogels against gram-negative E. coli revealed inhibitory effects of the BNC/GO hydrogels that intensified with an increase in the concentration of GO. Furthermore, an in vitro wound scratch assay demonstrated that BNC/C-GO hydrogels promote better cell migration, confirming their superior biocompatibility and suitability as active wound dressings, albeit limited by loading fraction due to agglomeration. These findings shed light on the performance and limitations of GOs for diverse applications, emphasizing the significance of exploring the influence of different methods and source materials of GOs.

Antibacterial and angiogenic potential of iron oxide nanoparticles-stabilized acrylate-based scaffolds for bone tissue engineering applications.

Pickering emulsion polymerization, stabilized by inorganic nanoparticles such as iron oxide nanoparticles (IONPs), can be used to fabricate scaffolds with the desired porosity and pore size. These nanoparticles create stable emulsions that can be processed under harsh polymerization conditions. IONPs, apart from serving as an emulsifier, impart beneficial bioactivities such as antibacterial and pro-angiogenic activity. Here, we coated IONPs with three different weights of oleic acid (5.0 g, 7.5 g, and 10.0 g) to synthesize oleic acid-IONPs (OA-IONPs) that possess the desired hydrophobicity (contact angle > 100°). Next, glycidyl methacrylate and trimethylolpropane triacrylate were polymerized using the Pickering emulsion polymerization technique stabilized by the OA-IONPs. The physicochemical properties of the resulting porous scaffolds were thoroughly characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), and a universal testing machine (UTM). The SEM images confirmed the formation of a porous scaffold. The IONPs content, measured using inductively coupled plasma mass spectrometry (ICP-MS), was in the range of 22-26 µg/mg of the scaffold. The mechanical strengths of the scaffolds were in the range of cancellous bone. The degradation profile of the scaffolds varied between 29% and 41% degradation over 30 days. In vitro cytotoxicity studies conducted using the fibroblast (L929) and osteosarcoma (MG-63) cell lines proved that these scaffolds were non-toxic. SEM images showed that the MG-63 cells adhered firmly to the scaffolds and exhibited a well-spread morphology. The antibacterial activity was confirmed by percentage inhibition studies, SEM analysis of bacterial membrane distortion, and reactive oxygen species (ROS) generation in the bacteria. Chick chorioallantoic membrane assay showed that the total vessel length and branch points were significantly increased in the presence of the scaffolds. These results confirm the pro-angiogenic potential of the fabricated scaffolds. The physicochemical, mechanical, and biological properties of the material suggest that the developed scaffolds would be suitable for bone tissue engineering applications.

Quaternary ammonium salt-modified isabgol scaffold as an antibacterial dressing to improve wound healing.

Chronic wounds require suitable treatment and management strategies for proper healing. Among other causes, infection delays the healing of wounds and increases the risk of wound-related complications. In this study, an inherently antibacterial and biocompatible wound dressing is developed to enhance the healing. Chemical modification of a natural polysaccharide, Isabgol with epoxypropyltrimethylammonium chloride, renders antibacterial activity to the material. This is the first report of such chemical modification of this polymer for biomedical applications. The modified material is freeze-dried to obtain porous scaffolds. 13C NMR and FTIR analysis confirmed the modification of the Isabgol polymer chains with EPTMAC. SEM analysis confirmed the porous structure of the scaffold that would allow the exchange of gases and nutrients through the matrix. The material can swell up to 17 times its initial weight, allowing it to absorb wound exudates and maintain a moist environment at the wound site. Thermogravimetric analysis and compression testing showed that the scaffold has suitable thermal and mechanical properties. The material is antibacterial and can potentially prevent infections at the wound site. In vitro studies have confirmed that these scaffolds are cytocompatible and hemocompatible. These properties indicate that the EPTMAC-modified Isabgol scaffolds would be suitable for wound dressing applications.

Tissue engineered skin substitutes: A comprehensive review of basic design, fabrication using 3D printing, recent advances and challenges.

The multi-layered skin structure includes the epidermis, dermis and hypodermis, which forms a sophisticated tissue composed of extracellular matrix (ECM). The wound repair is a well-orchestrated process when the skin is injured. However, this natural wound repair will be ineffective for large surface area wounds. Autografts-based treatment is efficient but, additional pain and secondary healing of the patient limits its successful application. Therefore, there is a substantial need for fabricating tissue-engineered skin constructs. The development of a successful skin graft requires a fundamental understanding of the natural skin and its healing process, as well as design criteria for selecting a biopolymer and an appropriate fabrication technique. Further, the fabrication of an appropriate skin graft needs to meet physicochemical, mechanical, and biological properties equivalent to the natural skin. Advanced 3D bioprinting provides spatial control of the placement of functional components, such as biopolymers with living cells, which can satisfy the prerequisites for the preparation of an ideal skin graft. In this view, here we elaborate on the basic design requirements, constraints involved in the fabrication of skin graft and choice of ink, the probable solution by 3D bioprinting technique, as well as their latest advancements, challenges, and prospects.

Cancer nanomedicine: a review of nano-therapeutics and challenges ahead.

Cancer is known as the most dangerous disease in the world in terms of mortality and lack of effective treatment. Research on cancer treatment is still active and of great social importance. Since 1930, chemotherapeutics have been used to treat cancer. However, such conventional treatments are associated with pain, side effects, and a lack of targeting. Nanomedicines are an emerging alternative due to their targeting, bioavailability, and low toxicity. Nanoparticles target cancer cells via active and passive mechanisms. Since FDA approval for Doxil®, several nano-therapeutics have been developed, and a few have received approval for use in cancer treatment. Along with liposomes, solid lipid nanoparticles, polymeric nanoparticles, and nanoemulsions, even newer techniques involving extracellular vesicles (EVs) and thermal nanomaterials are now being researched and implemented in practice. This review highlights the evolution and current status of cancer therapy, with a focus on clinical/pre-clinical nanomedicine cancer studies. Insight is also provided into the prospects in this regard.

Biomimetic ion substituted and Co-substituted hydroxyapatite nanoparticle synthesis using Serratia Marcescens.

Biomimicry is becoming deep-rooted as part of bioceramics owing to its numerous functional advantages. Naturally occurring hydroxyapatite (HA) apart from primary nano structures are also characterised by various ionic substitutions. The ease of accommodating such key elements into the HA lattice is known to enhance bone healing properties of bioceramics. In this work, hydroxyapatite synthesized via biomimetic approach was substituted with individual as well as multiple cations for potential applications in bone repair. Ion substitutions of Sr, Mg and Zn was carried out on HA for the first time by using Serratia grown in a defined biomineralization medium. The individual ions of varying concentration substituted in Serratia HA (SHA) (Sr SHA, Mg SHA and Zn SHA) were analysed for crystallinity, functional groups, morphology and crystal size. All three showed decreased crystallinity, phase purity, large agglomerated aggregates and needle-shaped morphologies. Fourier transform infrared spectroscopy (FTIR) spectra indicated increased carbonate content of 5.8% resembling that of natural bone. Additionally, the reduced O-H intensities clearly portrayed disruption of HA lattice and subsequent ion-substitution. The novelty of this study lies primarily in investigating the co-substitution of a combination of 1% Sr, Zn and Mg in SHA and establishing the associated change in bone parameters. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images clearly illustrated uniform nano-sized agglomerates of average dimensions of 20-50 nm length and 8-15 nm width for Sr SHA; 10-40 nm length and 8-10 nm width for both Zn SHA and Mg SHA and 40-70 nm length and 4-10 nm width in the case of 1% Sr, Zn, Mg SHA. In both individual as well as co-substitutions, significant peak shifts were not observed possibly due to the lower concentrations. However, cell volumes increased in both cases due to presence of Sr2+ validating its dominant integration into the SHA lattice. Rich trace ion deposition was presented by energy dispersive X-ray spectroscopy (EDS) and quantified using inductively coupled plasma optical emission spectrometer (ICP-OES). In vitro cytotoxicity studies in three cell lines viz. NIH/3T3 fibroblast cells, MG-63 osteosarcoma cells and RAW 264.7 macrophages showed more than 90% cell viability proving the biocompatible nature of 1% Sr, Zn and Mg in SHA. Microbial biomineralization by Serratia produced nanocrystals of HA that mimicked "bone-like apatite" as evidenced by pure phase, carbonated groups, reduced crystallinity, nano agglomerates, variations in cell parameters, rich ion deposition and non-toxic nature. Therefore ion-substituted and co-substituted biomineralized nano SHA appears to be a suitable candidate for applications in biomedicine addressing bone injuries and aiding regeneration as a result of its characteristics close to that of the human bone.

Self-Assembled Inhalable Immunomodulatory Silk Fibroin Nanocarriers for Enhanced Drug Loading and Intracellular Antibacterial Activity.

In this study, a pH-induced self-assembly-based method has been developed to form silk fibroin nanoparticles (SFN-2) with a higher drug loading capacity (21.0 ± 2.1%) and cellular uptake than that of silk fibroin particles produced by a conventional desolvation method (SFN-1). Using the self-assembly method, rifampicin-encapsulated silk fibroin nanoparticles (R-SFN-2) were prepared with a size of 165 ± 38 nm at an optimum pH of 3.8. In silico analysis reveals that at acidic pH, the amino acid side chain charge neutralization of acidic residues, especially GLU64, promotes the formation of additional favorable interactions between the silk fibroin and the drug. The SFN-2 also possess a good aerosol property with a mass median aerodynamic diameter of 3.82 ± 0.71 µm and fine particle fraction of 64.0 ± 1.4%. These SFN-2 particles were selectively endocytosed by macrophages through clathrin- and caveolae-mediated endocytosis with a higher uptake efficiency (66.2 ± 2.1%) and were found to exhibit a sustained drug release in the presence of macrophage intracellular lysates. The cytokine and biomarker expression analyses revealed that SFN-2 could exhibit an immunomodulatory effect by polarizing the macrophages to an initial M1 phase and later M2 phase. Further, R-SFN-2 also exhibited an enhanced and sustained intracellular antibacterial activity against Mycobacterium smegmatis-infected macrophages than free rifampicin. Thus, the self-assembled silk fibroin particles with immunomodulatory action combined with a good aerosol and intracellular drug release property can be an attractive choice as a carrier for developing pulmonary drug delivery systems.

Nanohybrid-Reinforced Gelatin-Ureidopyrimidinone-Based Self-healing Injectable Hydrogels for Tissue Engineering Applications.

The traditional hydrogels are prone to break due to the applied stress. The deformation of the implanted hydrogels would result in the loss of structural integrity, leading to the failure of hydrogel functionalities and tissue regeneration. Self-healing hydrogels (AG-UPy), composed of oxidized alginate and ureidopyrimidinone-functionalized gelatin (G-UPy), were developed to address this challenge. These self-healing hydrogels possess two independent healing mechanisms, viz., Schiff base formation and UPy dimerization. These hydrogels were compared with oxidized alginate-gelatin (AG) hydrogels. AG-UPy hydrogels showed effective self-healing in a short time (about 2 min) after applying 800% strain, wherein recovery was not achieved with the AG hydrogel. However, the shear-thinning property of UPy made the AG-UPy hydrogel mechanically weaker than the AG hydrogel. To improve the mechanical strength of the AG-UPy hydrogel, we impregnated poly(ethylene glycol)-poly(urethane)/cloisite nanohybrid (PEG-PU/C) to prepare the AG-UPy/PEG-PU/C hydrogel. The incorporation of PEG-PU/C resulted in a 20-fold increase in the compression strength compared to that of the AG-UPy hydrogel. The AG-UPy/PEG-PU/C hydrogels also showed rapid self-healing. Incorporating the nanohybrid improved the cell proliferation by 2- and 1.25-fold compared to that of the AG and AG-UPy hydrogels, respectively. Therefore, PEG-PU/C combined with the UPy-functionalized polymer could be used to modulate mechanical strength and self-healing and enhance cell proliferation.

Modular amphiphilic poly(aryl ether)-based supramolecular nanomicelles: an efficient endocytic drug carrier.

A rationally designed amphiphilic poly(aryl ether)-based dendrimer self-assembles into nanomicelles and exhibits tunable morphology upon varying the hydrophilic chain length. The 30 nm-sized dendrimer nanomicelles successfully entrapped Doxorubicin, demonstrated the sustained release of Doxorubicin and can successfully penetrate cancer cells through caveolae-dependent endocytosis, compared to the free drug.

Screening and selection of camptothecin producing endophytes from Nothapodytes nimmoniana.

Endophytic fungi with the ability to produce plant based secondary metabolites are a potential alternative for producing the host plant metabolite and to prevent natural plants from extinction. To isolate a high metabolite yielding endophytic strain from plants, hundreds of endophytic strains are screened and tested for product yield separately under axenic state, before shortlisting the potential endophyte, which involves huge time consumption. In this study, strategies for screening and selection of high camptothecin yielding endophytes from their natural habitat were proposed. A correlation was built between the camptothecin yield in the explants and the endophytes isolated from them. In addition, camptothecin yield was compared between the endophytes isolated from young and matured plants. Further, camptothecin producers and non-producers strains were compared for their tolerance toward camptothecin. The study indicates that high camptothecin yielding endophytes were isolated from high yielding explants and younger plants and they were more tolerant to camptothecin in comparison to non-camptothecin yielding endophytes. Thus, choosing a young and high yielding explant for endophyte isolation, and use of camptothecin as a selective agent in the growth medium, can be instrumental in screening and selection of high camptothecin yielding endophytes from nature in relatively less time.

Accelerated Outgrowth of Neurites on Graphene Oxide-Based Hybrid Electrospun Fibro-Porous Polymeric Substrates.

Fabrication of a surface-engineered electrospun scaffold having biomimetic properties like the extracellular matrix (ECM) is essential for neural tissue engineering. An electroconductive and elastomeric scaffold with aligned fibers acting as a substrate may have a great impact on the directional outgrowth of neurites. In this study, we have electrospun electrically conductive, polyurethane-based elastomeric and topographically aligned fibro-porous neural scaffolds. Adhesive proteins of the ECM are documented to have an important role in controlling neuronal cell behavior, including cell adhesion, proliferation, and neurite outgrowth. These bio-adhesion proteins or nanomaterials mimicking their action, if used for surface modification of neural scaffolds, may have the potential to accelerate the nerve repair process. Thus, electrospun scaffolds fabricated were surface-engineered using a unique and modified single-step electrospraying technique to coat the scaffold surface with an exploratory bio-adhesion agent, a thin layer of graphene oxide (GO) films. The study was then carried out to determine if the GO-coated electrospun electroconductive polycarbonate urethane (PCU) substrate can improve the bio-interface attributes of these scaffolds or may alter the neurite outgrowth of PC-12 cells like any other bio-adhesion proteins. Therefore, the hybrid scaffolds with GO coatings were compared with similar scaffolds coated with poly-l-lysine (PLL) for neural cell adhesion, proliferation, and neurite extension. Neurite outgrowth studies showed that although the average neurite length was comparable on both GO- and PLL-coated surfaces, the length profile of neurites, when categorized based on length, showed an increased number of lengthier neurites on the GO-coated hybrid scaffolds. In particular, the study brings out an innovative surface engineering technique for the coating of GO on polymeric scaffolds. It may be further put together in designing of hybrid surfaces with nanotopographical biophysical cues on three-dimensional neural scaffolds, which in turn may stimulate an accelerated neuronal regeneration via providing an enhanced ECM like milieu.

Design and evaluation of Konjac glucomannan-based bioactive interpenetrating network (IPN) scaffolds for engineering vascularized bone tissues.

Synthetic bone grafts are being developed to overcome the limitations of conventional treatments for bone defects. In this study, we have fabricated bioactive binary and novel ternary interpenetrating polymer network (IPN) scaffolds using a combination of natural and synthetic polymers. The binary IPN scaffolds were prepared using Konjac glucomannan (KGM) and polyvinyl alcohol (PVA). In the novel ternary IPN scaffolds, polycaprolactone (PCL) was added to PVA and KGM. SEM images showed that these scaffolds were microporous with good interconnectivity. Compression testing confirmed that both the scaffolds are mechanically strong, with the ternary scaffolds having moduli comparable to the natural bone. In vitro cytocompatibility studies performed with NIH/3T3 fibroblasts cells and MG-63 osteosarcoma cells demonstrated the non-toxic and osseointegrating nature of the scaffolds. Confocal images confirmed that the cells migrated into the interconnected pores of the scaffolds. RT-PCR analysis showed that both binary and ternary scaffolds enhanced the expression of the major bone marker genes, viz., ALP, BMP-2, COLLAGEN-1, and OSTEOCALCIN. However, the expression of these osteogenic markers was significantly enhanced in the ternary scaffolds compared to the binary scaffolds. In vivo chick chorioallantoic membrane (CAM) assay shows that these scaffolds possess excellent pro-angiogenic properties. Hence, these desirable biological properties, coupled with the suitable physicochemical properties, make these IPN scaffolds ideal for treating bone defects.

Cysteine immobilisation on the polyethylene terephthalate surfaces and its effect on the haemocompatibility.

Nitric oxide (NO) is an important signalling molecule involved in haemostasis. NO, present as endogenous S-nitrosothiols, is released by cysteine through a transnitrosation reaction. To exploit this mechanism, cysteine was immobilised onto the different carboxylated polyethylene terephthalate (PET) surfaces using 1-step EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide) crosslinking mechanism. Immobilised cysteine concentration and NO release were dependent on the surface carboxyl density. Stability studies showed that the immobilised cysteine concentration and NO release reduced within 6 h. Immobilisation of cysteine derivatives eliminated the possibility of formation of polycysteine and its electrostatic interaction with the carboxylated PET. The immobilised cysteine concentration did not recover after DTT treatment, eliminating the possibility of disulphide bond formation. Further, cysteine was immobilised using a 2-step EDC crosslinking mechanism. Although the cysteine concentration reduced during stability studies, it recovered upon DTT treatment, indicating that cysteine forms amide bonds with the carboxylated PET and the observed decrease in cysteine concentration is probably due to the formation of disulphide bonds. The haemocompatibility of the cysteine immobilised PET surfaces showed similar results compared to the carboxylated PET. The loss of thiol groups due to the disulphide bond restricts the transnitrosation reaction. Hence, these materials can be used primarily in short-term applications.

Kinetic study of NTPDase immobilization and its effect of haemocompatibility on polyethylene terephthalate.

Poor haemocompatibility of material surfaces is a serious limitation that can lead to failure of blood-contacting devices and implants. In this work, we have improved the haemocompatibility of polyethylene terephthalate (PET) surfaces by immobilizing apyrase/ecto-nucleoside triphosphate diphosphohydrolase (NTPDase) on to the carboxylated PET. NTPDase immobilized PET surfaces scavenge the ADP released by activated platelets, which prevents further platelet activation and aggregation. The surface properties of the modified PET were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDAX), and contact angle measurement. The enzyme attachment and stability on the modified PET surfaces were evaluated. The kinetics of free enzyme and immobilized enzyme were studied and fitted using the Michaelis-Menten kinetic model. Both free and immobilized NTPDase followed Michaelis-Menten kinetics with similar Michaelis-Menten constants (Km). This suggests that the activity of NTPDase was unchanged upon immobilization. Protein adsorption and %hemolysis was significantly reduced for carboxylated PET and NTPDase immobilized PET surfaces compared to unmodified PET. Lactate dehydrogenase assay showed that the number of adhered platelets reduced by more than an order of magnitude for the NTPDase immobilized PET surface compared to unmodified PET. These results clearly indicate that NTPDase immobilization significantly enhances the haemocompatibility of PET surfaces.