An electrochemical immunosensor to minimize the nonspecific adsorption and to improve sensitivity of protein assays in human serum.

An electrochemical immunoassay which minimizes nonspecific protein adsorption and improves detection sensitivity of proteomic cancer biomarker is described. Our technique comprises two novel features: (i) a high density terminally functionalized poly(N-isopropyl acrylamide) 'brush' layer is grown by surface initiated reversible addition fragmentation chain transfer (RAFT) polymerization method from the electrode surface in order to minimize nonspecific adsorption of serum proteins and other biomolecules, and (ii) a signal amplifying 'bionanoconjugate' comprised of graphene oxide nanosheets decorated with CdSe quantum dots and recombinant single-chain variable fragments towards MSLN, is used to 'physically' amplify the anodic stripping voltammetric signal. This method enabled a detection limit of ca. 1 pg/mL MSLN (RSD=4.6%, n=4) spiked in serum samples. Because of the simple, specific and sensitive nature of this methodology, we feel that it may find potential use in serum-based protein diagnostics.

Femtomolar detection of a cancer biomarker protein in serum with ultralow background current by anodic stripping voltammetry.

An electrochemical immunosensor for the detection of a cancer biomarker protein in serum at femtomolar concentrations with ultralow background response has been developed, which consists of (i) a hydrophilic polyacrylic acid brush-modified indium tin oxide substrate as an antifouling substrate and (ii) a graphene-quantum dots-antibody 'bionanoconjugate' as a signal amplification label in voltammetric detection of targets in a glassy carbon electrode.

Graphene/quantum dot bionanoconjugates as signal amplifiers in stripping voltammetric detection of EpCAM biomarkers.

A sensitive electrochemical immunosensor for the detection of epithelial cell adhesion molecule (EpCAM) antigen, a common marker for tumors of epithelial origin, employing bionanoconjugates as signal-transduction labels has been developed. The bionanoconjugates were fabricated by carboxylation of the two-dimensional graphene oxide nanosheets (GRs) and immobilizing streptavidin and amine-functionalized CdSe quantum dots (QDs) on carboxylated GRs via carbodiimide coupling chemistry, followed by the immunoreaction with the biotinylated secondary antibodies. Since carboxylated GRs have a higher density of active sites, it allows a large number of CdSe QDs to be immobilized onto the surface of the bionanoconjugates, and hence, enhance the sensitivity of the immunosensor. The method enabled detection limits of 100 fg/mL and 1 pg/mL (based on the S/N=3) in PBS buffer and serum samples, respectively, using anodic stripping voltammetric readout. The immunosensor showed a good selectivity, reproducibility, and long-storage stability, and may become a promising technique for the early detection of tumor biomarker in clinical/biological samples.

Development of encoded particle-polymer arrays for the accelerated screening of antifouling layers.

A multiplexed screening methodology for the rapid development of antifouling polymer surfaces is presented. An array of protein resistant polymer layers with high grafting (>100 mg m(-2)) were polymerized on optically encoded particles. Multiplexed analysis showed a 97% reduction in nonspecific protein adsorption for all polymer layers created.

An organic matrix-mediated processing methodology to fabricate hydroxyapatite based nanostructured biocomposites.

An amorphous calcium phosphate precursor phase, which forms by adding orthophosphoric acid to a calcium hydroxide suspension, is transformed into crystalline hydroxyapatite by introducing polymer solutions. The nanostructured composite films formed by a solvent casting technique from the concentrated hybrid suspension are characterised for structure and mechanical properties.

In vitro apatite formation and its growth kinetics on hydroxyapatite/polyetheretherketone biocomposites.

The formation of biologically equivalent carbonate-containing apatite on the surface of synthetic hydroxyapatite (HA) is an important step leading to good bone healing. In this study, HA-reinforced polyetheretherketone (PEEK) composites were prepared by homogeneous mixing of HA and PEEK powders, compaction, and pressureless sintering. The bioactivity of HA/PEEK composite with 10, 20, 30 and 40 vol% HA was evaluated by immersing the composite disks in the simulated body fluid (SBF) for up to 4 weeks. The surface of composite with 40 vol% HA was covered by a layer of bone-like apatite just after 3 days of immersion, while 10 vol% HA was covered only after 28 days. This apatite layer was characterized by SEM, thin film X-ray diffractometer, attenuated total reflectance-Fourier transform infrared spectrometer (FTIR)/FTIR. Introducing a concept called apatite-forming capacity of SBF, growth kinetics of the apatite layer on the surface of the composite disks was carried out. The growth rate constant increased with HA volume fraction of the composite, suggesting that the bioactivity of the HA/PEEK composite increases with increasing HA volume fraction in the composite.