Monitoring the metabolic response to nanoencapsulated silibinin treatment in DMBA-induced oral carcinogenesis using endogenous fluorescence
Autofluorescence spectroscopy is a very sensitive tool for detecting early metabolic response after cancer treatment. The present work aims to investigate the chemopreventive effect of the prepared silibinin-loaded nanoparticles (SILNPs) relative to the efficacy of free silibinin (SIL) for monitoring the changes in the endogenous fluorophore emission and to quantify the metabolic changes in the redox state during 7,12-dimethylbenz[a]anthracene (DMBA) induced hamster buccal pouch (HBP) carcinogenesis using autofluorescence spectroscopy. Significant differences in the autofluorescence spectral signatures between the control and the experimental animals have been noticed under the excitation wavelength at 320 nm with emission ranging from 350–550 nm. The tumor tissues are characterized by a decrease in the emission of collagen, nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) compared to the control tissues. Further, the optical oxidation–reduction (redox) ratio is a measure of cellular metabolism and can be determined by the relative change in the fluorescence emission intensity of NADH and FAD. The optical redox ratio will provide sufficient information on metabolic changes associated with tumor transformation. The results revealed that a significant decrease in the optical redox ratio is observed in DMBA-induced tumor tissues, which indicates increased metabolic activity compared to the control tissues. Moreover, an oral administration of SIL and its nanoparticulates restored the status of endogenous fluorophore emission and led to a higher redox ratio in the buccal mucosa of DMBA-painted animals. On a comparative basis, treatment with nanoparticulate silibinin was found to be more effective than free silibinin for reducing the formation of squamous cell carcinoma and improving the status of endogenous fluorophore emission to a near normal range in DMBA-induced hamster buccal pouch carcinogenesis. Furthermore, the diagnostic algorithms based on principal component analysis followed by linear discriminant analysis (PC–LDA) achieved an overall diagnostic sensitivity of 96.46% and specificity of 93.64% for separating the control from the experimental groups. The results of this study further suggest that the fluorescence spectroscopic technique in conjunction with PC–LDA has a potential for rapid and sensitive detection of specific metabolic alteration and changes in the endogenous fluorophores in response to anti-cancer drug treatments.