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Journal of Nanoscience and Nanotechnology Vol. 15, 8016–8022, 2015 www.aspbs.com/jnn

Preparation and Characterization of Ophthalmic Lens Materials Containing Titanium Silicon Oxide and Silver Nanoparticles Jung-Won No1 , Dong-Hyun Kim1 , Min-Jae Lee2 , Duck-Hyun Kim2 , Tae-Hun Kim3 , and A-Young Sung2 ∗ 2

1 Department of Ophthalmic Optics, Sehan University, Jeonnam, 526-702, Korea Department of Optometry and Vision Science, Catholic University of Daegu, Gyeongbuk, 712-702, Korea 3 Department of Visual Optics, Baekseok University, Chungnam 330-704, Korea

Hydrogel ophthalmic lenses containing fluorine-substituted aniline group, titanium silicon oxide nanoparticles, and silver nanoparticles were copolymerized, and the physical and optical properties of the hydrogel lenses were measured. To produce the hydrophilic ophthalmic lenses, the additives were added to the mixture containing HEMA, NVP, MA, EGDMA, and AIBN. The cast mold method was used for the manufacture of the hydrogel ophthalmic lenses, and the produced lenses were completely soaked in a 0.9% NaCl normal saline solution for 24 hours for hydration. The physical properties of the produced macromolecule showed that the water content was 32.5–37.6%, the refractive index was 1.450–1.464, the UV-B transmittance was 0.5–35.2%, and the contact angle was between 56 and 69 . Also, the addition of aniline, titanium silicon oxide, and silver nanoparticles allowed the ophthalmic lenses to block UV. These results show that the produced macromolecule can be used as hydrophilic lenses for ophthalmologic purposes that can block UV.

Keywords: Titanium Silicon Oxide Nanoparticles, Silver Nanoparticles, Aniline Group, Spectral Transmittances.

1. INTRODUCTION Ophthalmic lenses are used to correct the vision by placing a lens in front of the eye, which offers comfort in activities as well as aesthetic features, making ophthalmic lenses more popular among the general population.1 Compared to the conventional spectacles, ophthalmic lenses offer various advantages, but due to their close proximity with the eyes, they need to have good biocompatibility or they can cause various ophthalmologic diseases. Currently, various studies are being carried out on high-functional ophthalmic lenses, aimed at reducing the risk of acquiring ophthalmologic diseases caused by hydrogel lenses.2–4 Also, many studies are focusing on nanomaterials such as gold, silver, and platinum nanoparticles, which offer antimicrobial properties to hydrogel ophthalmic lenses.5–7 Of the various organs of the human body, the eyes are the most easily exposed to infectious microorganisms, and contamination by hydrogel lenses can cause various ophthalmologic diseases and adverse events. While ∗

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E. coli, fungi, Pseudomonas aeruginosa, and staphylococci are the most common bacteria related to the eyes, such pathogens can also cause various types of ulcers as well as conjunctivitis.8–10 UV is also a major cause of eye diseases and can damage the cornea, retina, and lens.11 12 Although wearing sunglasses or UV-blocking spectacles can block UV, which can have hazardous effects on the eyes, wearing spectacles while already wearing ophthalmic lenses is inconvenient. Producing ophthalmic lenses with UV-blocking capabilities can address this problem. Various studies are currently being carried out on this topic, and attempts are being made to produce UV-blocking hydrogel lenses using nanomaterials.13–15 The characteristics of nanomaterials that absorb light from a specific spectrum allow them to be used as effective ingredients in UV-blocking hydrogel ophthalmic lenses. In this study, hydrogel ophthalmic lenses were copolymerized with silver nanoparticles, which are used in various areas due to their antimicrobial effects, and with titanium silicon oxide nanoparticles, to evaluate the optical properties of the produced lenses. The ophthalmic lenses were also 1533-4880/2015/15/8016/007

doi:10.1166/jnn.2015.11240

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Preparation and Characterization of Ophthalmic Lens Materials Containing Titanium Silicon Oxide

produced using aniline group, which is commonly used as a synthetic dye and offers a UV-blocking function, and the utility of the produced lenses for ophthalmologic purposes was evaluated.16

2. EXPERIMENTAL DETAILS 2.1. Reagents and Materials The HEMA (2-hydroxyethylmethacrylate) and AIBN (azobisisobutyronitrile) that were used in this experiment were products of JUNSEI, and the NVP (n-vinyl pyrrolidone) and EGDMA (ethylene glycol dimethacrylate) were products of ACROS ORGANICS. The MA (methacrylic acid) was a product of Crown Guaranteed Reagents, and the titanium silicon oxide nanoparticles, silver nanoparticles, 2,4-difluoroaniline, and 3,4-difluoroaniline that were used as functional additives were all products of Sigma-Aldrich. One of the samples that were used in the experiment contained HEMA, NVP, MA, and EGDMA as the basic combination, and was referred to as the reference sample. The samples consisting of 0.1% titanium silicon oxide nanoparticles and 0.6% silver nanoparticles added to the reference sample were referred to as the RTS samples. The samples where 4-difluoroaniline was added at each ratio to the RTS sample were referred to as the RTS-_2,4A1, RTS-_2,4A3, RTS-_2,4A5, RTS-_2,4A7, and RTS-_2,4A10 samples, respectively, while the samples where 3,4-difluoroaniline was added at each ratio were referred to as the RTS-_3,4A1, RTS-_3,4A3, RTS-_3,4A5, RTS-_3,4A7, and RTS-_3,4A10 samples. The mixture ratios of the different samples are shown in Table I. 2.2. Macromolecule Copolymerization The macromolecule that was used in this study was copolymerized using HEMA, the main ingredient of hydrophilic hydrogel ophthalmic lenses, and NVP and MA, which are also hydrophilic materials. AIBN was used as the initiator, and EGDMA as the cross-linking agent.

Also, the macromolecule was copolymerized using different ratios of additives. After preparing each sample, a stirrer was used at a 1,700 rpm motor speed for approximately 50 min to mix the samples. The copolymerization of the samples was carried out in a micro oven, and the final hydrogel lenses were produced using the cast mold method. The produced ophthalmic lenses were completely soaked in a 0.9% NaCl normal saline solution for 24 hours before the measurement of their physical and optical properties. 2.3. Physical and Optical Properties The refractive-index measurement of the ophthalmic lenses was carried out (based on ISO 18369-4:2006) using an ABBE Refractometer (NAR-1T, ATAGO, Japan). Each of the measurements was made three times to improve the accuracy. The gravimetric method was used (based on ISO 18369-4:2006) to measure and calculate the water contents. The sessile drop method was used to measure the contact angle and the wettability of the surface of each lens sample. The spectral transmittance was measured with a spectral transmittance meter (TOPCON TM-2, Japan), and the transmittances for UV-B, UV-A, and visual light were expressed in percentages. Also, FESEM (JSM-7500F + EDS, Oxford) was used for the surface analysis of the produced copolymer. An atomic force microscope (XE-100, Parks System) was used to analyze the nanoparticles in the copolymer.

3. RESULTS AND DISCUSSION 3.1. Polymerization and Production of the Macromolecule The analysis of the color of each functional hydrogel lens showed that the reference sample, to which no additive was added, was transparent and colorless. Also, the RTS samples, where titanium silicon oxide and silver nanoparticles were added, exhibited a light yellowish color while the RTS_3,4A and RTS_2,4A samples, where aniline group was added, exhibited a light brownish color.

Table I. Percent composition of samples. Unit: % Sample Reference RTS RTS-_2,4A1 RTS-_2,4A3 RTS-_2,4A5 RTS-_2,4A7 RTS-_2,4A10 RTS-_3,4A1 RTS-_3,4A3 RTS-_3,4A5 RTS-_3,4A7 RTS-_3A10

2,4 3,4 HEMA NVP MA EGDMA TiSiO Silver DFA DFA 93.90 88.81 88.03 86.51 85.03 83.61 81.57 88.03 86.51 85.03 83.61 81.57

4.69 4.44 4.40 4.33 4.25 4.18 4.08 4.40 4.33 4.25 4.18 4.08

0.94 0.89 0.88 0.87 0.85 0.84 0.82 0.88 0.87 0.85 0.84 0.82

0.47 0.44 0.44 0.43 0.43 0.42 0.41 0.44 0.43 0.43 0.42 0.41

– 0.09 0.09 0.09 0.09 0.08 0.08 0.09 0.09 0.09 0.08 0.08

– 5.33 5.28 5.19 5.10 5.02 4.89 5.28 5.19 5.10 5.02 4.89

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– – 0.88 2.60 4.25 5.85 8.16 – – – – –

– – – – – – – 0.88 2.60 4.25 5.85 8.16

Figure 1. The color of manufactured contact lens with additives. [(a) Ref. (b) RTS, (c) RTA_2,4A, (d) RTA_3,4A].

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Figure 2.

SEM image of ophthalmic lens sample (RTS).

Overall, the color of each lens sample darkened as the ratio of the aniline group increased, and the RTS_3,4A samples exhibited a darker color than the RTS_2,4A samples. The colors of the produced contact lenses are shown in Figure 1. Meanwhile, the analysis of the surfaces and nanoparticles using FESEM showed that particles with diameters of 20–70 nm were evenly distributed on the surface of the ophthalmic lenses. The SEM analysis of the lenses containing nanoparticles is shown in Figure 2. 3.2. Physical Properties With regard to the refractive indices of the copolymerized lens samples, that of the reference sample was 1.4330, which is within the range of general hydrogel ophthalmic

Figure 3.

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lenses (n = 14300–1.4350). The refractive index of the RTS sample, to which titanium silicon oxide and silver nanoparticles were added, was 1.4340. Although the samples with added nanoparticles showed a slightly higher refractive index, the difference was not significant, indicating that the nanoparticles did not have a significant impact on the refractive index. The average refractive indices of the RTS_2,4A samples, to which 2,4difluoroaniline was added, were 1.4350 for RTS_2,4A1, 1.4355 for RTS_2,4A3, 1.4360 for RTS_2,4A5, 1.4365 for RTS_2,4A7, and 1.4370 for RTS_2,4A10. The average refractive indices of the RTS_3,4A samples, to which 3,4difluoroaniline was added, were 1.4350 for RTS_3,4A1, 1.4360 for RTS_3,4A3, 1.4370 for RTS_3,4A5, 1.4380 for RTS_3,4A7, and 1.4390 for RTS_3,4A10. Overall, the refractive index tended to increase as the ratio of aniline group increased. The changes in the refractive indices of the different samples are shown in Figure 4. As for the water contents of the copolymerized ophthalmic lens samples, that for the reference sample was 38.06%, which is similar to the water content of generally used hydrogel ophthalmic lenses. The water content of the RTS sample, to which titanium silicon oxide and silver nanoparticles were added, was 38.33%. Although the samples with added nanoparticles showed slightly higher water contents, the difference was not significant, indicating that the nanoparticles did not have a significant impact on the water content. The average water contents of the RTS_2,4A samples, to which 2,4difluoroaniline was added, were 38.27% for RTS_2,4A1,

Surface analysis of hydrogel ophthalmic lens by AFM (RTS).


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Figure 4.


Effect of difluoroaniline on refractive index (a: RTS_2,4A, b: RTS_3,4A).

37.94% for RTS_2,4A3, 37.82% for RTS_2,4A5, 37 for RTS_ 2,4A7, and 37.55% for RTS_2,4A10. Overall, although the water content showed a decrease as the ratio of 2,4-difluoroaniline increased, the difference was not significant, indicating that the addition of 2,4-difluoroaniline

Figure 5.

does not result in hydrophobicity. The average water contents of the RTS_3,4A samples, to which 3,4difluoroaniline was added, were 38.04% for RTS_3,4A1, 37.85% for RTS_3,4A3, 37.37% for RTS_3,4A5, 37.21% for RTS_3,4A7, and 37.04% for RTS_3,4A10. Although

Effect of difluoroaniline on water content (a: RTS_2,4A, b: RTS_3,4A).


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Figure 6.

Contact angle of samples. [(a) Ref. (b) RTS_2,4A10, (c) RTS_3,4A10].

the water content showed a decrease as the ratio of 3,4-difluoroaniline increased, the difference was not significant, as in the case with 2,4-difluoroaniline. The changes in the water contents of the different samples are shown in Figure 5. For the contact angles of the contact lens samples, that of the reference sample was 62.52 while that of the RTS sample, to which titanium silicon oxide and silver nanoparticles were added, was 63.46. For the RTS sample, although the contact angle slightly increased, the change was minimal, which indicates that nanoparticles do not have a significant impact on the contact angles of contact lenses. The above measurements also showed that the titanium silicon oxide and silver nanoparticles did not affect the wettability of the produced hydrogel lenses. Meanwhile, the contact angles of the RTS_2,4A samples, where 2,4-difluoroaniline was added to the RTS sample at each ratio, were in the range of 64.21–73.80. Overall, the contact angle increased as the ratio of 2,4difluoroaniline increased, which is estimated to be due to the decrease in wettability. Meanwhile, the contact angles of the RTS_3,4A samples, where 3,4-difluoroaniline was added to the RTS sample at each ratio, were in the range of 66.58–75.67. The contact angle increased as the ratio of 3,4-difluoroaniline increased, which is estimated to be due to the decrease in wettability. While the contact angles of

Figure 7.

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Spectral transmittance of samples (Ref. and RTS).

the RTS_3,4A samples were slightly larger than those of the RTS_2,4A samples, the difference was not significant, and the contact angles of the two sets of samples proved to be identical overall. Images of the measured contact angles of the samples are shown in Figure 6. 3.3. Optical Properties With regard to the average spectral transmittances of the produced lenses, those of the reference sample, to which no additive was used, were 91.6% for visual light, 86.4% for UV-B, and 89.8% for UV-A. The transmittance of the

Figure 8. Spectral transmittance of samples [(a) Ref. vs. RTS_2,4A10, (b) RTS_2,4A1 vs. RTS_2,4A10].


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Figure 9. Spectral transmittance of samples [(a) Ref. vs. RTS_3,4A10, (b) RTS_3,4A1 vs. RTS_3,4A10].

reference sample was high for all the ranges of the spectrum, and the reference was not able to block UV. The transmittances of the RTS sample, where titanium silicon oxide and silver nanoparticles were added to the basic combination (Ref. sample), were 23.8% for UV-B, 47.0% for UV-A, and 82.2% for visual light. The transmittance for UV was low for the samples with added nanoparticles, and the transmittance was particularly low for UV-B. Also, although the transmittance for visual light was lower than that of the reference sample, this is estimated to be due to the color and not the transparency. The spectral Table II.

Spectral transmittance of samples. Unit: %

Sample

UV-B

UV-A

Vis.

Reference RTS RTS-_2,4A1 RTS-_2,4A3 RTS-_2,4A5 RTS-_2,4A7 RTS-_2,4A10 RTS-_3,4A1 RTS-_3,4A3 RTS-_3,4A5 RTS-_3,4A7 RTS-_3A10

864 238 172 130 114 88 74 140 84 52 40 30

89.8 47.0 40.6 35.6 33.0 29.6 26.4 37.0 31.2 27.4 26.4 24.0

91.6 82.2 80.6 76.4 75.4 74.2 73.0 79.8 78.4 77.0 76.6 75.2


transmittances of the RTS sample, where titanium silicon oxide and silver nanoparticles were added to the reference sample, are shown in Figure 6. The average transmittances of the RTS_2,4A samples, where 2,4-difluoroaniline was added to the RTS sample at each ratio, were 7.423.8% for UV-B, 26.4–47.0% for UV-A, and 73.0–82.2% for visual light. For the RTS_2.4A samples, the transmittance for all the ranges of the spectrum showed a decrease as the ratio of 2,4-difluoroaniline increased, and the transmittance showed a particularly significant drop for UV light, showing that 2,4-difluoroaniline selectively blocks UV. The comparison of the spectral transmittances of the reference and RTS_2,4A samples are shown in Figure 7. The average transmittances of the RTS_3,4A samples, where 3,4-difluoroaniline was added to the RTS sample at each ratio, were 3.0–23.8% for UV-B, 24.0–47.0% for UV-A, and 75.2–82.2% for visual light. For the RTS_3,4A samples, the spectral transmittance showed a decrease for all the ranges of the spectrum as the ratio of 3,4-difluoroaniline increased. In particular, the transmittance showed a significant drop in UV, showing that 3,4-difluoroaniline can selectively block UV, and the transmittance for UV was lower than that of 2,4-difluoroaniline. The blocking rate for UV-B and UV-A increased in all the samples as the ratio of aniline group increased. Also, the transmittance for visual light was appropriate for a general-purpose hydrogel lens. Meanwhile, the analysis of the UV blocking rate of the samples showed that the samples with added 3,4-difluoroaniline offer a higher UV blocking property than the samples with added 2,4difluoroaniline. The comparison for the spectral transmittances of the reference and RTS_2,4 and 3,4 samples is shown in Figures 8–9. The results of the spectraltransmittance measurements for all the samples are shown in Table II.

4. CONCLUSION The benefits of hydrogel lenses produced by adding titanium silicon oxide nanoparticles, silver nanoparticles, and aniline group to a basic combination of HEMA, NVP, MA, and EGDMA, which are the main components of hydrophilic ophthalmic lenses, were investigated. The refractive index, water content, contact angle, and spectral transmittance were measured to investigate the physical and optical properties of the produced samples. The comparison of the colors of the samples that were used in this study showed that the reference sample was colorless while the samples with added titanium silicon oxide and silver nanoparticles had a yellowish color. Also, the samples with added aniline group exhibited a brownish color, which may allow them to be used as ingredients for pigmented lenses. The measurements of the physical and optical properties of the samples showed that the refractive index and contact angle increased as the ratio of aniline group increased. Also, the RTS samples, to which titanium 8021


silicon oxide and silver nanoparticles were added, offered a UV blocking property (23.8% for UV-B, 47.0% for UVA) and visible transmittance (82.2%). The measurements of the spectral transmittances of the samples with added 2,4- and 3,4-difluoroaniline showed that the average transmittances of the RTS_2,4A samples were 7.40–23.8% for UV-B, 26.4–47.0% for UV-A, and 73–82.2% for visual light while the average transmittances of the RTS_3,4A samples were 3.0–23.8% for UV-B, 24.0–47.0% for UVA, and 75.2–82.2% for visual light. It is thus concluded that the produced macromolecule can offer various uses for UV-blocking ophthalmic lenses as well as tinted hydrogel lenses for high-functional macromolecules.

References and Notes 1. T.-H. Kim, G.-R. Min, and A.-Y. Sung, J. Korean Oph. Opt. Soc. 10, 151 (2005). 2. T.-H. Kim, D.-E. Kim, and A.-Y. Sung, J. Kor. Chem. Soc. 53, 547 (2009).

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3. T.-H. Kim and A.-Y. Sung, J. Kor. Chem. Soc. 54, 761 (2010). 4. T.-H. Kim and A.-Y. Sung, J. Kor. Chem. Soc. 53, 340 (2009). 5. K.-H. Ye, S.-H. Cho, and A.-Y. Sung, J. Kor. Chem. Soc. 53, 542 (2009). 6. K.-H. Ye and A.-Y. Sung, J. Kor. Chem. Soc. 54, 99 (2010). 7. K.-H. Ye and A.-Y. Sung, J. Kor. Chem. Soc. 54, 222 (2010). 8. H.-T. Choi, D.-W. Lee, M. Ahn, N.-C. Cho, and I.-C. You, J. KoreanOphthalmol. Soc. 53, 934 (2012). 9. J.-Y. Lee, S.-K. Chung, and D.-G. Hwang, J. Korean Ophthalmol. Soc. 40, 40 (1999). 10. D.-E. Hart, W. Reindel, H.-M. Proskin, and M.-F. Mowrey-McKee, Optometry. Vision Sci. 70, 185 (1993). 11. J.-A. Zuclich, Health Phys. 56, 671 (1989). 12. S.-R. Johar, U.-M. Rawal, N.-K. Jain, and A.-R. Vasavada, Photochem. Photobiol. 78, 306 (2003). 13. T.-H. Kim, D.-H. Kim, and A.-Y. Sung, J. Korean. Vis. Sci. 15, 147 (2013). 14. A.-Y. Sung, T.-H. Kim, and K.-H. Ye, J. Kor. Chem. Soc. 55, 98 (2011). 15. T.-H. Kim and A.-Y. Sung, J. Korean Vis. Sci. 15, 119 (2010). 16. T.-H. Kim, S.-A. Cho, and A.-Y. Sung, J. Kor. Chem. Soc. 55, 308 (2011).

Received: 21 July 2014. Accepted: 28 November 2014.

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