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Sarah Ann LeBlanc, Mohit S Verma, Lyndon William Jones, Frank Gu; Detecting bacteria colorimetrically on contact lens cases using immobilized gold nanoparticles. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2268.
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© ARVO (1962-2015); The Authors (2016-present)
Non-compliance in contact lens care practices leads to the growth of bacteria and biofilms in contact lens cases, increasing the wearer’s risk of contracting both microbial and infiltrative keratitis. Improving compliance requires a simple method for warning the user of bacterial contamination. We developed a colorimetric biosensor using gold nanoparticles that can be applied to contact lens case surfaces for the detection of bacteria.
Gold nanoparticles were synthesized using a seed-mediated surfactant-assisted growth method. The sensor surface was created by immobilizing a single layer of gold nanoparticles onto glass coverslips using layer-by-layer electrostatic interactions. To simulate the use of a contact lens case, the sensor surface was submerged in a saline solution of Staphylococcus aureus at 108 CFU/mL overnight followed by rinsing and drying. The resulting color change was characterized using ultraviolet-visible spectroscopy and hue-saturation-value (HSV) analysis of digital photographs. The interactions of the bacteria with the nanoparticles were explored using scanning electron microscopy (SEM).
The sensor surface produced a visible color change, from blue to purple, after incubation with Staphylococcus aureus. In addition to being detectable by the naked eye, the color change was quantified by a significant change in hue using the HSV color scale. Furthermore, a significant decrease in the gold nanoparticle 650/525nm absorbance peak ratio confirmed the visual observation. SEM shows that the local interactions of the immobilized gold nanoparticles with bacteria that deposited on the surface are responsible for the change in the absorbance peak ratio. Using the same procedure, the gold nanoparticles were successfully immobilized onto polypropylene, which is commonly used in contact lens cases.
Immobilized gold nanoparticles can be used as a surface-based colorimetric biosensor for visual detection of bacterial contamination. This biosensor is a promising platform for incorporation within contact lens cases. It can provide a cheap, simple, consumer-level technology allowing users to know when a contact lens case becomes contaminated with bacteria and should be replaced. The technology will thus lead to increased compliance and reduction of contact-lens induced microbial and infiltrative keratitis.
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