Journal of Fluorescence

, Volume 24, Issue 6, pp 1639–1650 | Cite as

The Effect of Fluorescent Labels on Protein Sorption in Polymer Hydrogels

  • Allan Guan
  • Zhenyu Li
  • K. Scott Phillips


Hydrogels are an increasingly important class of medical device materials that enable diverse and unique function, but can also be subject to significant biofouling and contamination. Although it is challenging to accurately quantify protein biofouling in hydrogels, spectroscopic detection of fluorescently labeled proteins is one method with the potential to provide direct, sensitive quantitation in transparent materials. Therefore, it is important to understand how fluorophores can affect protein-material interactions in hydrogels. This work uses an independent method, native ultraviolet fluorescence (native UV) of proteins, in conjunction with labeled protein fluorescence and the bicinchoninic acid assay (BCA), to assess the effect of fluorescent labels on protein sorption in polymer hydrogels. Bovine serum albumin (BSA) and lysozyme (LY) were labeled with two common but structurally different fluorophores and used as model biofouling proteins in three contact lens hydrogel materials. Native UV was used to directly measure both labeled and unlabeled protein sorption, while orthogonal measurements were performed with extrinsic fluorescence and BCA assay to compare with the native UV results. Sorption of labeled proteins was found to be <2-fold higher than unlabeled proteins on most protein-material combinations, while differences of up to 10-fold were observed for labeled BSA in more hydrophobic hydrogels. Fluorescence recovery after photobleaching (FRAP) also showed that the fluorescent label chemistry can significantly affect surface adsorption of sorbed proteins on the internal surfaces of hydrogels. This study reveals the complex nature of fluorophore-protein-material interactions and shows the potential of native UV for investigating unlabeled protein biofouling in hydrogels.


Hydrogel Fluorophore Fluorescent label Sorption Biofouling Protein Labeling Interference Contact lens Medical device Adsorption Absorption Fluorescence Fluorescence recovery after photobleaching (FRAP) Photobleaching Intrinsic fluorescence UV fluorescence Residues Microplate Structure Lysozyme Ionic Hydrohobic BCA assay Calibration Response Transparent (Hydroxyethyl) methacrylate (HEMA) Silicone Bicinchoninic acid Polymer 



Dr. Kim Sapsford (FDA) and Center for Devices and Radiological Health.

The mention of commercial products, their sources, or their use in connection with material reported herein is not to be construed as either an actual or implied endorsement of such products by the Department of Health and Human Services.

Supplementary material

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Copyright information

© © Springer Science+Business Media New York (outside the USA) 2014

Authors and Affiliations

  1. 1.Department of Biomedical EngineeringThe George Washington UniversityWashingtonUSA
  2. 2.Office of Medical Products and Tobacco, Center for Devices and Radiological Health, Office of Science and Engineering Laboratories, Division of Chemistry and Materials ScienceUnited States Food and Drug AdministrationSilver SpringUSA

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