A new portable sulfide monitor with a zinc-oxide semiconductor sensor for daily use and field study

ORGANOLEPTIC AND HALITOMETRIC ASSESSMENTS DO NOT CORRELATE WELL IN INTRA-ORAL HALITOSIS: A SYSTEMATIC REVIEW AND META-ANALYSIS

BACKGROUND

The gold standard method for diagnosing oral halitosis is the subjective organoleptic measurement. Device-supported methods are also widespread worldwide. The challenges and safety concerns around performing organoleptic measurements during pandemics and the diversity of measuring device alternatives raised our clinical question: which halitometer is the most suitable for diagnosing halitosis?

METHODS

This systematic review was registered in PROSPERO (ID CRD42022320024). The search was performed on March 23, 2022 in the following electronic databases: MEDLINE, Embase, Scopus, Web of Science, and CENTRAL. Adult populations with or without halitosis were included, and patients with systemic diseases were excluded. Organoleptic (subjective) measurement and the device-supported (objective) methods were compared; the primary outcome was the correlation coefficient, and the secondary was the specificity and sensitivity of the devices. QUADAS-2 and QUADAS-C were used to evaluate the risk of bias in the studies. Random-effects meta analyses were performed on the outcomes, and the secondary outcomes were plotted on a common ROC plot.

RESULTS

A total of 1231 records were found in the 5 databases. After the selection process, 76 articles were eligible for the systematic review, and 14,635 patients were involved in the qualitative analysis. The pooled Spearman's correlation coefficient (c.c.) for sulfide monitors was 0.65; 95% CIs: [0.53-0.74]; I2 = 95%, P < .01. The pooled Spearman's c.c. for portable gas chromatographs was 0.69; 95% CIs: [0.63-0.74]; I2 = 12%, P < .01. The pooled Spearman's c.c. for gas chromatographs was 0.76; 95% CIs: [0.67-0.83]; I2 = 0%, P < .01.

DISCUSSION

None of the most commonly used halitometers proved to be significantly superior to the others. Halimeter and OralChroma measurements did not correlate well with the organoleptic level of oral halitosis in adults. Therefore, better halitometers need to be developed as an alternative to organoleptic measurements.

Highly Sensitive and Selective NiO/WO3 Composite Nanoparticles in Detecting H2S Biomarker of Halitosis

Indirectly monitoring halitosis via the detection of hydrogen sulfide (H₂S) biomarkers using gas sensors is a newly emerging technique. However, such H₂S sensors are required with critically high selectivity and sensitivity, as well as a ppb-level detection limit, which remains technologically challenging. To address such issues, here, we have developed highly sensitive and selective H₂S sensors with NiO/WO₃ nanoparticles (NPs), which have been synthesized by firstly hydrolyzing WO₃ NPs and subsequently decorating with NiO NPs in a hydrothermal process. Theoretically, the NiO/WO₃ NPs assist in forming a thicker electron depletion layer, adsorbing more oxygen species O₂^- to oxidize H₂S and finally release more electrons. Beneficially, 2.1 wt % NiO/WO₃ NPs show high sensitivity to H₂S (R_a/R_g = 15031 ± 1370 @ 10 ppm, 100 °C), which is 42.6-fold higher than that of the pristine WO₃ NPs (R_a/R_g = 353 ± 5.6 @ 10 ppm, 100 °C). Further, the H₂S sensor shows ppb-level detection limit (R_a/R_g = 4.95 ± 2.9 @ 0.05 ppm, 100 °C) and high selectivity. Practically, NiO/WO₃ NP sensor prototype has been employed to detect the simulated exhaled halitosis compared with that of gas chromatography, revealing a close concentration of H₂S. Our investigation offers an experimental base in future intelligent medical applications.

Selective Detection of Target Volatile Organic Compounds in Contaminated Humid Air Using a Sensor Array with Principal Component Analysis

We investigated selective detection of the target volatile organic compounds (VOCs) nonanal, n-decane, and acetoin for lung cancer-related VOCs, and acetone and methyl i-butyl ketone for diabetes-related VOCs, in humid air with simulated VOC contamination (total concentration: 300 μg/m³). We used six “grain boundary-response type” sensors, including four commercially available sensors (TGS 2600, 2610, 2610, and 2620) and two Pt, Pd, and Au-loaded SnO₂ sensors (Pt, Pd, Au/SnO₂), and two “bulk-response type” sensors, including Zr-doped CeO₂ (CeZr10), i.e., eight sensors in total. We then analyzed their sensor signals using principal component analysis (PCA). Although the six “grain boundary-response type” sensors were found to be insufficient for selective detection of the target gases in humid air, the addition of two “bulk-response type” sensors improved the selectivity, even with simulated VOC contamination. To further improve the discrimination, we selected appropriate sensors from the eight sensors based on the PCA results. The selectivity to each target gas was maintained and was not affected by contamination.

Detection of Atmospheric Methyl Mercaptan Using Wavelength Modulation Spectroscopy with Multicomponent Spectral Fitting

Detection of methyl mercaptan (CH₃SH) is essential for environmental atmosphere assessment and exhaled-breath analysis. This paper presents a sensitive CH₃SH sensor based on wavelength modulation spectroscopy (WMS) with a mid-infrared distributed feedback interband cascade laser (DFB-ICL). Multicomponent spectral fitting was used not only to enhance the sensitivity of the sensor but also to determine the concentration of interferents (atmospheric water and methane). The results showed that the uncertainties in the measurement of CH₃SH, H₂O, and CH₄ were less than 1.2%, 1.7% and 2.0%, respectively, with an integration time of 10 s. The CH₃SH detection limit was as low as 7.1 ppb with an integration time of 295 s. Overall, the reported sensor, boasting the merits of high sensitivity, can be used for atmospheric methyl mercaptan detection, as well as multiple components detection of methyl mercaptan, water, and methane, simultaneously.

Facile Au catalyst loading on the inner shell of hollow SnO2 spheres using Au-decorated block copolymer sphere templates and their selective H2S sensing characteristics

Hollow SnO2 spheres functionalized by Au catalysts were synthesized via the use of Au-decorated block copolymer (Au-BCP) sphere templates. Uniformly distributed Au nanoparticles on BCP spheres were prepared by the infiltration of Au precursors into polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) spheres. A thin SnO2 layer was coated on the Au-BCP spheres using RF sputtering at room temperature without morphological deformation of the spheres. The Au nanoparticles were uniformly transferred from the Au-BCP spheres to the inner shells of the hollow SnO2 spheres followed by decomposition of BCP spheres. The Au-loaded hollow SnO2 spheres exhibited a superior H2S sensitivity (Rair/Rgas = 17.4 at 5 ppm) with remarkably selective characteristics with a minor response (Rair/Rgas < 2.5 at 5 ppm) toward other interfering gases. Our results pave the way for a new catalyst loading method using Au-BCP spheres for the uniformly distributed Au NPs on the SnO2 layers.

Instrumental assessment of halitosis for the general dental practitioner

At the moment there are no clear protocols for the assessment of bad breath. An organoleptic evaluation is still the reference. To date there are several tools available to detect and quantify specific compounds related to halitosis. This paper reviews the available information on three sulphur monitors (OralChroma™ (CHM-1), Halimeter® and Breathtron®), in order to suggest guidance for the general dental practitioner. All three devices showed an acceptable correlation with organoleptic scores. The Halimeter® and Breathtron® seem the most appropriate devices for a general dental practitioner, because they are easy to handle. Because of its capacity of distinguishing between different sulphur compounds and due to its time-consuming and complicated use, the OralChroma™ (CHM-1) seems more suitable in a research environment.

Microbial volatile compounds in health and disease conditions

Microbial cultures and/or microbial associated diseases often have a characteristic smell. Volatile organic compounds (VOCs) are produced by all microorganisms as part of their normal metabolism. The types and classes of VOC produced is wide, including fatty acids and their derivatives (e.g. hydrocarbons, aliphatic alcohols and ketones), aromatic compounds, nitrogen containing compounds, and volatile sulfur compounds. A diversity of ecological niches exist in the human body which can support a polymicrobial community, with the exact VOC profile of a given anatomical site being dependent on that produced by both the host component and the microbial species present. The detection of VOCs is of interest to various disciplines, hence numerous analytical approaches have been developed to accurately characterize and measure VOCs in the laboratory, often from patient derived samples. Using these technological advancements it is evident that VOCs are indicative of both health and disease states. Many of these techniques are still largely confined to the research laboratory, but it is envisaged that in future bedside 'VOC profiling' will enable rapid characterization of microbial associated disease, providing vital information to healthcare practitioners.

Laser spectroscopy on volatile sulfur compounds: possibilities for breath analysis

There is an emerging interest in the detection of volatile sulfur compounds (VSCs) in the breath environment, given their biological relevance as potential signatures of several pathological conditions. Particularly, laser-based spectroscopic sensors are candidates for conducting accurate breath diagnostics in clinical settings. With these aims in mind, the current status of VSC sensing via laser absorption spectroscopy is reviewed in this paper. Attention has been focused on the most promising exhaled markers of pathological conditions, namely hydrogen sulfide, carbonyl sulfide, methanethiol, carbon disulfide and dimethyl sulfide. Details of the most relevant spectroscopic studies conducted on such molecules are presented, together with suggestions on the future direction of this challenging analytical field.

Using multiple array sensing and non-invasive data capture as a model for polypharmacy error detection

Developing standards and technology models that will facilitate e-prescribing is one of the key action items in the federal government's plan to build a nationwide electronic health information infrastructure in the United States. E-prescribing has the potential to drive change in the healthcare industry, but the unavailability of diagnostic testing and detection equipment outside of clinical settings makes expanded collection and use of information problematic. Most solutions are provider-based, and limited by organization-wide startup & maintenance costs, and risk-averse data distribution policies. Objective, consumer-provided standardized data can facilitate the use of distributed information networks in polypharmacy detection and avoidance. In this technology review we propose here one promising model for polypharmacy management and integrated diagnostics through the use of breath-based, multiple array sensing and data capture.

Designing a reliable leak bio-detection system for natural gas pipelines

Monitoring of natural gas (NG) pipelines is an important task for economical/safety operation, loss prevention and environmental protection. Timely and reliable leak detection of gas pipeline, therefore, plays a key role in the overall integrity management for the pipeline system. Owing to the various limitations of the currently available techniques and the surveillance area that needs to be covered, the research on new detector systems is still thriving. Biosensors are worldwide considered as a niche technology in the environmental market, since they afford the desired detector capabilities at low cost, provided they have been properly designed/developed and rationally placed/networked/maintained by the aid of operational research techniques. This paper addresses NG leakage surveillance through a robust cooperative/synergistic scheme between biosensors and conventional detector systems; the network is validated in situ and optimized in order to provide reliable information at the required granularity level. The proposed scheme is substantiated through a knowledge based approach and relies on Fuzzy Multicriteria Analysis (FMCA), for selecting the best biosensor design that suits both, the target analyte and the operational micro-environment. This approach is illustrated in the design of leak surveying over a pipeline network in Greece.

Proposed model for ONCHIT pre-case biosurveillance using multiple array sensing and non-invasive data capture

Recent initiatives by the US ONCHIT highlight the need for electronic population health data collection relating to aspects of Public Health Case (PH Case) reporting and Adverse Event (AE) reporting. Proposed solutions to date have been primarily provider-based, limited by organization-wide startup & maintenance costs, and hampered by risk-averse data distribution policies. Little attention has been given to consumer-focused, distributed data collection models, where objective, consumer-provided standardized data can be used prior to case identification to facilitate earlier use of extensible and distributed information networks in biosurveillance. We propose here one promising model for pre-case biosurveillance management, employing the use of breath-based, multiple array sensing and data capture. The conceptual applications employed in this technology set are provided by way of illustration, and may also serve as a transformative model for emerging EMR/EHR requirements.

Application of a quartz microbalance based gas sensor array for the study of halitosis

Research into the monitoring and control of oral malodor has nowadays received new stimulus from the importance gained by this phenomenon as a medical and social problem. In this paper the performance of an electronic nose to detect this manifestation has been investigated in order to explore the possibility of using this instrument as a complement to those already existing for the assessment of oral malodor. In particular, a breath sampling procedure has been optimized to maximize the transfer to the sensors of those molecules that are known to be associated with the malodor. The sensitivity of electronic nose sensors to hydrogen sulfide, butyric acid and valeric acid-three compounds known to play a major role in halitosis-has been measured and the results indicate that the threshold limits are compatible with halitosis detection. An experiment with real and artificial samples indicates the possibility of identifying halitosis-affected individuals and of discriminating them according to breath composition.