Formulation and characterization of antimicrobial quaternary ammonium dendrimer in poly(methyl methcarylate) bone cement.

The use of novel antimicrobial molecules in bone cement can improve efficiency of recuperation after arthroplasty or joint replacement surgeries, avoiding the risks associated with antibiotic resistant antimicrobial agents. Nanomaterials particularly dendrimers are particularly useful for making broad spectrum killing agents owing to their large surface areas and functionalities. Therefore, we have synthesized generation 1 quaternary ammonium dendrimer of tripropylene glycol diacrylate (TPGDA) using octyl iodide (OI) [TPGDA G1.0 (=) quaternary octyl iodide (QOI)] and capitalized on their capabilities of contact killing based mechanism. We formulated different TPGDA G1.0 (=) QOI antimicrobial agent loaded liquid component composed of methyl methacrylate monomer and N,N-dimethyl-p-toluidine coinitiator. Different polymethyl methacrylate (PMMA) based experimental bone cement formulations were made and dendrimer concentration was optimized. Mechanical strength and compressive modulus of modified bone cement decreased on increasing concentrations and 10% was optimized for further analysis. The mechanical strength of bone cement yield the similar trend in wet conditions bone cement immersed in artificially created stimulated body fluids. Ten percent TPGDA G1.0 (=) QOI in bone cement was sufficient to kill gram positive and negative bacteria and its property is retained even after a period of 30 days. Thus novel dendritic structures show promise for clinical antimicrobial activity while retaining mechanical properties of bone cements. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 521-530, 2017.

Novel functionalized fluorescent polymeric nanoparticles for immobilization of biomolecules.

Novel, size controlled fluorescent polymeric nanoparticles (FPNP) were synthesized having acetoacetoxy functionality on the surface for immobilization of biomolecules which can be utilized as biomarkers and labels in fluoroimmunoassays. Core-shell nanoparticles of poly(styrene, St-methyl methacrylate, MMA-acetoacetoxy ethyl methacrylate, AAEM), stabilized by various concentrations of surfactant, sodium lauryl sulphate (SLS), were obtained by facile miniemulsion co-polymerization encapsulated with pyrene molecules in their hydrophobic core. Analytical, spectroscopic and imaging characterization techniques revealed the formation of stable, monodisperse, spherical nano sized particles exhibiting high luminescence properties. Particles with 1% SLS (S1) showed good dispersion stability and fluorescence intensity and were chosen as ideal candidates for further immobilization studies. Steady state fluorescence studies showed 10 times higher fluorescence intensity of S1 nanoparticles than that of pyrene solution in solvent-toluene at the same concentration. Environmental factors such as pH, ionic strength and time were found to have no effect on fluorescence intensity of FPNPs. Surface ß-di-ketone groups were utilized for the covalent immobilization of enzyme conjugated antibodies without any activation or pre-treatment of nanoparticles.

Highly sensitive detection of Salmonella typhi using surface aminated polycarbonate membrane enhanced-ELISA.

The identification of pathogenic bacteria in water is important for addressing preventive and treatment issues regarding health and safety. A highly sensitive and specific solid-phase sandwich ELISA procedure was developed for the detection of typhoid causing extremely lethal water borne pathogen Salmonella typhi (S. typhi) on modified isopore polycarbonate (PC) black membranes. PC membranes were chemically derivatized to generate amino groups on the surface maintaining their pysico-optico properties. Surface modified PC membranes were characterized by ATR-FTIR spectrometer, goniometer and scanning electron microscope. Polyclonal somatic 'O' type antibodies (Abs) against whole cell S. typhi were immobilized on them by following the amine glutaraldehyde chemistry. Antibody immobilized membranes captured S. typhi from buffer solution and this complex was detected colourimetrically using HRP labelled S. typhi Ab. A detection limit of 2×10(3)cells/ml of bacteria was achieved with the modified PC membranes without any pre-enrichment step as against 10(6)-10(7)CFU/ml of bacteria by typical ELISA method. The assay was demonstrated to be specific for the target bacteria when compared with other cross-reactant water borne pathogens. The intra- and inter-assay precision for 10(4) and 10(5)cells/ml was 5.3-7.4 and 10.3-19.7% respectively. The developed immunoassay for the detection of S. typhi is simple, easy to handle, sensitive specific, reproducible and cost effective in comparison with the commercially existing immunochromatographic assays.

Selective capturing and detection of Salmonella typhi on polycarbonate membrane using bioconjugated quantum dots.

Present work demonstrates the utilization of surface modified polycarbonate (PC) membrane as solid phase and antibody conjugated CdSe/ZnS quantum dots (QDs) as fluorescent label for the sensitive and selective detection of Salmonella typhi (S. typhi) in water in a period of 2.5h. PC membrane was surface modified with glycine and activated by EDC/NHS for immobilization of S. typhi specific IgG. Antibody immobilized porous PC membrane was incubated with bacteria contaminated water for immunocapturing of S. typhi. Antibody conjugated QDs were also prepared by using carbodiimide chemistry. Both modified PC membrane and quantum dots were characterized by using various modern analytical tools. It was estimated that 1.95 molecules of QDs were successfully bio-conjugated per unit of IgG. PC membrane with captured bacteria was incubated with prepared IgG conjugated QDs for the formation of sandwich complex. Analysis of the regions of interest (ROI) in fluorescent micrographs showed that newly developed method based on PC and fluorescent QDs has 100 times higher detection sensitivity (100 cells/mL) as compared with detection using conventional dye (FITC) based methods.