Laser-induced fluorescence: Progress and prospective for in vivo cancer diagnosis

Adaptive optics-based wavefront-enhanced laser-induced fluorescence (WELIF) for improved analytical performance

The current study proposes a novel optical approach based on an adaptive optics (AO) system to enhance the fluorescence intensity in the laser-induced fluorescence (LIF) technique. The proposed method, wavefront-enhanced LIF (WELIF), relies mainly on compensating for the aberrations arising from the excitation-laser wavefront. The AO system consists of an active correction element (deformable mirror (DM)) integrated with a Shack-Hartmann wavefront sensor (SHWFS). The overall system operates in a closed-loop configuration to compensate for the laser beam aberrations in real time. The performance of the interaction of the aberration-free excitation laser beam with solid samples, e.g., bone, leaf, polymer sheet, and with liquid samples, e.g., extra virgin olive oil (EVOO), showed a pronounced improvement in the fluorescence peak intensity. As an analytical application example, detailed WELIF measurements have been performed on five EVOO brands to demonstrate the validity of the new approach. Furthermore, the effectiveness of the proposed system was evaluated by measuring the enhancement factor, i.e., the ratio between the fluorescence peak intensity after aberration compensation (AC) relative to the initial peak intensity before aberration compensation (BC). The results reveal that the fluorescence peak intensities have been enhanced with ranges from 20% to 98% after compensation (AC). Besides, the results were statistically assessed based on the receiver operator characteristic (ROC) curve (84% sensitivity AC and 82% BC) and partial least squares regression, PLSR, with a 0.94 coefficient of determination AC compared to 0.90 BC.

Discrimination of normal and cancerous human skin tissues based on laser-induced spectral shift fluorescence microscopy

A homemade spectral shift fluorescence microscope (SSFM) is coupled with a spectrometer to record the spectral images of specimens based on the emission wavelength. Here a reliable diagnosis of neoplasia is achieved according to the spectral fluorescence properties of ex-vivo skin tissues after rhodamine6G (Rd6G) staining. It is shown that certain spectral shifts occur for nonmelanoma/melanoma lesions against normal/benign nevus, leading to spectral micrographs. In fact, there is a strong correlation between the emission wavelength and the sort of skin lesions, mainly due to the Rd6G interaction with the mitochondria of cancerous cells. The normal tissues generally enjoy a significant red shift regarding the laser line (37 nm). Conversely, plenty of fluorophores are conjugated to unhealthy cells giving rise to a relative blue shift i.e., typically SCC (6 nm), BCC (14 nm), and melanoma (19 nm) against healthy tissues. In other words, the redshift takes place with respect to the excitation wavelength i.e., melanoma (18 nm), BCC (23 nm), and SCC (31 nm) with respect to the laser line. Consequently, three data sets are available in the form of micrographs, addressing pixel-by-pixel signal intensity, emission wavelength, and fluorophore concentration of specimens for prompt diagnosis.

Hybrid laser activated phycocyanin/capecitabine treatment of cancerous MCF7 cells

Laser-induced fluorescence is recently used as an efficient technique in cancer diagnosis and non-invasive treatment. Here, the synergic therapeutical efficacies of the Capecitabine (CAP) chemodrug, photosensitive Phycocyanin (PC) and graphene oxide (GO) under laser irradiation were investigated. The therapeutical efficacies of diverse concentrations of CAP (0.001-10 mg/ml) and PC (0.5-10 mg/ml) alone and with laser irradiation on human breast adenocarcinoma (MCF-7) cells were examined. The interactional effects of 100 mW SHG Nd:YAG laser at 532nm and GaAs laser at 808 nm ranging power of 150 mW- 2.2W were considered. The contribution of graphene oxide (GO) in biocompatible concentrations of 2.5-20 ng/ml and thermal characteristics of laser exposure at 808 nm on GO + fluorophores have been studied. The effects of the bare and laser-excited CAP + PC on cell mortality have been obtained. Despite the laser irradiation could not hold up the cell proliferation in the absence of drug interaction considerably; however, the viability of the treated cells (by a combination of fluorophores) under laser exposure at 808 nm was significantly reduced. The laser at 532 nm excited the fluorescent PC in (CAP + PC) to trigger the photodynamic processes via oxygen generation. Through the in-vitro experiments of laser-induced fluorescence (LIF) spectroscopy of PC + CAP, the PC/CAP concentrations of the maximum fluorescence signal and spectral shifts have been characterized. The synergic effects of the laser exposures and (CAP + PC) treatment at different concentrations were confirmed. It has been shown here that the laser activation of (CAP + PC) can induce the mortality of the malignant cells by reducing the chemotherapeutic dose of CAP to avoid its non-desirable side effects and by approaching the minimally invasive treatment. Elevation of the laser intensity/exposure time could contribute to the therapeutic efficacy. Survival of the treated cells with a combination of GO and fluorophores could be reduced under laser exposure at 808 nm compared to the same combination therapy in the absence of GO. This survey could benefit the forthcoming clinical protocols based on laser spectroscopy for in-situ imaging/diagnosis/treatment of adenocarcinoma utilizing PC + CAP + GO.

Spectroscopic Characteristics of Xeloda Chemodrug

Introduction: Spectroscopic properties of Xeloda chemodrug have been studied over varying concentrations ranging between 0.001 and 10 mg/mL, using laser-induced fluorescence (LIF) spectroscopy. The alternative photoluminescence (PL) and near infrared (NIR) measurements are carried out to authenticate the obtained results by the LIF method. Methods: The XeCl laser as the excitation coherent source with 160 mJ/pulse at 308 nm is employed for LIF measurements of the fluorophore of interest in the modular spectroscopic set-up. Results: Xeloda as a significant chemodrug acts as a notable fluorophore. LIF, PL and NIR spectroscopy techniques are employed to investigate the spectral properties of the chemodrug in terms of concentration. The maximum LIF peak intensity of Xeloda is achieved at λmax=410.5 nm and the characteristic concentration of CP1=0.05 mg/mL. PL signals are in good agreement with the data given by the LIF measurements. The characteristic NIR spectra of Xeloda as solid evidence of chemical bonding formation attest to fluorescence quenching at the fluorophore concentration of ~ 0.2 mg/ mL. Besides, the spectral shift of fluorescence signals which is obtained in terms of fluorophore concentration- demonstrating as a diagnostic marker for the purpose of optimized chemotherapy. Conclusion: Xeloda exhibits outstanding fluorescence properties over the allowable concentration in human serum (Cmax). These characteristics could benefit potential advantage of simultaneous laser-based imaging of cell-chemodrug interaction over in-vivo studies.

In vivo diagnosis of skin cancer with a portable Raman spectroscopic device

In this study, we performed in vivo diagnosis of skin cancer based on implementation of a portable low-cost spectroscopy setup combining analysis of Raman and autofluorescence spectra in the near-infrared region (800-915 nm). We studied 617 cases of skin neoplasms (615 patients, 70 melanomas, 122 basal cell carcinomas, 12 squamous cell carcinomas and 413 benign tumors) in vivo with a portable setup. The studies considered the patients examined by GPs in local clinics and directed to a specialized Oncology Dispensary with suspected skin cancer. Each sample was histologically examined after excisional biopsy. The spectra were classified with a projection on latent structures and discriminant analysis. To check the classification models stability, a 10-fold cross-validation was performed. We obtained ROC AUCs of 0.75 (0.71-0.79; 95% CI), 0.69 (0.63-0.76; 95% CI) and 0.81 (0.74-0.87; 95% CI) for classification of a) malignant and benign tumors, b) melanomas and pigmented tumors and c) melanomas and seborrhoeic keratosis, respectively. The positive and negative predictive values ranged from 20% to 52% and from 73% to 99%, respectively. The biopsy ratio varied from 0.92:1 to 4.08:1 (at sensitivity levels from 90% to 99%). The accuracy of automatic analysis with the proposed system is higher than the accuracy of GPs and trainees, and is comparable or less to the accuracy of trained dermatologists. The proposed approach may be combined with other optical techniques of skin lesion analysis, such as dermoscopy- and spectroscopy-based computer-assisted diagnosis systems to increase accuracy of neoplasms classification.

Porphyrinoids in photodynamic diagnosis and therapy of oral diseases

Photodynamic methods have found application not only in the treatment process as photodynamic therapy but also for the early detection of neoplastic lesions and tumors as photodynamic diagnosis. Early detection of the disease allows not only to avoid the patient’s lifetime risk but also significantly reduce the costs of anticancer therapy, which are increasing every year. There is a constant search for new and more effective photosensitizers which will provide safety in therapy while maintaining efficiency. This paper summarizes recent reports focused on the photodynamic diagnosis of oral cancers. Moreover, it shows methods of the photodynamic treatment of oral verrucous hyperplasia, erythroleukoplakia, and oral leukoplakia. The treatment of choice for these diseases is a surgical excision, which always leads to scar formation. Photodynamic therapy provides a new scar-less tool for the treatment.

Combined Raman and autofluorescence ex vivo diagnostics of skin cancer in near-infrared and visible regions

The differentiation of skin melanomas and basal cell carcinomas (BCCs) was demonstrated based on combined analysis of Raman and autofluorescence spectra stimulated by visible and NIR lasers. It was ex vivo tested on 39 melanomas and 40 BCCs. Six spectroscopic criteria utilizing information about alteration of melanin, porphyrins, flavins, lipids, and collagen content in tumor with a comparison to healthy skin were proposed. The measured correlation between the proposed criteria makes it possible to define weakly correlated criteria groups for discriminant analysis and principal components analysis application. It was shown that the accuracy of cancerous tissues classification reaches 97.3% for a combined 6-criteria multimodal algorithm, while the accuracy determined separately for each modality does not exceed 79%. The combined 6-D method is a rapid and reliable tool for malignant skin detection and classification.

Autofluorescence Signatures of Seven Pathogens: Preliminary in Vitro Investigations of a Potential Diagnostic for Acanthamoeba Keratitis

PURPOSE

Acanthamoeba keratitis can cause devastating damage to the human cornea and is often difficult to diagnose by routine clinical methods. In this preliminary study, we investigated whether Acanthamoeba may be distinguished from other common corneal pathogens through its autofluorescence response. Although only a small number of pathogens were studied, the identification of a unique Acanthamoeba signature would indicate that autofluorescence spectroscopy as a diagnostic method merits further investigation.

METHODS

Samples of 7 common pathogens (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Elizabethkingia miricola, Achromobacter ruhlandii, Candida albicans, and Acanthamoeba castellanii) in solution were excited with ultraviolet light at a number of successive, narrow wavebands between 260 and 400 nm, and their fluorescence response recorded. Principal Component Analysis was used to allow better visualization of the differences in response to UV light for different species.

RESULTS

Acanthamoeba was found to possess a characteristic autofluorescence response and was easily distinguished from E. coli, S. aureus, P. aeruginosa, E. miricola, A. ruhlandii, and C. albicans over a wide range of excitation wavelengths. We also found a clear discrimination between E. coli, C. albicans, and P. aeruginosa at an excitation wavelength of 274 nm, whereas E. miricola, S. aureus, and A. ruhlandii could be separated using an excitation wavelength of 308 nm.

CONCLUSIONS

Our results, although preliminary, indicate that autofluorescence spectroscopy shows promise as a diagnostic technique for keratitis. We intend to expand the set of pathogens studied before assessing the feasibility of the technique in vivo by introducing cultures onto pig corneas.