Adam K. Wanekaya

Herein, we demonstrate the use of lysozyme (Lys) as a model to fabricate a protein carrier system based on gold nanoparticles (AuNPs) via the Layer-by-Layer (LbL) technology. Poly(ethyleneimine) (PEI) and poly(sodium 4-styrenesulfonate) (PSS) were used as cationic and anionic polymers respectively to grow oppositely charged layers. Mild aqueous conditions were utilized to avoid protein denaturation and activity instead of organic solvents that have been used in other encapsulation systems. Two different strategies were used: (A) lysozyme acting as a reducing and stabilizing agent in the formation of AuNPs at a temperature of 45 ± 2 °C followed by only two subsequent polymeric layers deposited by LbL, and (B) citrate acting as a reducing agent prior to stabilization of the AuNPs by mercaptoundecanoic acid. Dynamic light scattering, UV-vis spectroscopy, IR spectroscopy and transmission electron microscopy were used to characterize the nanoconjugates. Furthermore, the enzymatic activity of the resulting protein/nanoparticle conjugates was evaluated using the bacteria Micrococcus lysodeikticus as a substrate.

Two-dimensional fluorescence difference spectroscopy (2-D FDS) was used to determine the unique spectral signatures of zinc oxide (ZnO), magnesium oxide (MgO), and 5% magnesium zinc oxide nanocomposite (5% Mg/ZnO) and was then used to demonstrate the change in spectral signature that occurs when physiologically important proteins, such as angiotensin-converting enzyme (ACE) and ribonuclease A (RNase A), interact with ZnO nanoparticles (NPs). When RNase A is bound to 5% Mg/ZnO, the intensity is quenched, while the intensity is magnified and a significant shift is seen when torula yeast RNA (TYRNA) is bound to RNase A and 5% Mg/ZnO. The intensity of 5% Mg/ZnO is quenched also when thrombin and thrombin aptamer are bound to the nanocomposite. These data indicate that RNA–protein interaction can occur unimpeded on the surface of NPs, which was confirmed by gel electrophoresis, and importantly that the change in fluorescence excitation, emission, and intensity shown by 2-D FDS may indicate specificity of biomolecular interactions.

We report the development of a novel, simple, and highly effective polymeric material with nanoscale dimensions for use in removal of heavy metal ions from aqueous media. The nanomaterial was ∼ 200 nm in diameter and several microns long and was fabricated in the form of nanowires via template‐directed electrochemical polymerization. The nanowires were covalently modified by cysteine, a nonessential amino acid with very high binding constants for selected toxic heavy metal ions, such as, As³⁺, Cd²⁺, Pb²⁺, and Cu²⁺. We demonstrated rapid and efficient removal of As³⁺, Cd²⁺, Pb²⁺, and Cu²⁺ ions from natural water samples. The arsenic removal capacity was found to be ∼ 160 mg As³⁺ per gram of the material, a substantially greater removal capacity than other materials reported to date. The removal capacity of other heavy metals ions was also rapid and effective, their concentrations becoming undetectable in a matter of minutes after treatment with the nanowires. These nanowires have demonstrated potential that could lead to a low cost, novel, and highly effective technique for use in treatment of drinking water and for other environmental remediation purposes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A sensitive voltammetric method for detection of trace heavy metal ions using chemically modified carbon nanotubes (CNTs) electrode surfaces is described. The CNTs were covalently modified with cysteine prior to casting on electrode surfaces. Cysteine is an amino acid with high affinities towards some heavy metals. In this assay, heavy metals ions accumulated on the cysteine‐modified CNT electrode surfaces prior to being subjected to differential pulse anodic stripping voltammetry analysis. The resulting peak currents were linearly related to the concentrations of the metal ions. The method was optimized with respect to accumulation time, reduction time and reduction potential. The detection limits were found to be 1 ppb and 15 ppb for Pb²⁺ and Cu²⁺ respectively. The technique was used for the detection of Pb²⁺ and Cu²⁺ in spiked lake water. The average recoveries of Pb²⁺ and Cu²⁺ were 96.2% and 94.5% with relative standard deviations of 8.43% and 7.53% respectively. The potential for simultaneous detection of heavy metal ions by the modified CNTs was also demonstrated.

We report the electrochemical deposition of poly(pyrrolepropylic acid) nanowires, their covalent modification with antibodies and their conversion into potential functional sensor devices. The nanowires and the devices were characterised by optical microscopy, fluorescence microscopy, electron microscopy and electrical measurements. Fluorescence images, current–voltage (I–V) profiles and real-time sensing measurements demonstrated a rapid and highly sensitive and selective detection of human serum albumin (HSA), a substance that has been used to diagnose incipient renal disease. The detection is based on the selective binding of HSA onto anti-HSA that is covalently attached to the nanowires. The binding changes the electrical properties of the nanowires thus enabling the real-time detection. Whilst the utility of the research was demonstrated for protein binding/detection, the technology could easily be designed for the detection of other analytes by the modification of polymer nanowires with other analyte-specific molecules/biomolecules. Therefore, the technology has the potential to positively impact broad analytical applications in the biomedical, environmental and other sectors. Real-time dynamic current response on sequential exposure of buffer, bovine serum albumin (BSA) and human serum albumin (HSA) onto anti-HSA modified poly (pyrrolepropylic acid) nanowires. Fluorescence images of poly(pyrrolepropylic acid) nanowire (top right) and polypyrrole nanowire control (bottom right) after sequential treatment with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), anti HSA and fluorophore-labeled HSA.