Determination of monoamine neurotransmitters and their metabolites in a mouse brain microdialysate by coupling high-performance liquid chromatography with gold nanoparticle-initiated chemiluminescence

Advantageous sensitivity in the DNA homolog of the RNA dopamine aptamer

A competitive enzyme-linked aptamer assay for DA was performed by using two aptamers, individually; one is a 57 mer-RNA aptamer and the other is its homolog DNA aptamer. The difference between the RNA aptamer and the DNA aptamer are based on their particular nucleotides. It is known that the lack of a hydroxyl group in the 2' position of DNA is related with its chemical and biological stability. Thus, the use of the DNA homolog of the RNA aptamer could improve the affinity toward DA due to stability and finally, lower the detection limit. In this paper, we report advantageous sensitivity and specificity of its homolog DNA aptamer assay as compared to the RNA aptamer assay. Both aptamer assays were performed with 0.01 µg mL⁻¹ of each aptamer and 1.205 × 10⁻⁸ M DA-HRP conjugate using the optimized method. A dose-response curve was constructed, and the limit of detection for the DA was determined as 6.3 × 10⁻⁸ M for RNA aptamer assay, and 3.2 × 10⁻¹² M for the homolog DNA aptamer assay, respectively. These results demonstrated that the assay sensitivity was more than 10⁴ times improved with the DNA homolog of the RNA aptamer compared to its original RNA aptamer obtained through SELEX process. Also these results confirmed that the DNA homolog of the RNA aptamer can maintained the binding site and retained a function in both structure. Thus, the switching to the DNA version of RNA aptamer is possible to bind more stably and still able to bind to dopamine.

Highly sensitive, stable, and precise detection of dopamine with carbon dots/tyrosinase hybrid as fluorescent probe

The carbon dots/tyrosinase hybrid as a low-cost fluorescent probe for the detection of dopamine exhibits high sensitivity, stability, and precision.

Molecularly imprinted polymer based on CdTe@SiO2 quantum dots as a fluorescent sensor for the recognition of norepinephrine

A fluorescent sensor with recognition ability for norepinephrine was simply prepared and actually used to determine norepinephrine in rat plasma.

Determination of cysteine, homocysteine, cystine, and homocystine in biological fluids by HPLC using fluorosurfactant-capped gold nanoparticles as postcolumn colorimetric reagents

We have demonstrated for the first time the suitability of fluorosurfactant-capped spherical gold nanoparticles as HPLC postcolumn colorimetric reagents for the direct assay of cysteine, homocysteine, cystine, and homocystine. The success of this work was based on the use of an on-line tris(2-carboxyethyl)phosphine reduction column for cystine and homocystine. Several parameters affecting the separation efficiency and the postcolumn colorimetric detection were thoroughly investigated. Under the optimized conditions, cysteine, homocysteine, cystine, and homocystine in human urine and plasma samples were determined. Detection limits for cysteine, homocysteine, cystine, and homocystine ranged from 0.16-0.49 μM. The accuracy in terms of recoveries ranged between 94.0-102.1%. This proposed method was rapid, inexpensive, and simple.

Single molecular functionalized gold nanoparticles for hydrogen-bonding recognition and colorimetric detection of dopamine with high sensitivity and selectivity

In this work, we developed a low-cost, facile, sensitive, and selective colorimetric method for the quantitative determination of dopamine, based on 4-amino-3-hydrazino-5-mercapto-1,2,4-triazol (AHMT) functionalized gold nanoparticles (AHMP-AuNPs) as a model probe. Dopamine could induce the aggregation of the AHMT-AuNPs through hydrogen-bonding interactions, which caused the colloidal solution changed from red to blue. And the color change was in situ monitored for the quantitative determination of dopamine in human serum and urine samples. The developed approach is simple, without using complex financial instruments and adding other metal salts or ions for improving sensitivity.

The neurotoxic potential of engineered nanomaterials

The expanding development and production of engineered nanomaterials (ENMs) have diverse and far-reaching potential benefits in consumer products, food, drugs, medical devices and for enhancing environmental cleanup and remediation. The knowledge of potential implications of ENMs, including the potential for inadvertent exposures and adverse neurotoxic consequences, is lagging behind their development. A potential risk for neurotoxicity arises if exposure leads to systemic absorption and distribution to the nervous system. This paper is the summary of a symposium entitled Neurotoxicity Potential of Engineered Nanomaterials presented at the 2011 Xi'an International Neurotoxicology Conference held June 5-9 in Xi'an China. The following topics were featured in the symposium: the toxicokinetics of engineered nanomaterials; differential uptake of nanoceria in brain and peripheral organs; translocation into the brain and potential damage following nanoparticle exposure; and the retina as a potential site of nanomaterial phototoxicity. Each of these topics is discussed fully in sections of the manuscript. The promising benefits of ENM technology can be best realized if the potential risks are first understood and then minimized in product and system designs.

Capillary ultrahigh performance liquid chromatography with elevated temperature for sub-one minute separations of basal serotonin in submicroliter brain microdialysate samples

Improving the time resolution in microdialysis coupled to high performance liquid chromatography (HPLC) requires that the volume of the separation system be decreased. A low-volume separation permits smaller microdialysate volumes to be injected without suffering a sensitivity loss from dilution. Thus, improved time resolution can be achieved with offline analysis simply by decreasing the separations system volume. For online (near real-time) analysis, there is a further requirement. The separation speed must be at least as fast as the sampling time. Here, the combined use of high column pressures and temperatures, sub-2-μm stationary phase particles, capillary columns, and sensitive, low dead-volume detection resulted in a retention time for the neurotransmitter serotonin of less than 1 min in a 500 nL dialysate sample volume. Two sensitive detectors, photoluminescence following electron transfer (PFET) and electrochemical, were used for the detection of subnanomolar concentrations of serotonin in brain microdialysate samples. The general principles developed are applicable to a wide range of separations with the additional advantages of increases in sample throughput and decreases in mobile phase usage.

Development of superparamagnetic high-magnetization C18-functionalized magnetic silica nanoparticles as sorbents for enrichment and determination of methylprednisolone in rat plasma by high performance liquid chromatography

In this study, a novel extraction and enrichment technique based on superparamagnetic high-magnetization C(18)-functionalized magnetic silica nanoparticles (C(18)-MNPs) as sorbents was successfully developed for the determination of methylprednisolone (MP) in rat plasma by high performance liquid chromatography (HPLC). The synthesized silica-coated magnetite modified with chlorodimethyl-n-octadecylsilane was about 320 nm in diameter with strong magnetism and high surface area. It provided an efficient way for extraction and concentration of MP in the samples through hydrophobic interaction by the interior C(18) groups. Moreover, MP adsorbed with C(18)-MNPs could be simply and rapidly isolated through placing a strong magnet on the bottom of container, and then easily eluted from C(18)-MNPs by n-hexane solution. Extraction conditions such as amounts of C(18)-MNPs added, adsorption time and desorption solvent, were investigated. Method validations including linear range, detection limit, precision, and recovery were also studied. The results showed that the proposed method based on C(18)-MNPs was a simple, accurate and high efficient approach for the analysis of MP in the complex plasma samples.