The development of rapid and reliable point-of-care testing (POCT) devices requires optical platforms capable of combining fast readout, sensitivity, and robustness. In this work, a fully integrated optoelectronic platform for fluorescence detection in multichannel microfluidic chips is presented, based on a parallel optical interrogation strategy. The platform employs a diffractive optical element (DOE) to achieve simultaneous excitation of multiple microchannels and an array of waveguide absorption filters (WAFs) for parallel fluorescence collection and efficient rejection of excitation light. This configuration eliminates mechanical scanning and enables optical interrogation within a few seconds. The platform is integrated with a microfluidic handling system and dedicated control software, allowing automated execution of immunoassays. Stability and reproducibility were demonstrated through repeated chip loading experiments, showing low variability across microchannels. As a proof of concept, a fluorescence sandwich immunoassay for C-reactive protein (CRP) was implemented in plasma, achieving a limit of detection of 0.32 µg mL⁻1 with good intra- and inter-chip reproducibility. The proposed approach demonstrates the potential of parallel optical architectures for the development of rapid, scalable, and reliable fluorescence-based POCT platforms.

The combination of optical fiber and phototheranostic agents has emerged as a promising strategy to address the challenges of limited light penetration depth and systemic toxicity of nanomaterials. However, the multiplexing potential of fiber-optic probes remains underrated, resulting in enlarged incisions, repeated invasive procedures, and a lack of real-time therapeutic feedback. Herein, we propose a scheme for single‑fiber multifunctional integration leveraging wavelength division multiplexing technology. As a proof-of-concept, by co-immobilizing pH indicator, temperature indicator, and photothermal agent with non-overlapped excitation bands onto tapered optical fiber surface, a fiber-optic theranostic probe enabling closed-loop tumor photothermal therapy was developed. Pre-treatment, the probe can achieve tumor edge identification through revealing the tumor pH gradient. Intra-treatment, the photothermal agent can convert optical energy into heat for photothermal therapy, while simultaneous temperature monitoring enables precise thermal dose control. Post-treatment, rapid efficacy assessment can be achieved via real-time monitoring of the reversal of acidic tumor microenvironment. Animal experiments validate the excellent therapeutic efficacy and biocompatibility of the probe. This research opens new avenues for multifunctional fiber-optic theranostic platforms, where modular wavelength assignment enables customizable minimally invasive interventions and feedback monitoring, holding significant promise for both clinical practice and mechanistic exploration.

Cancer remains a leading global health challenge, causing nearly 10 million deaths annually. We report a multifunctional magnetite-based dendrimer nanocarrier (MAGSiAG1) and its ibuprofen-loaded form (IBU@MAGSiAG1) for synergistic anti-cancer, anti-inflammatory, hyperthermia, and diagnostic applications. FTIR, XRD, TGA, DLS, and zeta potential analyses confirm successful sequential functionalization, dendrimer formation, and ibuprofen loading, resulting in spherical nanocarriers with an average hydrodynamic size of 70 nm and near-neutral surface charge (-39 mV) suitable for tumor penetration and systemic stability. VSM measurements reveal superparamagnetic behavior with saturation magnetization decreasing from 75 emu/g to 35-40 emu/g, ensuring strong magnetic responsiveness while maintaining colloidal stability. Under an alternating magnetic field (150 Oe), IBU@MAGSiAG1 achieves therapeutic temperatures (similar to 45 degrees C) via Neel and Brownian relaxation. In vitro relaxivity measurements showcase high T2 relaxivity coefficient (r(2) = 358.88 +/- 5 mM(-1) s(-1) for MAGSiAG1, 335 +/- 49.8 mM(-1) s(-1) for IBU@MAGSiAG1), empowering effective MRI contrast. Drug loading efficiency exceeds 90%, with pH-responsive release profile that demonstrates accelerated ibuprofen release in acidic conditions (tumor-mimicking pH 5.0-6.5) and slower release at physiological pH (similar to 7.4). Cytotoxicity studies on MCF-7 human cancer cells reveal good viability (85-90%) at 250-400 mu g/mL of drug concentration range, while higher concentrations (similar to 400 mu g/mL) reduce viability to similar to 60%, indicating therapeutic potential. Good biocompatibility of the developed nanocarriers is attained using with EA.hy926 endothelial cells, ensuring safe systemic delivery. Overall, IBU@MAGSiAG1 showcases high multifunctionality by integrating hyperthermia, controlled drug release, and MRI contrast into a single platform, paving the way for novel therapeutic targeted treatments in cancers that might advance personalized medicine approaches.

Glass-based microfluidic devices have emerged as powerful platforms for biosensing and bioassays due to their superior chemical resistance, optical transparency, and high thermal stability. Compared to inorganic, organic polymeric, and paper-based materials, glass offers superior mechanical robustness, precise microfabrication capabilities, and long-term stability. These properties make glass an ideal substrate for precise and reproducible bioanalytical applications, particularly in bacterial detection. This review provides an overview of the three main topics in glass-based microfluidic biosensing systems: fabrication, detection techniques and applications. The fabrication techniques including photolithography, laser micromachining, wet and dry etching, and bonding strategies are discussed. Furthermore, electrochemical and optical detection techniques in glass-based microfluidic biosensors are illustrated. Additionally, we explore the application of glass-based microfluidic systems in biosensing and bioassay platforms, highlighting their role in improving analytical performance through enhanced sensitivity, and stability. The application of glass-based microfluidic devices for bacterial sensing is critically examined, focusing on electrochemical and optical detection methods. Finally, we highlight the current challenges and future perspectives in advancing glass-based microfluidics for bacterial biosensing, emphasizing the need for scalable manufacturing, enhanced sensitivity, and improved portability.

Alzheimer's disease (AD) is a progressive neurological disorder that gradually impairs all cognitive functions. The diagnosis typically requires a combination of cognitive assessments, neuroimaging techniques, and biomarker analysis. In healthy neurons, Tau protein stabilizes microtubules, which are vital for maintaining the structure and proper functioning of nerve cells. However, elevated levels of Tau in cerebrospinal or other body fluids can be related to the progression of Alzheimer's disease. This study introduces an optical technique that employs a dual label-free and fluorescence operation mode to detect Tau protein in both standard running buffer and cerebrospinal fluid. This innovative method enables label-free analysis of the bio-conjugation process on biochips used for resolved fluorescence-based Tau detection. This work successfully demonstrates Tau protein detection in both matrixes, achieving an outstanding limit of detection of 2.4 pM in cerebrospinal fluid. Moreover, the analysis of the dose-response curve allows to estimate the dissociation constant (K-D = 18 nM) for Tau interactions, yielding values that are in excellent agreement with existing literature using other techniques. These aspects highlight the added value of this technique, providing a valuable tool for investigating Alzheimer's-related biomarkers, as demonstrated in this study with Tau protein.

An optical fibre sensor with a long period grating (LPG) is described for the binding protein FKBP12 detection. An ad-hoc synthesized recognition element is immobilised on the fibre surface in correspondence of the LPG by using a home-made microfluidic flow-cell. Measurement is performed by flowing solutions in the flow-cell with increasing FKBP12 concentration and measuring the shift of the LPG resonant peak.

Recent advances in optical sensing technologies underpin the development of high-performance, surface-sensitive analytical tools capable of reliable and precise detection of molecular targets in complex biological media in non-laboratory settings. Optical fibre sensors guide light to and from a region of interest, enabling sensitive measurements of localized environments. This positions optical fibre sensors as a highly promising technology for a wide range of biochemical and healthcare applications. However, their performance in real-world biological media is often limited by the absence of robust post-modification strategies that provide both high biorecognition and antifouling capabilities. In this study, we present the proof-of-concept antifouling and biorecognition performance of a polymer brush nano-coating synthesized at the sensing region of optical fibre long-period grating (LPG) sensors. Using a newly developed antifouling terpolymer brush (ATB) composed of carboxybetaine methacrylamide, sulfobetaine methacrylamide, and N-(2-hydroxypropyl)methacrylamide, we achieve state-of-the-art antifouling properties. The successful on-fibre ATB synthesis is confirmed through scanning electron microscopy (SEM), fluorescence microscopy, and label-free bio-detection experiments based on antibody-functionalized ATB-coated LPG optical fibres. Despite the challenges in handling optical fibres during polymerization, the resulting nano-coating retains its remarkable antifouling properties upon exposure to blood plasma and enables biorecognition element functionalization. These capabilities are demonstrated through the detection of IgG in buffer and diluted blood plasma using anti-IgG-functionalized ATB-coated sensing regions of LPG fibres in both label-based (fluorescence) and label-free real-time detection experiments. The results show the potential of ATB-coated LPG fibres for use in analytical biosensing applications.

MicroRNAs (miRNAs) are small non-coding RNAs (18-22 nucleotides) that regulate gene expression and are associated with various diseases, including Laryngeal Cancer (LCa), which has a high mortality rate due to late diagnosis. Traditional methods for miRNA detection present several drawbacks (time-consuming steps, high cost and high false positive rate). Early-stage diagnosis and selective detection of miRNAs remain challenging. This study proposes a 3D flexible biosensor that combines nanofibers (NFs), gold nanoparticles (AuNPs), and an inverse molecular sentinel (iMS) for enzyme-free, SERS-based detection of miRNA-223-3p, evaluated as a potential LCa biomarker. The electrospun flexible nanofibers decorated with AuNPs enhance Raman signal. Selective detection of miRNA-223-3p is achieved by immobilizing an iMS-DNA probe labeled with a Raman reporter (Cyanine 3) on the AuNPs. The iMS distinctive stem-and-loop structure undergoes a conformational change upon interaction with the miRNA-223-3p, producing an "on to off" SERS signal. The proposed sensor demonstrated a linear detection range from 10 to 250 fM, with a limit of detection (LOD) of 19.50 +/- 0.05 fM. The sensor selectivity was confirmed by analyzing the SERS signal behaviour in the presence of both Noncomplementary miRNA and miRNA with three mismatched base pairs. This easily fabricable sensor requires no amplification and offers key advantages, including sensitivity, flexibility, and cost-effectiveness.

In this study, we present an innovative approach for the detection of Tau protein, a key biomarker of Alzheimer disease, using enhanced fluorescence detection. The methodology utilizes a bio-conjugation process to adapt 1D photonic crystal surface for precise molecular recognition. Our results demonstrate the successful detection of Tau protein in a simple environment, with a detection limit of 0.5 ng/mL and a quantification limit of 1.2 ng/mL. This work introduces optical disposable biochips as a novel diagnostic tool for Alzheimer disease and related neurodegenerative disorders, addressing critical challenges in biomarker detection and paving the way for advancements in therapeutic development.

Achieving a high figure of merit alongside exceptional sensitivity is critical for advancing optical biosensors capable of ultra-low limits of detection. In this work, we investigate the performance of D-shaped single-mode fiber devices coated with 1D photonic crystal stacks. These nano-assembled layers, composed of alternating high- and low-refractive-index (RI) materials, enable the excitation of Bloch surface waves (BSWs). By systematically varying the RI contrast between the layers, we demonstrate that while a moderate increase in RI contrast improves sensitivity and narrows the full width at half maximum (FWHM) of the BSW resonance, the sensitivity tends to stabilized as we further increase the RI contrast, while the FWHM still can be pushed towards a higher FoM. Real-world applicability is validated through the detection of immunoglobulin G (IgG) at record-low concentrations of 70 aM, leveraging the solution as a versatile, operando, high-performance biosensing platform.

Recirculating Aquaculture Systems (RAS) have revolutionized the protein production sector in aquaculture, leading to significant growth and expansion of the industry. Despite the success of RAS in aquaculture, there are challenges related to stress in fish raised in these systems, which can impact their food intake, growth, and overall well-being. One of the major limitations in the aquaculture industry is the lack of smart sensors for real-time detection of stress hormones like cortisol, hindering our ability to understand and effectively manage the welfare of fish in these systems. In this work, a graphene oxide (GO) coated long period grating (LPG) was fabricated into a double-clad optical fiber (DCF) with W-shaped refractive index profile. The working point of the device was tuned to the mode transition region to enhance its sensitivity against outer medium changes. It was further integrated into a microfluidic system and the fiber surface was functionalized with specific anti-cortisol antibodies for the detection of cortisol. Finally, the performance of this immunosensor was evaluated for a cortisol concentration range of 0.01 ng/mL to 100 ng/mL, a wide working range of concentrations of relevant interest, achieving a limit of detection (LOD) of 0.06 ng/mL. Moreover, a selectivity test using testosterone and glucose as interfering substances was carried out.

Detecting multiple analytes simultaneously, crucial in disease diagnosis and treatment prognosis, remains challenging. While planar sensing platforms demonstrate this capability, optical fiber sensors still lag behind. An operando dual lossy mode resonance (LMR) biosensor fabricated on a D-shaped single-mode fiber (SMF) is proposed for quantification of clinical indicators of inflammatory process, like in COVID-19 infection. Dual LMRs, created via two-step deposition process, yield a nanostructure with distinct SnO2 thicknesses on the flat surface of the fiber. Theoretical and experimental analyses confirm its feasibility, showing a sensitivity around 4500 nm/RIU for both LMRs. A novel insight in spatially-separated biofunctionalization of the sensitive fiber regions is validated through fluorescence assays, showcasing selectivity for different immunoglobulins. Real-time and label-free detection of two inflammatory markers, C-reactive protein and D-dimer, empowers the platform capability with a minimum detectable concentration below 1 μg/mL for both biomolecules, which is of clinical interest. This proof-of-concept work provides an important leap in fiber-based biosensing for effective and reliable multi-analyte detection, presenting a novel, compact and multi-functional analytical tool.