Shaswat Barua

One step preparation of a biocompatible, antimicrobial reduced graphene oxide–silver nanohybrid as a topical antimicrobial agent

A reduced graphene oxide–silver nanohybrid (Ag–RGO) was prepared by simultaneous reduction of graphene oxide and silver ions, using the aqueous extract of the Colocasia esculenta leaf. The nanohybrid demonstrated better antimicrobial activity than the individual nanomaterials. Excellent cytocompatibility was observed for peripheral blood mononuclear cells (PBMCs) and mammalian red blood cells (RBCs). An acute dermal toxicity study on wistar rats confirmed no induction of direct or indirect toxicity to the host. Thus, this nanohybrid holds potential for applications as a non-toxic topical antimicrobial agent in dressings, bandages, ointments etc.

Biocompatible high performance hyperbranched epoxy/clay nanocomposite as an implantable material

Polymeric biomaterials are in extensive use in the domain of tissue engineering and regenerative medicine. High performance hyperbranched epoxy is projected here as a potential biomaterial for tissue regeneration. Thermosetting hyperbranched epoxy nanocomposites were prepared with Homalomena aromatica rhizome oil-modified bentonite as well as organically modified montmorillonite clay. Fourier transformed infrared spectroscopy, x-ray diffraction and scanning and transmission electron microscopic techniques confirmed the strong interfacial interaction of clay layers with the epoxy matrix. The poly(amido amine)-cured thermosetting nanocomposites exhibited high mechanical properties like impact resistance (>100 cm), scratch hardness (>10 kg), tensile strength (48-58 MPa) and elongation at break (11.9-16.6%). Cytocompatibility of the thermosets was found to be excellent as evident by MTT and red blood cell hemolytic assays. The nanocomposites exhibited antimicrobial activity against Staphylococcus aureus (ATCC 11632), Escherichia coli (ATCC 10536), Mycobacterium smegmatis (ATCC14468) and Candida albicans (ATCC 10231) strains. In vivo biocompatibility of the best performing nanocomposite was ascertained by histopathological study of the brain, heart, liver and skin after subcutaneous implantation in Wistar rats. The material supported the proliferation of dermatocytes without induction of any sign of toxicity to the above organs. The adherence and proliferation of cells endorse the nanocomposite as a non-toxic biomaterial for tissue regeneration.

Copper–copper oxide coated nanofibrillar cellulose: a promising biomaterial

Nanocellulose is gaining impetus as a hierarchical material in many advanced applications. The isolation of nanocellulose from easily available bio-resources is an area to be delved into thoroughly. This article highlights the isolation of nanofibrillar cellulose from an abundant natural source, Colocasia esculenta, by a chemical method. The nanofibrils were coated with copper–copper oxide nanoparticles through a ‘green’ reductive technique using the alcoholic extract of Terminalia chebula fruit. The prepared fibrils and the nanohybrid were characterized by Fourier transformed infrared spectroscopy, X-ray diffraction and transmission electron microscopic studies. The coated nanofibrils showed promising antimicrobial activity against Staphyllococcus aureus, Escherichia coli and Candida albicans. The nanohybrid was quite compatible with peripheral blood mononuclear cells (PBMC) as well as mammalian red blood cells (RBCs). The structural integrity of bovine serum albumin (BSA) was unaltered upon interaction with the nanohybrid. The biocompatible and antimicrobial nanohybrid presented here possesses high potential to be used as a biomaterial in a suitable niche of modern biomedical fields.

Self-healable castor oil based tough smart hyperbranched polyurethane nanocomposite with antimicrobial attributes

Here, castor oil-based tough hyperbranched polyurethane/sulfur nanoparticles decorated reduced graphene oxide (HPU/SRGO) nanocomposites are fabricated with different weight% of nanohybrid. Tremendous enhancement of mechanical properties, such as tensile strength (from 7.2 to 24.3 MPa), tensile modulus (from 3.3 to 137.7 MPa), toughness (from 25.4 to 313.52 MJ m−3) and elongation at break (from 710% to 1456%), is observed upon incorporation of nanohybrid in HPU matrix due to strong interaction between SRGO and HPU matrix. The nanocomposite exhibited excellent repeatable self-healing (within 50–60 s at 360 W under microwave and 5–7.5 min under sunlight) and shape recovery (within 30–50 s at 360 W under microwave and 1–3 min under sunlight). The nanocomposite also demonstrated profound microbial inhibitory effect against Staphylococcus aureus, Escherichia coli and Candida albicans. Thus, the studied nanocomposite has tremendous potential for various advanced applications.

Green silver nanoparticles: enhanced antimicrobial and antibiofilm activity with effects on DNA replication and cell cytotoxicity

Biofabricated metal nanoparticles are biocompatible, inexpensive and eco-friendly. They find immense utility in the domain of biomedical and materials science. The present work focuses on the ‘green’ synthesis of silver nanoparticles (AgNPs) using the methanolic extract of Syzygium cumini leaf. AgNPs showed the characteristic surface plasmon resonance peak at 442 nm. The XRD pattern confirmed the formation of face centered cubic AgNPs. The nanoparticles were uniformly distributed within a narrow size range of 10–20 nm. The particles exhibited significant antimicrobial activity against a panel of pathogens like Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Mycobacterium smegmatis, Trichophyton rubrum, Aspergillus sp and Candida albicans. Alterations in membrane permeability of AgNP treated microbial cells were evident from scanning electron microscope images. The replication fidelity of small (1500 bp) DNA fragments in the presence of AgNPs was compromised in a dose-dependent fashion and addition of bovine serum albumin (BSA) to PCR reactions reversed the effect of AgNPs. Besides, the prepared nanoparticles inhibited biofilm formation in a wide range of AgNP concentrations. Significantly, cytotoxicity assays showed good compatibility of AgNPs with human embryonic kidney cells (HEK 293). In summary, the study suggests an eco-friendly, cost effective and biocompatible approach for synthesizing AgNPs, which may act as a potential template for designing novel antibacterial, antifungal and antibiofilm agents.

Biocompatible hyperbranched epoxy/silver–reduced graphene oxide–curcumin nanocomposite as an advanced antimicrobial material

Fouling due to bacteria, fungi and algae is a serious problem in the domains of biomedical research, paints and coatings. Toxicity of the prevailing antimicrobial systems demands benign materials with adequate antimicrobial properties. In this context, thermosetting hyperbranched epoxy/silver–reduced graphene oxide–curcumin nanocomposites with antimicrobial attributes against bacteria, fungi and algae are reported here for the first time. The nanocomposite also exhibited high mechanical properties with tensile strength: 54–65 MPa and elongation at break: 17–21%. Ultrasonication, the ‘green’ tool was used to immobilize curcumin onto the silver–reduced graphene oxide nanohybrid. The nanocomposites inhibited the growth of Staphylococcus aureus and Candida albicans, the microorganisms found in surgical infection sites, with minimum inhibitory concentrations of 38 and 41 μg mL−1 at 3% loading of the immobilized nanohybrid. Further, the nanocomposite prevented the growth of the green microalgae Chlorella sp. Moreover, in vitro and in vivo bio-assays confirmed the biocompatibility of the prepared nanocomposite. This study endorses the nanocomposite as an efficient antimicrobial material for different advanced applications from biomedical domains to marine coatings.

s-Triazine-based biocompatible hyperbranched epoxy adhesive with antibacterial attributes for sutureless surgical sealing

Endeavors have been made over last few decades to relieve mankind from painful suturing during surgery, especially in the case of pediatrics. A few surgical sealants or tissue adhesives have been designed; however, biocompatibility and degradation concerns limit their use. Herein, an s-triazine-based hyperbranched epoxy, along with a poly(amido amine) hardener, was used to develop a highly biocompatible surgical sealant. The epoxy can be cross-linked up to 62% at room temperature. Furthermore, the sealant exhibited antibacterial activity against Staphylococcus aureus, the most notorious microorganism that causes surgical site infections. The sealant is degradable under physiological conditions and the degraded products are non-toxic. Thus, here we demonstrate the major merits of the present sealant such as high mechanical stability, optimum balance between strength and flexibility, biocompatibility and degradability.

Plant extract–mediated green silver nanoparticles: Efficacy as soil conditioner and plant growth promoter

Recently, concerns have been raised regarding the ultimate fate of silver nanoparticles (SNPs) after their release into the environment. In this study, the environmental feasibility of plant leaf (Thuja occidentalis) extract-mediated green SNPs (GSNPs) was assessed in terms of their effects on soil physicochemical properties and crop growth in comparison to conventionally synthesized silver nanoparticles (CSNPs). Upon application of GSNPs, soil pH shifted toward neutrality, and substantial increments were observed in water holding capacity (WHC), cation exchange capacity (CEC), and N/P availability. The mechanism behind the enhanced availability of N was verified through lab-scale experiments in which GSNP-treated soils efficiently resisted nitrate leaching, thereby sustaining N availability in root zone soil layers. However, retardation in nutrient availability and enzyme activity was apparent in soils treated with 100 mg kg-1 of either CSNPs or GSNPs. Remarkable improvements in leaf area index (LAI), leaf number, chlorophyll content, nitrate reductase (NR) activity, and Phaseolus vulgaris pod yield were observed after the application of low doses of GSNPs (25-50 mg kg-1). The true benefit of GSNP application to soil was substantiated through experiments on plant uptake of nutrients, NR expression, and ferredoxin gene expression in P. vulgaris leaves.

Electrochemical detection of monosodium glutamate in foodstuffs based on Au@MoS2/chitosan modified glassy carbon electrode

We report an amperometric immunosensor for the detection of monosodium glutamate (MSG) using a glassy carbon electrode modified with gold nanoparticle decorated on a molybdenum disulfide/chitosan (Au@MoS2/Ch) nanocomposite. In the present detection technique, Au@MoS2/Ch was used as a conductive matrix and anti-glutamate antibody was immobilized on to its surface via carbodiimide coupling method. Chemical and morphological attributes of the various components of the immunosensor were confirmed by UV-vis spectroscopy, SEM, TEM and XRD analysis. Electrochemical characterizations were carried out by CV, DPV and EIS. Overall results showed the effective fabrication of highly conductive Au@MoS2/Ch nanocomposite for sensitive electrochemical detection of MSG. A linear relationship was perceived between the change in current and concentration of MSG. The relationship was found to be consistent in the detection range of 0.05-200 µM. Statistical validation of the assay showed limit of detection and limit of quantification values as 0.03 and 0.1 µM, respectively (R2 = 0.99).