Autofluorescence based diagnostic techniques for oral cancer

Label-Free Assessment of Key Biological Autofluorophores: Material Characteristics and Opportunities for Clinical Applications

Autofluorophores are endogenous fluorescent compounds that naturally occur in the intra and extracellular spaces of all tissues and organs. Most have vital biological functions - like the metabolic cofactors NAD(P)H and FAD+, as well as the structural protein collagen. Others are considered to be waste products - like lipofuscin and advanced glycation end products - which accumulate with age and are associated with cellular dysfunction. Due to their natural fluorescence, these materials have great utility for enabling non-invasive, label-free assays with direct ties to biological function. Numerous technologies, with different advantages and drawbacks, are applied to their assessment, including fluorescence lifetime imaging microscopy, hyperspectral microscopy, and flow cytometry. Here, the applications of label-free autofluorophore assessment are reviewed for clinical and health-research applications, with specific attention to biomaterials, disease detection, surgical guidance, treatment monitoring, and tissue assessment - fields that greatly benefit from non-invasive methodologies capable of continuous, in vivo characterization.

Early Detection of Oral Potentially Malignant Disorders: A Review on Prospective Screening Methods with Regard to Global Challenges

Oral cancer is a cancer type that is widely prevalent in low-and middle-income countries with a high mortality rate, and poor quality of life for patients after treatment. Early treatment of cancer increases patient survival, improves quality of life and results in less morbidity and a better prognosis. To reach this goal, early detection of malignancies using technologies that can be used in remote and low resource areas is desirable. Such technologies should be affordable, accurate, and easy to use and interpret. This review surveys different technologies that have the potentials of implementation in primary health and general dental practice, considering global perspectives and with a focus on the population in India, where oral cancer is highly prevalent. The technologies reviewed include both sample-based methods, such as saliva and blood analysis and brush biopsy, and more direct screening of the oral cavity including fluorescence, Raman techniques, and optical coherence tomography. Digitalisation, followed by automated artificial intelligence based analysis, are key elements in facilitating wide access to these technologies, to non-specialist personnel and in rural areas, increasing quality and objectivity of the analysis while simultaneously reducing the labour and need for highly trained specialists.

Label-Free Optical Technologies for Middle-Ear Diseases

Medical applications of optical technology have increased tremendously in recent decades. Label-free techniques have the unique advantage of investigating biological samples in vivo without introducing exogenous agents. This is especially beneficial for a rapid clinical translation as it reduces the need for toxicity studies and regulatory approval for exogenous labels. Emerging applications have utilized label-free optical technology for screening, diagnosis, and surgical guidance. Advancements in detection technology and rapid improvements in artificial intelligence have expedited the clinical implementation of some optical technologies. Among numerous biomedical application areas, middle-ear disease is a unique space where label-free technology has great potential. The middle ear has a unique anatomical location that can be accessed through a dark channel, the external auditory canal; it can be sampled through a tympanic membrane of approximately 100 microns in thickness. The tympanic membrane is the only membrane in the body that is surrounded by air on both sides, under normal conditions. Despite these favorable characteristics, current examination modalities for middle-ear space utilize century-old technology such as white-light otoscopy. This paper reviews existing label-free imaging technologies and their current progress in visualizing middle-ear diseases. We discuss potential opportunities, barriers, and practical considerations when transitioning label-free technology to clinical applications.

Review of the Role of Nanotechnology in Overcoming the Challenges Faced in Oral Cancer Diagnosis and Treatment

Throughout the world, oral cancer is a common and aggressive malignancy with a high risk of morbidity, mortality, and recurrence. The importance of early detection in cancer prevention and disease treatment cannot be overstated. Conventional therapeutic strategies have minor difficulties but considerable side effects and unfavourable consequences in clinical applications. Hence, there is a requirement for effective ways for early detection and treatment of oral cancer. At present, numerous forms of nanoparticles have piqued researchers' interest as a potentially useful tool for diagnostic probes and medicinal devices. Because of their inherent physicochemical properties and customizable surface modification, they are able to circumvent some of restrictions and accomplish the intended diagnostic and therapeutic impact. Nanotechnology is a unique field that has revolutionised the industry and is paving the way for new treatments for oral cancer. It can help with a better diagnosis with less harmful substances and is setting current guidelines for treatment. The use of nanotechnology in cancer diagnosis, therapy, and care improves clinical practise dramatically. The different types of nanoparticles that have been developed for the diagnosis and therapy of oral cancers will be covered in this study. The difficulties and potential uses of nanoparticles in the treatment and diagnosis of oral cancer are then highlighted. In order to emphasise existing difficulties and potential remedies for oral cancer, a prospective view of the future is also provided.

Bimodal polarization-sensitive imaging and diffuse reflectance spectroscopy facilitated rapid augmented reality for tissue stratification

We reported the development of a bimodal large field of view (~95 cm² ) polarization-sensitive (PS) imaging and point-wise diffuse reflectance (DR) spectroscopy platform synergising the advantages of the two modalities. PS-DR spectroscopy allows simultaneous label-free biochemical and structural analysis of the investigated tissue. For real applications, the PS imaging first grossly stratified tissue into different categories, followed by high information dimension PS-DR spectroscopy ascertaining ambiguous tissue regions identified by the PS imaging. Tested on a tissue phantom consisting of porcine esophagus muscularis propria and submucosa, it has demonstrated the system developed could complete tissue interrogation within 0.6 minutes and with separation accuracy of 95.87%. Further test on tissue phantom consisting of natural and crushed bovine tendon mimicking normal and cancerous breast tissues validated the potential of system developed to effectively and rapidly investigate large tissue area, facilitating augmented tissue boundary demarcation.

Utilization of gold nanoparticles for the detection of squamous cell carcinoma of the tongue based on laser-induced fluorescence and diffuse reflectance characteristics: an in vitro study

Squamous cell carcinoma is a very common type of oral cancer that affects the health of people with an unacceptably high mortality rate attributed to the difficulties in detecting the disease at an early stage. Therefore, effective techniques for early diagnosis and effective therapy of oral cancer are necessary. In the present study, we exploit the ability of gold nanoparticles (AuNPs) to undergo coupled surface plasmon resonance when closely spaced to improve diagnosing squamous cell carcinoma of the tongue. The prepared AuNPs are characterized by UV-VIS spectroscopy, dynamic light scattering, Fourier transform infrared spectroscopy, and transmission electron microscopy. The size of the prepared AuNPs is 12 ± 2 nm with narrow size distributions and exhibited high stability with a zeta potential of - 16.5 mV. The light fluorescence of the normal and cancer cells is recorded before and after NP addition using a spectrometer upon excitation by 405-nm laser irradiation. Furthermore, the light reflectance of the examined samples is measured at different laser wavelengths (red to NIR region). The obtained results show that the cancer cells mixed with AuNPs produce a higher fluorescence peak at 489.2 nm than the cancer cells without AuNPs. Moreover, the optical diffuse reflectance analyses reveal that the addition of AuNPs enhances cancer detection especially at the 635-nm irradiation with sensitivity (94%), specificity (87%), and overall accuracy (91%).

Superior in vivo Wound-Healing Activity of Mycosynthesized Silver Nanogel on Different Wound Models in Rat

Wound healing is a complex phenomenon particularly owing to the rise in antimicrobial resistance. This has attracted the attention of the scientific community to search for new alternative solutions. Among these, silver being antimicrobial has been used since ancient times. Considering this fact, the main goal of our study was to evaluate the wound-healing ability of mycofabricated silver nanoparticles (AgNPs). We have focused on the formulation of silver nanogel for the management of wounds in albino Wistar rats. Mycosynthesized AgNPs from Fusarium oxysporum were used for the development of novel wound-healing antimicrobial silver nanogel with different concentrations of AgNPs, i.e., 0.1, 0.5, and 1 mg g^-1. The formulated silver nanogel demonstrated excellent wound-healing activity in the incision, excision, and burn wound-healing model. In the incision wound-healing model, silver nanogel at a concentration of 0.5 mg g^-1 exhibited superior wound-healing effect, whereas in the case of excision and burn wound-healing model, silver nanogel at the concentrations of 0.1 and 1 mg g^-1 showed enhanced wound-healing effect, respectively. Moreover, silver nanogel competently arrests the bacterial growth on the wound surface and offers an improved local environment for scald wound healing. Histological studies of healed tissues and organs of the rat stated that AgNPs at less concentration (1 mg g^-1) do not show any toxic or adverse effect on the body and promote wound healing of animal tissue. Based on these studies, we concluded that the silver nanogel prepared from mycosynthesized AgNPs can be used as a promising antimicrobial wound dressing.

Skin's green autofluorescence at dorsal centremetacarpus may become a novel biomarker for diagnosis of lung cancer

It is critical to discover novel biomarkers of lung cancer for establishing economical technology for diagnosis of lung cancer. Our study has suggested that the autofluorescence (AF) of the skin may become a novel biomarker of this type: First, development of lung cancer led to a significant increase in the skin's green AF in a mouse model of lung cancer; second, lung cancer patients had significantly higher skin's green AF at certain positions compared with healthy volunteers and pulmonary infection patients; and third, using the skin's green AF intensity at dorsal centremetacarpus as the variable, the areas under curve (AUC) for differentiating lung cancer patients and pulmonary infection patients and for differentiating lung cancer patients and healthy volunteers was 0.871 and 0.813, respectively. Collectively, our study has indicated that the skin's green AF at dorsal centremetacarpus may become a novel biomarker for establishing a ground-breaking diagnostic strategy for lung cancer.

Applications of Laser-Induced Fluorescence in Medicine

Fluorescence is the most sensitive spectroscopic method of analysis and fluorescence methods. However, classical analysis requires sampling. There are new needs for real-time analyses of biological materials, without the need for sampling. This article presents examples of proprietary applications of laser-induced fluorescence (LIF) in medicine with such methods. A classic example is the analysis of photosensitizers using the photodynamic treatment method (PDT). The level and kinetics of accumulation and excretion of sensitizers in the body are examined, as well as the optimal exposure time after the application of compounds. The LIF method is also used to analyze endogenous fluorophores; it has been used to detect neoplasms, e.g., lung cancer or gynecological and dermatological diseases. Furthermore, it is used for the diagnosis of early stages of tooth decay or detection of fungi. The article will present the construction of sensors based on the LIF method—fiber laser spectrometers and investigated fluorescence spectra in individual applications. Examples of fluorescence imaging, e.g., dermatological, and dental diagnostics and measuring systems will be presented. The advantage of the method is it has greater sensitivity and easily detects lesions early compared to the methods used in observing the material in reflected light.

Advancements in diagnostic techniques for oral cancer detection

Oral malignancy is among the highest prevalent malignancies all over the world. In comparison to systemic malignancies such as lung cancer and colon cancer, they are frequently overlooked by the general public. Nevertheless, they can be exceedingly lethal if left ignored, regardless at the early stage of the condition. Dentists are the finest qualified healthcare specialists in this sector and are responsible for detecting benign and potentially malignant oral conditions such as oral cancers. Oral carcinoma's high prevalence and delayed appearance are serious international medical concerns. Early detection and management of oral carcinoma are the key goals of the World Health Organization (WHO). The identification of key clinical manifestations during the preliminary oral examination can enhance the patient's likelihood of living. Unfortunately, the conventional technology's practical value is limited by a number of drawbacks. Current advancements in optical scanning techniques, such as tissue-fluorescence imaging and optical coherence tomography, have proven to be quite effective. In particular, nanoparticle-based immunosensors, genomics, and salivary biomarkers, epigenetics and microarray have all received a lot of attention. Raising awareness about frequent dental examinations and using noninvasive, effective, and cost-effective screening tools would improve initial stage detection of oral carcinoma and improve patients' longevity.

In Vivo Imaging-Based Techniques for Early Diagnosis of Oral Potentially Malignant Disorders-Systematic Review and Meta-Analysis

Objectives: Oral potentially malignant disorders (OPMDs) are lesions that may undergo malignant transformation to oral cancer. The early diagnosis and surveillance of OPMDs reduce the morbidity and mortality of patients. Diagnostic techniques based on medical images analysis have been developed to diagnose clinical conditions. This systematic review and meta-analysis aimed to evaluate the efficacy of imaging-based techniques compared to the gold standard of histopathology to assess their ability to correctly identify the presence of OPMDs. Design: Literature searches of free text and MeSH terms were performed using MedLine (PubMed), Scopus, Google Scholar, and the Cochrane Library (from 2000 to 30 June 2020). The keywords used in the search strategy were: (“oral screening devices” or “autofluorescence” or “chemiluminescence” or “optical imaging” or “imaging technique”) and (“oral dysplasia” or “oral malignant lesions” or “oral precancerosis”). Results: The search strategy identified 1282 potential articles. After analyzing the results and applying the eligibility criteria, the remaining 43 papers were included in the qualitative synthesis, and 34 of these were included in the meta-analysis. Conclusions: None of the analyzed techniques based on assessing oral images can replace the biopsy. Further studies are needed to explore the role of techniques-based imaging analysis to identify an early noninvasive screening method.

Current Insights into Oral Cancer Diagnostics

Oral cancer is one of the most common head and neck malignancies and has an overall 5-year survival rate that remains below 50%. Oral cancer is generally preceded by oral potentially malignant disorders (OPMDs) but determining the risk of OPMD progressing to cancer remains a difficult task. Several diagnostic technologies have been developed to facilitate the detection of OPMD and oral cancer, and some of these have been translated into regulatory-approved in vitro diagnostic systems or medical devices. Furthermore, the rapid development of novel biomarkers, electronic systems, and artificial intelligence may help to develop a new era where OPMD and oral cancer are detected at an early stage. To date, a visual oral examination remains the routine first-line method of identifying oral lesions; however, this method has certain limitations and as a result, patients are either diagnosed when their cancer reaches a severe stage or a high-risk patient with OPMD is misdiagnosed and left untreated. The purpose of this article is to review the currently available diagnostic methods for oral cancer as well as possible future applications of novel promising technologies to oral cancer diagnosis. This will potentially increase diagnostic options and improve our ability to effectively diagnose and treat oral cancerous-related lesions.

Use of autofluorescence and fluorescent probes as a potential diagnostic tool for oral cancer: A systematic review

INTRODUCTION

The prognosis of patients with Oral squamous cell carcinoma (OSCC) are directly related to the stage of development of the tumor at the time of diagnosis, but it is estimated an average delay in diagnosis of 2-5 months. New non-invasive techniques for the early diagnosis of OSCC are being developed, such as methodologies to detect spectral changes of tumor cells. We conducted a systematic review to analyze the potential use of autofluorescence and/or fluorescent probes for OSCC diagnosis.

MATERIAL AND METHODS

Four databases (PubMed, Scopus, Embase and Web of Science) were used as research sources. Protocol was registered with PROSPERO. It was included studies that evaluated tissue autofluorescence and/or used fluorescent probes as a method of diagnosing and/or treatment of oral cancer in humans.

RESULTS

Forty-five studies were selected for this systematic review, of which 28 dealt only with autofluorescence, 18 on fluorescent probes and 1 evaluated both methods. The VELscope® was the most used device for autofluorescence, exhibiting sensitivity (33%-100%) and specificity (12%-88.6%). 5-Aminolevulinic acid (5-ALA) was the most used fluorescent probe, exhibiting high sensitivity (90%-100%) and specificity (51.3%-96%). Hypericin, rhodamine 6 G, rhodamine 610, porphyrin and γ-glutamyl hydroxymethyl rhodamine green have also been reported.

CONCLUSION

Thus, the autofluorescence and fluorescent probes can provide an accurate diagnosis of oral cancer, assisting the dentist during daily clinical activity, but it is not yet possible to suggest that this method may replace histopathological examination.

Efficacy of Fluorescence Technology vs Conventional Oral Examination for the Early Detection of Oral Pre-Malignant Lesions. A Clinical Comparative Study

BACKGROUND AND OBJECTIVE

Oral cancer is one of the most common malignancies that affect human beings across the world and early detection of oral cancer is believed to reduce the morbidity significantly. Fluorescence diagnosis is emerging as a promising method in the differentiation of cancerous lesions and thus helping in the determination of resolution for the surgical resection of affected area of malignancy very accurately. The aim of this study was to evaluate the usefulness of an autofluorescence hand held device (OralID) to detect oral premalignant lesions.

METHODS

98 potentially high-risk oral cancer patients were divided into two groups (n=49/group). Both the groups were first examined by conventional oral examination under white light and oral findings were noted. Subjects under group B were further examined under fluorescence light through hand held device, i.e. OralID. After the examinations, a surgical biopsy sample was taken from the suspected lesions under local anaesthesia from both the groups to confirm the diagnosis through histopathological analysis.

RESULTS

The positive potential malignant lesions (PMLs) observed in Group A when compared with biopsy reporting was 89.47% true positive while in Group B was 95.24%. The sensitivity reported of Group A was 89.47% and Group B was 97.56%. We observed 8.09% more sensitivity and 11.36% more specificity when we incorporate adjunctive the fluorescence examination using OralID.

CONCLUSION

Results from this study suggests that OralID is a true adjunct to conventional oral examination in detecting early potential malignant changes in subjects visiting for regular dental check-up.

Rhenium (I) Complexes as Probes for Prokaryotic and Fungal Cells by Fluorescence Microscopy: Do Ligands Matter?

Re(I) complexes have exposed highly suitable properties for cellular imaging (especially for fluorescent microscopy) such as low cytotoxicity, good cellular uptake, and differential staining. These features can be modulated or tuned by modifying the ligands surrounding the metal core. However, most of Re(I)-based complexes have been tested for non-walled cells, such as epithelial cells. In this context, it has been proposed that Re(I) complexes are inefficient to stain walled cells (i.e., cells protected by a rigid cell wall, such as bacteria and fungi), presumably due to this physical barrier hampering cellular uptake. More recently, a series of studies have been published showing that a suitable combination of ligands is useful for obtaining Re(I)-based complexes able to stain walled cells. This review summarizes the main characteristics of different fluorophores used in bioimage, remarking the advantages of d⁶-based complexes, and focusing on Re(I) complexes. In addition, we explored different structural features of these complexes that allow for obtaining fluorophores especially designed for walled cells (bacteria and fungi), with especial emphasis on the ligand choice. Since many pathogens correspond to bacteria and fungi (yeasts and molds), and considering that these organisms have been increasingly used in several biotechnological applications, development of new tools for their study, such as the design of new fluorophores, is fundamental and attractive.

Nanotechnology: a promising method for oral cancer detection and diagnosis

Oral cancer is a common and aggressive cancer with high morbidity, mortality, and recurrence rate globally. Early detection is of utmost importance for cancer prevention and disease management. Currently, tissue biopsy remains the gold standard for oral cancer diagnosis, but it is invasive, which may cause patient discomfort. The application of traditional noninvasive methods-such as vital staining, exfoliative cytology, and molecular imaging-is limited by insufficient sensitivity and specificity. Thus, there is an urgent need for exploring noninvasive, highly sensitive, and specific diagnostic techniques. Nano detection systems are known as new emerging noninvasive strategies that bring the detection sensitivity of biomarkers to nano-scale. Moreover, compared to current imaging contrast agents, nanoparticles are more biocompatible, easier to synthesize, and able to target specific surface molecules. Nanoparticles generate localized surface plasmon resonances at near-infrared wavelengths, providing higher image contrast and resolution. Therefore, using nano-based techniques can help clinicians to detect and better monitor diseases during different phases of oral malignancy. Here, we review the progress of nanotechnology-based methods in oral cancer detection and diagnosis.

Single- and two-photon imaging of human micrometastases and disseminated tumour cells with conjugates of nanobodies and quantum dots

Early detection of malignant tumours and, especially, micrometastases and disseminated tumour cells is still a challenge. In order to implement highly sensitive diagnostic tools we demonstrate the use of nanoprobes engineered from nanobodies (single-domain antibodies, sdAbs) and fluorescent quantum dots (QDs) for single- and two-photon detection and imaging of human micrometastases and disseminated tumour cells in ex vivo biological samples of breast and pancreatic metastatic tumour mouse models expressing human epidermal growth factor receptor 2 (HER2) or carcinoembryonic antigen (CEA). By staining thin (5–10 µm) paraffin and thick (50 µm) agarose tissue sections, we detected HER2- and CEA-positive human tumour cells infiltrating the surrounding tissues or metastasizing to different organs, including the brain, testis, lung, liver, and lymph nodes. Compared to conventional fluorescently labelled antibodies the sdAb-HER2-QD and sdAb-CEA-QD nanoprobes are superior in detecting micrometastases in tissue sections by lower photobleaching and higher brightness of fluorescence signals ensuring much better discrimination of positive signals versus background. Very high two-photon absorption cross-sections of QDs and small size of the nanoprobes ensure efficient imaging of thick tissue sections unattainable with conventional fluorescent probes. The nanobody–QD probes will help to improve early cancer diagnosis and prognosis of progression by assessing metastasis.

Tissue Fluorescence Imaging (VELscope) for Quick Non-Invasive Diagnosis in Oral Pathology

Oral squamous cell carcinoma is the most common form of malignancy of the oral cavity; its incidence is increasing and late-stage presentation is common. It is usually predated by oral premalignant disorders. For this reason, early diagnosis is fundamental to reduce the malignant transformation of oral premalignant disorders and for increase the survival rate for oral cancer. Scraping the surface of the lesion is useful for having cytological features of the investigated tissue. The features of smears of oral premalignant lesions are the keratinization growth (red, orange, brown), the increased nuclear area and so the nuclear hyperchromatism, the nuclear pleomorphism, and the chromatin clumping. All those features are essential for doing the right diagnosis. However, the oral disease should be recognized at the first view by the clinical investigation without touching the lesions avoiding possible alteration in the cells of the tissue. The current standard of incisional biopsy with histology is painful for patients and involves a delay, although histology is completed. The aim of this article is to evaluate the effectiveness of other available tests that are unobtrusive and provide immediate results like the tissue fluorescence imaging.

Violet and blue light-induced green fluorescence emissions from dental caries

BACKGROUND

The objective of this laboratory study was to compare violet and visible blue LED light-elicited green fluorescence emissions from enamel and dentine in healthy or carious states.

METHODS

Microscopic digital photography was undertaken using violet and blue LED illumination (405 nm and 455 nm wavelengths) of tooth surfaces, which were photographed through a custom-made stack of green compensating filters which removed the excitation light and allowed green fluorescence emissions to pass. Green channel pixel data were analysed.

RESULTS

Dry sound enamel and sound root surfaces showed strong green fluorescence when excited by violet or blue lights. Regions of cavitated dental caries gave lower green fluorescence, and this was similar whether the dentine in the lesions was the same colour as normal dentine or was darkly coloured. The presence of saliva on the surface did not significantly change the green fluorescence, while the presence of blood diluted in saliva depressed green fluorescence.

CONCLUSIONS

Using violet or blue illumination in combination with green compensating filters could potentially aid in the assessment of areas of mineral loss.

Narrow band imaging versus autofluorescence imaging for head and neck squamous cell carcinoma detection: a prospective study

Objectives:

This study aimed to compare the diagnostic effectiveness of narrow band imaging and autofluorescence imaging for malignant laryngopharyngeal tumours.

Methods:

Between May 2010 and October 2010, 50 consecutive patients with suspected laryngopharyngeal tumour underwent endoscopic laryngopharynx examination. The morphological characteristics of laryngopharyngeal lesions were analysed using high performance endoscopic systems equipped with narrow band imaging and autofluorescence imaging modes. The diagnostic effectiveness of white light image, narrow band imaging and autofluorescence imaging endoscopy for benign and malignant laryngopharyngeal lesions was evaluated.

Results:

Under narrow band imaging endoscopy, the superficial microvessels of squamous cell carcinomas appeared as dark brown spots or twisted cords. Under autofluorescence imaging endoscopy, malignant lesions appeared as bright purple. The sensitivity of malignant lesion diagnosis was not significantly different between narrow band imaging and autofluorescence imaging modes, but was better than for white light image endoscopy (χ2 = 12.676, p = 0.002). The diagnostic specificity was significantly better in narrow band imaging mode than in both autofluorescence imaging and white light imaging mode (χ2 = 8.333, p = 0.016).

Conclusion:

Narrow band imaging endoscopy is the best option for the diagnosis and differential diagnosis of laryngopharyngeal tumours.