The DNA thrombin aptamer has been extensively investigated, and the coupling of this aptamer to different transduction principles has demonstrated the wide applicability of aptamers as bioreceptors in bioanalytical assays. The goal of this work was to design an aptamer-based sandwich assay with electrochemical detection for thrombin analysis in complex matrixes, using a simple target capturing step by aptamer-functionalized magnetic beads. The conditions for the aptamer immobilization and for the protein binding have been first optimized by surface plasmon resonance, and then transferred to the electrochemical-based assay performed onto screen-printed electrodes. The assay was then applied to the analysis of thrombin in buffer, spiked serum, and plasma and high sensitivity and specificity were found. Moreover, thrombin was generated in situ in plasma by the conversion of its precursor prothrombin, and the formation of thrombin was followed at different times. The concentrations detected by the electrochemical assay were in agreement with a simulation software that mimics the formation of thrombin over time (thrombogram). The proposed work demonstrates that the high specificity of aptamers together with the use of magnetic beads are the key features for aptamer-based analysis in complex matrixes, opening the possibility of a real application to diagnostics or medical investigation.

Aptamer-based assays represent a modern and attractive approach in bioanalytical chemistry. The DNA thrombin aptamer has been extensively investigated, and the coupling of this aptamer to different transduction principles has demonstrated the wide applicability of aptamers as bioreceptors in bioanalytical assays. The goal of this work was to critically evaluate all the parameters that can influence the sensor performances by using the thrombin aptamer immobilized onto piezoelectric quartz crystals. The optimization of the immobilization and the binding protocol was of paramount importance, and improvements in analytical performances could be obtained by optimizing simple steps in immobilization and assay conditions. Moreover, the work demonstrated the possibility of using aptamer-based sensors in complex matrixes, opening the possibility of a real application to diagnostics or medical investigation.

Biocompatible chitosan/gold nanorods films are fabricated and tested as laser‐activatable adhesives. When exposed to near‐infrared laser light the nanoparticles carry out efficient photothermal conversion, which activates the polar groups of chitosan strands and mediates functional adhesion with a biological tissue. This technology may enable a number of key applications in medicine including tissue repair, wound dressing and drug delivery.

Gold nanorods exhibit intense optical absorption bands in the near-infrared region of principal interest for applications in biomedical optics, which originate from sharp plasmon resonances. This high absorbance, combined with the biochemical inertness and targetability of gold nanoparticles, makes these materials excellent candidates to provide contrast in photoacoustic imaging and for other applications such as the selective hyperthermia of cancer. One issue demoting the potential of gold nanorods as contrast agents in photoacoustic applications is their limited photostability, which falls below relevant permissible exposure limits. In particular, when gold nanorods are resonantly excited by laser pulses in the nanosecond duration regime, there may occur phenomena like reshaping into rounder nanoparticles as well as fragmentation and sublimation, which modify their optical absorption bands and hinder their efficiency of photoacoustic conversion. Here we investigate the influence of nanoparticle size on the photostability and reproducibility of photoacoustic conversion of gold nanorods embedded in biomimetic phantoms. We compare samples containing gold nanorods with different sizes but the same shapes and overall optical densities. We demonstrate clear size effects as the thresholds of optical fluences for nanoparticle deformation improve from below 2 to above 6 mJ/cm2 with nanoparticle miniaturization from 22 to 5 nm effective radii. We interpret these results in terms of a better thermal coupling and faster heat dissipation from smaller nanoparticles to their environment, originating from their larger specific surface area.

The development of a RNA-aptamer-based optical biosensor (aptasensor) for C-reactive protein (CRP) is reported. CRP is an important clinical biomarker; it was the first acute-phase protein to be discovered (1930) and is a sensitive systemic marker of inflammation and tissue damage. It has also a prognostic value for patients with acute coronary syndrome. The average concentration of CRP in serum is 0.8 ppm and it increases in response to a variety of inflammatory stimuli, such as trauma, tissue necrosis, infection and myocardial infarction. The interaction between the 44-base RNA aptamer and the target analyte CRP is studied. In particular, the influence of the aptamer immobilization procedure (chemistry, length, concentration), as well as the binding conditions, i.e., the influence on the binding of different buffers, the presence of Ca2+ ion and the specificity (against human serum albumin) have been evaluated. Using the best working conditions, we achieved a detection limit of 0.005 ppm, with good selectivity towards human serum albumin. Some preliminary experiments in serum are reported.