July 2019
Volume 60, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2019
A radioactive labelling technique for evaluating the uptake and release of myristamidopropyl dimethylamine (MAP-D) from contact lenses
Author Affiliations & Notes
  • Alan Yee
    Centre for Ocular Research and Education (CORE), University of Waterloo, Waterloo, Ontario, Canada
  • Vivian WY Chan
    Centre for Ocular Research and Education (CORE), University of Waterloo, Waterloo, Ontario, Canada
  • Miriam L Heynen
    Centre for Ocular Research and Education (CORE), University of Waterloo, Waterloo, Ontario, Canada
  • Lyndon William Jones
    Centre for Ocular Research and Education (CORE), University of Waterloo, Waterloo, Ontario, Canada
  • Footnotes
    Commercial Relationships   Alan Yee, None; Vivian Chan, None; Miriam Heynen, None; Lyndon Jones, Alcon (F), Alcon (S), Alcon (C), Allergan (F), CooperVision (F), CooperVision (S), CooperVision (C), GL Chemtech (F), J&J Vision (F), J&J Vision (S), J&J Vision (C), Menicon (F), Nature's Way (F), Novartis (F), Novartis (C), Ophtecs (C), Santen (S), Shire (F), Shire (S), SightGlass (F)
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 6370. doi:https://doi.org/
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      Alan Yee, Vivian WY Chan, Miriam L Heynen, Lyndon William Jones; A radioactive labelling technique for evaluating the uptake and release of myristamidopropyl dimethylamine (MAP-D) from contact lenses. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6370. doi: https://doi.org/.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : The uptake and subsequent release of biocides from contact lens (CL) materials is of relevance as it has been linked with outbreaks of microbial keratitis and potential cytotoxic responses. Previous uptake and release studies of myristamidopropyl dimethylamine (MAP-D; ALDOX®) have used light-scattering techniques, which are time consuming and have relatively low sensitivity. The purpose of this study was to develop a radioactive labelling technique in order to improve the accuracy and sensitivity of biocide uptake and release to CL materials.

Methods : Four soft CL materials (lotrafilcon A, balafilcon A, senofilcon A, etafilcon A) were tested (N=4). Radioactive (14C) MAP-D was purchased from Moravek Inc. (California, USA). The lenses were incubated in PBS (ISO 18369-3) solution containing radioactive MAP-D (5µg/mL) for 8 hours. After the incubation period of 8 hours, the lenses were placed into the release condition. The release of MAP-D was assessed over 24 hours in 2 mL of PBS. Aliquots were removed at 0.25, 0.5, 1, 2, 4, 8, and 24 hour time points and added to scintillation fluor (PerkinElmer, USA). The samples were counted for their radioactive signal (CPM) using the LS6500 Beckman Coulter liquid scintillation beta counter (Beckman Coulter, ON, CA). The CPM was converted to µg of MAP-D based on a standard curve.

Results : After the incubation period of 8 hours, the uptake of MAP-D by etafilcon A (2.78±0.19µg) was significantly different than lotrafilcon A (4.69±0.1µg, p<0.01), balafilcon A (4.55±0.31µg, p<0.01), and senofilcon A (4.35±0.13µg, p<0.01). The total amount of MAP-D released by etafilcon A (1.41±0.09µg) was significantly greater than lotrafilcon A (0.27±0.02µg, p<0.01), balafilcon A (0.23±0.04µg, p<0.01), and senofilcon A (0.21±0.01µg, p<0.01). The results demonstrate that the uptake of MAP-D was higher for all silicone hydrogel (SH) lenses and lower for the conventional hydrogel lens. The release profile of etafilcon A was greater than the SH lenses, with a burst release of 0.33µg at 0.25 hr.

Conclusions : Radioactive labelling of MAP-D offers a highly sensitive, accurate way of assessing the uptake and release profiles of biocides to CL materials. Future studies using this methodology will investigate the profiles for other biocides, such as polyhexamethylene biguanide (PHMB), a common biocide used in CL solutions.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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