Shilpa N. Sawant

Biocompatibility studies on polyaniline and polyaniline-silver nanoparticle coated polyurethane composite.

Biocompatibility of medical grade polyurethane coated with polyaniline (PANi) and polyaniline-silver nanoparticle composite (PANi-AgNp) is reported here. These modified films showed 23 and 18% of 3T3 L1 cell death when compared to 41% with virgin polyurethane (PU) after 48h of incubation, respectively. All the surfaces elucidated inflammatory response in the form of enhanced expressions of the proinflammatory cytokines genes, TNF-α and IL-6. But these values were less (by 20%) on modified films than on the bare PU. Attachment of Pseudomonas and Bacillus were markedly less on PANi-AgNp coated surface (by 90.6 and 50.5%, respectively) when compared to the uncoated PU. As the CFU counts decreases on the nanoparticle coated PU, the adsorbed carbohydrate as well as protein content on to the surface of polymer decreases accordingly, indicating less attachment. A 20% reduction in the thickness of biofilm was observed in PANi-AgNp coated PU surface. A very strong positive correlation is observed between the contact angles of the polymers and the various biological parameters (namely colony forming units, protein, carbohydrate, cell death and inflammatory response), indicating hydrophilic surfaces prevent bacterial biofilm as well as are compatible to cells when compared to hydrophobic surfaces. Coating PU with PANi and PANi+AgNp renders the surface conductive, suggesting potential application in electrochemical biosensors. In addition, these modifications make the surface more biocompatible than the original PU.

Polyaniline-Based Highly Sensitive Microbial Biosensor for Selective Detection of Lindane

A highly sensitive, selective, and rapid, whole-cell-based electrochemical biosensor was developed for detection of the persistent organochlorine pesticide γ-hexachlorocyclohexane (γ-HCH), commonly known as lindane. The gene linA2 encoding the enzyme γ-hexachlorocyclohexane (HCH) dehydrochlorinase (LinA2), involved in the initial steps of lindane (γ-HCH) biotransformation, was cloned and overexpressed in Escherichia coli . The lindane-biodegrading E. coli cells were immobilized on polyaniline film. The rapid and selective degradation of lindane and concomitant generation of hydrochloric acid by the recombinant E. coli cells in the microenvironment of polyaniline led to a change in its conductivity, which was monitored by pulsed amperometry. The biosensor could detect lindane in the part-per-trillion concentration range with a linear response from 2 to 45 ppt. The sensor was found to be selective to all the isomers of hexachlorocyclohexane (HCH) and to pentachlorocyclohexane (PCCH) but did not respond to other aliphatic and aromatic chlorides or to the end product of lindane degradation, i.e., trichlorobenzene (TCB). The sensor also did not respond to other commonly used organochlorine pesticides like DDT and DDE. On the basis of experimental results, a rationale has been proposed for the excellent sensitivity of polyaniline as a pH sensor for detection of H(+) ions released in its microenvironment.

Synthesis of mesostructured polyaniline using mixed surfactants, anionic sodium dodecylsulfate and non-ionic polymers and their applications in H2O2 and glucose sensing

Mesostructured polyaniline was prepared by the self-assembly of a mixture of an anionic surfactant, sodium dodecylsulfate and a non-ionic polymeric surfactant (polyethylene glycol, and block-co-polymers such as Pluronic P123 and Brij-35). Materials were characterized by a complementary combination of X-ray diffraction, Scanning electron microscopy, Fourier-transform infrared spectrometer and UV-visible spectrophotometer. Mesostructured polyaniline was used for construction of biosensor, which displayed excellent electrocatalytic response for the detection of H(2)O(2) and glucose compared to conventional polyaniline. The electrocatalytic response observed in the case of mesostructured polyaniline can be correlated with the large surface area and nanopores which enhances the accessibility of H(2)O(2)/glucose molecule to the active site that result in high observed current. The methodology adopted in the present study provides a new platform for the fabrication of polyaniline based high-performance glucose and other biosensors.

Antibiofilm properties of silver and gold incorporated PU, PCLm, PC and PMMA nanocomposites under two shear conditions.

Silver and gold nanoparticles (of average size ∼20–27 nm) were incorporated in PU (Polyurethane), PCLm (Polycaprolactam), PC (polycarbonate) and PMMA (Polymethylmethaacrylate) by swelling and casting methods under ambient conditions. In the latter method the nanoparticle would be present not only on the surface, but also inside the polymer. These nanoparticles were prepared initially by using a cosolvent, THF. PU and PCLm were dissolved and swollen with THF. PC and PMMA were dissolved in CHCl3 and here the cosolvent, THF, acted as an intermediate between water and CHCl3. FTIR indicated that the interaction between the polymer and the nanoparticle was through the functional group in the polymer. The formation of E.coli biofilm on these nanocomposites under low (in a Drip flow biofilm reactor) and high shear (in a Shaker) conditions indicated that the biofilm growth was higher (twice) in the former than in the latter (ratio of shear force = 15). A positive correlation between the contact angle (of the virgin surface) and the number of colonies, carbohydrate and protein attached on it were observed. Ag nanocomposites exhibited better antibiofilm properties than Au. Bacterial attachment was highest on PC and least on PU nanocomposite. Casting method appeared to be better than swelling method in reducing the attachment (by a factor of 2). Composites reduced growth of organisms by six orders of magnitude, and protein and carbohydrate by 2–5 times. This study indicates that these nanocomposites may be suitable for implant applications.

Synthesis of surfactant encapsulated nickel hexacyanoferrate nanoparticles and deposition of their Langmuir-Blodgett film

Sodium hexametaphosphate (HMP) stabilized nickel hexacyanoferrate (NiHCF) nanoparticles were prepared in aqueous solution and were successfully extracted into an organic phase using cetyltrimethylammonium bromide (CTAB) as the surfactant. Dynamic Light Scattering (DLS) studies suggest that the average size of the nanoparticles is retained during the extraction process from the aqueous to the organic phase. X-Ray diffraction, cyclic voltammetry, IR spectroscopy and magnetic measurements carried on the organic phase shows specific signatures of the presence of the surfactant encapsulated NiHCF nanoparticles. Transmission Electron Microscopy (TEM) measurements show that the average size of these surfactant encapsulated nanoparticles in the organic phase is about 22 nm, and as has been suggested by DLS studies, it does not change with respect to repeated evaporation and re-extraction processes of the organic phase. Pressure–area isotherms of the organic phase in a Langmuir–Blodgett (LB) trough, with water as subphase, indicate stable monolayer formation of the surfactant-encapsulated NiHCF nanoparticles at the air–water interface. Multi-layered deposition of the surfactant-encapsulated nanoparticles onto an indium tin oxide (ITO) coated glass slide could also be carried out using the LB technique. Cyclic voltammetry studies on these LB multilayers confirm regular and systematic transfer of the NiHCF nanoparticles on the ITO substrate. The method described here is the first of its kind with respect to the synthesis of surfactant encapsulated molecular magnetic nanoparticles and subsequent deposition of their LB films.

Water dispersible Ag@polyaniline-pectin as supercapacitor electrode for physiological environment

Designing the supercapacitor electrode material for implantable electronic medical devices (IEMDs) requires careful consideration because of the need for materials which are inherently high in capacitance, biocompatibility, and antibacterial activity and are able to work in physiological environment. For the first time, we report the synthesis of a nanocomposite which has the aforementioned properties and demonstrate the nanocomposite as a supercapacitor electrode material operating in physiological fluids. In the first step, water dispersible polyaniline-pectin (PANI-PEC) nanoparticles were synthesized using biopolymer pectin (PEC) as the stabilizer. In the second step, the synthesized PANI-PEC was treated with a silver nitrate solution to afford silver nanoparticles (Ag NPs) decorated PANI-PEC nanocomposite (Ag@PANI-PEC). PANI-PEC acted as a reducing agent to convert silver ions to Ag NPs, thus eliminating the need of an exogenous reducing agent. Ag@PANI-PEC displays a specific capacitance of 140, 290, 144 and 121 F g-1 in phosphate buffer saline, blood, urine and serum, respectively, which are all physiological fluids. Furthermore, due to the use of biopolymer PEC, PANI-PEC and Ag@PANI-PEC exhibited biocompatibility and the presence of silver on Ag@PANI-PEC rendered antibacterial properties to the latter, thus making them an ideal material for in vivo implants. These findings establish the feasibility of using the nanocomposite as a potential material for energy storage device in IEMDs.

Polyaniline–Prussian blue hybrid: synthesis and magnetic behaviour

We report the synthesis of an organic–inorganic hybrid material composed of a conducting polyaniline (PANI) matrix and Prussian blue (PB) network, the latter formed in situ in the polymer matrix. The hybrid was prepared by treating FeCl4 −-doped PANI with K3Fe(CN)6 unlike the previously reported method of potential cycling to obtain alternate layers of PANI and PB. Cyclic voltammetry and X-ray photoelectron spectroscopy investigations confirmed the formation of a network typical of PB inside the PANI matrix. Infrared spectroscopy points to the formation of an extended network between Fe in PANI matrix and Fe from K3Fe(CN)6. Magnetization studies of the hybrid material showed ferromagnetic ordering with a T c of about 6 K.

Pectin coated polyaniline nanoparticles for an amperometric glucose biosensor

An amperometric glucose sensor based on a nanoparticulate form of polyaniline (PAni) is reported herein. The PAni nanoparticles were synthesized using pectin (PAni–Pec NPs) and functionalized with glucose oxidase (GOx-PAni–Pec NPs) to create a highly specific biosensor. Biopolymer pectin stabilizes the colloidal nanoparticles of PAni while also allowing homogenous and a high degree of functionalization of the nanoparticles with glucose oxidase via covalent coupling. This helped to arrest enzyme leaching and enhance biosensor stability. The biosensor showed high sensitivity (79.49 μA mM−1 cm−2), wide linear range (0.06–4 mM) and a low detection limit (43.5 μM) at a working potential of 0.6 V. The sensitivity exhibited by GOx-PAni–Pec NPs reported herein was three times higher than that of conventional polyaniline for the same amount of GOx immobilized by a physical adsorption method. Efficient loading and organization of GOx on the nanoparticles could afford adequate availability of the substrate to the enzyme sites leading to better sensitivity. The biosensor did not respond to the presence of electroactive interferents (ascorbic acid, urea, and uric acid) coexisting with glucose in physiological fluids, thereby revealing its specificity. The analytical performance of the biosensor was evaluated for estimation of glucose in blood serum samples. The reliability and stability of the glucose biosensor indicate its potential for application in routine analysis of glucose in physiological fluids.

In vitro biocompatiblity of modified polycarbonate as a biomaterial

Nitrated and aminated polycarbonates were prepared chemically, characterized and tested in vitro as a possible biomaterial. Adhesion of Staphylococcus aureus NCIM 5021, Escherichia coli NCIM 2931 and Proteus vulgaris NCIM 2813 and the presence of carbohydrate, protein, CFU and ATP on these surfaces were examined. Cytotoxicity of these surfaces was investigated by growing L929 mouse fibroblast cells. NO2-PC was more hydrophilic than un-PC and reduced adhesion of bacterial protein and carbohydrate. NH2-PC was the most hydrophilic surface biofilm prevention and increased proliferation of the fibroblast cells. The motility of all the three organisms decreased on aminated surface when compared to that on the other two. This study indicated that reducing the surface hydrophobicity alone was not sufficient to develop a biocompatible material, but providing favorable surface functional groups was also a necessary criterion. A strong correlation was observed between the hydrophobicity of the polymer surface and the zeta potential of the organism with bacterial attachment (CFU/ml). A multi-linear regression model with these two parameters was able to fit the observed bacterial attachment data well.