Wear effects on microscopic morphology and hyaluronan uptake in siloxane‐hydrogel contact lenses

Tavazzi, Silvia; Tonveronachi, Martina; Fagnola, Matteo; Cozza, Federica; Ferraro, Lorenzo; Borghesi, A.; Ascagni, Miriam; Farris, Stefano

doi:10.1002/jbm.b.33278

Cited by 22 publications

(23 citation statements)

References 23 publications

(22 reference statements)

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“…For Filcon V CLs, Fig. 3 shows similar structures as recently reported elsewhere for the same material [15], where the presence of a porous layer close to the CL surface was discussed. For Senofilcon A, only few pores were rarely observed in the peripheral region of the CLs.…”

Section: Discussionsupporting

confidence: 83%

“…3). As mentioned before, detailed information on the properties of this material are reported elsewhere [15]. No significant pores were observed for the Senofilcon A CLs (Fig.…”

Section: (Vi)mentioning

confidence: 61%

“…NaCl aqueous solution to deionized water ( Typically, large pores are less numerous than small ones [15], so that a very crude approximation of the mean size of the pores is reasonably 0.2 m. This approximated value allows to calculate the approximated mean content of water in one pore (~4 10 -12 mg) and, in turn, the approximated number of pores in a CL (~ 7 10 12 ) as the ratio between the total amount of water in one CL (~30 mg) and the mean content of water in one pore.…”

Section: Discussionmentioning

confidence: 99%

“…Three types of commercial CLs were taken into consideration: (i) Methafilcon 1B (Safilens, IV FDA group) [13], a hydroxyl-ethyl-methacrylate (HEMA) copolymer and methacrylic acid (MA), (ii) Filcon V (Safilens, I FDA group) [15] containing dimethyl-acrylamide, tris-trimethylsilys, poly-(dimethyl-siloxane)-dimethacrylate, ethyleneglycol-dimethacrylate, phthalocyanine copper, (iii) Senofilcon A (Johnson&Johnson, I FDA group) containing polydimethyl-siloxane (PDMS), N,Ndimethylacrylamide (DMA), polyvinyl-pyrrolidone, and HEMA. Only in one case, the CLs were rinsed in saline aqueous solution (0.9% NaCl) purchased from Alcon Italia, to compare their hydration volume in either saline solution or deionized water.…”

Section: Methodsmentioning

confidence: 99%

“…HA can also be considered a model system to discuss the uptake capability of the CLs and to investigate the uptake mechanisms of ocular drugs, as potential controlled-release delivery platforms [1][2][3][4][5][6]. A recent work was reported on the HA distribution and penetration depth inside a siloxane-hydrogel CL [15]. HA was found to fill the CL pores, which could be seen by electronic and fluorescence microscopic techniques on the surface of the CL (Filcon V).…”

Section: Introductionmentioning

confidence: 99%

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Mechanically triggered solute uptake in soft contact lenses

Tavazzi

Ferraro

Fagnola

et al. 2015

Colloids and Surfaces B: Biointerfaces

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Molecular arrangement plays a role in the diffusion of water and solutes across soft contact lenses. In particular, the uptake of solutes in hydrated contact lenses can occur as long as free water is available for diffusion. In this work, we investigated the effect of mechanical vibrations of low frequency (200 Hz) on the solute uptake. Hyaluronan, a polysaccharide of ophthalmic use, was taken as example of solute of interest. For a specific water-hydrated hydrogel material, differential scanning calorimetry experiments showed that a large fraction of the hydration water accounted for loosely-bound water, both before and after one week of daily-wear of the lenses. The size (of the order of magnitude of few hundreds of nanometers) of hyaluronan in aqueous solution was found to be less than the size of the pores of the lens observed by scanning electron microscopy. However, solute uptake in already-hydrated lenses was negligible by simple immersion, while a significant increase occurred under mechanical vibrations of 200 Hz, thus providing experimental evidence of mechanically triggered enhanced solute uptake, which is attributed to the release of interfacial loosely-bound water. Also other materials were taken into consideration. However, the effectiveness of mechanical vibrations for hyaluronan uptake is restricted to lenses containing interfacial loosely-bound water. Indeed, loosely-bound water is expected to be bound to the polymer with bonding energies of the order of magnitude of 10-100 J/g, which are compatible with the energy input supplied by the vibrations.

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Section: Discussionsupporting

confidence: 83%

“…3). As mentioned before, detailed information on the properties of this material are reported elsewhere [15]. No significant pores were observed for the Senofilcon A CLs (Fig.…”

Section: (Vi)mentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanically triggered solute uptake in soft contact lenses

Tavazzi

Ferraro

Fagnola

et al. 2015

Colloids and Surfaces B: Biointerfaces

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Advanced morphological analysis of siloxane‐hydrogel contact lenses

Ţălu

2021

Microscopy Res & Technique

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The purpose of this work is to provide a better understanding of three‐dimensional (3‐D) surface texture of siloxane‐hydrogel contact lenses (CLs) using atomic force microscopy (AFM) and stereometric analysis. The 3‐D surface texture characterization of unworn/worn siloxane‐hydrogel CLs made of Filcon V (I FDA group) was performed with stereometric analysis. The atomic force microscopy (AFM) measurements of surface roughness and micromorphology of CLs were made using a Nanoscope V MultiMode (Bruker) in intermittent‐contact mode, in air, on square areas of 5 × 5 μm. Stereometric study of 3‐D surface texture was made according with ISO 25178‐2:2012 for CLrins (taken from the blister and rinsed with deionized water); CLss (preserved for 12 hr in saline solution and rinsed with deionized water); CLworn‐smooth (worn for 8 hr and presenting the smooth type morphology), and CLworn‐sharp (worn for 8 hr and presenting the sharp‐type morphology). The 3‐D surface texture of siloxane‐hydrogel CLs was found to have specific morphological characteristics. Statistical parameters revealed local geometrical and morphological spatial structures at nanometer scale attributed to the specific interactions at the CLs surface. Before wear, the surface micromorphology of Filcon V CLs is regular with uniformly distributed microasperities and relatively small heights (Sq = 0.6 nm). After 12 hr in saline, it is found that the micromorphology changes relatively easily, but retaining the main morphological characteristics (Sq = 1.2 nm). After 8 hr of wear, there are two typical micromorphologies: smooth type, characterized by gutter structures and isolated microasperities (Sq = 2.5 nm), while the sharp type has an appearance with compactly arranged microasperities of hill type flanked by compactly arranged microregions of valley type (Sq = 2.2 nm). Surface statistical parameters allow manufacturers in developing the next generation of CLs with improved surface texture while improving biocompatibility and minimizing the impact of the material on corneal physiology. Furthermore, the micro‐elastohydrodynamic lubrication due to surface texture at a nanometer scale between the back surface of the CL with the corneal surface and the front surface of the CL with the under‐surface of the eyelid can be deeper and more nuanced to understand in light of modern tribological theories.

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Microscopic investigations of surface texture of siloxane‐hydrogel contact lenses

Stach

Ţălu

Głuchaczka

et al. 2019

Polymer Engineering & Sci

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Purpose: The objective of this article was to investigate experimentally the 3‐D surface of unworn/worn contact lenses (CLs) using stereometric analysis applied to atomic force microscopy (AFM) micrographs. Materials and methods: Fractal and stereometric analyses were applied in micromorphology investigations of siloxane‐hydrogel CLs made of Filcon V. Qualitative and quantitative study of surface texture was made using statistical parameters of 3‐D surface roughness, according with ISO 25178‐2: 2012 for: CLrins (unworn CLs taken from the blister and rinsed with deionized water); CLworn‐smooth (worn for 8 h and presenting a smooth‐type morphology), and CLworn‐sharp (worn for 8 h and presenting a sharp‐type morphology). Results: Fractal analysis reveals fractal nature at nanometer scale of all surface samples. The fractal dimensions determined by enclosing boxes method of the studied samples are: Df = 2.25 ± 0.01 for CLrins, Df = 2.29 ± 0.01 for CLworn‐smooth and Df = 2.40 ± 0.01 for CLworn‐sharp. Conclusions: Surface statistical parameters can be deduced by analyses of micromorphology and fractal structure of the 3‐D surface of CLs. The variation of these parameters provides quantitative information on the effects of wear, such as in the cases of the two morphologies which can be found after 8 h wear of Filcon V CLs. POLYM. ENG. SCI., 59:E442–E451, 2019. © 2019 Society of Plastics Engineers

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Wear effects on microscopic morphology and hyaluronan uptake in siloxane‐hydrogel contact lenses

Cited by 22 publications

References 23 publications

Mechanically triggered solute uptake in soft contact lenses

Mechanically triggered solute uptake in soft contact lenses

Advanced morphological analysis of siloxane‐hydrogel contact lenses

Microscopic investigations of surface texture of siloxane‐hydrogel contact lenses

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