Alzheimer’s Disease (AD) is a severe neurodegenerative disorder, marked by cognitive decline, memory loss, and behavioral skill impairment. Actually, amyloid β-peptide 1-42 (Aβ (1-42)) is one of the main recognized AD biomarkers. The possibility of detect Aβ (1-42) at very low concentration in different biological fluids allow the early-stage diagnosis, which currently represents the most efficacious AD therapy. To date, optical detection techniques have gained rising attention for the development of Aβ (1-42) sensors based on the analyses of liquid samples. In this context, optical metallic nanoconstructs are promising alternative for the development of novel rapid and low-cost methods for the targeting of Aβ (1-42) in fluids. Herein, diagnostic platforms are based on gold citratecapped nanoparticles (AuNPs), whose aggregation can be modulated by the presence of the target biomarker as a function of its concentration and has been smartly used to develop colorimetric assays. The performances of this novel system are validated for specific detection of synthetic ß- amyloid peptide (Aß) in liquid fluids with high selectivity and sensitivity down to the nanomolar.
KEYWORDS: Raman spectroscopy, Polydimethylsiloxane, Liquids, Surface enhanced Raman spectroscopy, 3D printing, Signal detection, Optical fibers, Lab on a chip, Gold
Optical detection techniques have been extensively implemented for liquid biosensing and, among all, surface enhanced Raman spectroscopy (SERS) constitutes the one of the most promising analytical method as alternative to current traditional bioassays. With the attempt to develop point-of-impact diagnostic devices, in the present study, advanced and standard manufacturing processes were successfully combined with nanoparticles (NPs) engineering for the development of multifunctional lab-on-chips (LoCs) that integrate SERS sensors for liquid optical probing. As a matter of fact, LoCs allow to handle easily micro- to nanoliters volumes of samples as well as to perform multifunctional analyses on the same restricted volumes while avoiding cross-contaminations. Furthermore, due to the exploitation of 3D printing process, the LoCs design can be rapidly prototyped to highly integrate networks of channels and detection chambers of varied size and shape smartly arranged with respect to the Raman set-up in order to optimize signal delivery and collection. Within the detection chambers, SERS functionality is achieved by the selective interaction of the target analytes with gold NPs with embedded optical fibers positioned at different excitation and collection angles. The resulting SERS-fluidic devices, characterized by different detection configurations, represent highly versatile SERS-fluidic platforms providing high repeatability, high sensitivity and speed of analysis, possibly revolutionizing liquid biopsy by making it costless, on-chip, handy, and easy to use.
Liquid biopsies represent a minimally invasive tool for the precocious diagnosis of widespread diseases as well as for routinely patients monitoring by tracking selective biomarkers. Optical detection techniques based on surface enhanced Raman spectroscopy (SERS) are capable of providing information on the molecular content of analyzed samples thus representing one of the most promising analytical method in clinical research, as alternative to traditional bioassays. With the attempt to realize point-of-impact diagnostic devices, in the present study 3D printing and soft-lithography processes were combined with plasmonic nanoparticles (NPs) synthesis for the development of multifunctional lab-onchips (LOCs) integrating SERS sensors for liquid probing. As a matter of fact, LOCs enable to easily handle small volumes of samples as well as to perform multifunctional analyses. This is crucial for pathologies whose diagnosis relies on the ratio of more than one biomarker. To this end, being based on a 3D printing process, the overall design of the devices was rapidly prototyped to integrate channels and detection chambers aligned with optical fibers and portable Raman probes for signal delivering and collection. SERS functionality was achieved by immobilization of gold NPs whose chemistry was modified to enhance NPs deposition and stability. Finally, we are exploring direct laser writing for the integration of mechanical and optical microcomponents needed for liquids control and signal delivering and collection, respectively. The final devices collecting multiple functions and detection configurations will provide high sensitivity, speed of analysis, low sample and reagent consumption, measurement automation and standardization on a highly integrated dynamic platform that will revolutionize liquid biopsy making it costless, on-chip, handy and easy to use.
Optical detection techniques based on surface enhanced Raman spectroscopy (SERS) can provide relevant information on molecular and protein composition of biological samples, thus enabling to discriminate between physiological and pathological conditions. With the attempt to develop point-of-impact diagnostics devices, in this study we combine lowcost fabrication processes with surface functionalization strategies for the fabrication of SERS-active polymeric substrates engineered to selectively detect specific biomarkers. By reversibly coupling these devices with the distal end of portable Raman instruments, SERS measurements could be potentially implemented for the early diagnosis of widespread pathologies by SERS analysis of liquid biopsies.
Optical detection techniques based on surface enhanced Raman spectroscopy (SERS) and capable of providing relevant information on molecular and protein composition of biological samples, are gaining rising attention in clinical research as alternatives to traditional detection assays. Meanwhile, due to the technological advances in compact instrumentation as well as in nanofabrication processes, SERS probes based on portable guided-wave systems, have been implemented thus providing for easier accessibility into complex environments and enabling for real-time in situ detection of low concentrated target analytes. In the present study, low-cost fabrication processes were successfully combined with surface functionalization strategies for the fabrication of disposable SERS-active substrates, engineered to tightly fit the distal end of portable Raman instruments. Being based on a polymer casting fabrication process, the overall design of the substrates can be easily adapted to the varied geometry of the probes to be fit, thus guaranteeing high design versatility. SERS-functionality was achieved by immobilization of gold nanoparticles whose size and shape directly affect the plasmonic properties of the substrates. Moreover, SERS substrates can be further modified by covalently binding molecules acting as baits to selectively fish target biomarkers within heterogeneous samples thereby increasing the specificity of SERS signals. Finally, these sensors represent a powerful tool potentially implementable for the early diagnosis of widespread pathologies by real-time SERS analysis of liquid biopsy.
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