Modern approaches for detection of volatile organic compounds in metabolic studies focusing on pathogenic bacteria:Current state of the art

Pathogenic microorganisms produce numerous metabolites,including volatile organic compounds(VOCs).Monitoring these metabolites in biological matrices(e.g.,urine,blood,or breath)can reveal the presence of specific microorganisms,enabling the early diagnosis of infections and the timely implementation of tar-geted therapy.However,complex matrices only contain trace levels of VOCs,and their constituent com-ponents can hinder determination of these compounds.Therefore,modern analytical techniques enabling the non-invasive identification and precise quantification of microbial VOCs are needed.In this paper,we discuss bacterial VOC analysis under in vitro conditions,in animal models and disease diagnosis in humans,including techniques for offline and online analysis in clinical settings.We also consider the advantages and limitations of novel microextraction techniques used to prepare biological samples for VOC analysis,in addition to reviewing current clinical studies on bacterial volatilomes that address inter-species in-teractions,the kinetics of VOC metabolism,and species-and drug-resistance specificity.

Comment on in vivo corneal confocal microscopic analysis in patients with keratoconus

Dear Editor,The article by Bitirgen et al;published in the journal presents an interesting analysis of keratoconus patients and controls by in vivo corneal confocal microscopy.However,addressing the following observations regarding the study design used by the authors may help add another dimension to the discussion.The age range of the patient group has been stated as 18-41y and for controls as 18-37y.Although the mean age is similar

Implantable optical fiber microelectrode with anti-biofouling ability for in vivo photoelectrochemical analysis

In-situ monitoring of neurochemicals is of vital importance for the understanding of brain functions.Microelectrode-based photoelectrochemical(PEC) sensing has emerged as a promising tool for in vivo analysis since it inherits the merits of both optical and electrochemical methods. However, the in-situ excitation of photoactive materials on the photoelectrode in living body is still a challenge because of limited tissue penetration depth of light. To circumvent this problem, we herein developed an implantable optical fiber(OF)-based microelectrode for in vivo PEC analysis. The working electrode was constructed by coating Au film as conducting layer and CdS@ZnO as photoactive material on a micron-sized OF,which was free of the limitation of light penetration in biological tissues. Further decoration of an antibiofouling layer on the surface made the sensor robust in biosamples. It was successfully applied for monitoring Cu^(2+) level in three different brain regions in the rat model of cerebral ischemia/reperfusion.

Single-atom electrocatalysis: a new approach to in vivo electrochemical biosensing

Modulation of interfacial electron transfer has been proven to pave a new approach to in vivo electrochemical monitoring of brain chemistry;however,designing and establishing highly efficient electrocatalytic scheme towards neurochemicals remain a longstanding challenge.Here,we find that recently established single-atom catalyst(SAC)can be used for catalyzing the electrochemical process of physiologically relevant chemicals and thus offers a new avenue to in vivo electrochemical biosensing.To prove this new concept,we used Co single-atom catalyst(Co-SAC),in which the atomic active sites are dispersed in ordered porous N-doping carbon matrix at atomic level,as an example of SACs for analyzing glucose as the physiologically relevant model chemicals.We found that Co-SAC catalyzes the electrochemical oxidation of hydrogen peroxide(H2O2)at a low potential of ca.+0.05 V(vs.Ag/AgCl).This property was further used for developing an oxidase-based glucose biosensor that was used subsequently as a selective detector of an online electrochemical system(OECS)for continuous monitoring of microdialysate glucose in rat brain.The OECS with Co-SAC-based glucose biosensor as the online detector was well responsive to glucose without interference from other electroactive species in brain microdialysate.This study essentially offers a new approach to in vivo electrochemical analysis with SACs as electrocatalysts to modulate interfacial electron transfer.