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Collagen is an endogenous fluorophore that accounts for about 70% of all proteins of human skin, so it can be an optical marker for structural abnormalities in tissues registered by laser fluorescent diagnostics in vivo. Using the examples of such abnormalities as scars, scleroderma and basal cell carcinoma, this study shows the differences between coefficients of fluorescent contrast k_f(λ) of abnormalities from the ones for healthy tissues at fluorescent excitation wavelength 360–380 nm. It is shown that scars and dysplasia are characterized by reduced values of k_f(λ) for collagen. Due to high turbidity and phase heterogeneousness as well as variation of parameters of blood microcirculation and concentrations of other related chromophores, there is no mathematical model that precisely calculates the concentration of collagen in tissues only with the use of the value of fluorescent signal intensity. So, probably, the best marker of the pathological process is a comprehensive representation of k_f(λ) for all endogenous fluorophores, i.e., for all used visible wavelengths. In this case identification of abnormal tissues is quite possible by detecting some deviations of coefficients k_f(λ) for the optically identical and symmetrical regions of the human body.

Changes of the blood vessels and collagen are associated with the development of abnormal cervical cells. Recently, optical coherence tomography and Mueller polarization images were used to provide information regarding the presence of collagen fibers in the cervical tissue. However, most of these methods need a lot of time for image recording and are expensive. In addition, the general survey on the absorption and distribution characteristics of collagen and blood in the cervical is still lacking. In this study, we developed a colposcopy combining cross-polarized image and image processing algorithm with an efficient analytical model to map the distribution of blood and collagen in the uterine. For this system’s proof of concept, we captured and processed the case of cervical ectopy and Nabothian cyst. The results show that the distribution of blood and collagen maps matched with anatomical and physiological when compared with Lugol’s iodine images. This technology has some advantages, such as low cost, real time, and can replace the use of acetic acid or Lugol’s iodine in the future.

Collagen is the major component of the extracellular matrix in skin, tendon, cartilage, cornea, bone, etc., and as a main structural protein is the key determinant of mechanical and functional properties of tissues and organs. Proper balance between synthesis and degradation of collagen fibers is critical for maintaining normal physiologic function; therefore, the modification of collagen fibers in a controlled manner is of high importance for biomedicine. In this work, using second harmonic generation (SHG) and two-photon excited auto-fluorescence (TPEF) microscopy, we revealed that hypericin, a natural pigment extracted from plant, induced structural modification of collagen based tissues. Dynamics of the process was monitored by time-lapse multiphoton imaging. It was demonstrated that hypericin–mediated process was considerably irreversible and has a potential to be used for destroying of abnormal tissues and treatment of some diseases.

Collagen is the most abundant natural protein found in living systems. While there is a whole family of different collagen types, each differing in sequence, the properties that make this protein so attractive as the building blocks for medical devices, are reflected largely by the unique fibrillar structure of the molecule, as well as defined functional regions that interact with the surrounding cells and other matrix components. As a commercial medical product, collagen can be part of the natural tissue used in the device, or it can be fabricated as a reconstituted product from animal or recombinant sources. Both types of uses have distinct properties that convey advantages and disadvantages to the end product. This review examines the chemistry and biology of collagen and describes some well-documented examples of collagen-based medical devices produced in one or other of these formats.