Hydrogel micropatches for sampling and profiling skin metabolites.

Metabolites excreted by skin have a huge potential as disease biomarkers. However, due to the shortage of convenient sampling/analysis methods, the analysis of sweat has not become very popular in the clinical setting (pilocarpine iontophoresis being a prominent exception). In this report, a facile method for sampling and rapid chemical profiling of skin metabolites excreted with sweat is proposed. Metabolites released by skin (primarily the constituents of sweat) are collected into hydrogel (agarose) micropatches. Subsequently, they are extracted in an online analytical setup incorporating nanospray desorption electrospray ionization and an ion trap mass spectrometer. In a series of reference measurements, using bulk sampling and electrospray ionization mass spectrometry, various low-molecular-weight metabolites are detected in the micropatches exposed to skin. The sampling time is as short as 10 min, while the desorption time is 2 min. Technical precision of micropatch analysis varies within the range of 3-42%, depending on the sample and the method of data treatment; the best technical precision (≤10%) has been achieved while using an isotopically labeled internal standard. The limits of detection range from 7 to 278 pmol. Differences in the quantities of extracted metabolites are observed for the samples obtained from healthy individuals (intersubject variabilities: 30-89%; n = 9), which suggests that this method may have the potential to become a semiquantitative assay in clinical analysis and forensics.

Isotope label-aided mass spectrometry reveals the influence of environmental factors on metabolism in single eggs of fruit fly.

In order to investigate the influence of light/dark cycle on the biosynthesis of metabolites during oogenesis, here we demonstrate a simple experimental protocol which combines in-vivo isotopic labeling of primary metabolites with mass spectrometric analysis of single eggs of fruit fly (Drosophila melanogaster). First, fruit flies were adapted to light/dark cycle using artificial white light. Second, female flies were incubated with an isotopically labeled sugar ((13)C(6)-glucose) for 12 h--either during the circadian day or the circadian night, at light or at dark. Third, eggs were obtained from the incubated female flies, and analyzed individually by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS): this yielded information about the extent of labeling with carbon-13. Since the incorporation of carbon-13 to uridine diphosphate glucose (UDP-glucose) in fruit fly eggs is very fast, the labeling of this metabolite was used as an indicator of the biosynthesis of metabolites flies/eggs during 12-h periods, which correspond to circadian day or circadian night. The results reveal that once the flies adapted to the 12-h-light/12-h-dark cycle, the incorporation of carbon-13 to UDP-glucose present in fruit fly eggs was not markedly altered by an acute perturbation to this cycle. This effect may be due to a relationship between biosynthesis of primary metabolites in developing eggs and an alteration to the intake of the labeled substrate - possibly related to the change of the feeding habit. Overall, the study shows the possibility of using MALDI-MS in conjunction with isotopic labeling of small metazoans to unravel the influence of environmental cues on primary metabolism.

Multifunctional Fe3O4/alumina core/shell MNPs as photothermal agents for targeted hyperthermia of nosocomial and antibiotic-resistant bacteria.

AIMS: The appearance of antibiotic-resistant bacterial strains is a serious problem in medical treatment. Thus, it is imperative to explore new therapeutic approaches and antibiotics with which to treat patients suffering from bacterial infections. MATERIALS & METHODS: In this work, we propose a targeted hyperthermia therapeutic approach using alumina-coated iron oxide magnetic nanoparticles (Fe(3)O(4)/alumina core/shell MNPs) as photothermal agents to selectively kill bacteria. RESULTS: Fe(3)O(4) MNPs possess photothermal capabilities under near-infrared (NIR) light illumination. The temperature of the MNP suspension (1.33 µg/µl, 60 µl) under illumination with NIR light increased 20°C over 5 min. Functionalization of the surface of the MNPs with an alumina coating allows them to have targeting capability toward bacteria. The prepared Fe(3)O(4)/alumina core/shell MNPs possess several desirable features, including magnetic properties, absorption capability in the NIR region and the ability to target bacteria. The magnetic properties of the Fe(3)O(4)/alumina MNPs allow conjugated target species to aggregate at a specific location under a magnetic field. A NIR laser can then be used to specifically irradiate the aggregated spot to photokill target bacteria. The cell growth of nosocomial bacteria, including Gram-positive, Gram-negative and antibiotic-resistant bacterial strains, can be effectively inhibited by over 95% within 10 min of light irradiation when targeted by Fe(3)O(4)/alumina MNPs. CONCLUSION: This approach provides a potential therapeutic approach for treating patients suffering from nosocomial and antibiotic-resistant bacterial infections.