Elucidating polyethylene microplastic degradation mechanisms and metabolic pathways via iron-enhanced microbiota dynamics in marine sediments.

The extensive use of plastics has given rise to microplastics, a novel environmental contaminant that has sparked considerable ecological and environmental concerns. Biodegradation offers a more environmentally friendly approach to eliminating microplastics, but their degradation by marine microbial communities has received little attention. In this study, we used iron-enhanced marine sediment to augment the natural bacterial community and facilitate the decomposition of polyethylene (PE) microplastics. The introduction of iron-enhanced sediment engendered an augmented bacterial biofilm formation on the surface of polyethylene (PE), thereby leading to a more pronounced degradation effect. This novel observation has been ascribed to the oxidative stress-induced generation of a variety of oxygenated functional groups, including hydroxyl (-OH), carbonyl (-CO), and ether (-C-O) moieties, within the microplastic substrate. The analysis of succession in the community structure of sediment bacteria during the degradation phase disclosed that Acinetobacter and Pseudomonas emerged as the principal bacterial players in PE degradation. These taxa were directly implicated in oxidative metabolic pathways facilitated by diverse oxidase enzymes under iron-facilitated conditions. The present study highlights bacterial community succession as a new pivotal factor influencing the complex biodegradation dynamics of polyethylene (PE) microplastics. This investigation also reveals, for the first time, a unique degradation pathway for PE microplastics orchestrated by the multifaceted marine sediment microbiota. These novel insights shed light on the unique functional capabilities and internal biochemical mechanisms employed by the marine sediment microbiota in effectively degrading polyethylene microplastics.

Phytotoxic effects of polyethylene microplastics combined with cadmium on the photosynthetic performance of maize (Zea mays L.).

Microplastics (MPs) and cadmium (Cd) has attracted increasing attention due to their combined toxicity to terrestrial vegetation. Photosynthesis which utilizes light energy to synthesize organic substances is crucial for crop production. However, the plant photosynthetic response to the joint toxicity of MPs and Cd is still unknown. Here, we studied the effects of polyethylene (PE) MPs on the photosynthetic performance of two maize cultivars Xianyu 335 (XY) and Zhengdan 958 (ZD) grown in a Cd contaminated soil. Results showed that the leaf Cd concentration in XY and ZD reached 26.1 and 31.9 µg g-1, respectively. PE-MPs did not influence the leaf Cd content, but posed direct and negative effects on photosynthesis by increasing the malondialdehyde content, reducing the chlorophyll content, inhibiting photosynthetic capacity, disrupting the PSII donor side, blocking electron transfer in different photosystems, and suppressing the oxidation and reduction states of PSI. Transcriptomic analysis revealed that the inhibitory effect of combined PE-MPs and Cd on maize photosynthesis was attributed to suppressed expression of the genes encoding PSII, PSI, F-type ATPase, cytochrome b6/f complex, and electron transport between PSII and PSI. Using WGCNA, we identified a MEturquoise module highly correlated with photosynthetic traits. Hub genes bridging carbohydrate metabolism, amino acid metabolism, lipid metabolism, and translation provided the molecular mechanisms of PE-MPs and Cd tolerance in maize plants. The comprehensive information on the phytotoxicity mechanisms of Cd stress in the presence or absence of PE-MPs on the photosynthesis of maize is helpful for cloning Cd and PE-MP resistance genes in the future.

Myogenic differentiation of human myoblasts and Mesenchymal stromal cells under GDF11 on NPoly-ɛ-caprolactone-collagen I-Polyethylene-nanofibers.

BACKGROUND: For the purpose of skeletal muscle engineering, primary myoblasts (Mb) and adipogenic mesenchymal stem cells (ADSC) can be co-cultured and myogenically differentiated. Electrospun composite nanofiber scaffolds represent suitable matrices for tissue engineering of skeletal muscle, combining both biocompatibility and stability Although growth differentiation factor 11 (GDF11) has been proposed as a rejuvenating circulating factor, restoring skeletal muscle function in aging mice, some studies have also described a harming effect of GDF11. Therefore, the aim of the study was to analyze the effect of GDF11 on co-cultures of Mb and ADSC on poly-ε-caprolactone (PCL)-collagen I-polyethylene oxide (PEO)-nanofibers. RESULTS: Human Mb were co-cultured with ADSC two-dimensionally (2D) as monolayers or three-dimensionally (3D) on aligned PCL-collagen I-PEO-nanofibers. Differentiation media were either serum-free with or without GDF11, or serum containing as in a conventional differentiation medium. Cell viability was higher after conventional myogenic differentiation compared to serum-free and serum-free + GDF11 differentiation as was creatine kinase activity. Immunofluorescence staining showed myosine heavy chain expression in all groups after 28 days of differentiation without any clear evidence of more or less pronounced expression in either group. Gene expression of myosine heavy chain (MYH2) increased after serum-free + GDF11 stimulation compared to serum-free stimulation alone. CONCLUSIONS: This is the first study analyzing the effect of GDF11 on myogenic differentiation of Mb and ADSC co-cultures under serum-free conditions. The results of this study show that PCL-collagen I-PEO-nanofibers represent a suitable matrix for 3D myogenic differentiation of Mb and ADSC. In this context, GDF11 seems to promote myogenic differentiation of Mb and ADSC co-cultures compared to serum-free differentiation without any evidence of a harming effect.

Toxic effects of microplastic (polyethylene) exposure: Bioaccumulation, hematological parameters and antioxidant responses in crucian carp, Carassius carassius.

The purpose of this study was to evaluate the toxic effects of polyethylene microplastics (PE-MPs) by measuring the bioaccumulation, hematological parameters, and antioxidant responses in crucian carp (Carassius Carassius) exposed to waterborne 22-71 µm PE-MPs. C. carassius (mean weight, 24.0 ± 2.1 g; mean length, 13.1 ± 1.2 cm) were exposed to PE-MPs at concentration of 0, 4, 8, 16, 32, and 64 mg/L for 2 weeks. The accumulation of PE-MPs in each tissue of C. carassius was significantly increased in proportion to the PE-MPs concentration; the highest accumulation was observed in the intestine, followed by the gills and liver. Hematological parameters, plasma components and antioxidants responses were significantly affected by PE-MPs in a concentration-dependent manner. Exposure to ≥32 mg/L PE-MPs induced a significant decrease in red blood cells (RBCs), hemoglobin (Hb) content, and hematocrit values. However, exposure to ≥32 mg/L PE-MPs induced oxidative stress in the liver, gill, and intestine of C. carassius, thereby resulting in a significant increase in the levels of superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) and a decrease in glutathione (GSH) levels. The effects of interaction between the PE-MPs and exposure periods showed no significant changes in bioaccumulation, hematological parameters, plasma components and antioxidant responses. These finding indicate that the exposure to ≥32 mg/L PE-MPs could cause a significant accumulation in specific tissues of C. carassius, resulting in changes in hematological parameters, plasma components, and antioxidant responses. However, the interaction between PE-MPs and exposure periods had no significant effects, thereby suggesting the lack of toxicological interactions between PE-MPs and exposure periods in C. carassius.

Metabolic profile of mesenchymal stromal cells and macrophages in the presence of polyethylene particles in a 3D model.

BACKGROUND: Continuous cross talk between MSCs and macrophages is integral to acute and chronic inflammation resulting from contaminated polyethylene particles (cPE); however, the effect of this inflammatory microenvironment on mitochondrial metabolism has not been fully elucidated. We hypothesized that (a) exposure to cPE leads to impaired mitochondrial metabolism and glycolytic reprogramming and (b) macrophages play a key role in this pathway. METHODS: We cultured MSCs with/without uncommitted M0 macrophages, with/without cPE in 3-dimensional gelatin methacrylate (3D GelMA) constructs/scaffolds. We evaluated mitochondrial function (membrane potential and reactive oxygen species-ROS production), metabolic pathways for adenosine triphosphate (ATP) production (glycolysis or oxidative phosphorylation) and response to stress mechanisms. We also studied macrophage polarization toward the pro-inflammatory M1 or the anti-inflammatory M2 phenotype and the osteogenic differentiation of MSCs. RESULTS: Exposure to cPE impaired mitochondrial metabolism of MSCs; addition of M0 macrophages restored healthy mitochondrial function. Macrophages exposed to cPE-induced glycolytic reprogramming, but also initiated a response to this stress to restore mitochondrial biogenesis and homeostatic oxidative phosphorylation. Uncommitted M0 macrophages in coculture with MSC polarized to both M1 and M2 phenotypes. Osteogenesis was comparable among groups after 21 days. CONCLUSION: This work confirmed that cPE exposure triggers impaired mitochondrial metabolism and glycolytic reprogramming in a 3D coculture model of MSCs and macrophages and demonstrated that macrophages cocultured with MSCs undergo metabolic changes to maintain energy production and restore homeostatic metabolism.

Soil properties, microbial diversity, and changes in the functionality of saline-alkali soil are driven by microplastics.

With the intensification of microplastic (MP) pollution, the impact of MPs on soil ecosystems has garnered considerable attention. We investigated the effects of two commonly used MPs, polyethylene (PE) and polypropylene (PP), at different sizes and doses, on the properties and microbial communities in saline-alkali soil. We found that MP treatment significantly reduced the electrical conductivity but somewhat enhanced the enzyme activities and effective nutrient content of the soil. Microbial diversity is affected by the type, dose, size and interaction of MPs, with fungi being more sensitive than bacteria. Under high-dose PE treatment, the dominant bacteria and fungi enriched, and the diversity indexes declined significantly. Meanwhile, under high-dose PP treatment, several unique bacteria and fungi with low abundance were observed, which eventually increased the diversity indexes. Moreover, PE exerted a stronger effect on bacterial function than PP. High-dose PE treatment suppressed the nitrogen fixation potential of soil bacteria. However, high-dose PP treatment promoted that. In conclusion, our findings showed that PE exerts a stronger negative effect on saline-alkali soil ecosystems than PP. Our findings help bridge the knowledge gap in the impact of MPs on saline-alkaline soils and provide guidance for the rational use of agricultural plastics in saline-alkaline soils.

Uptake, Transport, and Toxicity of Pristine and Weathered Micro- and Nanoplastics in Human Placenta Cells.

BACKGROUND: The first evidence of micro- and nanoplastic (MNP) exposure in the human placenta is emerging. However, the toxicokinetics and toxicity of MNPs in the placenta, specifically environmentally relevant particles, remain unclear. OBJECTIVES: We examined the transport, uptake, and toxicity of pristine and experimentally weathered MNPs in nonsyncytialized and syncytialized BeWo b30 choriocarcinoma cells. METHODS: We performed untargeted chemical characterization of pristine and weathered MNPs using liquid chromatography high-resolution mass spectrometry to evaluate compositional differences following particle weathering. We investigated cellular internalization of pristine and weathered polystyrene (PS; 0.05-10µm) and high-density polyethylene (HDPE; 0-80µm) particles using high-resolution confocal imaging and three-dimensional rendering. We investigated the influence of particle coating with human plasma on the cellular transport of PS particles using a transwell setup and examined the influence of acute MNP exposure on cell viability, damage to the plasma membrane, and expression of genes involved in steroidogenesis. RESULTS: Chemical characterization of MNPs showed a significantly higher number of unique features in pristine particles in comparison with weathered particles. Size-dependent placental uptake of pristine and weathered MNPs was observed in both placental cell types after 24 h exposure. Cellular transport was limited and size-dependent and was not influenced by particle coating with human plasma. None of the MNPs affected cell viability. Damage to the plasma membrane was observed only for 0.05µm PS particles in the nonsyncytialized cells at the highest concentration tested (100µg/mL). Modest down-regulation of hsd17b1 was observed in syncytialized cells exposed to pristine MNPs. DISCUSSION: Our results suggest that pristine and weathered MNPs are internalized and translocated in placental cells in vitro. Effects on gene expression observed upon pristine PS and HDPE particle exposure warrant further examination. More in-depth investigations are needed to better understand the potential health risks of MNP and chemicals associated with them under environmentally relevant exposure scenarios. https://doi.org/10.1289/EHP10873.

Fabrication of antimicrobial polymeric films by compression molding of peptide assemblies and polyethylene.

This paper presents compression molding of peptide assemblies with low-density polyethylene (LDPE) for the robust production of antimicrobial polymeric films. These films show a significant reduction of colony-forming units and plaque-forming units. Moreover, they significantly inhibited the growth of three different fungi. These innovative active polymeric films can potentially be applied for medical device wrapping, food packaging, and agriculture applications.

The antibacterial potency and antibacterial mechanism of a commercially available surface-anchoring quaternary ammonium salt (SAQAS)-based biocide in vitro.

AIMS: To determine the antimicrobial potency of a surface-anchored quaternary ammonium salt (SAQAS)-based biocide during in vitro wet and dry fomite assays and to determine the mechanism of killing bacteria on the surface. METHODS AND RESULTS: Wet and dry fomite assays were established in vitro for a commercially available biocide (SAQAS-A) applied to glass and low-density polyethylene (LDPE) surfaces. Both wet and dry fomite tests showed the active killing of Gram-positive and Gram-negative bacteria but not endospores. Assays measuring membrane permeability (ATP and DNA release), bacterial membrane potential and bacterial ROS production were correlated with the time-to-kill profiles to show SAQAS-A activity in suspension and applied to a surface. CONCLUSIONS: SAQAS-A is an effective biocide against model strains of vegetative bacteria. The killing mechanism for SAQAS-A observed minimal membrane depolarization, a surge in ROS production and assessment of membrane permeability supported the puncture of cells in both suspension and surface attachment, leading to cell death. SIGNIFICANCE AND IMPACT OF THE STUDY: SAQAS represents effective surface biocides against single challenges with bacteria through a mechanical killing ability that supports real-world application if their durability can be demonstrated to maintain residual activity.

The formation of specific bacterial communities contributes to the enrichment of antibiotic resistance genes in the soil plastisphere.

Soil serves as a major reservoir of both antibiotic resistance genes (ARGs) and microplastics. However, the characteristics of the antibiotic resistome in the soil plastisphere remain largely unknown. In this study, we used metagenomic approaches to reveal the changing patterns of ARGs and the bacterial community and their associations in response to three types of microplastics (light density polyethylene, LDPE; polypropylene, PP; polystyrene, PS) using particles 550 µm or 75 µm in diameter. The total ARG abundances significantly increased in the plastisphere and varied across plastic types. The LDPE plastisphere had the highest ARG total abundance and lowest Shannon diversity index, indicating that this plastic had the most severe negative impact on soil bacterial diversity. The PP plastisphere contained higher relative abundances of the pathogenic bacteria Acinetobacter johnsonii and Escherichia coli, demonstrating the higher pathogenic risk of the microbial communities enriched in the plastisphere. Specifically, multidrug resistance genes (ceoB and MuxB) co-existed with more than four microbial taxa, increasing the potential risk of ARG spread in pathogenic bacteria. These findings implied that the plastisphere acts as a hotspot for acquiring and spreading antibiotic resistance and may have long-term negative effects on the soil ecosystem and human health.

Macrophages Modulate the Function of MSC- and iPSC-Derived Fibroblasts in the Presence of Polyethylene Particles.

Fibroblasts in the synovial membrane secrete molecules essential to forming the extracellular matrix (ECM) and supporting joint homeostasis. While evidence suggests that fibroblasts contribute to the response to joint injury, the outcomes appear to be patient-specific and dependent on interactions between resident immune cells, particularly macrophages (Mφs). On the other hand, the response of Mφs to injury depends on their functional phenotype. The goal of these studies was to further explore these issues in an in vitro 3D microtissue model that simulates a pathophysiological disease-specific microenvironment. Two sources of fibroblasts were used to assess patient-specific influences: mesenchymal stem cell (MSC)- and induced pluripotent stem cell (iPSC)-derived fibroblasts. These were co-cultured with either M1 or M2 Mφs, and the cultures were challenged with polyethylene particles coated with lipopolysaccharide (cPE) to model wear debris generated from total joint arthroplasties. Our results indicated that the fibroblast response to cPE was dependent on the source of the fibroblasts and the presence of M1 or M2 Mφs: the fibroblast response as measured by gene expression changes was amplified by the presence of M2 Mφs. These results demonstrate that the immune system modulates the function of fibroblasts; furthermore, different sources of differentiated fibroblasts may lead to divergent results. Overall, our research suggests that M2 Mφs may be a critical target for the clinical treatment of cPE induced fibrosis.

Circular pOlyethylene drape in preVEntion of suRgical site infection (COVER trial): study protocol for a randomised controlled trial.

INTRODUCTION: Surgical site infection (SSI) after abdominal surgery remains a significant cause of morbidity and is associated with an increased socioeconomic burden and a reduced quality of life. Circular wound protectors have been expected to reduce the risk of SSI, but previous studies reported conflicting results on their protective effects. The purpose of this study was to evaluate the efficacy of circular wound protectors in reducing SSI in open abdominal surgery. METHODS AND ANALYSIS: The circular pOlyethylen drape in preVEntion of suRgical site infection (COVER) trial investigates whether the application of a dual-ring circular plastic wound protector reduces the rate of SSI in patients undergoing elective or emergent open abdominal surgery related to the gastrointestinal tract, regardless of the type of wound classified by the Centers for Disease Control. The COVER trial is a multicentre, randomised controlled clinical trial with two parallel arms-one using a dual-ring wound protector with circular polyethylene drape and the other using conventional surgical dressing gauze. The primary outcome will measure the rate of SSI within 30 days after surgery in two groups. Statistical analysis of the primary end point will be based on the intention-to-treat population. The sample size was determined to achieve a study power of 80% with 95% two-sided confidence limits. Considering a dropout rate of up to 5%, a total of 458 patients, 229 patients in each group, will be enrolled in this study. ETHICS AND DISSEMINATION: The trial protocol and informed consent document have been reviewed and approved by the institutional review board at each participating centre. Written informed consent will be obtained from each study participant. The clinical outcomes of this trial will be submitted to an international peer-reviewed journal and presented at international conferences. TRIAL REGISTRATION NUMBER: NCT03170843.

Early changes in serum osteocalcin and body weight are predictive of implant fixation in a rat model of implant loosening.

Biomarkers are of interest to identify patients at risk for peri-implant osteolysis and aseptic loosening. We used a rat model of particle-induced peri-implant osteolysis to investigate if early changes in biomarkers were associated with subsequent implant fixation strength. Implants were placed in rat femora, which were then challenged with intra-articular knee injections of either clean polyethylene, lipopolysaccharide-doped polyethylene, or cobalt-chromium alloy particles, with particle-free vehicle serving as control (n ≥ 8 per group). Rats were weighed weekly, blood was collected at weeks 0, 3, 5, and 6, and locomotor behavior was assessed 4 days before study conclusion. Rats were euthanized 6 weeks post surgery. Week 6 serum was analyzed for five bone remodeling markers, while longitudinal serum was assessed for osteocalcin. Bone-implant contact, peri-implant trabecular architecture, and implant fixation strength were measured. Rats challenged with cobalt-chromium particles had a significant reduction in implant fixation strength compared with the vehicle-control group (P = .034). This group also had elevated serum osteocalcin (P = .005), depressed weight gain (P = .001) and less frequent rearing behavior (P = .029). Regardless of group, change in serum osteocalcin at week 3 (r = -.368; P = .046), change in weight at week 2 (r = .586; P < .001), as well as weight change at all other time intervals were associated with fixation strength. The finding that early alterations in serum osteocalcin and body weight were predictive of subsequent implant fixation strength supports continued investigation of biomarkers for early detection of peri-implant osteolysis and implant loosening. Further, change in biomarker levels was found to be more indicative of implant fixation status than any single measurement.

Osteogenic Differentiation of Human Adipose Tissue-Derived MSCs by Non-Toxic Calcium Poly(ethylene phosphate)s.

There is a current clinical need for the development of bone void fillers and bioactive bone graft substitutes. The use of mesenchymal stem cells (MSCs) that are seeded into 3D scaffolds and induce bone generation in the event of MSCs osteogenic differentiation is highly promising. Since calcium ions and phosphates promote the osteogenic differentiation of MSCs, the use of the calcium complexes of phosphate-containing polymers is highly prospective in the development of osteogenic scaffolds. Calcium poly(ethylene phosphate)s (PEP-Ca) appear to be potentially suitable candidates primarily because of PEP's biodegradability. In a series of experiments with human adipose-tissue-derived multipotent mesenchymal stem cells (ADSCs), we demonstrated that PEP-Ca are non-toxic and give rise to osteogenesis gene marker, bone morphogenetic protein 2 (BMP-2) and mineralization of the intercellular matrix. Owing to the synthetic availability of poly(ethylene phosphoric acid) block copolymers, these results hold out the possibility for the development of promising new polymer composites for orthopaedic and maxillofacial surgery.

Local Biological Reactions and Pseudotumor-Like Tissue Formation in relation to Metal Wear in a Murine In Vivo Model.

Metal wear debris and released ions (CoCrMo), which are widely generated in metal-on-metal bearings of hip implants, are also found in patients with metal-on-polyethylene bearings due to the mechanically assisted crevice corrosion of modular taper junctions, including head-neck and neck-stem taper interfaces. The resulting adverse reactions to metal debris and metal ions frequently lead to early arthroplasty revision surgery. National guidelines have since been published where the blood metal ion concentration of patients must consistently be monitored after joint replacement to prevent serious complications from developing after surgery. However, to date, the effect of metal particles and metal ions on local biological reactions is complex and still not understood in detail; the present study sought to elucidate the complex mechanism of metal wear-associated inflammation reactions. The knee joints in 4 groups each consisting of 10 female BALB/c mice received injections with cobalt chrome ions, cobalt chrome particles, and ultra-high-molecular-weight polyethylene (UHMWPE) particles or PBS (control). Seven days after injection, the synovial microcirculation and knee joint diameter were assessed via intravital fluorescence microscopy followed by histological evaluation of the synovial layer. Enlarged knee diameter, enhanced leukocyte to endothelial cell interactions, and an increase in functional capillary density within cobalt chrome particle-treated animals were significantly greater than those in the other treatment groups. Subsequently, pseudotumor-like tissue formations were observed only in the synovial tissue layer of the cobalt chrome particle-treated animals. Therefore, these findings strongly suggest that the cobalt chrome particles and not metal ions are the cause for in vivo postsurgery implantation inflammation.

Bleaching and necrosis of staghorn coral (Acropora formosa) in laboratory assays: Immediate impact of LDPE microplastics.

The impact of low-density polyethylene (LDPE) microplastics (<100 µm; P100-A P100-B, P100-C, 100-200 µm; P200, 200-500 µm; P500) on Acropora formosa was investigated. This study investigated the bleaching and necrosis extent of A. formosa caused by LDPE contamination via laboratory assay. The staghorn coral ingested the microplastics, resulting in bleaching and necrosis that concomitantly occurred with the release of zooxanthellae. P100-A experimentation was the worst case, showing bleaching by day 2 (10.8 ±â€¯2.2%) and continued bleaching to 93.6% ±â€¯2.0 by day 14 followed by 5.9 ±â€¯2.5% necrosis. The overall results confirmed that the LDPE concentration impacts coral health. We highlighted that microplastics have been ingested and partially egested. Their presence showed either a direct or indirect impact on coral polyps via direct interaction or through photosynthesis perturbation due to microplastics that cover the coral surface.

Promoting osteoblast proliferation on polymer bone substitutes with bone-like structure by combining hydroxyapatite and bioactive glass.

Mimicking the structural features of natural bone has been demonstrated to bring pronounced advantages for mechanical reinforcement of polymeric orthopedic substitutes that are composed of bioinert polymer matrix and bioactive fillers. However, to trigger effective bone formation and implant integration, the bioactivity of bone substitutes plays a vital role. We hypothesized that the use of hydroxyapatite (HA) and bioactive glass (BG), compared to the use of HA alone, could improve the biological properties of polymer-based bone substitutes. Herein, high-density polyethylene (PE) composites loaded with HA and BG were fabricated using a modified injection molding machine that can provide intense shear flow to regulate the hierarchical structure of the composites. Morphological observation revealed that bone-like structures were formed in both HA/PE and BG/HA/PE composites, showing highly oriented interlocked shish kebabs. In addition, the bioactive fillers were distributed uniformly. Osteoblast proliferation was promoted by the combination of HA and BG. The mechanism was the upregulation of Runx2 expression (1.51 ±â€¯0.17) with BG and the activation of the TAZ/YAP (1.41/0.64) signaling pathway, which accelerated the generation of ossification-related proteins. BG can regulate microRNA to promote the mRNA expression of Runx2. The silencing of Runx2 expression can inhibit BG-induced osteoblast proliferation. These results suggest that the BG/HA/PE composites having a bone-like structure have high potential as bone substitutes to repair large bone defects.

Vitronectin promotes the vascularization of porous polyethylene biomaterials.

Rapid implant vascularization is a prerequisite for successful biomaterial engraftment. Vitronectin (VN) is a matricellular glycoprotein well known for its capability to interact with growth factors, proteases, and protease inhibitors/receptors. Since such proteins are highly relevant for angiogenic processes, we hypothesized that VN contributes to the tissue integration of biomaterials. Employing different in vivo and ex vivo microscopy techniques, engraftment of porous polyethylene (PPE) implants was analyzed in the dorsal skinfold chamber model in wild-type (WT) and VN-/- mice. Upon PPE implantation, vascularization of this biomaterial was severely compromised in animals lacking this matricellular protein. Proteome profiling revealed that VN deficiency does not cause major changes in angiogenic protein composition in the implants suggesting that VN promotes PPE vascularization via mechanisms modulating the activity of angiogenic factors rather than by directly enriching them in the implant. Consequently, surface coating with recombinant VN (embedded in Matrigel®) accelerated implant vascularization in WT mice by enhancing the maturation of a vascular network. Thus, VN contributes to the engraftment of PPE implants by promoting the vascularization of this biomaterial. Surface coating with VN might provide a promising strategy to improve the vascularization of PPE implants without affecting the host's integrity. STATEMENT OF SIGNIFICANCE: Porous polyethylene (PPE) is a biomaterial frequently used in reconstructive surgery. The proper vascularization of PPE implants is a fundamental prerequisite for its successful engraftment in host tissue. Although the overall biocompatibility of PPE is good, there are less favorable application sites for its use in tissue reconstruction mostly characterized by low blood supply. Employing advanced in vivo microscopy methods and proteomic analyses in genetically engineered mice, we here describe a previously unrecognized function of vitronectin (VN) that enables this abundantly present glycoprotein to particularly promote the vascularization of PPE biomaterial. These properties of VN specifically facilitate the formation of a dense vessel network within the implant which relies on modulating the activity of angiogenic mediators rather than on the enrichment of these factors in the implant. Consequently, surface coating with this matricellular protein effectively accelerated and intensified implant vascularization which might be beneficial for its implementation at unfavorable sites for implantation without affecting the host's integrity.

Scaffold-Assisted Artificial Hair Implantation in a Rat Model.

IMPORTANCE: Current treatments for alopecia with autograft hair transplantation face limitations that may preclude complete hair restoration and leave patients with donor site scars. Scaffold assisted artificial hair implantation as demonstrated in a rat model may provide an adjunct for hair restoration without donor site morbidity. OBJECTIVE: To design and create porous high-density polyethylene (PHDPE) and expanded polytetrafluoroethylene (ePTFE) hair-bearing scaffolds and evaluate their biocompatibility in a rat model. DESIGN, SETTING, AND PARTICIPANTS: For this single-institution randomized prospective animal study, 34 Sprague Dawley rats were randomly selected into 2 groups: 24 rats for direct implantation and 10 rats for delayed implantation. The direct-implantation group was randomly divided into 3 subgroups of 8 rats, which were observed for 2, 12, and 24 week. INTERVENTIONS: Each rat dorsum was implanted with 4 scaffolds-PHDPE and ePTFE with and without hair-in a randomized 4-quadrant manner. The rats in the direct-implantation group were observed to their selected time points of 2, 12, and 24 weeks. The rats in the delayed-implantation group were observed for 4 weeks at which, all well-healed scaffolds without hair were then percutaneously implanted with 2 follicular units of hair. These rats were then observed for another 4 weeks. MAIN OUTCOMES AND MEASURES: During the clinical observation period, scaffolds were observed for signs of infection, extrusion, and persistence of follicular units. Following sacrifice, sagittal sections of scaffold and surrounding skin were fixed in formalin, stained with hematoxylin-eosin, and evaluated for degree of fibrovascular invasion and acute and chronic inflammation. RESULTS: Overall 94.5% (86 of 91) of the scaffolds were well healed at time of evaluation (2 week, 100% [32 of 32]; 12 week, 96.3% [26 of 27]; 24 week, 87.5% [28 of 32]); while 85.6% of artificial hair follicular units were intact at time of evaluation (2 week, 93.8% [30 of 32]; 12 week, 86.7% [26 of 30]; 24 week, 75.0% [21 of 28]). Within the delayed implant group 100% (19 of 19) of the hair-implanted scaffolds were well healed at 8 weeks, with 94.7% (36 of 38) of the follicular units intact; 100% of the delayed-hair implant scaffolds were well healed with 86.1% (36 of 38) of the follicular units intact. Kaplan-Meier log-rank analysis showed no significant difference in survival between ePTFE and PHDPE scaffolds, as well as scaffolds with hair and scaffolds without hair. Upon histological analysis, overall scaffolds with hair were noted to have greater chronic inflammation (95% CI, -0.81 to -1.10; P = .01), and PHDPE was noted to have significantly great fibrovascular integration (95% CI, -11.42 to -1.96; P = .01) compared with ePTFE. CONCLUSIONS AND RELEVANCE: Overall, PHDPE and ePTFE hair bearing scaffolds were well tolerated in a rat model. Progressive loss of artificial hair may be percutaneously implanted without significant increases in infection or extrusion. LEVEL OF EVIDENCE: NA.

Modulation of Protein Adsorption and Cell Proliferation on Polyethylene Immobilized Graphene Oxide Reinforced HDPE Bionanocomposites.

The uniform dispersion of nanoparticles in a polymer matrix, together with an enhancement of interfacial adhesion is indispensable toward achieving better mechanical properties in the nanocomposites. In the context to biomedical applications, the type and amount of nanoparticles can potentially influence the biocompatibility. To address these issues, we prepared high-density polyethylene (HDPE) based composites reinforced with graphene oxide (GO) by melt mixing followed by compression molding. In an attempt to tailor the dispersion and to improve the interfacial adhesion, we immobilized polyethylene (PE) onto GO sheets by nucleophilic addition-elimination reaction. A good combination of yield strength (ca. 20 MPa), elastic modulus (ca. 600 MPa), and an outstanding elongation at failure (ca. 70%) were recorded with 3 wt % polyethylene grafted graphene oxide (PE-g-GO) reinforced HDPE composites. Considering the relevance of protein adsorption as a biophysical precursor to cell adhesion, the protein adsorption isotherms of bovine serum albumin (BSA) were determined to realize three times higher equilibrium constant (Keq) for PE-g-GO-reinforced HDPE composites as compared to GO-reinforced composites. To assess the cytocompatibility, we grew osteoblast cell line (MC3T3) and human mesenchymal stem cells (hMSCs) on HDPE/GO and HDPE/PE-g-GO composites, in vitro. The statistically significant increase in metabolically active cell over different time periods in culture for up to 6 days in MC3T3 and 7 days for hMSCs was observed, irrespective of the substrate composition. Such observation indicated that HDPE with GO or PE-g-GO addition (up to 3 wt %) can be used as cell growth substrate. The extensive proliferation of cells with oriented growth pattern also supported the fact that tailored GO addition can support cellular functionality in vitro. Taken together, the experimental results suggest that the PE-g-GO in HDPE can effectively be utilized to enhance both mechanical and cytocompatibility properties and can further be explored for potential biomedical applications.