Optimization of Saliva Collection and Immunochromatographic Detection of Salivary Pepsin for Point-of-Care Testing of Laryngopharyngeal Reflux

All-Inclusive Sensing Tablet with Integrated Passive Mixer for Ultraviscous Solutions

Developing low-cost and easy-to-use point-of-care devices is necessary for timely disease diagnosis and health monitoring. Here, we introduce all-inclusive, tablet-based chemo/biosensors with rapid automixing features, capable of mixing in highly viscous solutions with viscosities up to 1700 mPa·s. These tablets are created using a simple powder compression method and contain all necessary reagents to perform assays in a "drop-and-detect" manner, without the need for vigorous shaking or vortex mixing. As proof of concept, we demonstrated the applicability of our Speedy tablets for detecting nitrite in human saliva, a challenging medium due to its viscosity. The strong mixing capability of the proposed tablets ensured consistent and reliable results across range of viscosities, from low to high, while delivering an excellent detection range of 0.03-1.50 mg/dL, covering nitrite levels in human saliva. Additionally, we developed a straightforward method to encapsulate enzymes in trehalose, making them bulkier and more stable using only a mist sprayer, nonstick tray, and spatula, eliminating the need for expensive equipment. This approach allowed us to incorporate small amounts of enzymes into tablet formulations and fabricate the first automixing tablet biosensor. These biosensors were used for the bienzymatic detection of glucose in real human urine within the biologically relevant range of 0.3-2.5 mM, indicating the compatibility of automixing tablets with bioreagents. Each tablet costs less than $0.30 to produce and remains stable for at least one month at room temperature. The affordability and convenience of our tablets make them a valuable addition to the array of diagnostic tools.

Changes of Pepsin Concentration in Saliva Sample According to Storage Period

OBJECTIVES

To determine whether the concentration of pepsin in the saliva sample changes according to the storage period of the sample.

METHODS

Forty eight patients with suspected laryngopharyngeal reflux were included in this study. Saliva samples were collected from each patient and each sample divided into six and stored for different period of time. Pepsin concentration was measured using enzyme-linked immunosorbent assay. A comparison was made between the pepsin concentration measured immediately and the concentration measured after storage for 1 week, 2 weeks, 1 month, 3 months, and 6 months.

RESULTS

No significant difference in pepsin concentrations were detected between the sample analyzed immediately and those analyzed at 1 week, 2 weeks, 1 month, and 3 months after saliva collection. A significant difference in pepsin concentration was observed in the sample analyzed immediately and the sample analyzed 6 months after saliva collection.

CONCLUSIONS

Pepsin concentration in saliva samples did not demonstrate a significant difference between the concentration measured immediately and the concentration measured 3 months after saliva collection, although a significant difference was observed in the concentration measured 6 months after collection.

A Paper-Based Sensor for the Detection of Gastroesophageal Reflux Disease Utilizing a Cleavable Fluorescent Polymer

Nowadays, gastroesophageal reflux disease (GERD) has emerged as one of the major hazards to the health of the upper gastrointestinal tract, and there is an urgent need for a low-cost, user-friendly, and non-invasive detection method. Herein, a paper-based sensor (CP sensor) for the non-invasive screening of GERD is proposed. The sensor is structured as a specially shaped cellulose paper strip embedded with fluorescent colloids, which are self-assembled from a cleavable synthetic fluorescent polymer (P4). Benefiting from the introduction of amide bonds and the unique assembled structure of the nanocolloids, the pepsin in the sample solution will hydrolyze the water-soluble branches in the micellar shell during detection, resulting in a corresponding output of the fluorescent signal. This responsiveness, which can be observed by the naked eye, is so sensitive with a minimum detectable concentration for pepsin as low as 0.3 ng·mL-1. Clinical trials have further demonstrates that the designed paper sensor is capable of providing improved accuracy in the early diagnosis of GERD.

A rapid and highly sensitive fluorescence immunochromatographic test strip for pepsin detection in human hypopharyngeal saliva

Pepsin serves as a potential biomarker for laryngopharyngeal reflux disease (LPRD). The reported methods for detecting pepsin still have limitations, such as long reaction times and low sensitivity. Therefore, it is crucial to develop a rapid, simple and sensitive detection method. In this study, a fluorescence immunochromatographic test strip was designed for point-of-care diagnostics of LPRD. To obtain optimal fluorescence immunochromatographic conditions, key experimental factors, including microsphere particle size, binding pH, and resuspension dilution ratio, were systematically evaluated. The optimal fluorescent microsphere size was determined to be 300 nm, the most suitable reaction pH was 8.0, and the ideal resuspension solution to storage solution ratio was 1 : 4. Under these optimal conditions, the sensor had a linear range of 2.5-100.0 ng mL-1 and a detection limit of 1.9 ng mL-1. The relative standard deviation was below 15% for both intra- and inter-batch reproducibility. Under accelerated damage conditions at 37 °C, the test value of the test strip could be kept basically unchanged for 14 days. There was no cross-reactivity of the test strip with pepsinogen I, pepsinogen II and other interferents. In the actual sample detection, the recovery rate was between 85% and 115%. Furthermore, the proposed method was demonstrated to be green and to exhibit strong applicability based on the evaluation using the AGREEprep and the BAGI. In addition, the method has the advantages of high sensitivity, accuracy, greenness and applicability, which can meet the needs of rapid quantitative on-site detection.

Salivary diagnostics: opportunities and challenges

Saliva contains a diverse array of biomarkers indicative of various diseases. Saliva testing has been a major advancement towards non-invasive point-of-care diagnosis with clinical significance. However, there are challenges associated with salivary diagnosis from sample treatment and standardization. This review highlights the biomarkers in saliva and their role in identifying relevant diseases. It provides an overview and discussion about the current practice of saliva collection and processing, and advancements in saliva detection systems from in vitro methods to wearable oral devices. The review also addresses challenges in saliva diagnostics and proposes solutions, aiming to offer a comprehensive understanding and practical guidance for improving saliva-based detection in clinical diagnosis. Saliva diagnosis provides a rapid, effective, and safe alternative to traditional blood and urine tests for screening large populations and enhancing infectious disease diagnosis and surveillance. It meets the needs of various fields such as disease management, drug screening, and personalized healthcare with advances in saliva detection systems offering high sensitivity, fast response times, portability, and automation. Standardization of saliva collection, treatment, biomarker discovery, and detection between different laboratories needs to be implemented to obtain reliable salivary diagnosis in clinical practice.

Enhanced modified poly-tyrosine voltammetric sensor for the quantification detection of salivary pepsin

Pepsin as an aspartic acid protease member and one of the three foremost proteolytic enzymes in the digestive system is essential to be detected. An electrochemically polymerized tyrosine film on carbon paste electrode (pTyr/CPE) has been synthesized by electro-polymerization donating an affordable electrochemical sensor to sense salivary pepsin as a diagnostic technique for gastroesophageal reflux disease (GRD) due to saliva collection is non-invasive and relatively comfortable. The pTyr/CPE was applied for Voltammetric sensing of pepsin and its quantification in phosphate buffer solution of pH 2.0 (PBS). Scanning electron microscopy (SEM) was conducted to learn the surface morphology. Cyclic voltammetry (CV), differential pulse voltammetry (DPVs), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were developed to realize the electrocatalytic activity of the sensor. The pTyr/CPE proceeded as a sensitive detector to pepsin with two linear ranges from 1 to 20 & 20 to 100 ng/mL donating two limits of detection as 0.5 & 0.09 ng/mL, respectively, and high selectivity toward pepsin, as well as stability and fast response of 1.5 s. Consequently, it is guessed that the pTyr/CPE sensor could be supportive for the initial diagnosis of GRD through the detection of pepsin in saliva. Finally, we quantified the pepsin levels in saliva samples of LPR patients (n = 2), showing that the results were agreeable with those from the electrochemical sensor.

Correlation Between Detection Results of Pepsin in Vocal Fold Polyp Tissues and the Postoperative Efficacy

PURPOSE

To explore the correlation between detection results of pepsin in vocal fold polyp tissues and the postoperative efficacy.

METHODS

The clinical data of 112 patients with vocal fold polyp who received surgical procedures in our hospital from June 2019 to March 2021 were retrospectively analyzed. The vocal fold morphology and vocal acoustic function were assessed at postoperative week 12. Using binary logistic regression, we explored whether the factors, ie, detection result of pepsin in vocal fold polyp tissue, microscopic suturing, the use of CO2 laser, and the history of smoking, affected the postoperative morphological repair of vocal fold polyps. Then, to observe and compare the influence of the detection results of pepsin on the recovery of vocal acoustic function, we divided the enrolled patients into the pepsin group and the pepsin-free group based on the postoperative detection results of pepsin in the polyp tissues by immunohistochemistry, RESULTS: In the 112 patients with vocal fold polyps, positive staining of pepsin in the postoperative samples was found in 76 patients (67.86%) and negative in 36 (32.14%). Totally 80 patients returned to normal in vocal fold morphology, among whom 32 (88.89%) were in pepsin-free group and 48 (63.16%) in pepsin group. Binary logistic regression showed that pepsin was a clinically significant indicator that affected the postoperative morphological recovery of the vocal fold (P = 0.003). Although hoarse voice was improved in all patients at postoperative week 12, the differences were statistically significant in the proportion of patients with grade, roughness, breathiness, asthenia, strain class G, voice handicap index, maximum phonation time, Jitter, Shimmer and noise-to-harmonic ratio between the pepsin group and the pepsin-free group (P < 0.05), with the pepsin-free group being superior to the pepsin group in the improvement of vocal acoustic function.

CONCLUSION

Pepsin in vocal fold polyps is a clinically significant indicator affecting the postoperative morphological recovery and acoustic efficacy, and patients with negative pepsin are superior to those with positive pepsin in the postoperative recovery of vocal fold morphology and function.

Determination of pepsin in human saliva using pepsin-susceptible peptide reporter and colorimetric dipstick assay: a prospective, cross-sectional study

A simple and effective pepsin detection assay is reported based on a pepsin-susceptible peptide (PSP) reporter degradation strategy. PSP, which can be specifically cleaved by pepsin, was modified with fluorescein isothiocyanate (FITC) and biotin at the N- and C-terminals to be used as a reporter for colorimetric detection of dipsticks. A universal lateral flow dipstick consisting of a streptavidin test line for biotin binding and a sample pad immobilized with a gold-labeled polyclonal (rabbit) anti-FITC antibody was used to verify PSP-based pepsin detection. When the PSP reporter reacts with pepsin in a tube, it cleaves into two fragments, and the cleaved fragments do not display any color on the test line. Therefore, the higher the concentration of pepsin is, the greater is the decrease in test line intensity (IT-line) and the higher is the control line intensity (IC-line). First, the PSP cleavage and dipstick assay conditions for pepsin detection was optimized. The ratio of color intensity (IT-line/IC-line) of PSP-based dipstick assay showed a linear relationship with log concentration of pepsin ranging between 4 and 500 ng/mL (R2 = 0.98, n = 6), with a limit of detection of 1.4 ng/mL. It also exhibited high specificity and good reproducibility. Finally, pepsin levels were quantified in saliva samples from healthy controls (n = 34) and patients with laryngopharyngeal reflux (LPR, n = 61). Salivary pepsin levels were higher in patients with LPR than in healthy controls. The salivary pepsin levels correlated with those measured using a conventional enzyme-linked immunosorbent assay kit. Therefore, this PSP-based dipstick assay is a convenient tool for assessing salivary pepsin levels.

Portable and Rapid Fluorescence Turn-On Detection of Total Pepsin in Saliva Based on Strong Electrostatic Interactions

Salivary pepsin has been proposed as a promising diagnostic marker for gastroesophageal reflux disease (GERD). However, the activity of human pepsin is strongly influenced by pH, and the acidic condition (pH ∼ 2) is optimal, which is a contradiction for the pepsin detection kit based on its catalytic activity. Thus, its accurate quantification in saliva (neutral pH) by readily rapid tools with simplicity and low cost is still challenging. Herein, a convenient fluorescence assay has been developed for the rapid detection of pepsin at neutral pH based on its electrostatic interaction with SYBR Green (SG) rather than the bioactivity. At neutral pH, the positively charged SG fluorophore can be effectively adsorbed by the negatively charged pepsin due to the low isoelectric point (pI) and large molecular size of pepsin. Thus, the molecular rotation of SG is limited, and its fluorescence intensity is significantly increased. The strategy was further confirmed to have the same fluorescence response as that of normally active and inactivated pepsin. Due to the unique pI of pepsin, the fluorescence strategy is highly selective for pepsin compared to other proteins. On the basis of this strategy, a smartphone-based fluorescence capture device integrated with a programmed Python program was fabricated for both color recognition and the accurate detection of pepsin within 3 min. Under the optimal conditions, this turn-on sensor allowed for the on-site analysis of pepsin with a detection limit of 0.2 μg/mL. Moreover, this strategy was successfully used to assess salivary pepsin to aid in the noninvasive diagnosis of GERD.

Salivary biomarkers: novel noninvasive tools to diagnose chronic inflammation

Several chronic disorders including type 2 diabetes (T2D), obesity, heart disease and cancer are preceded by a state of chronic low-grade inflammation. Biomarkers for the early assessment of chronic disorders encompass acute phase proteins (APP), cytokines and chemokines, pro-inflammatory enzymes, lipids and oxidative stress mediators. These substances enter saliva through the blood flow and, in some cases, there is a close relation between their salivary and serum concentration. Saliva can be easily collected and stored with non-invasive and cost-saving procedures, and it is emerging the concept to use it for the detection of inflammatory biomarkers. To this purpose, the present review aims to discuss the advantages and challenges of using standard and cutting-edge techniques to discover salivary biomarkers which may be used in diagnosis/therapy of several chronic diseases with inflammatory consequences with the pursuit to possibly replace conventional paths with detectable soluble mediators in saliva. Specifically, the review describes the procedures used for saliva collection, the standard approaches for the measurement of salivary biomarkers and the novel methodological strategies such as biosensors to improve the quality of care for chronically affected patients.

Pretreatment Methods for Human Nasopharyngeal Swabs to Increase the Signal to Noise Ratio of High Sensitivity Immunoassays

Mucous samples collected through nasopharyngeal (NP) swabs are considered gold standard specimens for the detection of respiratory pathogens. Matrices of these highly viscous samples often cause significant background noises in immunoassays, especially immunoassays with high sensitivity. We demonstrated such nonspecific background signals in both a chemiluminescence enzyme-linked immunosorbent assay (ELISA) and a novel highly sensitive immunoassay called Microbubbling SARS-CoV-2 Antigen Assay (MSAA). We developed and demonstrated the effectiveness of two quick sample pretreatment methods, filtration and preadsorption, to decrease nonspecific signals and increase the signal-to-noise ratio (SNR). Using these pretreatment methods, the SNR (at 3.6 × 10⁴ copies/mL of inactivated SARS-CoV-2) was increased by 42.4-fold (95% CI 41.0-43.8) and 67.1-fold (95% CI 57.9-76.3) in the MSAA, and 1.3-fold (95% CI 0.9-1.7) and 1.8-fold (95% CI 1.6-2.0) in the chemiluminescence ELISA assay. Sample pretreatment methods developed in this study are broadly adaptable for the development of immunoassays for highly viscous samples.

Does hypopharyngeal-esophageal multichannel intraluminal impedance-pH monitoring for the diagnosis of laryngopharyngeal reflux have to be 24 h?

PURPOSE

To investigate the diagnostic value of combined multi-timepoint salivary pepsin testing (MTPSPT) and hypopharyngeal-esophageal multichannel intraluminal impedance-pH monitoring (HEMII-pH) for laryngopharyngeal reflux (LPR) and whether an appropriate reduction in the duration of HEMII-pH would affect the accuracy of diagnosis of LPR.

METHODS

Recruited patients were studied with both MTPSPT and HEMII-pH. The diagnosis of LPR was based on the occurrence of > 1 reflux event and/or positive results on any of the MTPSPT. The diagnostic value of combined diagnosis was studied through combining a breakdown of the 24-h HEMII-pH finding and the results of the MTPSPT. The diagnostic value was expressed in terms of sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV).

RESULTS

Based on 24-h HEMII-pH and MTPSPT, the positive rate of LPR was 83.33% and 74.69%, respectively. According to the combined diagnosis, the positive rate of LPR was 90.74%. The sensitivity and specificity of the combined diagnosis both were 89.51% and 100%, when the HEMII-pH intervals were 7 a.m.-6 p.m. and 7 a.m.-7 p.m., respectively. However, when the monitoring time was extended to 8 p.m. and bedtime, the sensitivity, specificity, PPV and NPV of the combined diagnosis both were 100%.

CONCLUSIONS

The combination of MTPSPT and HEMII-pH increased the sensitivity and accuracy of diagnosis of LPR. For patients with positive MTPSPT results, the duration of HEMII-pH can be appropriately shortened to reduce patient sufferings.

Electrochemical detection of uric acid in undiluted human saliva using uricase paper integrated electrodes

In this study, we introduce a uricase-immobilized paper (UOx­-paper) integrated electrochemical sensor for detection of uric acid (UA) in saliva. The UOx was immobilized on the detection zone in the wax-patterned paper substrate. This UOx-paper was integrated with a Prussian blue­-modified, screen-printed carbon electrode after electropolymerization of o-phenylenediamine to construct an electrochemical cell for small-volume (20 μL) of samples. First, we optimized the fabrication conditions of UOx-paper. Next, the amperometric response of the UOx-paper-based electrochemical UA sensor was analyzed using a known concentration of UA standard solution in artificial saliva at an applied potential of − 0.1 V (versus Ag pseudo-reference electrode). The UOx-­paper based electrochemical UA sensor showed a sensitivity of 4.9 μA·mM⁻¹ in a linear range of 50 to 1000 μM (R² = 0.998), high selectivity and good reproducibility, as well as a limit of detection of 18.7 μM (0.31 mg/dL) UA. Finally, we quantified the UA levels in undiluted saliva samples of healthy controls (n = 20) and gout patients (n = 8). The levels were correlated with those measured with conventional salivary UA enzymatic assays as well as serum UA levels. The UOx-paper-based electrochemical UA sensor is a user-friendly and convenient tool to assess salivary UA levels.

Investigation of Whole and Glandular Saliva as a Biomarker for Alzheimer's Disease Diagnosis

Salivary Aβ40, Aβ42, t-tau, and p-tau 181 are commonly employed in Alzheimer's disease (AD) investigations. However, the collection method of these biomarkers can affect their levels. To assess the impact of saliva collection methods on biomarkers in this study, 15 healthy people were employed in the morning with six saliva collection methods. The chosen methods were then applied in 30 AD patients and 30 non-AD controls. The levels of salivary biomarkers were calculated by a specific enzyme-linked immunosorbent assay. The receiver operating characteristic was utilized to assess salivary biomarkers in AD patients. The results demonstrated that the highest levels of salivary Aβ40, Aβ42, t-tau, and p-tau were in different saliva collection methods. The correlations between different saliva biomarkers in the same collection method were different. Salivary Aβ40, Aβ42, t-tau, and p-tau had no significant association. Salivary Aβ42 was higher in AD than in non-AD controls. However, p-tau/t-tau and Aβ42/Aβ40 had some relevance. The area under the curve for four biomarkers combined in AD diagnosis was 92.11%. An alternate saliva collection method (e.g., USS in Aβ40, UPS in Aβ42, t-tau, SSS in p-tau 181) was demonstrated in this study. Moreover, combining numerous biomarkers improves AD diagnosis.

[The effect of expression of pepsin in vocal polyps on postoperative curative effect]

Objective:To investigate the effect of tissue pepsin expression of vocal polyps on the postoperative curative effect. Methods:Retrospectively analyze the data of 112 patients diagnosed with vocal cord polyps and undergone surgery from June 2019 to March 2021. The cases were divided into positive group and negative group according to the immunohistochemical pepsin expression. The preoperative reflux symptom index （RSI） and the reflux finding score （RFS） were compared, and the recovery of the voice acoustic function and postoperative vocal cord morphology were analyzed. Results:Among the postoperative specimens of 112 patients,76 cases were positive for pepsin staining, accounting for 67.9%, and 36 cases were negative, accounting for 32.1%. In the pepsin-positive group, 48 cases of vocal cord morphology returned to normal, and 20 cases remained scar or edema in the operation area, 8 cases of polyps relapsed; in the pepsin-negative group, a total of 32 cases of vocal cord morphology returned to normal, 4 cases of remained scar or edema in the operation area, no relapsed cases, the difference in vocal cord morphology recovery was significant （χ²=8.689, P=0.013）. The symptoms of hoarseness improved after 12 weeks. The differences between pre and post operative of G grade, VHI, MPT, fundamental frequency perturbation and amplitude perturbation assessed by GRBAS were significant （P<0.05）; postoperative G grade, VHI, MPT, fundamental frequency perturbation and amplitude perturbation were compared between the pepsin-positive group and the pepsin-negative group, and the differences were significant （all P<0.05）. Conclusion:The expression of pepsin in vocal polyps is a significant clinical indicator that affects the acoustic effect and morphological recovery of vocal cords after surgery. For patients with positive expression, acid suppression treatment should be strengthened after surgery.

Multitime point pepsin testing can double the rate of the diagnosis of laryngopharyngeal reflux

OBJECTIVE

To study the value of multitime point salivary pepsin testing (MTPSPT) for the diagnosis of laryngopharyngeal reflux (LPR).

STUDY DESIGN

Prospective noncontrolled.

METHODS

For patients who met the enrollment criteria, the reflux symptom index (RSI) and reflux finding score (RFS) were calculated and salivary pepsin testing was performed. The pepsin test was performed every hour from 7:00 a.m. to 6:00 p.m. by collecting fresh saliva samples. A single positive test result was needed for the diagnosis of LPR. The consistency in the diagnosis of LPR between the two methods was compared with the weighted Cohen's kappa statistic.

RESULTS

A total of 204 patients were included. The kappa value between the two methods was 0.566 (p = .00). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MTPSPT were 76.43%, 85.94%, 92.24%, and 62.5%, respectively. We also compared a single pepsin measure at 7 a.m. with the screening results based on the RSI and RFS, and found a much lower kappa agreement value (0.223, p = .00). The sensitivity, specificity, PPV, NPV, and false-negative rate of pepsin testing at 7 a.m. (fasting) were 37.86%, 92.18%, 91.38%, 40.41%, and 58.57%, respectively.

CONCLUSION

The use of the result of a single salivary pepsin test in the morning yields a relatively higher rate of missed diagnosis of LPR, and multitime point testing through a day increased the accuracy and sensitivity of detection of LPR twofold compared to a single morning fasting sample.

LEVEL OF EVIDENCE

3.

How I Approach Laryngopharyngoesophageal Reflux (LPR)

The purpose of this article is to review the cornerstone and most recent literature regarding laryngopharynoesophageal reflux (LPR) including epidemiological characteristics, pathophysiology, symptoms, diagnosis, and management. The role of pepsin in the pathophysiology of LPR is highlighted in addition to new diagnostic modalities and pharmacologic therapies that target pepsin.

Sorafenib Repurposing for Ophthalmic Delivery by Lipid Nanoparticles: A Preliminary Study

Uveal melanoma is the second most common melanoma and the most common intraocular malignant tumour of the eye. Among various treatments currently studied, Sorafenib was also proposed as a promising drug, often administered with other compounds in order to avoid resistance mechanisms. Despite its promising cellular activities, the use of Sorafenib by oral administration is limited by its severe side effects and the difficulty to reach the target. The encapsulation into drug delivery systems represents an interesting strategy to overcome these limits. In this study, different lipid nanoparticulate formulations were prepared and compared in order to select the most suitable for the encapsulation of Sorafenib. In particular, two solid lipids (Softisan or Suppocire) at different concentrations were used to produce solid lipid nanoparticles, demonstrating that higher amounts were able to achieve smaller particle sizes, higher homogeneity, and longer physical stability. The selected formulations, which demonstrated to be biocompatible on Statens Seruminstitut Rabbit Cornea cells, were modified to improve their mucoadhesion, evaluating the effect of two monovalent cationic lipids with two lipophilic chains. Sorafenib encapsulation allowed obtaining a sustained and prolonged drug release, thus confirming the potential use of the developed strategy to topically administer Sorafenib in the treatment of uveal melanoma.

A HiPAD Integrated with rGO/MWCNTs Nano-Circuit Heater for Visual Point-of-Care Testing of SARS-CoV-2

Nowadays, the main obstacle for further miniaturization and integration of nucleic acids point-of-care testing devices is the lack of low-cost and high-performance heating materials for supporting reliable nucleic acids amplification. Herein, reduced graphene oxide hybridized multi-walled carbon nanotubes nano-circuit integrated into an ingenious paper-based heater is developed, which is integrated into a paper-based analytical device (named HiPAD). The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still raging across the world. As a proof of concept, the HiPAD is utilized to visually detect the SARS-CoV-2 N gene using colored loop-mediated isothermal amplification reaction. This HiPAD costing a few dollars has comparable detection performance to traditional nucleic acids amplifier costing thousands of dollars. The detection range is from 25 to 2.5 × 1010 copies mL-1 in 45 min. The detection limit of 25 copies mL-1 is 40 times more sensitive than 1000 copies mL-1 in conventional real-time PCR instruments. The disposable paper-based chip could also avoid potential secondary transmission of COVID-19 by convenient incineration to guarantee biosafety. The HiPAD or easily expanded M-HiPAD (for multiplex detection) has great potential for pathogen diagnostics in resource-limited settings.

Pepsin and Laryngeal and Hypopharyngeal Carcinomas

Laryngeal and hypopharyngeal carcinomas are common malignant tumors of the head and neck, and the incidence of both is increasing. Laryngopharyngeal reflux refers to the retrograde flow of gastric contents into the larynx, oropharynx, and/or nasopharynx. It remains controversial whether laryngopharyngeal reflux is a risk factor for laryngeal and hypopharyngeal cancers. The refluxing substances mainly include hydrochloric acid, pepsin, and occasionally bile acids and bile salts, as well as bacteria that colonize the gastrointestinal tract. Loss of epithelium in the mucous membrane of the larynx and hypopharynx is thought to be caused by pepsin. Here, we review the relationships between laryngopharyngeal reflux and both laryngeal and hypopharyngeal carcinomas, as well as the significance of pepsin, methods of clinical detection, and the mechanism of carcinogenesis.