Label-free Analytics by Transmission Localized-SPR and its Application to Small Molecules Monitoring in Serum

In the frame of therapeutic drug monitoring and personalized medicine, point-of-care systems (POCs) that can help overcome long waiting times for results and costly procedures of clinical tests are highly desirable. At present, the detection of low-molecular-weight molecules with portable systems remains a challenge. In addition, measurements in serum have always been more complicated with respect to buffer solutions due to the occurrence of non-specific binding. This thesis presents a portable transmission-localized SPR (T-LSPR)-based setup that is intended to work as a POC for the detection of small molecules in serum. As a biorecognition element, a selected DNA aptamer specific to tobramycin (467 Da) has been used to functionalize a gold nanoislands (NIs) fluorine-doped tin oxide (FTO) covered glass that acts as a biosensor. As a proof of concept, real-time detection in TE buffer was performed by monitoring concentrations down to 0.5 µM and enabling the observation of association and dissociation phases. The extracted parameters match those obtained with a high-end commercial SPR system. Concentrations of tobramycin in undiluted serum down to 10 µM were measured. The interesting effect of the serum is that it masks the association kinetics of the tobramycin to the DNA aptamer. The quantification of the captured tobramycin is calculated at the beginning of the dissociation phase and leads to a linear calibration curve for the concentrations in the clinical range tested. The reason why the binding of tobramycin is hindered by the serum remains under investigation. The T-LSPR system employs low-cost, off-the-shelf components that make it possible to scale down the system to a palm size. The CMOS image sensor, employed as a light detector, forced the choice of the NIs to have resonance in the visible spectrum in order to match the sensitivity of the light detector. Despite the low sensitivity of the NIs FTO-coated glass slides, justified by the irregularity in size and pattern of the NIs and of the FTO substrate, the NIs exhibit extremely high stability in high-ionic solutions, standing continuous regeneration cycles without altering their sensing properties and without denaturation of the DNA aptamer on their surface. An algorithm for the extraction of the plasmon peak location of the resonance was developed. To increase the speed of data elaboration and to allow the real-time display of the results, hue was studied and used as an alternative parameter for plasmonic evaluation

A Portable Setup for Molecular Detection by Transmission LSPR

In the framework of bioanalytics and multiple array detection, we developed a fully portable and low-cost detection system based on Localized Surface Plasmon Resonance (LSPR) in a transmission configuration (T-LSPR). The transmission approach is suitable to be scaled to small dimension systems and to enable high-density array measurements on the same platform. Our setup is made out of off-the-shelf components and consists of a set of discrete light sources and a couple of light-detectors which enable a differential measurement setup. An algorithm fits the measured data and extracts the information of the plasmon peak position in the spectrum. The performance of our T-LSPR measurement system has been characterized on a set of Fluorinated Tin Oxide-coated glass slides covered with gold Nanoislands (NIs). The samples have been modified with a single-stranded DNA layer and a real-time DNA hybridization experiment has been performed. Here we demonstrate that the proposed T-LSPR device, based on the characterization of the plasmon peak with a differential approach, is able to monitor real-time DNA hybridization on surface, and to precisely measure the position of the peak with a standard deviation in wavelength of 0.2 nm

Comparison between front- and back-gating of Silicon Nanoribbons in real-time sensing experiments

Field-effect transistors (FETs) with open gate structures such as Silicon Nanoribbons (SiNRs) are promising candidates to become general platforms for ultrasensitive, label-free and real-time detection of biochemical interactions on surface. This work proposes and demonstrates the viability of a solution for integrating Ag/AgCl reference electrodes with the microfluidics. A comparison between different polarization schemes is carried out with an analysis of the respective advantages and disadvantages

Peak Shift Measurement of Localized Surface Plasmon Resonance by a Portable Electronic System

In recent years, the characterization of surface molecular layers by localized surface plasmon resonance (LSPR) has attracted a lot of interest thanks to its ability to provide a higher spatial resolution with respect to standard SPR. LSPR can be observed as a peak in the extinction spectrum of metal nanoparticles such as gold non-connected surface patterns. A plasmon peak red shift is caused both by the presence of molecular layers on the gold surface and by molecular binding events. The current study presents a portable transmission system to observe the LSPR phenomenon that extracts the peak location employing a discrete number of light sources. The peak location extraction is performed by an algorithm that takes into account the spectral characteristics of all the components. The performance of our LSPR measurement system has been characterized on a set of Fluorinated Tin Oxide-coated slides covered with nanoislands with a diameter of approximately 30 nm. The samples have been modified with a single-stranded DNA layer and the plasmonic peak location has been determined before and after surface treatment. The samples have been characterized in parallel with a high-end spectrophotometer. The results presented demonstrated the performance of our measurement system in determining the peak location with 1 nm precision. (C) 2012 Elsevier B.V. All rights reserved

Efficacy and safety of medical and surgical interventions for treating HIV-related lipodystrophy in women

HIV-related lipodistrophy syndrome in women is rarely described, and its progression is not well characterized

Effectiveness and durability of polyacrylamide hydrogel injections for treating HIV-related facial lipoatrophy

Polyacrylamide hydrogel injections implant (PHI) is stable, pH neutral, insoluble, non toxic injectable implant used for facial and body contour correction and reconstruction. The aim of our study was to assess objective and subjective effectiveness and durability of PHI in HIV-infected individuals with facial lipoatrophy