{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,27]],"date-time":"2026-02-27T01:21:18Z","timestamp":1772155278827,"version":"3.50.1"},"reference-count":27,"publisher":"Wiley","issue":"4","license":[{"start":{"date-parts":[[2017,3,14]],"date-time":"2017-03-14T00:00:00Z","timestamp":1489449600000},"content-version":"am","delay-in-days":365,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#am"},{"start":{"date-parts":[[2016,3,14]],"date-time":"2016-03-14T00:00:00Z","timestamp":1457913600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"DOI":"10.13039\/501100003141","name":"Consejo Nacional de Ciencia y Tecnolog\u00eda","doi-asserted-by":"publisher","award":["237664"],"award-info":[{"award-number":["237664"]}],"id":[{"id":"10.13039\/501100003141","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100002602","name":"American Society for Laser Medicine and Surgery","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100002602","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["EEC\u20101358296"],"award-info":[{"award-number":["EEC\u20101358296"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Lasers Surg Med"],"published-print":{"date-parts":[[2016,4]]},"abstract":"<jats:sec><jats:title>Background and Objective<\/jats:title><jats:p>Collagen gels containing cells are commonly used in tissue engineering, wound healing, and cancer research to investigate the interplay between cells and the extracellular matrix (ECM), as changes in the density and stiffness of the microenvironment are known to play a role in many diseases or pathological conditions. In these gels, the stiffness is regularly determined using destructive methods, such as indentation and tensile tests. Certain molecules native to cells and the ECM display fluorescence upon irradiation with ultraviolet light. The objective of the present study was to investigate the feasibility of using the endogenous, or innate, fluorescence of collagen gels containing fibroblasts as an optical marker to evaluate changes in the mechanical properties of the ECM.<\/jats:p><\/jats:sec><jats:sec><jats:title>Materials and Methods<\/jats:title><jats:p>Human foreskin fibroblasts cells at concentrations of 50,000 and 100,000 cells\/ml were cultured in three\u2010dimensional gels of type I collagen for 16 days. Fibroblast cells remodeled the ECM, contracting and increasing the stiffness of the gel. During this remodeling process, changes in mechanical properties and fluorescence were measured with an indentation test and a spectrofluorometer, respectively. Force and displacement measurements from the indentation test were used to calculate the elastic modulus of the gel. Maps of fluorescence intensity, at excitation\/emission of 240\u2013520\/290\u2013530\u2009nm, were used to identify the wavelengths of interest.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Fluorescence excitation\/emission maps exhibited two distinct excitation\/emission bands whose intensities increased as the fibroblasts remodeled and increased the stiffness of the ECM: The 290\/340\u2009nm band ascribed to tryptophan and the 330\/390\u2009nm band ascribed to cross\u2010links of collagen (pepsin\u2010digestible cross\u2010links). A Spearman correlation analysis, between the elastic modulus of the gel containing fibroblasts and the fluorescence of cross\u2010links of collagen, resulted in <jats:italic>R<\/jats:italic>\u2009=\u20090.95 (<jats:italic>P<\/jats:italic>\u2009&lt;\u20090.05) and <jats:italic>R<\/jats:italic>\u2009=\u20090.77 (<jats:italic>P<\/jats:italic>\u2009=\u20090.12) for 50,000 and 100,000\u2009cells\/ml, respectively.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>The endogenous fluorescence intensity ascribed to pepsin\u2010digestible cross\u2010links of collagen may serve as an optical marker to evaluate changes in the mechanical properties of the ECM; this is relevant to collagenous tissues for which pathological states are related to mechanical alterations, such as keratoconus in cornea and osteoarthritis in articular cartilage. Lasers Surg. Med. 48:377\u2013384, 2016. \u00a9 2016 Wiley Periodicals, Inc.<\/jats:p><\/jats:sec>","DOI":"10.1002\/lsm.22501","type":"journal-article","created":{"date-parts":[[2016,3,19]],"date-time":"2016-03-19T00:50:00Z","timestamp":1458348600000},"page":"377-384","source":"Crossref","is-referenced-by-count":8,"title":["Evaluation of cell and matrix mechanics using fluorescence excitation spectroscopy: Feasibility study in collagen gels containing fibroblasts"],"prefix":"10.1002","volume":"48","author":[{"given":"Juan Pablo","family":"Padilla\u2010Martinez","sequence":"first","affiliation":[{"name":"Wellman Center for Photomedicine Massachusetts General Hospital Boston Massachusetts"},{"name":"Department of Dermatology Harvard Medical School Boston Massachusetts"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ruisheng","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering Cornell University Ithaca New York"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Walfre","family":"Franco","sequence":"additional","affiliation":[{"name":"Wellman Center for Photomedicine Massachusetts General Hospital Boston Massachusetts"},{"name":"Department of Dermatology Harvard Medical School Boston Massachusetts"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2016,3,14]]},"reference":[{"key":"e_1_2_7_2_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.addr.2003.08.004"},{"key":"e_1_2_7_3_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1067-1927.2004.012208.x"},{"key":"e_1_2_7_4_1","doi-asserted-by":"publisher","DOI":"10.1242\/dmm.004077"},{"key":"e_1_2_7_5_1","doi-asserted-by":"publisher","DOI":"10.1038\/nmat4009"},{"key":"e_1_2_7_6_1","doi-asserted-by":"publisher","DOI":"10.1063\/1.3699176"},{"key":"e_1_2_7_7_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jbiomech.2004.03.004"},{"issue":"1","key":"e_1_2_7_8_1","first-page":"H52","article-title":"Neutral axis location in Bending and Youngs modulus of different layers of arterial\u2010Wall","volume":"265","author":"Yu Q","year":"1993","journal-title":"Am J Physiol"},{"key":"e_1_2_7_9_1","doi-asserted-by":"publisher","DOI":"10.1089\/ten.teb.2010.0520"},{"key":"e_1_2_7_10_1","doi-asserted-by":"publisher","DOI":"10.1098\/rsif.2011.0054"},{"key":"e_1_2_7_11_1","doi-asserted-by":"crossref","unstructured":"HajjarianZ NadkarniSK. 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