Methylene Blue as a Diagnostic Aid in the Early Detection of Potentially Malignant and Malignant Lesions of Oral Mucosa

A Systematic Review of Oral Biopsies, Sample Types, and Detection Techniques Applied in Relation to Oral Cancer Detection

Background: Early identification of the stage of oral cancer development can lead to better treatment outcomes and avoid malignant transformation. Therefore, this review aims to provide a comprehensive overview that describes the development of standardized procedures for oral sample collection, characterization, and molecular risk assessment. This can help investigators to choose the appropriate sampling method and downstream analyses for different purposes. Methods: This systematic review was conducted according to the PRISMA guidelines. Using both PubMed and Web of Science databases, four independent authors conducted a literature search between 15 and 21 June 2021. We used key search terms to broaden the search for studies. Non-conforming articles were removed using an EndNote-based and manual approach. Reviewers used a designed form to extract data. Results: This review included a total of 3574 records, after eliminating duplicate articles and excluding papers that did not meet the inclusion criteria. Finally, 202 articles were included in this review. We summarized the sampling methods, biopsy samples, and downstream analysis. The biopsy techniques were classified into tissue and liquid biopsy. The common sequential analysis of tissue biopsy includes histopathological examination such as H&E or IHC to identify various pathogenic features. Meanwhile, liquid samples such as saliva, blood, and urine are analyzed for the purpose of screening to detect mutations in cancer. Commonly used technologies are PCR, RT-PCR, high-throughput sequencing, and metabolomic analysis. Conclusions: Currently, tissue biopsies provide increased diagnostic value compared to liquid biopsy. However, the minimal invasiveness and convenience of liquid biopsy make it a suitable method for mass screening and eventual clinical adoption. The analysis of samples includes histological and molecular analysis. Metabolite analysis is rising but remains scarce.

Evaluation of methylene blue based photodynamic inactivation (PDI) against intracellular B-CoV and SARS-CoV2 viruses under different light sources in vitro as a basis for new local treatment strategies in the early phase of a Covid19 infection

The local antiviral photodynamic inactivation (PDI) may prove to be a helpful tool reducing the viral load in the nose and throat area in the early phase of a Covid19 infection. Both the infectivity and the prognosis of SARS-CoV-2 infections in the early phase can depend on the viral load in this area. The aim of our study was to find a simplified PDI therapy option against corona viruses in this region with low dose methylene blue (MB) as photosensitizer and use of LED light instead of laser. As a substitute for SARS-CoV2 viruses we started with BCoV infected U373 cells first. We used an 810nm diode laser with 300mW/cm2 and 100J/cm2 light dose as well as a 590 nm LED and a broadband LED with irradiation intensity of 10,000 lx each (irradiation time 2.5 and 10 min) and concentrations of the sensitizer of 0.001% and 0.0001%. The 0.001% MB sensitizer experiments showed similar results with all exposures. The logarithmic reduction factor varied between ≥ 5.29 and ≥ 5.31, (0.001% MB sensitizer) and ≥ 4.6 and ≥ 5.31 (0.0001% MB) respectively. Extending the LED irradiation time from 2 to 5 and 10 minutes did not change these results. In contrast approaches of BCoV-infected cells in the dark, treated with 0.001% and 0.0001% MB sensitizer alone, a lot of residual viruses could be detected after 10 minutes of incubation (RF 0.9 and RF 1.23 for 0.001% MB and 0.0001% MB respectively) In our SARS-CoV-2 experiments with VERO E6 infected cells the irradiation time was reduced to 1, 2 and 3 minutes for both concentrations with increasing broadband LED radiation intensity from 20 to 50 and 100.000 lx. (RF 4.67 for 0.001% and 0.0001% respectively). This showed a minimum concentration of 0.0001%MB and a minimum radiation intensity of 20,000 lx leads to a 99.99% reduction of intracellular and extracellular viruses after one minute exposure.

Methylene Blue as a Diagnosis and Screening Tool for Oral Cancer and Precancer

Objectives

To evaluate the accuracy of methylene blue (MB) for diagnosing oral cancer and precancer.

Data Sources

PubMed, Cochrane Database, Embase, Web of Science, SCOPUS, and Google Scholar.

Review Methods

Two authors working independently reviewed 6 databases from their dates of inception until April 2020. Studies exploring oral mucosal disorders as detected by MB were assessed. True-positive, true-negative, false-positive, and false-negative data were extracted for each study. Methodological quality was evaluated with the Quality Assessment of Diagnostic Accuracy Studies tool (v 2).

Results

Seven prospective and retrospective studies (N = 493) were included. The diagnostic odds ratio of MB was 20.017 (95% CI, 10.65-37.63, I2 = 23%). The area under the summary receiver operating characteristic curve was 0.699. Sensitivity was 0.903 (95% CI, 0.84-0.94, I2 = 54%), and specificity was 0.68 (95% CI, 0.60-0.75, I2 = 0%). The correlation between the sensitivity and the false-positive rate was –0.17, indicating an absence of heterogeneity.

Conclusions

Regarding diagnostic accuracy, MB had high sensitivity but low specificity, suggesting that it cannot be recommended as a replacement for the currently used standard of a scalpel biopsy with histologic assessment. Instead, it should be used as an adjunct to conventional assessment because of its low toxicity and price.

Methylene Blue Assay for Estimation of Regenerative Re-Epithelialization In Vivo

The rapidity with which epithelial cells cover a wound surface helps determine whether scarring or scar-less healing results. As methylene blue is a vital dye that is absorbed by damaged tissue but not undamaged epidermis, it can be used to assess wound closure. We sought to develop a quantitative methylene blue exclusion assay to estimate the timeframe for re-epithelialization in regenerating appendages in zebrafish and axolotls, two classic model systems of regeneration. Following application of methylene blue to the amputation plane and extensive washing, the regenerating tail was imaged in vivo until staining was no longer visible. The percent area of the amputation plane positive for methylene blue, representing the area of the amputation plane not yet re-epithelialized, was measured for each time point. The loss of methylene blue occurred rapidly, within ~2.5 h in larval and juvenile axolotls and <1 h in adult zebrafish, consistent with high rates of re-epithelialization in these models of regeneration. The assay allows simple, rapid estimation of the time course for regenerative re-epithelialization without affecting subsequent regenerative ability. This technique will permit comparison of re-epithelialization across different strains and stages, as well as under the influence of various pharmacological inhibitors that affect regeneration.