Analysis of silicon in human tissues with special reference to silicone breast implants

Silicone vs. Polyurethane Stent: The Final Countdown

Ureteric stents are conventionally used in daily urological practice. There is ongoing debate on the superiority of different stent materials, particularly in terms of patient tolerance. We conducted a literature review to compare silicone stents and stents made of other materials from a patient tolerability perspective. We conclude that silicone stents are better tolerated but further research is required.

Breastfeeding After Breast Implant Surgery

Breast surgery increases the risk for difficulties with milk production and breastfeeding. Research on lactation outcomes of breast augmentation with implants is reassuring, but reveals a significant risk of low milk production that varies with the type of surgery and position of the implants. Understanding the potential effects of breast implants on breastfeeding can help lactation professionals optimize outcomes for families with a history of augmentation mammaplasty.

Optimization and validation of a fast digestion method for the determination of major and trace elements in breast milk by ICP-MS

Breast milk guarantees all the nutrients required by infants during their first few months of life and remains the most important food source for their health and growth. However, the mother may transfer potentially toxic chemicals to the suckling infant through breastfeeding. The aim of this study was to optimize and validate a fast method for the determination of a total content of 34 elements (Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cs, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, Sb, Se, Si, Sn, Sr, Te, Ti, Tl, U, V, and Zn) in liquid and lyophilized breast milk. The samples were subjected to HNO₃:H₂O₂ (2:1) digestion in an open vessel heated in a water bath (WBD; 80 °C) and subsequently analysed by quadrupole inductively coupled plasma mass spectrometry equipped with a collision-reaction interface. The performance of the proposed method was evaluated in terms of selectivity, detection and quantification limits, linearity, accuracy, and robustness by using standard reference materials and filed samples of breast milk. Compared to microwave-assisted acid digestion, the proposed open vessel digestion allows a significant reduction in treatment time and sample manipulation, while maintaining a similar analytical performance. Masses of 0.5 g of breast milk were efficiently digested with the WBD treatment allowing a residual carbon content lower than 60 mg L^-1 and a residual acidity lower than 0.87 mol L^-1 in final digested samples. Thus, it shows great potential for application to routine analysis. The method provides satisfactory detection limits and good performance (trueness and recovery percentages 80-111%; coefficient of variation <10%; and relative repeatability <15%) and allows a high sample throughput for multi-elemental determination in human biomonitoring studies.

Carbon Ion Implantation: A Good Method to Enhance the Biocompatibility of Silicone Rubber

BACKGROUND

Silicone rubber and silicone rubber-based materials have been used as medical tissue implants in the field of plastic surgery for many years, but there are still some reports of adverse reactions to long-term implants. Earlier studies have shown that ion implantation could enhance the biocompatibility of biomaterials. However, whether ion implantation has a good effect on silicone rubber is unknown.

METHODS

Three types of carbon ion silicone rubber were obtained by implanting three doses of carbon ions. Then, the antibacterial adhesion properties and the in vivo host responses were evaluated. The antibacterial adhesion properties were examined by plate colony counting, fluorescence staining, and scanning electron microscopic observation. The host responses were evaluated by surveying inflammation and fiber capsule formation that developed after subcutaneous implantation in Sprague-Dawley rats for 7, 30, 90, and 180 days. In addition, the possible mechanism by which ion implantation enhanced the biocompatibility of the biomaterial was investigated and discussed.

RESULTS

Carbon ion silicone rubber exhibits less bacterial adhesion, less collagen deposition, and thinner and weaker tissue capsules. Immunohistochemical staining results for CD4, tumor necrosis factor-α, α-smooth muscle actin, and elastin showed the possible mechanism enhancing the biocompatibility of silicone rubber. These data indicate that carbon ion silicone rubber exhibits good antibacterial adhesion properties and triggers thinner and weaker tissue capsules. In addition, high surface roughness and high zeta potential may be the main factors that induce the unique biocompatibility of carbon ion silicone rubber.

CONCLUSION

Ion implantation should be considered for further investigation and application, and carbon ion silicone rubber could be a better biomaterial to decrease silicone rubber-initiated complications.

Haematic silicon in drowning

The aim of this paper was to evaluate silicon (Si) concentration in human whole ventricular blood as a further potential chemical marker in the diagnosis of drowning. We employed an acidic digestion for the extraction of soluble Si, and an alkaline digestion for the determination of total Si, including particulate matter, both arising from drowning medium. 29 suspected drowning situations, 24 in fresh water (Fw) and 5 in seawater (Sw), were examined. The difference in Si concentration between the left and right ventricular blood (Si ΔL-R) was measured and alkaline Si ΔL-R seems, indeed, a potentially significant complementary tool in the diagnosis of Fw drowning, because insoluble silicon fraction does not undergo hemo-dilution or hemo-concentration, and the ΔL-R is not affected by exogenous factors. In spite of the limited number of cases investigated, a good correlation was observed between the analytical results and the macro-microscopic autoptic findings.

Silicon: the evolution of its use in biomaterials

In the 1970s, several studies revealed the requirement for silicon in bone development, while bioactive silicate glasses simultaneously pioneered the current era of bioactive materials. Considerable research has subsequently focused on the chemistry and biological function of silicon in bone, demonstrating that the element has at least two separate effects in the extracellular matrix: (i) interacting with glycosaminoglycans and proteoglycans during their synthesis, and (ii) forming ionic substitutions in the crystal lattice structure of hydroxyapatite. In addition, the dissolution products of bioactive glass (predominantly silicic acids) have significant effects on the molecular biology of osteoblasts in vitro, regulating the expression of several genes including key osteoblastic markers, cell cycle regulators and extracellular matrix proteins. Researchers have sought to capitalize on these effects and have generated a diverse array of biomaterials, which include bioactive glasses, silicon-substituted hydroxyapatites and pure, porosified silicon, but all these materials share similarities in the mechanisms that result in their bioactivity. This review discusses the current data obtained from original research in biochemistry and biomaterials science supporting the role of silicon in bone, comparing both the biological function of the element and analysing the evolution of silicon-containing biomaterials.

The impact of cosmetic breast implants on breastfeeding: a systematic review and meta-analysis

BACKGROUND

Cosmetic breast augmentation (breast implants) is one of the most common plastic surgery procedures worldwide and uptake in high income countries has increased in the last two decades. Women need information about all associated outcomes in order to make an informed decision regarding whether to undergo cosmetic breast surgery. We conducted a systematic review to assess breastfeeding outcomes among women with breast implants compared to women without.

METHODS

A systematic literature search of Medline, Pubmed, CINAHL and Embase databases was conducted using the earliest inclusive dates through December 2013. Eligible studies included comparative studies that reported breastfeeding outcomes (any breastfeeding, and among women who breastfed, exclusive breastfeeding) for women with and without breast implants. Pairs of reviewers extracted descriptive data, study quality, and outcomes. Rate ratios (RR) and 95% confidence intervals (CI) were pooled across studies using the random-effects model. The Newcastle-Ottawa scale (NOS) was used to critically appraise study quality, and the National Health and Medical Research Council Level of Evidence Scale to rank the level of the evidence. This systematic review has been registered with the international prospective register of systematic reviews (PROSPERO): CRD42014009074.

RESULTS

Three small, observational studies met the inclusion criteria. The quality of the studies was fair (NOS 4-6) and the level of evidence was low (III-2 - III-3). There was no significant difference in attempted breastfeeding (one study, RR 0.94, 95% CI 0.76, 1.17). However, among women who breastfed, all three studies reported a reduced likelihood of exclusive breastfeeding amongst women with breast implants with a pooled rate ratio of 0.60 (95% CI 0.40, 0.90).

CONCLUSIONS

This systematic review and meta-analysis suggests that women with breast implants who breastfeed were less likely to exclusively feed their infants with breast milk compared to women without breast implants.

First step toward near-infrared continuous glucose monitoring: in vivo evaluation of antibody coupled biomaterials

Continuous glucose monitoring (CGM) is crucial in diabetic care. Long-term CGM systems however require an accurate sensor as well as a suitable measuring environment. Since large intravenous sensors are not feasible, measuring inside the interstitial fluid is considered the best alternative. This option, unfortunately, has the drawback of a lag time with blood glucose values. A good strategy to circumvent this is to enhance tissue integration and enrich the peri-implant vasculature. Implants of different optically transparent biomaterials (poly(methyl-methacrylate) [PMMA] and poly(dimethylsiloxane) [PDMS]) - enabling glucose monitoring in the near-infrared (NIR) spectrum - were surface-treated and subsequently implanted in goats at various implantation sites for up to 3 months. The overall in vivo biocompatibility, tissue integration, and vascularization at close proximity of the surfaces of these materials were assessed. Histological screening showed similar tissue reactions independent of the implantation site. No significant inflammation reaction was observed. Tissue integration and vascularization correlated, to some extent, with the biomaterial composition. A modification strategy, in which a vascular endothelial-cadherin antibody was coupled to the biomaterials surface through a dopamine layer, showed significantly enhanced vascularization 3 months after subcutaneous implantation. Our results suggest that the developed strategy enables the creation of tissue interactive NIR transparent packaging materials, opening the possibility of continuous glucose monitoring.

Macroporous silicone biomaterials with modified surface chemistry: Production and characterization

Porous and bioactive silicone biomaterials were developed for soft and cartilage tissue repair. A protocol, using compression molding, salt extraction, and supercritical carbon dioxide treatments, was used to obtain disk-shaped materials with specific pore sizes and morphologies by changing the process conditions. Highly open/interconnected macroporous silicone matrices, with an average pore size of 250–300 µm and porosities in the range of 60%–70%, were obtained by the extracting the NaCl particles. Subsequent treatment with supercritical carbon dioxide slightly decreased the average pore size but increased the porosity to 80%. The supercritical carbon dioxide treatment effectively removed the entrapped salt crystals from the silicone matrix that improved interconnectivity. The compression modulus decreased, while the compression strength was increased using this technique. The surfaces and pores of the silicone materials were modified by silanization to provide primary amine groups for cell attachment, proliferation, migration, and three-dimensional growth of model L929 fibroblast cells.

Size exclusion chromatography with evaporative light scattering detection as a method for speciation analysis of polydimethylsiloxanes. III. Identification and determination of dimeticone and simeticone in pharmaceutical formulations

The pharmaceutical industry is one of the more important sectors for the use of polydimethylsiloxanes (PDMS), which belong to the organosilicon polymers. In drugs for internal use, they are used as an active pharmaceutical ingredient (API) called dimeticone or simeticone. Due to their specific chemical nature, PDMS can have different degrees of polymerization, which determine the molecular weight and viscosity. The Pharmacopoeial monographs for dimeticone and simeticone, only give the permitted polymerization and viscosity range. It is, however, essential to know also the degree of polymerization or the specific molecular weight of PDMS that are present in pharmaceutical formulations. In the literature there is information about the impact of particle size, and thus molecular weight, on the toxicity, absorption and migration in living organisms. This study focused on the use of a developed method - the exclusion chromatography with evaporative light scattering detector (SEC-ELSD) - for identification and determination of dimeticone and simeticone in various pharmaceutical formulations. The method had a high degree of specificity and was suitable for speciation analysis of these polymers. So far the developed method has not been used in the control of medicinal products containing dimeticone or simeticone.

Dissolution behavior of calcium phosphate nanocrystals deposited on titanium alloy surfaces

We have recently shown that a new implant surface design, achieved by the deposition of discrete nanocrystals of calcium phosphate on microtopographically complex titanium-based substrates, accelerates osteoconduction and also renders the implant surface bone bonding. Thus, we wished to examine the elution behavior of these calcium phosphate nanocrystals and their modulation in vivo. We first compared the total amount of calcium phosphate on these implants with that of plasma-sprayed implants, by measuring the eluted calcium using atomic absorption spectrophotometry. We then plotted their dissolution behavior in vitro as a function of pH relevant to physiological conditions. To assess their structural stability in vivo for periods of up to 1 month, we placed samples in diffusion chambers, implanted them in the abdominal cavity of rats, and examined their surfaces by scanning electron microscopy following retrieval. Our results show that these nanocrystals are stable at normal pH but, as expected, dissolve at acidic pH, and that they remain unchanged when exposed to body fluid in vivo for up to 1 month.

Dietary Silica Modifies the Characteristics of Endothelial Dilation in Rat Aorta

Considering the importance of nitric oxide generation in the regulation of vessel tone, reduced endothelial nitric oxide synthase (eNOS) expression in alveolar macrophages exposed to short-term silica (Si) suggests the possibility of Si-induced changes in endothelial functions. In this experimental study, the functional changes of the endothelial cells were investigated in the aortic rings of rats subjected to 50 mg Si/kg body weight in their drinking water for 8 days. Norepinephrine elicited contractility and dilation response to acetylcholine (ACh) was significantly high in the aortic rings of Si-treated group. Alteration in receptor-independent endothelial response to A23187 in the aortic rings of Si-exposed rats was less obvious, but sodium nitroprusside (SNP)-elicited dilation was reduced significantly. A23187-induced relaxation was fully eliminated with N-nitro-L-arginine methyl ester (L-NAME) pretreatment, whereas 19.24 +/- 4.36% of ACh response was L-NAME resistant and eliminated with 10-5 M tetraethylammonium (TEA). Despite a significant reduction in the share of NO, the contribution of indomethacine (IND)-sensitive relaxation to ACh response remained unchanged in Si group. As a result, our findings demonstrated that Si both modifies the characteristics of endothelial relaxants and attenuates smooth muscle cell responsiveness to NO. Si-induced reduced NO association with elevated endothelium-derived hyperpolarizing factor (EDHF) in response to ACh, together with reduced NO sensitization, might have clinical importance in cardiovascular pathology.

The nature of platinum in silicones for biomedical and healthcare use

Silicone is an important biomaterial in many different biomedical and healthcare applications. Network formation in one type of silicone relies upon a chemical crosslinking reaction that typically employs a platinum catalyst. As a consequence, low concentrations of platinum may remain in certain medical devices designed for human use. The characteristics of platinum in silicone before, during, and after the crosslinking reaction have been well described in the literature. This review summarizes the relevant literature on the organometallic and analytical chemistry of platinum in silicone and thus provides a foundation for understanding the effects this platinum may have, if any, in the various biomedical and healthcare applications where it may be present.

Effects of Silica on Mitochondrial Functions of the Proximal Tubule Cells in Rats

AIM

Despite the belief that silica (Si) is an inert and non-toxic ingredient, latest studies indicated that it is a potent mitochondria activator and Si-induced ROS generation is involved in the inflammatory reactions of silicotic lungs. Si cytotoxicity has been well studied in phagocytic cells, but its effects on the mitochondria of proximal tubule cells which are continuously exposed to filtered blood-borne soluble Si were not known.

METHODS

Using renal cortical slices and isolated mitochondria, the effect of high dietary Si on the mitochondrial functions of proximal tubule cells was studied in rats exposed to 50 mg/kg sodium metasilicate-containing water for 8 days.

RESULTS

Digested Si did not accumulate in kidney cortex, it was totally eliminated in the urine. Glomerular filtration rate as well as urine output were normal. Despite unaltered blood and cortex Si levels, ammonia production of cortical slices and isolated mitochondria was increased significantly and this was further increased by L-NAME pre-treatment. Elevated mitochondrial oxygen utilization was associated with increased ammonia production. Cyclosporin-A-sensitive mtPTP increase was associated with unchanged K(ATP) channels in the mitochondria of Si-exposed rats.

CONCLUSION

These results suggested that dietary Si increases both extracellular and intracellular ammoniagenesis by elevating mitochondrial oxygen utilisation.

Determination of siloxanes, silicon, and platinum in tissues of women with silicone gel-filled implants

Silicone [poly(dimethylsiloxane)] gel used in breast implants has been known to migrate through intact silicone elastomer shells, resulting in the clinically observable "gel bleed" on the implant surface. Although silicon concentrations in capsular tissues of women with silicone prostheses have been measured with element-specific silicon analyses, no silicone-specific investigation of these tissues has been performed as yet.A combination of element-specific inductively coupled plasma high-resolution isotope dilution mass spectrometry (ICP-HR-IDMS) and species-specific gas chromatography coupled mass spectrometry (GC-MS) was used to analyze silicon, platinum, and siloxanes in prosthesis capsule, muscle, and fat tissues of women (n=3) who had silicone gel-filled breast implants and in breast tissue of non-augmented women (n=3) as controls.In all tissues of augmented women, siloxanes, in particular octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) were identified. Depending on the siloxane species and type of tissue analyzed, siloxane levels in the range of about 10-1,400 ng g(-1) were detected; total silicon was found in all tissue samples in the range of about 8,900-85,000 ng g(-1). Higher platinum levels ranging from 25-90 ng g(-1 )were detected in fibrin layer and fat tissue of two patients with prostheses. No siloxanes were detected in control breast tissue samples. This investigation of human tissues by a combination of element-specific and species-specific analytical techniques clearly demonstrates for the first time that platinum and siloxanes leak from prostheses and accumulate in their surrounding tissues.

Distribution of silicon/e in tissues of mice of different fibrinogen genotypes following intraperitoneal administration of emulsified poly(dimethylsiloxane) [correction of poly(dimethysiloxane)]

Following injection into the abdominal cavity of a C57BL/6 mouse, droplets of emulsified PDMS visible by light microscopy (diameter > or = 1 microm) disseminate to multiple organs of the animal. Because fibrinogen may facilitate dissemination, we compared histologically the accumulation of PDMS droplets in lymph nodes, lungs, spleen, liver, and left kidney of Fib +/+, Fib +/-, and Fib -/- mice of C57BL/6 background 35 and 75 days after intraperitoneal injection of an emulsion of the polymer. We also used ICP-AES to assess the accumulation of silicon in the lymph nodes, livers, and spleens of the animals. The emulsion droplets ranged in diameter from approximately 0.04 to approximately 80 microm. PDMS droplets visible by light microscopy were in all organs of both Fib +/+ mice and Fib +/- mice. In those animals, droplets were invariably either within or adjacent to inflammatory cells, predominantly macrophages. In contrast, PDMS droplets were visible in none of the organs of Fib -/- mice. Despite the absence of visible droplets in them, the lymph nodes, livers, and spleens of Fib -/- mice, like the corresponding organs of Fib +/+ and Fib +/- mice, contained measurable silicon after 35 and 75 days. The amount of silicon, however, was always greater in the organs of Fib +/+ and Fib +/- mice than in the organs of Fib -/- mice. We attribute the presence of silicon in organs that had no histologic evidence of droplets to diffusion of the very smallest droplets/soluble species of PDMS from the abdominal cavity. Taken together, our data and observations implicate a role for fibrinogen in the dissemination of larger PDMS droplets in vivo. We propose this role involves recognition of droplet-bound fibrinogen by macrophages and, perhaps, other inflammatory cells, and the subsequent fibrinogen-facilitated ingestion and/or extracellular movement of the droplets by those cells.