ABSTRACT
Objective:To evaluate the skin development and repair process of X-ray radiation damage in rat with non-invasive two-photon excitation fluorescence (TPEF) imaging technology in vivo. Methods:Totally 24 SD rats were randomly divided into four groups including X-ray irradiated group (25, 35 and 45 Gy) and non-irradiation control group. At different times after irradiation, the degree of skin injury was evaluated, and the pathological changes of nicotinamide adenine dinucleotide (phosphate) [NAD(P)H] and collagen fiber fluorescence signals in epidermal cells were detected in vivo by TPEF imaging technology. Results:At 10 d post-irradiation, the skin of irradiation groups showed erythema and desquamation. At 15-20 d post-irradiation, the skin of radiation groups developed progressive exudation, edema and ulcers with increasing radiation dose. On day 25, the skin began to repair in the 25 Gy group, however, the skin of other groups still had exudation and ulcers. On day 10, NAD(P)H fluorescence signal in epidermal cells of irradiation groups decreased and the fluorescence signal of collagen fibers in papillary layer and reticular layer of irradiation groups reduced, which were significantly lower than that of normal control group ( t=24.145, 28.303, 26.989, 6.654, 7.510, 7.997, P<0.05). On day 30, fluorescence signal of NAD(P)H and collagen fibers in epidermal cells and dermis began to repair, the cell from stratum granulosum, stratum spinosum, and stratum basale in the 25 Gy group showed fluorescence signal, the other groups did not show. The fluorescence signal of collagen fibers in the 25 Gy group were gradually increased in papillary layer and reticular layer, however, they were significantly lower than normal control group ( t=115.133, 17.431, P<0.05), the skin of 45 Gy group did not show fluorescence signal of collagen fibers. Conclusions:The damage and repair process of epidermal cells and dermal collagen fiber can be detected noninvasively by TPEF imaging technology after X-ray irradiation in vivo.
ABSTRACT
Two photon fluorescence microscopy and the numerous technical advances to it have served as valuable tools in biomedical research. The fluorophores (exogenous or endogenous) absorb light and emit lower energy photons than the absorption energy and the emission (fluorescence) signal is measured using a fluorescence decay graph. Additionally, high spatial resolution images can be acquired in two photon fluorescence lifetime imaging (2P-FLIM) with improved penetration depth which helps in detection of fluorescence signal in vivo. 2P-FLIM is a non-invasive imaging technique in order to visualize cellular metabolic, by tracking intrinsic fluorophores present in it, such as nicotinamide adenine dinucleotide, flavin adenine dinucleotide and tryptophan etc. 2P-FLIM of these molecules enable the visualization of metabolic alterations, non-invasively. This comprehensive review discusses the numerous applications of 2P-FLIM towards cancer, neuro-degenerative, infectious diseases, and wound healing.
Subject(s)
Absorption , Communicable Diseases , Flavin-Adenine Dinucleotide , Fluorescence , Microscopy, Fluorescence , NAD , Photons , Tryptophan , Wound HealingABSTRACT
Photodynamic therapy (PDT) has emerged as a more effective and promising treatment towards cancer therapy. PDT is a minimally invasive and spatially selective medical technique to destroy cancer cells without drug resistance, which has been increasingly applied in the clinical praxis alongside surgery, chemotherapy and radiotherapy. However, traditional PDTs use a high energy one-photon laser beam, which is far from the efficient optical window of mammalian tissue (650−950 nm). Moreover, it has great limitations in the depth of penetration, and induces the undesired light toxicity. The development of photosensitizers has always been a bottleneck to the effective application of PDT in clinical practice. From the first generation of hematoporphyrin derivatives to the third-generation photosensitizers with tumor targeting ability, they meet the urgent clinical needs to some extent, but they still can not satisfy the requirements of two-photon PDT. Therefore, the development of photosensitizers, which are capable of two-photon activated PDT, has become a promising approach. Among the various two-photon absorption photosensitizers, ruthenium (Ⅱ) polypyridyl complexes have been recognized as excellent candidates due to their attractive photophysical properties. This review is prepared to summarize the recent achievements in the application of ruthenium (Ⅱ) polypyridyl complexes as photosensitizers for two-photon PDT, as well as to provide guidance for the design of two-photon activated photosensitizers in future research.