The electroanalytical detection of the neurotransmitter dopamine (DA) in the presence of uric acid (UA) is explored for the first time using commercially procured nanodiamonds (NDs). These are electrically wired via surface modification upon screen-printed graphite macroelectrodes (SPEs). The surface coverage of the NDs on the SPEs was explored in order to optimize electroanalytical outputs to result in well-resolved signals and in low limits of detection. The (electro)analytical outputs are observed to be more sensitive than those achieved at bare (unmodified) SPEs. Such responses, previously reported in the academic literature have been reported to be electrocatalytic and have been previously attributed to the presence of surface sp² carbon and oxygenated species on the surface of the NDs. However, XPS analysis reveals the commercial NDs to be solely composed of nonconductive sp³ carbon. The low/negligible electroconductivity of the NDs was further confirmed when ND paste electrodes were fabricated and found to exhibit no electrochemical activity. The electroanalytical enhancement, when using NDs electronically wired upon SPEs, is attributed not to the NDs themselves being electrocatalytic, as reported previously, but rather changes in mass transport where the inert NDs block the underlying electroactive SPEs and create a random array of graphite microelectrodes. The electrode was applied to simultaneous sensing of DA and UA at pH 5.5. Figures of merit include (a) low working potentials of around 0.27 and 0.35 V (vs. Ag/AgCl); and (b) detection limits of 5.7 × 10⁻⁷ and 8.9 × 10⁻⁷ M for DA and UA, respectively. The electroanalytical enhancement of screen-printed electrodes modified with inert/non-conductive nanodiamonds is due to a change in mass transfer where the inert nanodiamonds facilitate the production of a random microelectrode array.

In an attempt to enhance chitosan biological activities, biopolymeric Schiff bases of chitosan and different salicylaldehydes and their palladium(II) and platinum(II) complexes were synthesized and tested. The chemical structures of these derivatives were characterized using ¹H-NMR, FTIR spectroscopy and XPRD. Thermal analysis was done through TGA/DTG-DTA. Electronic absorption spectra and surface morphologies were analyzed by SEM-EDAX. Chitosan and its derivatives were evaluated for their in vitro antimicrobial activity against two common bacterial and fungal plant pathogens Pseudomonas syringae pv. tomato and Fusarium graminearum, respectively, and for their antitumor activity against a human breast cancer cell line (MCF-7). It was found that, compared to the nonmodified chitosan, chitosan modified with Schiff bases and their complexes was highly toxic against the MCF-7 cell line and had antibacterial effects against P. syringea. However, the modified chitosan derivatives had less pronounced antifungal effects against F. graminearum compared to the nonmodified chitosan, suggesting different modes of action.