Synthesis of Cu-doped carbon dot/chitosan film composite as a catalyst for the colorimetric detection of hydrogen peroxide and glucose.

The use of colloidal nanoparticles suffers from the drawbacks of potential color interference and substrate-induced aggregation. To overcome the limitations, a catalyst was developed by crosslinking Cu-doped carbon dots (Cu-CDs) with chitosan. Cu-CDs with high peroxidase activity were prepared by using a rapid microwave-assisted method. The Cu-CDs containing 6.88% of Cu had an average particle size of 2.25 nm and exhibited 9% of fluorescence quantum yield. The nanozyme/film composite was prepared by crosslinking between the amino groups of Cu-CDs and those of chitosan via a glutaraldehyde linker. A H2O2-mediated tetramethylbenzidine (TMB) oxidation reaction was use to evaluate the peroxidase activity of the film. Based on the TMB color changes, colorimetric assays were developed for the detection of H2O2 and glucose at an absorption wavelength 652 nm. Under the optimal conditions, the linear ranges for H2O2 and glucose were 0.625-40 µM and 1.9-125 µM, respectively, and the detection limits were 0.12 µM and 0.69 µM, respectively. The colorimetric assay was also applied to analyze diluted human serum samples spiked with glucose. Furthermore, this biodegradable, non-toxic, and easy-to-handle nanozyme composite could be stored for over 4 weeks without a significant decrease in activity.

Boron, and nitrogen co-doped carbon dots as a multiplexing probe for sensing of p-nitrophenol, Fe (III), and temperature.

Boron and nitrogen co-doped carbon dots (B, N-CDs) were fabricated through a simple, one-step hydrothermal reaction of citric acid, boric acid, and tris base. The obtained B, N-CDs exhibit excitation-dependent fluorescence, high quantum yield (QY), biocompatibility, photostability, and aqueous solubility. The QY was substantially increased to 57% by doping boron atoms. Furthermore, the fluorescence intensity of B, N-CDs was temperature-dependent and decreased linearly from 283 to 333 K. The prepared B, N-CDs were used as a fluorescence probe for the detection ofpara-nitrophenol (p-NP) and Fe (III) ions with low detection limits of 0.17µM and 0.30µM, respectively. Moreover, the presence of p-NP could be further confirmed by a colorimetric assay. The fluorescent probe has been applied to determine p-NP and Fe (III) in a spiked serum sample and spiked water samples (lake and tap water). Moreover, the as-prepared B, N-CDs were of low toxicity and capable of bioimaging.

Mesoporous Polydopamine Nanoparticles Attenuate Morphine Tolerance in Neuropathic Pain Rats by Inhibition of Oxidative Stress and Restoration of the Endogenous Antioxidant System.

Oxidative stress resulting from reactive oxygen species (ROS) is known to play a key role in numerous neurological disorders, including neuropathic pain. Morphine is one of the commonly used opioids for pain management. However, long-term administration of morphine results in morphine antinociceptive tolerance (MAT) through elevation of ROS and suppression of natural antioxidant defense mechanisms. Recently, mesoporous polydopamine (MPDA) nanoparticles (NPS) have been known to possess strong antioxidant properties. We speculated that morphine delivery through an antioxidant nanocarrier might be a reasonable strategy to alleviate MAT. MPDAs showed a high drug loading efficiency of ∼50%, which was much higher than conventional NPS. Spectral and in vitro studies suggest a superior ROS scavenging ability of NPS. Results from a rat neuropathic pain model demonstrate that MPDA-loaded morphine (MPDA@Mor) is efficient in minimizing MAT with prolonged analgesic effect and suppression of pro-inflammatory cytokines. Additionally, serum levels of liver enzymes and levels of endogenous antioxidants were measured in the liver. Treatment with free morphine resulted in elevated levels of liver enzymes and significantly lowered the activities of endogenous antioxidant enzymes in comparison with the control and MPDA@Mor-treated group. Histopathological examination of the liver revealed that MPDA@Mor can significantly reduce the hepatotoxic effects of morphine. Taken together, our current work will provide an important insight into the development of safe and effective nano-antioxidant platforms for neuropathic pain management.

Fluorescent Mesoporous Nanoparticles for ß-Lactamase Screening Assays.

We present a sensitive and rapid screening method for the determination of ß-lactamase activity of antibiotic-resistant bacteria, by designing a pH-sensitive fluorescent dye-doped mesoporous silica nanoparticle encapsulated with penicillin G as a substrate. When penicillin G was hydrolysed by ß-lactamase and converted into penicilloic acid, the acidic environment resulted in fluorescence quenching of the dye. The dye-doped mesoporous nanoparticles not only enhanced the ß-lactamase-catalyzed reaction rate but also stablized the substrate, penicillin G, which degrades into penicilloic acid in a water solution without ß-lactamase. Twentyfive clinical bacterial samples were tested and the antibiotic resistant and susceptible strains were identified. The proposed method may detect the presence of ß -lactamases of clinically relevant samples in less than 1 hour. Moreover, the detection limit of ß-lactamase activity was as low as 7.8×10-4 U/mL, which was determined within two hours.

Scope and Applications of Nanomedicines for the Management of Neuropathic Pain.

Neuropathic pain, resulting from the dysfunction of the peripheral and central nervous system, occurs in a variety of pathological conditions including trauma, diabetes, cancer, HIV, surgery, multiple sclerosis, ischemic attack, alcoholism, spinal cord damage, and many others. Despite the availability of various treatment strategies, the percentage of patients achieving adequate pain relief remains low. The clinical failure of most effective drugs is often not due to a lack of drug efficacy but due to the dose-limiting central nervous system (CNS) toxicity of the drugs that preclude dose escalation. There is a need for cross-disciplinary collaborations to meet these challenges. In this regard, the integration of nanotechnology with neuroscience is one of the most important fields. In recent years, promising preclinical research has been reported in this field. This review highlights the current challenges associated with conventional neuropathic pain treatments, the scope for nanomaterials in delivering drugs across the blood-brain barrier, and the state and prospects of nanomaterials for the management of neuropathic pain.