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Biocompatible Surface Coatings for Silicone-Based Implants
Published in Gilson Khang, Handbook of Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine, 2017
Jiyeon Ham, Sunah Kang, Ji-Ung Park, Yan Leea
Optimization of surgical technique and subtle changes to the surface of the silicone implants have been tried to decrease the risk of capsular contracture and other side effects. It has been reported that the incidence of capsular contracture can decrease from 59%–65% to 11% by using silicone implants with textured surfaces rather than smooth surfaces,13–16 although some contradictory reports exist.17 Additionally, submuscular placement of the implants have been recognized to show less capsular contracture than subglandular placement.18,19
New Elastomers: Biomacromolecular Engineering via Carbocationic Polymerization
Published in Anil K. Bhowmick, Current Topics in ELASTOMERS RESEARCH, 2008
To understand the complications related to breast implants, understanding the chemistry and material properties of silicones is important.55,56 Silicone gel is produced from low molecular weight (MW) chains by cross-linking. The silicone rubber shell is produced by cross-linking high-MW long chains. Cross-linking is induced by peroxides and heat or catalyzed by metals such as platinum. Similarly to other thermoset rubbers, cross-linked silicone rubber is very weak and must be reinforced.46 Medical-grade silicone is reinforced with about 30 wt% SiO2 particles to reach a tensile strength of about 10 MPa with about 400%–600% elongation, less than half of the strength of other filled rubbers.46 The bond angle in Si–O–Si is much higher than in C–C–C; as a consequence, silicones are known to be highly permeable. This is the reason for “gel bleed”: when the non-cross-linked low-MW polymer and silicone oil plasticizer seep through the shell. In addition, the shell can rupture, and then the released gel can migrate.17,52,54 The extent of gel bleed is dependent on the MW of the components and the degree of cross-linking of both the gel and shell, and the surface area of the prosthesis. It was shown that diffusion of the dimethylsiloxane small molecules out of the envelope can be reduced by using an additional layer of another elastomer, such as poly(methylphenylsiloxane) or fluorosilicone. However, the shell itself has been found to release low-MW moieties even without contacting the gel. Gel bleed and capsular contracture are believed to be correlated by some, although the trigger for capsule formation and calcification remains unproven. Two hypotheses have been suggested: hypertropic scar theory and infectious stimulus. To support this latter theory, substantial reduction in capsule thickness was demonstrated by the use of sodium 2-mercaptoethane sulfonate in a New Zealand White Rabbit Model.57 For the material scientist, there is indication that capsule formation is somehow material-specific. For example, a remarkable decrease of capsular contracture was reported with polyurethane-foam-covered implants.17 Texturing the surface of silicone is suggested to have a positive influence, but experimental data (micron-scale texturing) do not seem to support this hypothesis.58,59 At sites of implants where silicone was absent, no mineral deposition was found.60 Hydrophilization of the implant surface is believed to improve tissue interaction, but contradictions exist—for instance, poly(acrylic-acid)-grafted surface showed poorer cell-binding capability than silicone itself, while both covalent and adsorptive binding of fibronectin and Gly-Arg-Gly–Asp-Ser (GRDGS) improved cell–material interactions.59 A recent study claimed poly(2-hydroxyethyl methacrylate) hydrogel as a capsule-resistant material in vivo in rats.61 Unfortunately, no clinical solution exists today to prevent capsule formation.
Elucidating factors influencing machine learning algorithm prediction in spasticity assessment: a prospective observational study
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Natiara Mohamad Hashim, Jingye Yee, Nurul Atiqah Othman, Khairunnisa Johar, Cheng Yee Low, Fazah Akhtar Hanapiah, Noor Ayuni Che Zakaria
Forty-eight persons diagnosed with central nervous system pathology were undergoing inpatient rehabilitation and attending outpatient rehabilitation clinics that fulfilled inclusion, and exclusion criteria were recruited. In this study, we employed a non-probability convenience sampling technique. The inclusion criteria include (1) presence of any central nervous system pathology that gives rise to spasticity. (2) Good cognitive function determined by MMSE (Mini-Mental State Examination) score of 24 or less made available from patients’ clinical notes. The exclusion criteria are (1) any elbow joint or forearm pathology secondary to non-neurological cause (e.g. fracture, tendinitis). (2) Presence of elbow joint contracture secondary to bone pathology (e.g. consolidated fracture, sarcoma, heterotrophic ossification). (3) Hyperkinetic movement disorder or involuntary muscle contraction at rest. (4) Patient who received less than 4 months of botulinum toxin injection.
Bra preferences of breast cancer survivors treated with mastectomy and prosthetic reconstruction
Published in International Journal of Fashion Design, Technology and Education, 2020
Susanne M. Wroblewski, Maureen S. MacGillivray, Chin-I. Cheng
Breast cancer survivors who have had mastectomy and breast reconstruction value comfort over every other bra preference reported and are specifically concerned with wing and underband comfort. Designers should consider sensitivities related to compression at incision sites, capsular contracture, radiation burns, and lymphedema-related swelling. Reconstructed breasts differ in shape from natural breasts. Finding a bra cup that accommodates the wider, shallower breast can be difficult (Steligo, 2013). Bras should provide coverage of inconsistencies in breast shape and size due to reconstruction asymmetry. Cups should not deflect under compression to allow visibility of nipple variations. Similarly, bras should hide rough or uneven skin surface texture due to lumpectomy or radiation burns without drawing attention to the bra, as a smooth look under clothing is of high priority during selection. Bra fitters in all types of retail settings should be trained to address the needs of all types of bra wearers including women who have had mastectomy surgery and reconstruction. Designers should focus on thermal comfort, especially as it pertains to providing warmth to the wearer. Secondarily, breathability should be considered. Participants did not like underwires, therefore designers need to develop other support strategies. Survivors of mastectomy can suffer from a variety of shoulder mobility limitations and protective posturing that can reduce the effectiveness of traditional shoulder strap designs. Bra straps that allow adjustment in length as well as placement on the shoulder would be beneficial to this group.
Cardiovascular effects of diesel exhaust inhalation: photochemically altered versus freshly emitted in mice
Published in Journal of Toxicology and Environmental Health, Part A, 2019
Haiyan Tong, Jose Zavala, Rachel McIntosh-Kastrinsky, Kenneth G. Sexton
For assessment of contractile function, a latex balloon on the tip of a polyethylene catheter was inserted through the left atrium into the left ventricle. The catheter was connected to a pressure transducer (Argon Medical Devices, Athens, TX) at the same height as the heart. The pressure of the left-ventricular balloon was inflated to 0–5 cmH2O. A PowerLab system was used to collect and process the heart rate, left-ventricular-developed pressure (LVDP = LV peak minus end-diastolic pressure), and contractility (dP/dt) data (AD Instruments, Milford, MA). All hearts were perfused for 20 min when the baseline measurements were taken prior to initiating 20 min of global no-flow ischemia followed by 2 hr reperfusion. The onset of ischemic contracture was detected when the left-ventricular pressure began to increase during ischemia. Recovery of LVDP, expressed as % of initial pre-ischemic LVDP, was measured at 60 min of reperfusion after 20 min of ischemia.