title: Real-time optical measurement of biologically relevant thermal damage in tissue-mimicking hydrogels containing bovine serum albumin.
abstract: OBJECTIVE
  In controlled laboratory studies of hyperthermia and thermal ablation, translucent hydrogels containing bovine serum albumin (BSA) are often employed as tissue-mimicking materials due to the change in their opacity that takes place as they accumulate heat damage. In this work we demonstrate the biological relevance of this optical metric of thermal damage, as well as establish the physical mechanisms that link it with quantifiable damage to the proteins embedded in the gel.
  
  
  METHODS
  We applied Fourier transform infrared (FTIR) spectroscopy, turbidity analysis using ultraviolet-visible (UV/VIS) spectroscopy, and size exclusion chromatography (SEC) to samples of heat-treated, aqueous bovine serum albumin (BSA). We also measured the rates of survival in heated suspensions of breast cancer cells using a colorimetric assay.
  
  
  RESULTS
  Using FTIR spectroscopy and SEC, we show that the intermolecular beta-sheet content of the protein ensemble rises in heat treatments above 60 degrees C, which causes aggregate formation. Furthermore, by applying UV/VIS spectroscopy we demonstrate that the opacity of the hydrogel increases past 60 degrees C due to the formation of insoluble protein aggregates that scatter incident light. Finally, we illustrate that the viability of human breast cancer cells follows a similar trend to measurements of BSA polyacrylamide hydrogel opacity at various temperatures from 37 degrees C to 90 degrees C.
  
  
  CONCLUSIONS
  Our work establishes a causal link between the degree of BSA denaturation in hydrogel and the opacity of the medium. Furthermore, our results demonstrate that BSA hydrogels provide a simple physical model for quantifying biologically relevant heat damage in real time during controlled laboratory studies of hyperthermia and thermal ablation.
authors.affiliation: Institute of Biomedical Engineering, University of Oxford, Oxford, UK. sacha.nandlall@eng.ox.ac.uk
authors.forename: Sacha D
authors.initials: SD
authors.lastname: Nandlall
authors.forename: Heiko A
authors.initials: HA
authors.lastname: Schiffter
authors.forename: Sebastian
authors.initials: S
authors.lastname: Vonhoff
authors.forename: Miriam
authors.initials: M
authors.lastname: Bazán-Peregrino
authors.forename: Manish
authors.initials: M
authors.lastname: Arora
authors.forename: Constantin-C
authors.initials: CC
authors.lastname: Coussios
mesh_terms: D000180:Acrylic Resins; D000818:Animals; D001943:Breast Neoplasms; D002417:Cattle; D045744:Cell Line, Tumor; D002470:Cell Survival; D002850:Chromatography, Gel; D005260:Female; D006358:Hot Temperature; D006801:Humans; D020100:Hydrogels / Q000737:chemistry*; D009391:Nephelometry and Turbidimetry; D011489:Protein Denaturation; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000180:Acrylic Resins; D020100:Hydrogels; C016680:polyacrylamide gels; D012710:Serum Albumin, Bovine