196,034 research outputs found
Contact lenses delivering nitric oxide under daylight for reduction of bacterial contamination
No full textOcular infection due to microbial contamination is one of the main risks associated with the wearing of contact lens, which demands novel straightforward strategies to find reliable solutions. This contribution reports the preparation, characterization and biological evaluation of soft contact lenses (CL) releasing nitric oxide (NO), as an unconventional antibacterial agent, under daylight exposure. A tailored NO photodonor (NOPD) was embedded into commercial CL leading to doped CL with an excellent optical transparency (transmittance = 100%) at λ ≥ 450 nm. The NOPD results homogeneously distributed in the CL matrix where it fully preserves the photobehavior exhibited in solution. In particular, NO release from the CL and its diffusion in the supernatant physiological solution is observed upon visible light illumination. The presence of a blue fluorescent reporting functionality into the molecular skeleton of the NOPD, which activates concomitantly to the NO photorelease, allows the easy monitoring of the NO delivery in real-time and confirms that the doped CL work under daylight exposure. The NO photoreleasing CL are well-tolerated in both dark and light conditions by corneal cells while being able to induce good growth inhibition of Staphylococcus aureus under visible light irradiation. These results may pave the way to further engineering of the CL with NOPD as innovative ocular devices activatable by sunlight
Synthesis and characterization of new tyrosine capped anisotropic silver nanoparticles and their exploitation for the selective determination of iodide ions
No full textThe assessment of the iodine status of natural waters is crucial for focusing future strategies for controlling and monitoring iodine deficiency disorders (IDD). Nanoparticles have been increasingly used as sensors for several organic and inorganic analytes. In this study, we report the synthesis of new Tyrosine Capped Anisotropic Silver Nanoparticles (AgNPs). The AgNPs were characterized by TEM, UV–vis spectroscopy, and polarized and depolarized dynamic light scattering measurements, and were used for the quantitative determination of iodide ions in the presence of excess chloride ions. Both anions gave rise to an etching of the tips of the nanoprims converting them in rounded nanoplates. However, iodide ions perform this etching much better than chloride ones, allowing for their selective determination in tap waters. Fluoride and bromide anions give rise to a more efficient etching than chloride ions, but their presence does not interfere with iodide determination. This method was also used to determine the concentration of iodide in a sample of drinking water
Spoon-shaped polymer waveguides to excite multiple plasmonic phenomena: A multisensor based on antibody and molecularly imprinted nanoparticles to detect albumin concentrations over eight orders of magnitude
No full textA polymeric multimode waveguide, characterized by a pioneering spoon-shaped geometry, was herein proposed for the first time to devise Surface Plasmon Resonance (SPR) biochemical sensors. The plasmon excitation was enabled by layering a gold nanofilm of ∼60 nm onto the spoon-waveguide. As a consequence of the waveguide's extra-ordinary geometry, two distinct sensing regions were identified: a planar one, located on the spoon's neck, and a concave one on the bowl, with angled surfaces. The bulk sensitivity (Sn) is correlated both to the way the light was launched in/collected from the sensor (parallel or orthogonal to the main axis of the waveguide) and to the sensing area interrogated (planar-neck or angled-bowl), indicating that the sensor's performance can be conveniently tuned, depending on the chosen measuring configuration. The SPR sensor's characterization showed Sn equal to 750 nm/RIU for the neck and to 950 nm/RIU for the bowl. To further inspect the peculiar sensing-features and assess the application niches, the spoon-shaped waveguide was functionalized with two kinds of receptors, both specific for human serum albumin (HSA): an antibody on the bowl region (high Sn); molecularly imprinted nanoparticles (nanoMIPs) on the neck region (low Sn). The experimental results showed a limit of detection (LOD) for the immune-sensor of 280 pM and an LOD for the nanoMIP-sensor of 4.16 fM. The overall response of the HSA multi-sensor encompassed eight orders of magnitude, suggesting that the spoon-shaped waveguide's provides multi-scale detection and holds potential to devise multi-analyte sensing platforms
New fluorescent-labelled nanoparticles: synthesis, characterization and interactions with cysteine and homocysteine to evaluate their stability in aqueous solution
No full textFluorescent-labelled nanoparticles conjugate the SPR of nanomaterials as well as the fluorescence properties of the capping dye. In this work, we report a study on the synthesis of fluorescent l-tyrosine (l-Tyr) and fluorescein (Fluo)-capped silver nanoparticles (AgNPs) carried out by a fine-tuning of the analytical concentration of the reagents. The AgNPs have been characterized by TEM, UV–Vis, ATR–FTIR, and photoluminescence (PL) spectroscopy and DLS. The adsorption of cysteine and homocysteine on the surface of the nanoparticles has been studied to evaluate their overall evolution in solution and their possible interactions with more complex systems, such as proteins. Opposed to homocysteine, cysteine induces aggregation either of tyrosine- and fluorescein-capped nanoparticles, which are therefore promising systems for the discrimination of biothiols. Furthermore, tyrosine-capped AgNPs, in spite of the better coordinating characteristics of this amino acid with respect to fluorescein, show aggregation abilities with cysteine greater than the fluorescein-capped ones that are unexpectedly more stable and thus less prone to aggregation phenomena
Toward Nano- and Microplastic Sensors: Identification of Nano- and Microplastic Particles via Artificial Intelligence Combined with a Plasmonic Probe Functionalized with an Estrogen Receptor
No full textNano- and microplastic particles are a global and emerging environmental issue that might pose potential threats to human health. The present work exploits artificial intelligence (AI) to identify nano- and microplastics in water by monitoring the interaction of the sample with a sensitive surface. An estrogen receptor (ER) grafted onto a gold surface, realized on a nonexpensive and easy-to-produce plastic optical fiber (POF) platform in order to excite a surface plasmon resonance (SPR) phenomenon, has been developed in order to carry out a “smart” sensitive interface (ER-SPR-POF interface). The ER-SPR-POF interface offers output data useful for exploiting a machine learning-based approach to achieve nano- and microplastic particle sensors. This work developed a proof-of-concept sensor through a training phase carried out by different particles, in terms of materials and size. The experimental results have demonstrated that the proposed “smart” ER-SPR-POF interface combined with AI can be used to identify the kind of particles in terms of the materials (polystyrene; poly(methyl methacrylate)) and size (20 μm; 100 nm) with an accuracy of 90.3%
Estradiol Detection for Aquaculture Exploiting Plasmonic Spoon-Shaped Biosensors
No full textIn this work, a surface plasmon resonance (SPR) biosensor based on a spoon-shaped waveguide combined with an estrogen receptor (ERα) was developed and characterized for the detection and the quantification of estradiol in real water samples. The fabrication process for realizing the SPR platform required a single step consisting of metal deposition on the surface of a polystyrene spoon-shaped waveguide featuring a built-in measuring cell. The biosensor was achieved by functionalizing the bowl sensitive surface with a specific estrogen receptor (ERα) that was able to bind the estradiol. In a first phase, the biosensor tests were performed in a phosphate buffer solution obtaining a limit of detection (LOD) equal to 0.1 pM. Then, in order to evaluate the biosensor’s response in different real matrices related to aquaculture, its performances were examined in seawater and freshwater. The experimental results support the possibility of using the ERα-based biosensor for the screening of estradiol in both matrices
An Efficient Bio-Receptor Layer Combined with a Plasmonic Plastic Optical Fiber Probe for Cortisol Detection in Saliva
No full textCortisol is a clinically validated stress biomarker that takes part in many physiological and psychological functions related to the body’s response to stress factors. In particular, it has emerged as a pivotal tool for understanding stress levels and overall well-being. Usually, in clinics, cortisol levels are monitored in blood or urine, but significant changes are also registered in sweat and saliva. In this work, a surface plasmon resonance probe based on a D-shaped plastic optical fiber was functionalized with a glucocorticoid receptor exploited as a highly efficient bioreceptor specific to cortisol. The developed plastic optical fiber biosensor was tested for cortisol detection in buffer and artificial saliva. The biosensor response showed very good selectivity towards other hormones and a detection limit of about 59 fM and 96 fM in phosphate saline buffer and artificial saliva, respectively. The obtained detection limit, with a rapid detection time (about 5 min) and a low-cost sensor system, paved the way for determining the cortisol concentration in saliva samples without any extraction process or sample pretreatment via a point-of-care test
A NANO-PLASMONIC BIOSENSOR FOR FAST AND HIGHLY SENSITIVE DETECTION OF NANOPLASTICS
No full textNanoplastics are a global emerging environmental problem. Despite the relevance of the issue, fast, quantitative and reliable in situ analytical approaches to determine nanoplastics are not yet readily available. The aim of this work was to devise an optical sensor with the goal of direct detecting and quantifying nanoplastics in seawater. The biosensor was developed by grafting onto a gold-nanograting (GNG) plasmonic platform1 a biological receptor2 as recognition element. As a result, the biosensor required just minute sample volumes (2 μL), allowed rapid detection (3 minutes) and enabled to determine nanoplastics in simulated seawater with a linear dynamic concentrations range across five orders of magnitude (1 - 10000 ng/mL), thus encompassing the expected environmental loads. At last, the ER-GNG biosensor was tested on real seawater samples and the results were verified by a conventional approach, confirming the ER-GNG sensor offers a straightforward and highly sensitive method for the direct in-field nanoplastics monitoring
A plasmonic gold nano-surface functionalized with the estrogen receptor for fast and highly sensitive detection of nanoplastics
No full textNanoplastics are a global emerging environmental problem whose effects might pose potential threats to the human's health. Despite the relevance of the issue, fast, reliable and quantitative in situ analytical approaches to determine nanoplastics are not yet available. The aim of this work was to devise an optical sensor with the goal of direct detecting and quantifying nanoplastics in seawater without sample pre-treatments. To this purpose, a nano-plasmonic biosensor was developed by exploiting an Estrogen Receptor (ER) recognition element grafted onto a polymer-based gold nanograting (GNG) plasmonic platform. The ER-GNG biosensor required just minute sample volumes (2 μL), allowed rapid detection (3 min) and enabled to determine nanoplastics in simulated seawater with a linear dynamic concentrations range of 1–100 ng/mL, thus encompassing the expected environmental loads. The nanostructured grating (GNG) provided remarkable performance enhancements, extending the measurement range across five orders of magnitude, thanks to the both the SPR and the localized SPR phenomena occurring at the GNG chip. At last, the ER-GNG biosensor was tested on real seawater samples collected in the Naples area and the results (∼30 ng/mL) were verified by a conventional approach (filtration and evaporation), confirming the ER-GNG sensor offers a straightforward and highly sensitive method for the direct in-field nanoplastics monitoring
Plasmonic sensor combined with a microcuvette device for monitoring molecule binding processes at ultra-low concentrations
No full textA novel sensing strategy is presented to monitor receptor-target pair interactions at ultra-low concentrations without functionalization processes. The biosensing is made by a sensitive chip and a surface plasmon resonance (SPR) probe connected in series, both built up on multimode plastic optical fibers (POFs). The SPR probe is a conventional D-shaped POF platform, while the capture platform consists of three microholes, containing a few hundred nanoliters each, made in the core of a modified POF. The microholes are filled with a specific receptor solution, which selectively captures the target present in the samples dropped over the filled microholes. Any variation occurring in the microholes due to the molecule binding processes changes the mode profile of the propagated light in the POF's core, modifying the plasmonic effects proportionally to the phenomena under scrutiny. As a proof of concept, the interactions of two receptor-target pairs, estradiol and cortisol to the respective receptors, namely Estrogen Receptor alpha protein (ER) and Glucocorticoid Receptor (GR), were monitored over time in the attomolar range. The receptor-target pair interactions are observed at ultra-low concentrations (order of aM) by monitoring the resonance wavelength shift over time. The proposed sensing approach stands for a novel class of laboratory instrumentation with unprecedented capabilities in terms of compactness, ultra-high sensitivity and low-cost
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