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Marmo AC, Grunlan MA. Biomedical Silicones: Leveraging Additive Strategies to Propel Modern Utility. ACS Macro Lett 2023; 12:172-182. [PMID: 36669481 PMCID: PMC10848296 DOI: 10.1021/acsmacrolett.2c00701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 01/18/2023] [Indexed: 01/21/2023]
Abstract
Silicones have a long history of use in biomedical devices, with unique properties stemming from the siloxane (Si-O-Si) backbone that feature a high degree of flexibility and chemical stability. However, surface, rheological, mechanical, and electrical properties of silicones can limit their utility. Successful modification of silicones to address these limitations could lead to superior and new biomedical devices. Toward improving such properties, recent additive strategies have been leveraged to modify biomedical silicones and are highlighted herein.
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Affiliation(s)
- Alec C. Marmo
- Department
of Materials Science and Engineering Texas
A&M University, College
Station, Texas 77843-3003, United States
| | - Melissa A. Grunlan
- Department
of Biomedical Engineering, Department of Materials Science and Engineering,
Department of Chemistry Texas A&M University, College Station, Texas 77843-3003, United
States
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Marmo AC, Lott LR, Pickett JH, Koller HE, Nitschke BM, Grunlan MA. Amphiphilic silicones for the facile dispersion of carbon nanotubes and formation of soft skin electrodes. ACS Appl Polym Mater 2023; 5:775-783. [PMID: 37033151 PMCID: PMC10078240 DOI: 10.1021/acsapm.2c01757] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Flexible, dry skin electrodes represent a potentially superior alternative to standard Ag/AgCl metal electrodes for wearable devices used in long-term monitoring. Herein, such electrodes were formed using a facile method for dispersing carbon nanotubes (CNTs) in a silicone matrix using custom amphiphilic dispersive additives (DSPAs). Using only brief mixing and without the use of solvents or surface modification of CNTs, twelve poly(ethylene oxide)-silanes (PEO-SAs) of varying crosslinkability, architecture, siloxane tether length, and molar ratio of siloxane:PEO were combined with an addition cure silicone and CNTs. Nearly all PEO-SA modified silicone-CNT composites demonstrated improved conductivity compared to the unmodified composite. Best conductivities correlated to composites prepared with PEO-SAs that formed micelles of particular sizes (d ~ 200 - 300 nm) and coincided to PEO-SAs with a siloxane:PEO molar ratio of ~ 0.75 - 3.00. Superior dispersion of CNT by such PEO-SAs was exemplified by scanning electron microscopy (SEM). Advantageously, modified composites retained their moduli, rather than becoming more rigid. Resultant electrodes fabricated with modified composites showed skin-electrode impedance comparable to that of Ag/AgCl electrodes. Combined, these results demonstrate the potential of silicone-CNT composites prepared with PEO-SA DSPAs as flexible, dry electrodes as a superior alternative to traditional electrodes.
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Affiliation(s)
- Alec C Marmo
- Department of Materials Science and Engineering Texas A&M University, College Station, TX 77843-3003 (USA)
| | - Lucas R Lott
- Department of Biomedical Engineering Texas A&M University, College Station, TX 77843-3003 (USA)
| | - Jackson H Pickett
- Department of Biomedical Engineering Texas A&M University, College Station, TX 77843-3003 (USA)
| | - Harrison E Koller
- Department of Chemistry Texas A&M University, College Station, TX 77843-3003 (USA)
| | - Brandon M Nitschke
- Department of Biomedical Engineering Texas A&M University, College Station, TX 77843-3003 (USA)
| | - Melissa A Grunlan
- Department of Biomedical Engineering, Department of Materials Science and Engineering, Department of Chemistry Texas A&M University, College Station, TX 77843-3003 (USA)
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Marmo AC, Rodriguez Cruz JJ, Pickett JH, Lott LR, Theibert DS, Chandler HL, Grunlan MA. Amphiphilic silicones to mitigate lens epithelial cell growth on intraocular lenses. J Mater Chem B 2022; 10:3064-3072. [PMID: 35332909 DOI: 10.1039/d2tb00213b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Silicone intraocular lenses (IOLs) that resist lens epithelial cell (LEC) growth would greatly improve patient outcomes. Herein, amphiphilic surface modifying additives (SMAs) were incorporated into an IOL-type diphenyl silicone to reduce LEC growth without compromising opto-mechanical properties. The SMAs were poly(ethylene oxide)-silane amphiphiles (PEO-SAs) [H-Si-ODMSm-block-PEO8-OCH3], comprised of a PEO segment and siloxane tether of varying lengths (m = 0, 13, and 30). These three SMAs were each blended into the addition cure diphenyl silicone at varying concentrations (5, 10, 15, 20, and 25 μmol g-1) wherein the wt% of PEO was maintained for all SMAs at a given molar concentration. The chemical crosslinking and subsequent retention of SMAs in modified silicones was confirmed. Key material properties were assessed following equilibration in both air and aqueous environments. Silicones modified with SMAs having longer tethers (m = 13 and 30) underwent rapid and substantial water-driven restructuring of PEO to the surface to form highly hydrophilic surfaces, especially as SMA concentration increased. The % transmittance was also maintained for silicones modified with these particular SMAs. The moduli of the modified silicones were largely unchanged by the SMA and remained in the typical range for silicone IOLs. When the three SMAs were introduced at the highest concentration, modified silicones remained non-cytotoxic and LEC count and associated alpha-smooth muscle actin (α-SMA) expression decreased with increasing tether length. These results demonstrate the potential of silicones modified with PEO-SA SMAs to produce LEC-resistant IOLs.
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Affiliation(s)
- Alec C Marmo
- Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843, USA.
| | - J Jesus Rodriguez Cruz
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Jackson H Pickett
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Lucas R Lott
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Dustin S Theibert
- College of Optometry, The Ohio State University, Columbus, OH 43210, USA
| | - Heather L Chandler
- College of Optometry, The Ohio State University, Columbus, OH 43210, USA
| | - Melissa A Grunlan
- Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843, USA. .,Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA.,Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
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Suriboot J, Marmo AC, Ngo BKD, Nigam A, Ortiz-Acosta D, Tai BL, Grunlan MA. Amphiphilic, thixotropic additives for extrusion-based 3D printing of silica-reinforced silicone. Soft Matter 2021; 17:4133-4142. [PMID: 33735370 DOI: 10.1039/d1sm00288k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The ability to utilize extrusion-based, direct ink write (DIW) 3D printing to create silica-reinforced silicones with complex structures could expand their utility in industrial and biomedical applications. Sylgard 184, a common Pt-cure silicone, lacks the thixotropic behavior necessary for effective printing and its hydrophobicity renders cured structures susceptible to biofouling. Herein, we evaluated the efficacy of various PEO-silane amphiphiles (PEO-SAs) as thixotropic and surface modifying additives in Sylgard 184. Eight amphiphilic PEO-SAs of varying architecture (e.g. linear, star, and graft), crosslinkability, and PEO content were evaluated. Modified formulations were also prepared with additional amounts of silica filler, both hexamethyldisilazane (HMDS)-treated and dimethyldichlorosilane (DiMeDi)-treated types. Numerous PEO-SA modified silicone formulations demonstrated effective water-driven surface hydrophilicity that was generally diminished with the addition of HMDS-treated silica filler. While increased yield stress was observed for PEO-SA modified silicones with added HMDS-treated filler, none achieved the initial target for 3D printing (>1000 Pa). Only the formulations containing the DiMeDi-treated filler (17.3 wt%) were able to surpass this value. These formulations were then tested for their thixotropic properties and all surpassed the targets for recovered storage modulus (G') (>1000 Pa) and loss factor (<0.8). In particular, the triblock linear PEO-SA produced exceptionally high recovered G', low loss factor, and substantial water-driven restructuring to form a hydrophilic surface. Combined, these results demonstrate the potential of silicones modified with PEO-SA surface-modifying additives (SMAs) for extrusion-based, DIW 3D printing applications.
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Affiliation(s)
- Jakkrit Suriboot
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA.
| | - Alec C Marmo
- Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Bryan Khai D Ngo
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA.
| | - Aman Nigam
- Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, USA
| | | | - Bruce L Tai
- Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Melissa A Grunlan
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA. and Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843, USA and Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
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