Current Pharmaceutical Analysis - Volume 5, Issue 3, 2009

The current interest in micro- and nano- scale devices has lead to their development for biomedical analysis. This ranges from static nucleic acid and protein arrays to complex analytical techniques based on chromatographic and electrokinetic techniques utilizing small-bore capillaries and chips. This review will describe the range of technologies available and examine the different platforms used in micro- and nano-device driven design. Additionally, the review will cover specific devices and device-driven technologies, such as standard and chip-based capillary electrophoresis and nano-flow chromatography that either have potential or are currently available for biomedical analysis. With more laboratories turning towards high throughput, cost effective analytical processes there is a special need for biomedical analysis to be performed at the micro- and ultra-micro level because of limited sample availability. Although limited at present, micro- and nano- technologies have been successfully applied to the examination of not only basic research samples, but also to clinical samples. Currently, micro- analytical techniques hold the potential of being able to examine specialized samples such as single cells and their secretions, extremely small samples from newborn and young patients, precious limited material archive specimens, and perform real-time bedside monitoring.

One of the main histopathological features of Alzheimer's disease (AD) is the formation of neuritic plaques in the brain of AD individuals. The aggregation of amyloid beta (Aβ) peptides is central to the formation of the plaques. In its native form, Aβ is unfolded but self-assembles into a β-sheet structure of ordered fibrils under various conditions. It was originally proposed that fibrillar Aβ deposits cause the various symptoms of AD observed during its early and progressed stages but increasing evidence indicates that smaller, soluble forms of Aβ are the primary neurotoxic species. Still, the underlying mechanism of Aβ-induced neurotoxicity remains unknown. In order to fully understand which Aβ species are the most toxic under certain environmental conditions, we need sensitive analytical tools that are able to selectively detect the various stages of Aβ oligomerisation and assembly. Capturing these species would also aid in identifying potential therapeutic targets for the involved patho-physiological stages. Currently, Aβ oligomerisation and assembly are commonly studied using techniques such as microscopy, circular dichroism, fluorescence and light scattering spectroscopy. Label-free electrochemical aggregation of Aβ-peptides, surface plasmon resonance and agarose gel diffusion-based method have also been reported. In this paper, we review techniques used for analysing Aβ oligomerisation and assembly, emphasising those that provide information on Aβ aggregation kinetics. We will conclude by discussing the potential role nanotechnology has in enhancing the detection sensitivity and selectivity of Aβ oligomerisation and assembly.

A simple, rapid, reliable and fully validated square wave adsorptive stripping voltammetric procedure has been developed for the determination of rifampicin drug in bulk form, capsules and human urine in acetate buffer pH 5.0 which shows electrochemical reduction at a new Dysprosium nanowires modified carbon paste electrode (DyNW/CPE). In this paper, the modified carbon paste electrode (DyNW/CPE) exhibiting an electrocatalytic response toward the oxidation of RIF is described. The shift of the E1/2 values of RIF to more negative potentials upon the increase of pH indicated the involvement of protons in the electrode reaction and that the proton-transfer reaction precedes the electrode process properly. Based on the interfacial adsorptive character of the drug onto the electrode, a validated direct square-wave adsorptive stripping voltammetric (SWAdSV) procedure has been described for the trace determination of the drug in pharmaceutical and real samples. The catalytic action of the DyNW/CPE is attributed to the formation of the porous construction and the increase of efficient surface of the electrode, due to the adulteration of DyNW with carbon powders. The optimized operational conditions were investigated. The proposed procedure is much simpler, fast, sensitive, and achieved much lower limits. The limit of detection (LOD) 5.0x10-10 M and limit of quantitation (LOQ) 8.0x10-10 M was achieved respectively in pharmaceutical formulation and spiked human urine.

The atomic force microscope (AFM) is the subject of numerous papers and reports and is full of promises for nanoscience and nanotechnological applications. Pharmaceutical and biopharmaceutical studies using AFM have been functionalized during last two decades. Since, its invention in 1986, the number of published articles has considerably increased. Owing to its unique ability to not only image but also probe mechanical and chemical properties with sub nanometer resolution under physiological condition made it an attractive tool. It can be relatively easily operated in fluids, and thus experiments can be conducted under nearly physiological conditions, which pace its numerous applications in biological problems. In the field of pharmaceutical sciences, AFM presents a unique opportunity to study a variety of phenomena at the cellular and sub cellular level, down to individual (macro) molecular complexes. These advantages of AFM allowed the advent invention of fabrication variables, dynamic processes, drug structure-function relationships, in real time. This article reviews the study of AFM to investigate the crystal growth, polymorphism, particles, granules and coating morphology of solid dosage form for optimization of pharmaceutical behaviors. It also highlights the in situ biopharmaceutical investigation of cell-macromolecular surface, drug-drug, drug-cell, drug-DNA, DNA-protein, drugenzyme and antigen-antibody interactions, and disease mechanisms to understand the better physiological mechanisms associated with disease to rationalize the drug design and development.

In this work, water-compatible molecularly imprinted polymers (MIPs) were prepared for fast, accurate and selective solid-phase extraction of verapamil (VPM) from complex matrices such as biological fluids and human urine followed by its UV spectroscopic determination at 278 nm. The effective factors influencing the precipitation polymerization have been studied. Molecular recognition properties, binding capability and selectivity of the MIPs were evaluated and the results revealed that the obtained MIPs have high affinity for VPM in aqueous media. Equilibrium binding experiments were done to assess the performance of the MIP relative to non imprinted polymer (NIP). After optimization of molecularly imprinted solid-phase extraction (MISPE) method with 2 mL water plus 2 mL acetone as washing solvents and 5 mL of methanol and acetic acid (10:1, v/v) as elution solvent, successful imprinting was confirmed by comparison of the recoveries between NIP (4%) and MIP (97%) polymers. The binding capacity of the MIP for VPM was determined to be 196 mg g-1 (400 μmol g-1). Accuracy and precision were checked by the HPLC technique and the results did not present significant difference at 95% confidence levels according to the t-test.

High performance liquid chromatography (HPLC), gas chromatography (GC), capillary electrophoresis (CE) and a number of immunoassay methods have been extensively applied to the analysis of antiepileptic drugs (AEDs) since many years ago providing reliable and accurate results. In addition, spectrophotometric and spectrofluorometric methods were developed for the analysis of AEDs. The available chemical methods for the determination of AEDs in biological materials and pharmaceutical formulations are reviewed in this work. A number of immunoassay techniques described for AEDs assay and their application in clinical studies are also mentioned in the text. This review covers the available articles published since 2000 or the articles published before 2000 and were not reviewed in previous review articles (80 articles). A summary of all available analytical methods was also collected as Tables providing essential information (363 articles) for the readers. Total number of articles covered in this work is 394.