Clinical and radiographic outcomes of negative pressure wound therapy combined with polymethylmethacrylate sealant for wound management of Gustilo type III open tibia fractures.

OBJECTIVE: This study aimed to introduce a new wound management method combining negative pressure wound therapy and polymethylmethacrylate sealant for Gustilo type III open tibia fractures and to evaluate its clinical outcomes. METHODS: Among 186 patients who visited our institution for the treatment of open tibia fractures between January 2016 and December 2019, 20 male patients who sustained Gustilo type III open tibia fractures and were compelled to undergo delayed flap coverage using negative pressure wound therapy combined with polymethylmethacrylate sealant due to initial critical condition were enrolled in this study. We retrospectively investigated patients' demographics, interval between the injury and flap coverage, number of negative pressure wound therapy changes, flap survival, bone union time, and infection-induced complications. RESULTS: The mean interval from injury until flap coverage was 27.8 (range, 8-63) days. Most soft-tissue defects were reconstructed using free flaps (14/20, 70%); the anterolateral thigh flap was the most frequently used flap (12/20, 60%) in this study. Among 20 flaps trans- ferred, 16 flaps (80%) survived uneventfully, 1 flap (5%) developed partial necrosis, and 3 flaps (15%) failed. The mean follow-up period was 22.7 (range, 12- 43) months. A total of 17 patients (85%) achieved tibia fracture union. The mean bone union time was 31 (range, 12-81) weeks. With regard to infection-induced complications, 3 patients (15%) developed osteomyelitis and no patient showed superficial surgical site infection. CONCLUSION: Combination therapy using negative pressure wound therapy and polymethylmethacrylate sealant serves as a useful and reliable therapeutic strategy for wound management of Gustilo type III open tibia fractures, especially when delayed soft-tissue recon- struction is unavoidable. Corresponding author: Yoo Joon Sur yoojoon@catholic.ac.kr Content of this journal is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. LEVEL OF EVIDENCE: Level IV, Therapeutic Study.

Biodegradation Studies of Polyhydroxybutyrate and Polyhydroxybutyrate-co-Polyhydroxyvalerate Films in Soil.

Due to increased environmental pressures, significant research has focused on finding suitable biodegradable plastics to replace ubiquitous petrochemical-derived polymers. Polyhydroxyalkanoates (PHAs) are a class of polymers that can be synthesized by microorganisms and are biodegradable, making them suitable candidates. The present study looks at the degradation properties of two PHA polymers: polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-polyhydroxyvalerate (PHBV; 8 wt.% valerate), in two different soil conditions: soil fully saturated with water (100% relative humidity, RH) and soil with 40% RH. The degradation was evaluated by observing the changes in appearance, chemical signatures, mechanical properties, and molecular weight of samples. Both PHB and PHBV were degraded completely after two weeks in 100% RH soil conditions and showed significant reductions in mechanical properties after just three days. The samples in 40% RH soil, however, showed minimal changes in mechanical properties, melting temperatures/crystallinity, and molecular weight over six weeks. By observing the degradation behavior for different soil conditions, these results can pave the way for identifying situations where the current use of plastics can be replaced with biodegradable alternatives.

Use of Nucleating Agent NA11 in the Preparation of Polyvinylidene Fluoride Dual-Layer Hollow Fiber Membranes.

Polyvinylidene fluoride (PVDF) dual-layer hollow fiber membranes were simultaneously fabricated by thermally induced phase separation (TIPS) and non-solvent induced phase separation (NIPS) methods using a triple orifice spinneret (TOS) for water treatment application. The support layer was prepared from a TIPS dope solution, which was composed of PVDF, gamma-butyrolactone (GBL), and N-methyl-2-pyrrolidone (NMP). The coating layer was prepared from a NIPS dope solution, which was composed of PVDF, N,N-dimethylacetamide (DMAc), and polyvinylpyrrolidone (PVP). In order to improve the mechanical strength of the dual-layer hollow fiber, a nucleating agent, sodium 2,2'-methylene bis-(4,6-di-tert-butylphenyl) phosphate (NA11), was added to the TIPS dope solution. The performance of the membrane was evaluated by surface and cross-sectional morphology, water flux, mechanical strength, and thermal property. Our results demonstrate that NA11 improved the mechanical strength of the PVDF dual-layer hollow fiber membranes by up to 42%. In addition, the thickness of the coating layer affected the porosity of the membrane and mechanical performance to have high durability in enduring harsh processing conditions.

A Combination of Surgical and Chemical Induction in a Rabbit Model for Osteoarthritis of the Knee.

BACKGROUND: Appropriate animal models of osteoarthritis (OA) are essential to develop new treatment modalities for OA. A combination of surgical and chemical induction could be appropriate for OA models. METHODS: Rabbit knee OA models developed by surgical induction (anterior cruciate ligament transection [ACLT]), chemical induction (monosodium iodoacetate [MIA] injection), and a combination of both were compared to assess compositional and structural destruction of the knee joint. Twenty-one New Zealand white rabbits were randomly divided into 3 groups to induce OA (group 1: ACLT, n = 3; group 2: MIA [3, 6, 9 mg] injection, n = 9; group 3: ACLT + MIA [3, 6, 9 mg] injection, n = 9). RESULTS: In all groups, the Modified Mankin score was significantly higher in the osteoarthritis-induced knee than in the control. Modified Mankin scores were compared by category. The ACLT group was observed to score high in cartilage structure. In the MIA group, chondrocytes and matrix staining showed higher scores, and the ACLT+MIA group scored higher in all categories for cartilage structure, chondrocytes, matrix staining, and tidemark integrity. The ACLT + 3 mg MIA showed definite OA characteristics such as cartilage surface destruction and degeneration of cartilage layers, and the ACLT + 6 mg MIA and ACLT + 9 mg MIA showed more prominent OA characteristics such as cartilage surface destruction, matrix disorganization, and osteophyte formation. CONCLUSION: The combination of MIA injection and ACLT could be an appropriate method for OA induction in rabbit models.

Predicting the Mechanical Response of Polyhydroxyalkanoate Biopolymers Using Molecular Dynamics Simulations.

Polyhydroxyalkanoates (PHAs) have emerged as a promising class of biosynthesizable, biocompatible, and biodegradable polymers to replace petroleum-based plastics for addressing the global plastic pollution problem. Although PHAs offer a wide range of chemical diversity, the structure-property relationships in this class of polymers remain poorly established. In particular, the available experimental data on the mechanical properties is scarce. In this contribution, we have used molecular dynamics simulations employing a recently developed forcefield to predict chemical trends in mechanical properties of PHAs. Specifically, we make predictions for Young's modulus, and yield stress for a wide range of PHAs that exhibit varying lengths of backbone and side chains as well as different side chain functional groups. Deformation simulations were performed at six different strain rates and six different temperatures to elucidate their influence on the mechanical properties. Our results indicate that Young's modulus and yield stress decrease systematically with increase in the number of carbon atoms in the side chain as well as in the polymer backbone. In addition, we find that the mechanical properties were strongly correlated with the chemical nature of the functional group. The functional groups that enhance the interchain interactions lead to an enhancement in both the Young's modulus and yield stress. Finally, we applied the developed methodology to study composition-dependence of the mechanical properties for a selected set of binary and ternary copolymers. Overall, our work not only provides insights into rational design rules for tailoring mechanical properties in PHAs, but also opens up avenues for future high throughput atomistic simulation studies geared towards identifying functional PHA polymer candidates for targeted applications.

Characterization of Polyhydroxybutyrate-Based Composites Prepared by Injection Molding.

The waste generated by single-use plastics is often non-recyclable and non-biodegradable, inevitably ending up in our landfills, ecosystems, and food chain. Through the introduction of biodegradable polymers as substitutes for common plastics, we can decrease our impact on the planet. In this study, we evaluate the changes in mechanical and thermal properties of polyhydroxybutyrate-based composites with various additives: Microspheres, carbon fibers or polyethylene glycol (2000, 10,000, and 20,000 MW). The mixtures were injection molded using an in-house mold attached to a commercial extruder. The resulting samples were characterized using microscopy and a series of spectroscopic, thermal, and mechanical techniques. We have shown that the addition of carbon fibers and microspheres had minimal impact on thermal stability, whereas polyethylene glycol showed slight improvements at higher molecular weights. All of the composite samples showed a decrease in hardness and compressibility. The findings described in this study will improve our understanding of polyhydroxybutyrate-based composites prepared by injection molding, enabling advancements in integrating biodegradable plastics into everyday products.

Rapid custom prototyping of soft poroelastic biosensor for simultaneous epicardial recording and imaging.

The growing need for the implementation of stretchable biosensors in the body has driven rapid prototyping schemes through the direct ink writing of multidimensional functional architectures. Recent approaches employ biocompatible inks that are dispensable through an automated nozzle injection system. However, their application in medical practices remains challenged in reliable recording due to their viscoelastic nature that yields mechanical and electrical hysteresis under periodic large strains. Herein, we report sponge-like poroelastic silicone composites adaptable for high-precision direct writing of custom-designed stretchable biosensors, which are soft and insensitive to strains. Their unique structural properties yield a robust coupling to living tissues, enabling high-fidelity recording of spatiotemporal electrophysiological activity and real-time ultrasound imaging for visual feedback. In vivo evaluations of custom-fit biosensors in a murine acute myocardial infarction model demonstrate a potential clinical utility in the simultaneous intraoperative recording and imaging on the epicardium, which may guide definitive surgical treatments.

Tuning Thermal and Mechanical Properties of Polydimethylsiloxane with Carbon Fibers.

In order to meet the needs of constantly advancing technologies, fabricating materials with improved properties and predictable behavior has become vital. To that end, we have prepared polydimethylsiloxane (PDMS) polymer samples filled with carbon nanofibers (CFs) at 0, 0.5, 1.0, 2.0, and 4.0 CF loadings (w/w) to investigate and optimize the amount of filler needed for fabrication with improved mechanical properties. Samples were prepared using easy, cost-efficient mechanical mixing to combine the PDMS and CF filler and were then characterized by chemical (FTIR), mechanical (hardness and tension), and physical (swelling, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and coefficient of thermal expansion) analyses to determine the material properties. We found that hardness and thermal stability increased predictably, while the ultimate strength and toughness both decreased. Repeated tension caused the CF-filled PDMS samples to lose significant toughness with increasing CF loadings. The hardness and thermal degradation temperature with 4 wt.% CF loading in PDMS increased more than 40% and 25 °C, respectively, compared with the pristine PDMS sample. Additionally, dilatometer measurements showed a 20% decrease in the coefficient of thermal expansion (CTE) with a small amount of CF filler in PDMS. In this study, we were able to show the mechanical and thermal properties of PDMS can be tuned with good confidence using CFs.

Supporting data for impact of filler composition on mechanical and dynamic response of 3-D printed silicone-based nanocomposite elastomers.

This research reports on the physical and mechanical effects of various filler materials used in direct ink write (DIW) 3-D printing resins. The data reported herein supports interpretation and discussion provided in the research article "Impact of Filler Composition on Mechanical and Dynamic Response of 3-D Printed Silicone-based Nanocomposite Elastomers" [1]. The datasheet describes the model structures and the interaction energies between the fillers and the other components by using Molecular Dynamics (MD) simulations. This report includes mechanical responses of single-cubic (SC) and face-centered tetragonal (FCT) structures printed using new DIW resin formulations (polydimethylsiloxane-based silicones filled with aluminum oxide, graphite, or titanium dioxide). Using MD simulations and mechanical data, the overall flexibility and interactions between resin components are fully characterized.

Facile Fabrication of Superomniphobic Polymer Hierarchical Structures for Directional Droplet Movement.

We report a facile method for fabricating polymer hierarchical structures, which are the engineered, ratchet-like microscale structures with nanoscale dimples, for the directional movement of droplets. The fabricated polymer hierarchical structures with no surface modifier show hydrophobic, superhydrophobic, or omniphobic characteristics depending on their intrinsic polymer properties. Further treatment with a surface modifier endows the polymer surfaces with superomniphobicity. The fabricated polymer substrates with no surface modifier enable the movement of the water droplet along the designed track at almost no inclination of the substrate.

Evaluation of the MicroScan MICroSTREP plus antimicrobial panel for testing ß-hemolytic streptococci and viridans group streptococci.

BACKGROUND: In order to determine the clinical usefulness of the MicroScan (Siemens Healthcare Diagnostics, USA) MICroSTREP plus antimicrobial panel (MICroSTREP) for testing antimicrobial susceptibility of ß-hemolytic streptococci (BHS) and viridans group streptococci (VGS), we compared the accuracy of MICroSTREP with that of the CLSI reference method. METHODS: Seventy-five BHS and 59 VGS isolates were tested for antimicrobial susceptibility to ampicillin, penicillin, cefotaxime, meropenem, erythromycin, clindamycin, levofloxacin, and vancomycin by using MICroSTREP and the CLSI agar dilution method. RESULTS: The overall essential agreement with regard to minimum inhibitory concentrations (MICs) (within ±1 double dilution) between MICroSTREP and the CLSI reference method was 98.2%, and categorical agreement (CA) was 96.9%. For the BHS isolates, the CA for erythromycin was 96.0%, whereas that for cefotaxime, meropenem, levofloxacin, and vancomycin (for ampicillin, penicillin, and clindamycin; 98.7%) was 100%. For the VGS isolates, the CA for penicillin was 84.7% and that for erythromycin, clindamycin, and vancomycin (for meropenem, 86.5%; for ampicillin, 88.1%; and for cefotaxime and levofloxacin, 96.6%) was 100%. All categorical errors of penicillin and ampicillin in the VGS isolates were minor. CONCLUSIONS: The accuracy of MICroSTREP is comparable to that of the CLSI reference method, suggesting that this panel can be effective for testing antimicrobial susceptibility of BHS and VGS.