Acetylcholine (ACh) is one of the most crucial neurotransmitters of the cholinergic system found in vertebrates and invertebrates and is responsible for many processes in living organisms. Disturbances in ACh transmission are closely related to dementia in Alzheimer's and Parkinson's disease. ACh in biological samples is most often determined using chromatographic techniques, radioenzymatic assays, enzyme-linked immunosorbent assay (ELISA), or potentiometric methods. An alternative way to detect and determine acetylcholine is applying spectroscopic techniques, due to low limits of detection and quantification, which is not possible with the methods mentioned above. In this review article, we described a detailed overview of different spectroscopic methods used to determine ACh with a collection of validation parameters as a perspective tool for routine analysis, especially in basic research on animal models on central nervous system. In addition, there is a discussion of examples of other biological materials from clinical and preclinical studies to give the whole spectrum of spectroscopic methods application. Descriptions of the developed chemical sensors, as well as the use of flow technology, were also presented. It is worth emphasizing the inclusion in the article of multi-component analysis referring to other neurotransmitters, as well as the description of the tested biological samples and extraction procedures. The motivation to use spectroscopic techniques to conduct this type of analysis and future perspectives in this field are briefly discussed.

Photocatalysts based on TiO2 and its modification have become popular as promising materials for the sus-tainable photoproduction of hydrogen. In this work, novel Pt -Cu -TiO2 composites with different TiO2 nano -shapes and modified with biomass-derived reduced graphene oxide (rGO) are reported as promising photocatalysts for the generation of hydrogen from water-alcohol mixtures. The developed photocatalyst has been characterized by X-ray diffraction, X-ray fluorescence spectroscopy, Raman and Fourier-transform infrared spectroscopies, scanning electron microscopy and Brunauer-Emmett-Teller surface area analysis. The partial replacement of platinum with copper definitely lowered the cost of hydrogen photoproduction still keeping its high efficiency. Furthermore, the additional modification of the composite with rGO successfully boosted the amount of generated H2, which was ca. 27 mmol h-1 g-1.

Cancer has been one of the most prevalent diseases around the world for many years. Its biomarkers are biological molecules found in the blood or other body fluids of people with cancer diseases. These biomarkers play a crucial role not only in the diagnosis of cancer diseases, but also in risk assessment, selection of treatment methods, and tracking its progress. Therefore, highly sensitive and selective detection and determination of cancer biomarkers are essential from the perspective of oncological diagnostics and planning the treatment process. Immunosensors are special types of biosensors that are based on the recognition of an analyte (antigen) by an antibody. Sandwich immunosensors apply two antibodies: a capture antibody and a detection antibody, with the antigen 'sandwiched' between them. Immunosensors' advantages include not only high sensitivity and selectivity, but also flexible application and reusability. Surface-enhanced Raman spectroscopy, known also as the sensitive and selective method, uses the enhancement of light scattering by analyte molecules adsorbed on a nanostructured surface. The combination of immunosensors with the SERS technique further improves their analytical parameters. In this article, we followed the recent achievements in the field of sandwich SERS immunosensors for cancer biomarker detection and/or determination.

In this work we present a new sensitive electrochemical method for simultaneous determination of ciprofloxacin (antibiotic) and paracetamol (painkiller). For this purpose graphite electrode was modified with titanium dioxide sol as binding agent. TiO2 sol was enriched with gold nanoparticles and CMK-3 type mesoporous carbon, both increasing the composite conductivity, and Nafion, responsible for signal stabilization. Developed sensor has been characterized via cyclic voltammetry technique presenting LOD equal to 0.108 mu M and 0.210 mu M and sensitivity of 15.93 mu A mu M-1 and 11.56 mu A mu M-1 for ciprofloxacin and paracetamol, respectively. For both analytes two linear ranges from 1 to 10 mu M and from 10 to 52 mu M were found. Developed method enables to determine with high accuracy and precision ciprofloxacin and paracetamol traces in environmental water matrices as well as in certified reference standard of waste water matrix.

Antibiotics are an important class of drugs destined for treatment of bacterial diseases. Misuses and overuses of antibiotics observed over the last decade have led to global problems of bacterial resistance against antibiotics (ABR). One of the crucial actions taken towards limiting the spread of antibiotics and controlling this dangerous phenomenon is the sensitive and accurate determination of antibiotics residues in body fluids, food products, and animals, as well as monitoring their presence in the environment. Immunosensors, a group of biosensors, can be considered an attractive tool because of their simplicity, rapid action, low-cost analysis, and especially, the unique selectivity arising from harnessing the antigen-antibody interaction that is the basis of immunosensor functioning. Herein, we present the recent achievements in the field of electrochemical immunosensors designed to determination of antibiotics.

In this work, a novel voltammetric sensor was developed to determine amoxicillin (AMX). The electrode modification layer consisted of titanium dioxide sol (TiO2) modified with gold nanoparticles (AuNPs), CMK-3-type mesoporous carbon and Nafion. The morphology of the electrode composite was studied by scanning electron microscopy (SEM). Electrochemical behaviour of AMX at proposed electrode was studied. Effects of parameters comprising the amount of CMK-3 and AuNPs in matrix composite, pH of supporting electrolyte and incubation time on the sensitivity of developed sensor were examined. The analytical characteristics of the proposed sensor were assessed. The developed sensor exhibited linear response in two AMX concentration ranges: from 0.5 to 2.5M and from 2.5 to 133.0M, with sensitivity of 1420AmM(-1) (5071AmM(-1)cm(-2)) and 832A mM(-1) (2971AmM(-1)cm(-2)), respectively. The detection limit was evaluated as 0.3M. For verification purposes the sensor was successfully employed in determination of AMX in pharmaceutical product, mineral and environmental water using a flow-batch monosegmented sequential injection approach.

The main goal of the presented research was to develop a new nanocomposite modifying the surface of graphite electrode. The nanocomposite was based on titania dioxide sol enriched with different components including mesoporous carbon CMK-3, gold nanoparticles and Nafion mixed in different proportions. Based on the cyclic voltammetry measurements the developed sensors with different composites were characterized with respect to sensitivity towards Fe(II)/Fe(III) redox probe. Obtained calibration curves allowed to choose the best nanocomposite modifying the graphite electrode surface that can be employed in development of new (bio) sensors.

A voltammetric biosensor based on tyrosinase (TYR) was developed for determination of tyramine. Carbon material (multi-walled carbon nanotubes or mesoporous carbon CMK-3-type), polycationic polymer—i.e., poly(diallyldimethylammonium chloride) (PDDA), and Nafion were incorporated into titania dioxide sol (TiO2) to create an immobilization matrix. The features of the formed matrix were studied by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The analytical performance of the developed biosensor was evaluated with respect to linear range, sensitivity, limit of detection, long-term stability, repeatability, and reproducibility. The biosensor exhibited electrocatalytic activity toward tyramine oxidation within a linear range from 6 to 130 μM, high sensitivity of 486 μA mM−1 cm−2, and limit of detection of 1.5 μM. The apparent Michaelis–Menten constant was calculated to be 66.0 μM indicating a high biological affinity of the developed biosensor for tyramine. Furthermore, its usefulness in determination of tyramine in food product samples was also verified.

A tyrosinase-based amperometric biosensor is proposed for determination of bisphenol A (BPA) in a flow-batch monosegmented sequential injection system. The enzyme was entrapped in a sol–gel TiO2 matrix modified with multi-walled carbon nanotubes (MWCNTs), polycationic polymer poly(diallyldimethylammonium chloride), (PDDA) and Nafion. Morphology of TYR/TiO2/MWCNTs/PDDA/Nafion matrix composite was studied via scanning electron microscopy (SEM). Electrochemical behavior of the developed biosensor towards bisphenol A was examined and analytical characteristics were assessed with respect to linear range, biosensor sensitivity, limit of detection, long term stability, repeatability and reproducibility. Linear range of biosensor response was found between 0.28 and 45.05 µM with high sensitivity of 3263 µA mM−1 cm−2 and detection limit 0.066 µM. The approach was successfully employed for determination of BPA in natural samples.