Muthunarayanan Muthiah

Pectin/carboxymethyl cellulose/microfibrillated cellulose composite scaffolds for tissue engineering

Highly porous three-dimensional scaffolds made of biopolymers are of great interest in tissue engineering applications. A novel scaffold composed of pectin, carboxymethyl cellulose (CMC) and microfibrillated cellulose (MFC) were synthesised using lyophilisation technique. The optimised scaffold with 0.1% MFC, C(0.1%), showed highest compression modulus (~3.987 MPa) and glass transition temperature (~103 °C). The pore size for the control scaffold, C(0%), was in the range of 30-300 μm while it was significantly reduced to 10-250 μm in case of C(0.1%). Using micro computed tomography, the porosity of C(0.1%) was estimated to be 88%. C(0.1%) showed excellent thermal stability and lower degradation rate compared to C(0%). The prepared samples were also characterised using XRD and FTIR. C(0.1%) showed controlled water uptake ability and in vitro degradation in PBS. It exhibited highest cell viability on NIH3T3 fibroblast cell line. These results suggest that these biocompatible composite scaffolds can be used for tissue engineering applications.

Surface modification of iron oxide nanoparticles by biocompatible polymers for tissue imaging and targeting

Superparamagnetic iron oxide nanoparticles (SPIONs) are excellent MR contrast agents when coated with biocompatible polymers such as hydrophilic synthetic polymers, proteins, polysaccharides, and lipids, which improve their stability and biocompatibility and reduce their aggregation. Various biocompatible materials, coated or conjugated with targeting moieties such as galactose, mannose, folic acid, antibodies and RGD, have been applied to SPION surfaces to provide tissue specificity to hepatocytes, macrophages, and tumor regions in order to reduce non-specific uptake and improve biocompatibility. This review discusses the recent progress in the development of biocompatible and hydrophilic polymers for improving stability of SPIONs and describes the carbohydrates based biocompatible materials that are providing SPIONs with cell/tissue specificity as ligands.

Nanoparticle-mediated delivery of therapeutic genes: focus on miRNA therapeutics

Introduction: Micro RNAs (miRNA) are 21 – 23 nucleotides long and regulate the expression of coding genes by binding imperfectly with their 3′ UTR region. The miRNA profile is altered in pathological processes, making miRNAs good targets for drug therapy. Restoration of down-regulated miRNA or inhibition of overexpressed miRNA to return miRNA to its normal state is the basis of miRNA-based therapy. This review focuses on nanocarriers used for the delivery of miRNA that confer physical stability to the unstable RNA structure, protect the RNA from nuclease degradation and aid in effective silencing of target genes. Areas covered: The necessity of the nanocarrier for the delivery of the miRNA is emphasized and the recent research on liposome-, metal- and polymer-mediated miRNA delivery for the inhibition or replacement of the disease-related miRNA is summarized. Expert opinion: The size, charge and surface properties of nanocarriers have to be tuned to ensure effective and safe delivery of the miRNA in clinical practice. The immune responses related to the nanocarriers and the double-stranded nucleotide delivery remain to be addressed. Also, the binding of miRNAs to non-specific targets has to be studied in more detail because miRNAs have multiple targets due to partial binding unlike siRNA.

Suppression of post-angioplasty restenosis with an Akt1 siRNA-embedded coronary stent in a rabbit model.

Restenosis is the formation of blockages occurring at the site of angioplasty or stent placement. In order to avoid such blockages, the suppression of smooth muscle cells near the implanted stent is required. The Akt1 protein is known to be responsible for cellular proliferation, and specific inhibition of Akt1 gene expression results in the retardation of cell growth. To take advantage of these benefits, we developed a new delivery technique for Akt1 siRNA nanoparticles from a hyaluronic acid (HA)-coated stent surface. For this purpose, the disulfide cross-linked low molecular polyethyleneimine (PEI) (ssPEI) was used as a gene delivery carrier because disulfide bonds are stable in an oxidative extracellular environment but degrade rapidly in reductive intracellular environments. In this study, Akt1 siRNA showed efficient ionic interaction with the ssPEI carrier, which was confirmed by polyacrylamide gel electrophoresis. Akt1 siRNA/ssPEI nanoparticles (ASNs) were immobilized on the HA-coated stent surface and exhibited stable binding and localization, followed by time-dependent sustained release for intracellular uptake. Cellular viability on the nanoparticle-immobilized surface was assessed using A10 vascular smooth muscle cells, and the results revealed that immobilized ASNs exhibited negligible cytotoxicity against the adhering A10 cells. Transfection efficiency was quantified using a luciferase assay; the transgene expression of Akt1 suppression through the delivered Akt1 siRNA was measured using RT-PCR and western blot, demonstrating higher gene silencing efficiency when compared to other carriers. ASN coated on HA stents were deployed in the balloon-injured external iliac artery in rabbits in vivo. It was shown that the Akt1 released from the stent suppressed the growth of the smooth muscle at the peri-stent implantation area, resulting in the prevention of restenosis in the post-implantation phase.

Targeted delivery of mannan-coated superparamagnetic iron oxide nanoparticles to antigen-presenting cells for magnetic resonance-based diagnosis of metastatic lymph nodes in vivo

Metastatic lymph nodes (LN) originate from primary cancer cells that metastasize to the lymphatic system. It is difficult to non-invasively discriminate between metastatic LN and normal LN because of their similarities in size and shape. Magnetic resonance (MR) contrast agents are widely utilized to enhance the image contrast among different tissues. Currently available dextran-based contrast agents are non-specifically internalized by macrophages. Therefore, the aim of this study was to develop mannan-coated superparamagnetic iron oxide nanoparticles (mannan-SPION) for specific delivery to immune cells in LN by receptor-mediated endocytosis for facilitated uptake in the target cells and faster acquisition of MR images. Mannan is a water soluble polysaccharide with a high content of D-mannose residues that can be recognized by mannose receptors on activated macrophages and dendritic cells. Mannan-SPION are proven to be suitable for MRI due to their small size, excellent aqueous stability, and lower cytotoxicity. Mannan-SPION are taken up by antigen-presenting cells such as macrophages and dendritic cells, which could be confirmed by Prussian blue and fluorescent staining. In addition, mannan-SPION exhibit enhanced delivery efficiency in targeting macrophages in LN in vivo compared with polyvinyl alcohol (PVA)-SPION. More specifically, the enhancement of MRI of LN by mannan-SPION increased dramatically during the earlier stages after intravenous injection, compared with PVA-SPION as a control, which indicates the potential for successful and early detection of metastastatic LN.

Antibacterial and wound healing analysis of gelatin/zeolite scaffolds.

In this article, gelatin/copper activated faujasites (CAF) composite scaffolds were fabricated by lyophilisation technique for promoting partial thickness wound healing. The optimised scaffold with 0.5% (w/w) of CAF, G (0.5%), demonstrated pore size in the range of 10-350 μm. Agar disc diffusion tests verified the antibacterial role of G (0.5%) and further supported that bacterial lysis was due to copper released from the core of CAF embedded in the gelatin matrix. The change in morphology of bacteria as a function of CAF content in gelatin scaffold was studied using SEM analysis. The confocal images revealed the increase in mortality rate of bacteria with increase in concentration of incorporated CAF in gelatin matrix. Proficient oxygen supply to needy cells is a continuing hurdle faced by tissue engineering scaffolds. The dissolved oxygen measurements revealed that CAF embedded in the scaffold were capable of increasing oxygen supply and thereby promote cell proliferation. Also, G (0.5%) exhibited highest cell viability on NIH 3T3 fibroblast cells which was mainly attributed to the highly porous architecture and its ability to enhance oxygen supply to cells. In vivo studies conducted on Sprague Dawley rats revealed the ability of G (0.5%) to promote skin regeneration in 20 days. Thus, the obtained data suggest that G (0.5%) is an ideal candidate for wound healing applications.

Faujasites Incorporated Tissue Engineering Scaffolds for Wound Healing: In Vitro and In Vivo Analysis

Exploring the possibility of using inorganic faujasites in tissue engineering scaffolds is a prospective approach in regenerative medicine. Novel gelatin/hyaluronic acid (HA)/faujasite porous scaffolds with low surface energy were fabricated by lyophilization. The pore size of gelatin/HA scaffold was 50-2000 μm, whereas it was greatly reduced to 10-250 μm after incorporation of 2.4% (w/w) of faujasites in polymer matrix, GH(2.4%). Micro computed tomography analysis showed that the porosity of GH(2.4%) was 90.6%. The summative effect was ideal for growth of dermal fibroblasts and cellular attachment. XRD analysis revealed that the embedded faujasites maintained their crystallinity in the polymer matrix even though they interacted with the polymers as indicated by FT-IR analysis. Coupling with effective reinforcement of faujasites, GH(2.4%) demonstrated compression modulus of 929 ± 7 Pa and glass transition temperature of 31 ± 0.05 °C. It exhibited controlled swelling and degradation, allowing sufficient space for tissue regrowth. The latter is further supported by capability of faujasites to provide efficient oxygen supply to fibroblast cells. GH(2.4%) showed a cell viability of 91 ± 8% on NIH 3T3 fibroblast cell lines. The in vivo studies on Sprague-Dawley rats revealed its ability to enhance wound healing by accelerating re-epithelization and collagen deposition. These findings indicated its potential as excellent wound dressing material.

Natural Polymer/Inorganic Material Based Hybrid Scaffolds for Skin Wound Healing

Dermal tissue engineering focuses on the restoration of diseased and damaged tissues by using a combination of cells, biomaterials, and bioactive molecules. Inorganic substances like zeolites, clay, mesoporous silica, metals, and metal oxides are advanced materials used in wound healing research. They can improve the structural stability and bioactivity of bio polymeric scaffolds. Zeolites, clays, and mesoporous silica act as suitable carriers for drug delivery and when incorporated within scaffolds, serve as ideal matrices for promoting skin regeneration. This review focuses on various natural polymers/inorganic materials based composite scaffolds used for skin tissue engineering, highlighting their synthesis routes and mode of action by which wound healing is enhanced. Among the different inorganic materials used, the role of zeolites incorporated biocomposites for promoting blood coagulation, antibacterial effect; oxygen delivery to cells and wound healing are discussed in detail. The article thus includes recent attempts to explore the hidden potential of inorganic materials in dermal tissue engineering.

Synthesis and characterization of magnetic nanoparticle-embedded multi-functional polymeric micelles for MRI-guided gene delivery

AbstractSuperparamagnetic iron oxide nanoparticle (SPION)-based diagnostic properties with accompanying therapeutics such as drugs or genes have been explored for improvement of their therapeutic efficacy. Positively charged SPION-loaded polymersomes was prepared to deliver genes to the target sites; this process was concomitantly monitored by magnetic resonance imaging (MRI). The surface characteristics and morphology were respectively measured by dynamic light scattering and transmission electron microscopy. The complex between the polymer and the pDNA was confirmed by a gel retardation assay. The transfection efficiency and cytotoxicity in vitro were tested by treating of the CT-26 colon cancer cell line with luciferase-expressing plasmids/SPION complex. MRI was also used to check the detectability of SPION in vitro and in vivo. A SPION-loaded polymersome carrying genetic materials was delivered and then accumulated in the tumor site of the murine colon cancer xenograft model after intravenous injection, possibly through a passive targeting mechanism. The accumulation was monitored using clinical MRI. This result indicates that the SPION-loaded polymersome can be applied to MR imageguided gene therapy.

Mannose-poly(ethylene glycol)-linked SPION targeted to antigen presenting cells for magnetic resonance imaging on lymph node

The aim of this study is to prepare biocompatible and targetable nanoparticles in lymph nodes (LNs) for lymph node-specific magnetic resonance (MR) imaging. Mannan-coated superparamagnetic iron oxide nanoparticles (SPIONs) (mannan-SPION), carboxylic mannan-coated SPION (CM-SPION), and β-glucan-coated SPION (Glucan-SPION) have been developed to target antigen-presenting cells (APCs), for lymph node detection by MR imaging. In this study, mannose-polyethylene glycol (PEG) was prepared by conjugating D-mannopyranosylphenyl isothiocyanate and amine-PEG-carboxyl. The 3-aminopropyltriethoxysilane (APTES)-activated SPION and the mannose-PEG were cross-linked to produce mannose-PEG-linked SPION (Mannose-PEG-SPION). Mannose-PEG-SPION carrying mannose on the surface were assumed efficient at targeting APCs through the specific interactions of the mannose tethered on the Mannose-PEG-SPION and the mannose receptors on the antigen presenting cells. The hydrophilic PEG corona layer in the Mannose-PEG-SPION could be prevented from aggregation during the systemic circulation with accompanying enhanced specificity and minimized systemic toxicity. The accumulation of SPION in the lymph nodes led to increased negative enhancement in the MR images. In the in vivo study, rats were injected intravenously with Mannose-PEG-SPION and PEG-SPION, as a control and then tracked by MR imaging after 1 h, 2 h, 3 h, and 24 h. MR imaging on lymph nodes clearly revealed the preferential uptake of Mannose-PEG-SPION in immune cell-rich lymph nodes. The predominant accumulation of Mannose-PEG-SPION in the lymph nodes was also confirmed by Prussian blue staining. Based on these results, Mannose-PEG-SPION shows great potential for lymph node-specific MR imaging.