OPTICALLY CLEAR BIOCOMPATIBLE AND DURABLE HYDROPHILIC COATING PROCESS FOR CONTACT LENSES

Abstract

The present invention discloses methods for producing an optically clear, biocompatible and durable hydrophilic coating for contact lenses comprising the steps of first applying a polymer coating on the contact lenses by plasma polymerization of monomers containing ethylene glycol groups, followed by incubating the coated contact lenses at an elevated temperature to remove the volatile residual monomers trapped inside the coating. Advantageously, such methods produce an optically clear, biocompatible and durable hydrophilic surface for contact lenses in a dry, solvent-free process.

Claims

1. A method for producing a durable hydrophilic and optically clear coating for contact lens comprising the sequential steps of (i) applying a polymer coating on said contact lens using plasma polymerization of monomer compounds, wherein at least one monomer compound contains ethylene glycol group; (ii) incubating said contact lens at an elevated temperature to remove excess volatile monomers trapped in the polymer layer.

2. A method of claim 1, wherein said step (ii) is performed in a vacuum oven set at a temperature of higher than 30 C.

3. A method of claim 1, wherein said step (ii) is performed in a convection oven set at a temperature of higher than 30 C.

4. A method of claim 1, wherein said contact lens contains electronic components.

5. A method of claim 1, wherein said contact lens contains biosensor components.

6. A method of claim 1, wherein said contact lens contains biosensor enzymes.

7. A method of claim 1, wherein said contact lens contains glucose sensor components.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0013] FIG. 1 is a drawing representing the subject invention coating process for contact lenses. In the first step, the lens is coated by plasma polymerization of compounds containing ethylene glycol groups. In the second step, the lens is incubated at an elevated temperature to remove the residual monomers trapped in the coating.

[0014] FIG. 2 is a chart comparing the clarity of the contact lenses soaked in water for up to 24 hours. The contacted lenses are either coated with plasma polymerized PEG without post coating oven treatment, or coated with plasma polymerized PEG with post coating oven treatment to remove residual monomers.

[0015] FIG. 3 is a chart comparing the hydrophilicity of the contact lens surface. The hydrophilicity of the surface is characterized by water contact angle measurement using a 5 microliter water droplet. The contacted lenses are either uncoated, coated with plasma polymerized PEG without post coating oven treatment, or coated with plasma polymerized PEG with post coating oven treatment to remove residual monomers.

DETAILED DESCRIPTION OF THE INVENTION

[0016] With reference to FIG. 1, a contact lens is depicted of comprising a top surface and bottom surface. Both surfaces are coated by plasma polymerization of monomer compounds containing ethylene glycol groups to form a covalently immobilized layer of PEG polymer containing residual monomers. In the second step, the contact lens is incubated at an elevated temperature to remove residual monomers trapped in the polymer layer.

[0017] Any known technique can be used to generate plasma. The plasma may be generated using AC or DC power, radio-frequency (RF) power or micro-wave frequency power. Preferably, the plasma system uses a single radio-frequency (RF) power supply; typically at 13.56 MHz. The plasma system can either be capacitively coupled plasma, or inductively coupled plasma.

[0018] Many compounds containing ethylene glycol groups can be used for plasma polymerization. Preferably, the compounds are non-reactive (except when activated by plasma ionization) and non-toxic. Examples of such compounds include Tri(ethylene glycol) monoethyl ether (CH.sub.3CH.sub.2(OCH.sub.2CH.sub.2).sub.3OH) or Tri(ethylene glycol) monomethyl ether (CH.sub.3(OCH.sub.2CH.sub.2).sub.3OH).

[0019] Any known technique can be used to provide an elevated temperature for the evaporation and removal of residual monomers trapped in the polymer layer. Preferably, a vacuum oven or a convection oven is used for this step.

EXAMPLES

Example A

[0020] Contact lenses made of silicone elastomer are placed in a plasma polymerization reactor and subsequently coated with a 13.56 Hz radiofrequency plasma glow discharge in the presence of the vapor of Tri(ethylene glycol) monoethyl ether (CH.sub.3CH.sub.2(OCH.sub.2CH.sub.2).sub.3OH). After plasma polymerization coating, the contact lenses are incubated in a vacuum oven set at 70-80 C. for more than 8 hours.

Example B

[0021] Contact lenses made of silicone elastomer are placed in a plasma polymerization reactor and subsequently coated with a 13.56 Hz radiofrequency plasma glow discharge in the presence of the vapor of Tri(ethylene glycol) monoethyl ether (CH.sub.3CH.sub.2(OCH.sub.2CH.sub.2).sub.3OH). After plasma polymerization coating, the contact lenses are incubated in a convection oven set at 70-80 C. for more than 8 hours.

[0022] Example C

[0023] Contact lenses made of silicone elastomer are placed in a plasma polymerization reactor and subsequently coated with a 13.56 Hz radiofrequency plasma glow discharge in the presence of the vapor of Tri(ethylene glycol) monomethyl ether (CH.sub.3(OCH.sub.2CH.sub.2).sub.3OH). After plasma polymerization coating, the contact lenses are incubated in a vacuum oven set at 80 C. for more than 8 hours.

Example D

[0024] Contact lenses made of silicone elastomer are placed in a plasma polymerization reactor and subsequently coated with a 13.56 Hz radiofrequency plasma glow discharge in the presence of the vapor of Tri(ethylene glycol) monomethyl ether (CH.sub.3(OCH.sub.2CH.sub.2).sub.3OH). After plasma polymerization coating, the contact lenses are incubated in a convection oven set at 70-80 C. for more than 8 hours.

Example E

[0025] Silicone contact lenses coated with plasma polymerized PEG polymer with or without post-coating treatment to remove residual monomers are compared for optical clarity when soaked in water. Each lens is placed in a quartz cuvette filled with water, and the light transmittance through the lens at 550 nm is monitored using a UV-Vis spectrometer for up to 24 hours. As can be seen in FIG. 2, the light transmittance of the coated lens without post-coating treatment decreased significantly to approximately 60% after soaking in water for a few hours. In contrast, the light transmittance of the coated lens with post-coating treatment remains at >90% throughout 24 hours of soaking.

Example F

[0026] Silicone contact lenses coated with plasma polymerized PEG polymer with or without post-coating treatment to remove residual monomers are compared to uncoated lenses for hydrophilicity. The hydrophilicity of the surface is characterized by water contact angle measurement using a 5 microliter water droplet, and the contact angle measurement is performed after soaking the lenses in water for 1 hour. As can be seen in FIG. 3, the plasma polymerized PEG coating significantly improves the hydrophilicity (decreases the contact angle) compared to the uncoated lenses. Furthermore, the post-coating treatment does not affect the hydrophilicity of the coated contact lenses.

[0027] As will be appreciated by those skilled in the art, the subject invention can be used to produce a durable hydrophilic coating. By way of non-limiting example, the subject invention can be used to prepare surfaces of contact lenses made of silicone material, including contact lenses that contain electronic components and/or biosensing components such as glucose sensing enzymes.