Silicone-based bioscaffolds for cellular therapies

Sustained dual delivery of metronidazole and viable Lactobacillus crispatus from 3D-printed silicone shells

Bacterial vaginosis (BV) is an imbalance of the vaginal microbiome in which there are limited lactobacilli and an overgrowth of anaerobic and fastidious bacteria such as Gardnerella. The propensity for BV recurrence is high, and therapies involving multiple treatment modalities are emerging to meet this need. However, current treatments requiring frequent therapeutic administration are challenging for patients and impact user compliance. Three-dimensional (3D)-printing offers a novel alternative to customize platforms to facilitate sustained therapeutic delivery to the vaginal tract. This study designed a novel vehicle intended for dual sustained delivery of both antibiotic and probiotic. 3D-printed compartmental scaffolds consisting of an antibiotic-containing silicone shell and a core containing probiotic Lactobacillus were developed with multiple formulations including biomaterials sodium alginate (SA), polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyethylene oxide (PEO), and kappa-carrageenan (KC). The vehicles were loaded with 50 μg of metronidazole/mg polymer and 5 × 107 CFU of L. crispatus/mg scaffold. Metronidazole-containing shells exhibited cumulative drug release of 324.2 ± 31.2 μg/mL after 14 days. Multiple polymeric formulations for the probiotic core demonstrated cumulative L. crispatus recovery of >5 × 107 CFU/mg scaffold during this timeframe. L. crispatus-loaded polymeric formulations exhibited ≥2 log CFU/mL reduction in free Gardnerella in the presence of VK2/E6E7 vaginal epithelial cells. As a first step towards the goal of facilitating patient compliance, this study demonstrates in vitro effect of a novel 3D-printed dual antibiotic and probiotic delivery platform to target BV.

Evaluating CAPO®: A biocompatibility, transparency, and fitment assessment for use with CEREBO® in traumatic intracranial injury detection

Healthcare-associated infections (HAIs) are a global concern affecting millions of patients, requiring robust infection prevention and control measures. In particular, patients with traumatic brain injury (TBI) are highly susceptible to nosocomial infections, emphasizing the importance of infection control. Non-invasive near infrared spectroscopy (NIRS) device, CEREBO® integrated with a disposable component CAPO® has emerged as a valuable tool for TBI patient triage and this study evaluated the safety and efficacy of this combination. Biocompatibility tests confirmed safety and transparency assessments demonstrated excellent light transmission. Clinical evaluation with 598 enrollments demonstrated high accuracy of CEREBO® in detecting traumatic intracranial hemorrhage. During these evaluations, the cap fitted well and moved smoothly with the probes demonstrating appropriate flexibility. These findings support the efficacy of the CAPO® and CEREBO® combination, potentially improving infection control and enhancing intracranial hemorrhage detection for TBI patient triage. Ultimately, this can lead to better healthcare outcomes and reduced global HAIs.

Cytotoxicity studies and antibacterial modification of poly(ethylene 2,5-furandicarboxylate) nonwoven

Novel poly(ethylene 2,5-furandicarboxylate) PEF nonwovens were produced by solution electrospinning and further modification. To improve the wettability of the hydrophobic nonwovens with water, they were treated with sodium hydroxide. Cytotoxicity tests carried out with human keratinocytes confirmed that the nonwovens did not have a toxic effect on healthy cells. The hydrophilicity of the sodium hydroxide treated nonwoven favored the adherence of the cells and their growth. In turn, the two-step modification of the nonwovens by reactions with (3-mercaptopropyl)methyldimethoxysilane and silver nitrate permitted to deposit silver particles on the fiber surfaces. The bacteria growth inhibition zones around the tested specimens were observed evidencing their antibacterial activity against Escherichia coli and Staphylococcus aureus.

Formulation and characterization of pressure-assisted microsyringe 3D-printed scaffolds for controlled intravaginal antibiotic release

Bacterial vaginosis (BV) is a highly recurrent vaginal condition linked with many health complications. Topical antibiotic treatments for BV are challenged with drug solubility in vaginal fluid, lack of convenience and user adherence to daily treatment protocols, among other factors. 3D-printed scaffolds can provide sustained antibiotic delivery to the female reproductive tract (FRT). Silicone vehicles have been shown to provide structural stability, flexibility, and biocompatibility, with favorable drug release kinetics. This study formulates and characterizes novel metronidazole-containing 3D-printed silicone scaffolds for eventual application to the FRT. Scaffolds were evaluated for degradation, swelling, compression, and metronidazole release in simulated vaginal fluid (SVF). Scaffolds retained high structural integrity and sustained release. Minimal mass loss (<6%) and swelling (<2%) were observed after 14 days in SVF, relative to initial post-cure measurements. Scaffolds cured for 24 hr (50 °C) demonstrated elastic behavior under 20% compression and 4.0 N load. Scaffolds cured for 4 hr (50 °C), followed by 72 hr (4 °C), demonstrated the highest, sustained, metronidazole release (4.0 and 27.0 µg/mg) after 24 hr and 14 days, respectively. Based upon daily release profiles, it was observed that the 24 hr timepoint had the greatest metronidazole release of 4.08 μg/mg for scaffolds cured at 4 hr at 50 °C followed by 72 hr at 4 °C. For all curing conditions, release of metronidazole after 1 and 7 days showed > 4.0-log reduction in Gardnerella concentration. Negligible cytotoxicity was observed in treated keratinocytes comparable to untreated cells, This study shows that pressure-assisted microsyringe 3D-printed silicone scaffolds may provide a versatile vehicle for sustained metronidazole delivery to the FRT.

Release Kinetics of Metronidazole from 3D Printed Silicone Scaffolds for Sustained Application to the Female Reproductive Tract

Sustained vaginal administration of antibiotics or probiotics has been proposed to improve treatment efficacy for bacterial vaginosis. 3D printing has shown promise for development of systems for local agent delivery. In contrast to oral ingestion, agent release kinetics can be fine-tuned by the 3D printing of specialized scaffold designs tailored for particular treatments while enhancing dosage effectiveness via localized sustained release. It has been challenging to establish scaffold properties as a function of fabrication parameters to obtain sustained release. In particular, the relationships between scaffold curing conditions, compressive strength, and drug release kinetics remain poorly understood. This study evaluates 3D printed scaffold formulation and feasibility to sustain the release of metronidazole, a commonly used antibiotic for BV. Cylindrical silicone scaffolds were printed and cured using three different conditions relevant to potential future incorporation of temperature-sensitive labile biologics. Compressive strength and drug release were monitored for 14d in simulated vaginal fluid to assess long-term effects of fabrication conditions on mechanical integrity and release kinetics. Scaffolds were mechanically evaluated to determine compressive and tensile strength, and elastic modulus. Release profiles were fitted to previous kinetic models to differentiate potential release mechanisms. The Higuchi, Korsmeyer-Peppas, and Peppas-Sahlin models best described the release, indicating similarity to release from insoluble or polymeric matrices. This study shows the feasibility of 3D printed silicone scaffolds to provide sustained metronidazole release over 14d, with compressive strength and drug release kinetics tuned by the fabrication parameters.

Hybrid Materials with Antimicrobial Properties Based on Hyperbranched Polyaminopropylalkoxysiloxanes Embedded with Ag Nanoparticles

New hybrid materials based on Ag nanoparticles stabilized by a polyaminopropylalkoxysiloxane hyperbranched polymer matrix were prepared. The Ag nanoparticles were synthesized in 2-propanol by metal vapor synthesis (MVS) and incorporated into the polymer matrix using metal-containing organosol. MVS is based on the interaction of extremely reactive atomic metals formed by evaporation in high vacuum (10−4–10−5 Torr) with organic substances during their co-condensation on the cooled walls of a reaction vessel. Polyaminopropylsiloxanes with hyperbranched molecular architectures were obtained in the process of heterofunctional polycondensation of the corresponding AB2-type monosodiumoxoorganodialkoxysilanes derived from the commercially available aminopropyltrialkoxysilanes. The nanocomposites were characterized using transmission (TEM) and scanning (SEM) electron microscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD) and Fourier-transform infrared spectroscopy (FTIR). TEM images show that Ag nanoparticles stabilized in the polymer matrix have an average size of 5.3 nm. In the Ag-containing composite, the metal nanoparticles have a “core-shell” structure, in which the “core” and “shell” represent the M0 and Mδ+ states, respectively. Nanocomposites based on silver nanoparticles stabilized with amine-containing polyorganosiloxane polymers showed antimicrobial activity against Bacillus subtilis and Escherichia coli.

Synthesis and characterization of UV curable biocompatible hydrophilic copolymers containing siloxane units

Tissues are highly three-dimensional structure complexes composed of different cell types and their interactions. One of the main challenges in tissue engineering is the inability to produce large, highly perfused scaffolds in which cells can grow at a high cell density and viability. Poly(dimethyl siloxane) (PDMS) is used as a flexible, biocompatible cell culture substrate with tunable mechanical properties. However, its fragility and hydrophobicity still pose a challenge. Here, we present a new strategy for the three-step one-pot synthesis of novel biocompatible hydrophilic copolymers containing siloxane units. In the first step, free radical copolymerization of acrylic acid (AA), butyl methacrylate (BMA), and 2-hydroxyethyl methacrylate (HEMA) was carried out in dioxane (DO) solution in the presence of 2,2'-azodiisobutyronitrile (AIBN). In the second step, the copolymers were modified with diepoxypropoxypropyl-terminated polydimethylsiloxane (DE-PDMS), and in the third step, the copolymers were additionally modified with glycidyl methacrylate (GMA). The modified copolymers were characterized by FTIR, NMR spectroscopy and elemental analysis. Films of modified copolymers were prepared by UV curing. SEM studies revealed microphase separated morphology with distribution of PDMS domains. The mechanical properties of the films depended on the amount of incorporated silicone modifier. The films were more hydrophilic than PDMS films. All novel copolymers showed high biocompatibility.

Advances in surface modifications of the silicone breast implant and impact on its biocompatibility and biointegration

Silicone breast implants are commonly used for cosmetic and oncologic surgical indications owing to their inertness and being nontoxic. However, complications including capsular contracture and anaplastic large cell lymphoma have been associated with certain breast implant surfaces over time. Novel implant surfaces and modifications of existing ones can directly impact cell-surface interactions and enhance biocompatibility and integration. The extent of foreign body response induced by breast implants influence implant success and integration into the body. This review highlights recent advances in breast implant surface technologies including modifications of implant surface topography and chemistry and effects on protein adsorption, and cell adhesion. A comprehensive online literature search was performed for relevant articles using the following keywords silicone breast implants, foreign body response, cell adhesion, protein adsorption, and cell-surface interaction. Properties of silicone breast implants impacting cell-material interactions including surface roughness, wettability, and stiffness, are discussed. Recent studies highlighting both silicone implant surface activation strategies and modifications to enhance biocompatibility in order to prevent capsular contracture formation and development of anaplastic large cell lymphoma are presented. Overall, breast implant surface modifications are being extensively investigated in order to improve implant biocompatibility to cater for increased demand for both cosmetic and oncologic surgeries.

Antibacterial Properties of Silver Nanoclusters with Carbon Support on Flexible Polymer

Here, we aimed at the preparation of an antibacterial surface on a flexible polydimethylsiloxane substrate. The polydimethylsiloxane surface was sputtered with silver, deposited with carbon, heat treated and exposed to excimer laser, and the combinations of these steps were studied. Our main aim was to find the combination of techniques applicable both against Gram-positive and Gram-negative bacteria. The surface morphology of the structures was determined by atomic force microscopy and scanning electron microscopy. Changes in surface chemistry were conducted by application of X-ray photoelectron spectroscopy and energy dispersive spectroscopy. The changes in surface wettability were characterized by surface free energy determination. The heat treatment was also applied to selected samples to study the influence of the process on layer stability and formation of PDMS-Ag or PDMS-C-Ag composite layer. Plasmon resonance effect was determined for as-sputtered and heat-treated Ag on polydimethylsiloxane. The heating of such structures may induce formation of a pattern with a surface plasmon resonance effect, which may also significantly affect the antibacterial activity. We have implemented sputtering of the carbon base layer in combination with excimer laser exposure of PDMS/C/Ag to modify its properties. We have confirmed that deposition of primary carbon layer on PDMS, followed by sputtering of silver combined with subsequent heat treatment and activation of such surface with excimer laser, led to the formation of a surface with strong antibacterial properties against two bacterial strains of S. epidermidis and E. coli.

Breast Implant Illness (BII): Real Syndrome or a Social Media Phenomenon? A Narrative Review of the Literature

Breast implant illness (BII) is a condition characterized by elusive diagnostic criteria and self-reported diverse disabling and distressing physical and psychological symptoms. With currently significant increase in public awareness, BII is perhaps becoming the most controversial subject in aesthetic and reconstructive breast surgery, generating heated debates between those who do not believe such a condition exists and those who demand its acceptance as a recognized diagnosis. Silicone incompatibility has been associated with "autoimmune/inflammatory syndrome induced by adjuvants" (ASIA syndrome) or Shoenfeld's syndrome. It is still unclear, however, whether BII symptoms would have occurred if no implants had been placed in the first place. The purpose of this literature review is to analyze critically the current state of scientific evidence related to this condition. Though the psychosomatic theory is most likely, the mechanism of BII symptoms is probably multifactorial. At present, BII being an underlying connective tissue disorder cannot be confirmed; moreover, whether improved aesthetic outcome and patient's overall satisfaction with the profile of their reconstructed or augmented breasts translate into decreased self-reported BII symptoms is still not well elucidated. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Modeling the Mechanobiology of Cancer Cell Migration Using 3D Biomimetic Hydrogels

Understanding how cancer cells migrate, and how this migration is affected by the mechanical and chemical composition of the extracellular matrix (ECM) is critical to investigate and possibly interfere with the metastatic process, which is responsible for most cancer-related deaths. In this article we review the state of the art about the use of hydrogel-based three-dimensional (3D) scaffolds as artificial platforms to model the mechanobiology of cancer cell migration. We start by briefly reviewing the concept and composition of the extracellular matrix (ECM) and the materials commonly used to recreate the cancerous ECM. Then we summarize the most relevant knowledge about the mechanobiology of cancer cell migration that has been obtained using 3D hydrogel scaffolds, and relate those discoveries to what has been observed in the clinical management of solid tumors. Finally, we review some recent methodological developments, specifically the use of novel bioprinting techniques and microfluidics to create realistic hydrogel-based models of the cancer ECM, and some of their applications in the context of the study of cancer cell migration.

Enhancing islet transplantation using a biocompatible collagen-PDMS bioscaffold enriched with dexamethasone-microplates

Islet transplantation is a promising approach to enable type 1 diabetic patients to attain glycemic control independent of insulin injections. However, up to 60% of islets are lost immediately following transplantation. To improve this outcome, islets can be transplanted within bioscaffolds, however, synthetic bioscaffolds induce an intense inflammatory reaction which can have detrimental effects on islet function and survival. In the present study, we first improved the biocompatibility of polydimethylsiloxane (PDMS) bioscaffolds by coating them with collagen. To reduce the inflammatory response to PDMS bioscaffolds, we then enriched the bioscaffolds with dexamethasone-loaded microplates (DEX-µScaffolds). These DEX-microplates have the ability to release DEX in a sustained manner over 7 weeks within a therapeutic range that does not affect the glucose responsiveness of the islets but which minimizes inflammation in the surrounding microenvironment. The bioscaffold showed excellent mechanical properties that enabled it to resist pore collapse thereby helping to facilitate islet seeding and its handling for implantation, and subsequent engraftment, within the epididymal fat pad (EFP). Following the transplantation of islets into the EFP of diabetic mice using DEX-µScaffolds there was a return in basal blood glucose to normal values by day 4, with normoglycemia maintained for 30 days. Furthermore, these animals demonstrated a normal dynamic response to glucose challenges with histological evidence showing reduced pro-inflammatory cytokines and fibrotic tissue surrounding DEX-µScaffolds at the transplantation site. In contrast, diabetic animals transplanted with either islets alone or islets in bioscaffolds without DEX microplates were not able to regain glycemic control during basal conditions with overall poor islet function. Taken together, our data show that coating PDMS bioscaffolds with collagen, and enriching them with DEX-microplates, significantly prolongs and enhances islet function and survival.