Upconversion Nanoplatform for FRET‐Based Sensing of Dopamine and pH

Wavelength-Dependent Metal-Enhanced Fluorescence Biosensors via Resonance Energy Transfer Modulation

Fluorescence can be enhanced or quenched depending on the distance between the surface of a metal nanoparticle and the fluorophore molecule. Fluorescence enhancement by nearby metal particles is called metal-enhanced fluorescence (MEF). MEF shows promising potential in the field of fluorescence-based biological sensing. MEF-based biosensor systems generally fall into two platform categories: (1) a two/three-dimensional scaffold, or (2) a colloidal suspension. This review briefly summarizes the application studies using wavelength-dependent carbon dots (UV-VIS), noble metals (VIS), and upconversion nanoparticles (NIR to VIS), representative nanomaterials that contribute to the enhancement of fluorescence through the resonance energy transfer modulation and then presents a perspective on this topic.

A Comprehensive Review on Upconversion Nanomaterials-Based Fluorescent Sensor for Environment, Biology, Food and Medicine Applications

Near-infrared-excited upconversion nanoparticles (UCNPs) have multicolor emissions, a low auto-fluorescence background, a high chemical stability, and a long fluorescence lifetime. The fluorescent probes based on UCNPs have achieved great success in the analysis of different samples. Here, we presented the research results of UCNPs probes utilized in analytical applications including environment, biology, food and medicine in the last five years; we also introduced the design and construction of upconversion optical sensing platforms. Future trends and challenges of the UCNPs used in the analytical field have also been discussed with particular emphasis.

Molecular Probes, Chemosensors, and Nanosensors for Optical Detection of Biorelevant Molecules and Ions in Aqueous Media and Biofluids

Synthetic molecular probes, chemosensors, and nanosensors used in combination with innovative assay protocols hold great potential for the development of robust, low-cost, and fast-responding sensors that are applicable in biofluids (urine, blood, and saliva). Particularly, the development of sensors for metabolites, neurotransmitters, drugs, and inorganic ions is highly desirable due to a lack of suitable biosensors. In addition, the monitoring and analysis of metabolic and signaling networks in cells and organisms by optical probes and chemosensors is becoming increasingly important in molecular biology and medicine. Thus, new perspectives for personalized diagnostics, theranostics, and biochemical/medical research will be unlocked when standing limitations of artificial binders and receptors are overcome. In this review, we survey synthetic sensing systems that have promising (future) application potential for the detection of small molecules, cations, and anions in aqueous media and biofluids. Special attention was given to sensing systems that provide a readily measurable optical signal through dynamic covalent chemistry, supramolecular host-guest interactions, or nanoparticles featuring plasmonic effects. This review shall also enable the reader to evaluate the current performance of molecular probes, chemosensors, and nanosensors in terms of sensitivity and selectivity with respect to practical requirement, and thereby inspiring new ideas for the development of further advanced systems.

Facile transdermal delivery of upconversion nanoparticle by iontophoresis-responsive magneto-upconversion oleogel

The effective application of upconversion nanoparticle (UCNP) as a photo-medicine in skin cancers critically depends on a facile transdermal delivery process through topical route. Herein, combining two non-invasive techniques, i.e. skin permeation enhancement and alternating current (AC) induced iontophoresis, we report a controlled transdermal delivery of UCNP with a time advantage. We have synthesized a series of soybean oil-based oleogels termed as magneto-upconversion (MU) gels by incorporating a fixed amount of UCNP and different proportions of magnetic nanoparticle (MNP) using stearic acid-based gelator as a skin permeation enhancing agent. The microstructures of the synthesized MU gels were characterized by microscopy, X-Ray diffraction and vibrational spectroscopy. A detailed analysis of the electrical properties revealed a gradual increase in the electrical conductance in the MU gel series with increasing proportion of MNP. Such trend of conductance imparted proportional iontophoretic response within the respective MU gels, validated through the release of ciprofloxacin hydrochloride as a model drug preloaded within the oleogels. Through a series of skin permeation experiment using pig ear skin as animal model, we established that the UCNP was able to permeate the whole thickness of the skin within as little as 3 h, only when the two conditions, i.e. the presence of skin permeation enhancer and iontophoresis were met. Within the same time, UCNP permeation was enhanced by the presence of MNP in the MU gels upto 2 folds. Our study developed a rational method for the transdermal delivery of any electrically non-conducting nanoparticle in a faster and tunable way.

Copper Nanowires Modified with Graphene Oxide Nanosheets for Simultaneous Voltammetric Determination of Ascorbic Acid, Dopamine and Acetaminophen

Copper nanowires (Cu NWs) were modified with graphene oxide (GO) nanosheets to obtain a sensor for simultaneous voltammetric determination of ascorbic acid (AA), dopamine (DA) and acetaminophen (AC). The nanocomposite was obtained via sonication, and its structures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The electrochemical oxidation activity of the materials (placed on a glassy carbon electrode) was studied by cyclic voltammetry and differential pulse voltammetry. Due to the synergistic effect of Cu NWs and GO, the specific surface, electrochemical oxidation performance and conductivity are improved when compared to each individual component. The peaks for AA (-0.08 V), DA (+0.16 V), and AC (+0.38 V) are well separated. The sensor has wide linear ranges which are from 1-60 μM, 1-100 μM, and 1-100 μM for AA, DA, and AC, respectively, when operated in the differential pulse voltammetric mode. The detection limits are 50, 410 and 40 nM, respectively. Potential interferences by uric acid (20 μM), glucose (10 mM), NaCl (1 mM), and KCl (1 mM) were tested for AA (1 μΜ), DA (1 μΜ), and AC (1 μΜ) and were found to be insignificant. The method was successfully applied to the quantification of AA, DA, and AC in spiked serum samples.