Comparative Study of the Biological Degradation of Poly(3-Hydroxybutyrate-co-3-Hydroxyhexanoate) Microbeads in Municipal Wastewater in Environmental and Controlled Laboratory Conditions.

From April to June 2019, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3(HA)) microbead samples were exposed to an operational wastewater reclamation facility (WWRF) in an aerobic aeration basin in Athens, Georgia. Samples were withdrawn from the facility over a 13-week timeframe, and the particles were examined by Raman microscopy and thermogravimetric analysis/mass spectroscopy (TGA/MS) coupled with differential scanning calorimetry (DSC). The activated sludge from this facility was also used as an inoculum to examine carbon mineralization under controlled respirometry experiments to corroborate biological degradation rates determined from both the environmental and laboratory approach. Respirometry, Raman microscopy, and TGA/MS-DSC methods all measured similar biodegradation timelines for microbeads bound to an epoxy substrate, indicating that the three methods are temporally comparable and may be used to measure material biological degradation. Samples of epoxy-bound P3(HA) microbeads, free microbeads, the P3(HA) film, and poly(lactic acid) (PLA) film demonstrated carbon mineralization of 90.0, 89.4, 95.0, and 8.15%, respectively, relative to the cellulose positive control. Using a modified Gompertz growth model, the biological degradation rate coefficients (Rm) were determined for cellulose, P3(HA) film, epoxy-bound P3(HA) microbeads, and free P3(HA) microbeads and found to be 31.6, 30.2, 17.5, and 18.7 mL CO2·g-1·day-1, respectively. Moreover, P3(HA) microbeads can efficiently mineralize in WWRF infrastructure at a rate comparable to cellulose.

Direct Oral Anticoagulant Use in Special Populations: Elderly, Obesity, and Renal Failure.

PURPOSE OF REVIEW: The purpose of this review is to examine the safety and effectiveness of direct oral anticoagulants and provide recommendations for the treatment of venous thromboembolism and atrial fibrillation in obese patients, elderly patients, and patients with chronic kidney disease. RECENT FINDINGS: Multiple retrospective cohort studies have shown no difference in bleeding, stroke, or venous thromboembolism outcomes between DOACs and warfarin in patients who are obese, elderly, or those with chronic kidney disease or on dialysis. Some studies have shown that DOACs have a lower bleeding risk than warfarin in these populations. DOACs may be a safe and effective alternative to warfarin for the prevention of stroke in atrial fibrillation patients who are obese, elderly, or those with chronic kidney disease or on dialysis. Apixaban may improve clinical outcomes by lowering the risk of bleeding versus warfarin. DOACs may also be an effective and safe alternative to warfarin for the treatment of venous thromboembolism in obese patients; however, additional studies are needed to assess their use in elderly patients and those with CKD.

Ingested Micronizing Plastic Particle Compositions and Size Distributions within Stranded Post-Hatchling Sea Turtles.

From July 2015 to November 2016, 96 post-hatchling sea turtles were collected from 118 km of the Atlantic coastline in Florida, USA, including loggerhead, green, and hawksbill sea turtle species. Forty-five of the recovered turtles were rehabilitated and released, but the remaining 52 died and were frozen. At necropsy, the gastrointestinal tracts of most the turtles contained visible plastic, and collected particles of 27 individuals were chemically characterized by Raman microscopy as polyethylene, polypropylene, polyethylene terephthalate, and polystyrene. Mesoparticle plastic fragments 1.0-8.7 mm, microparticle fragments 20-1000 µm, and nanoparticles 5-169 nm were identified in the turtles. Polyethylene and polypropylene were the most common plastics ingested from specimens representing 54.1 and 23.7% of the total observed mesoparticles and 11.7 and 21.0% of the total observed microparticles, respectively. A plastic-to-body mass ratio of 2.07 mg/g was determined for this group. The authors suggest that ingestion of micronizing plastic by post-hatchling sea turtles is likely a substantial risk to survival of these endangered and threatened species. This study also provides some of the first evidence for the formation of nanoscopic plastic particles that we theorize forms in the post-hatchling and juvenile environment and are present post-ingestion.

Biodegradation of Poly(3-hydroxybutyrate- co-3-hydroxyhexanoate) Plastic under Anaerobic Sludge and Aerobic Seawater Conditions: Gas Evolution and Microbial Diversity.

Poly(3-hydroxybutyrate- co-3-hydroxyhexanoate) (poly(3HB- co-3HHx)) thermoplastics are a promising biodegradable alternative to traditional plastics for many consumer applications. Biodegradation measured by gaseous carbon loss of several types of poly(3HB- co-3HHx) plastic was investigated under anaerobic conditions and aerobic seawater environments. Under anaerobic conditions, the biodegradation levels of a manufactured sheet of poly(3HB- co-3HHx) and cellulose powder were not significantly different from one another over 85 days with 77.1 ± 6.1 and 62.9 ± 19.7% of the carbon converted to gas, respectively. However, the sheet of poly(3HB- co-3HHx) had significantly higher methane yield ( p ≤ 0.05), 483.8 ± 35.2 mL·g-1 volatile solid (VS), compared to cellulose controls, 290.1 ± 92.7 mL·g-1 VS, which is attributed to a greater total carbon content. Under aerobic seawater conditions (148-195 days at room temperature), poly(3HB- co-3HHx) sheets were statistically similar to cellulose for biodegradation as gaseous carbon loss (up to 83% loss in about 6 months), although the degradation rate was lower than that for cellulose. The microbial diversity was investigated in both experiments to explore the dominant bacteria associated with biodegradation of poly(3HB- co-3HHx) plastic. For poly(3HB- co-3HHx) treatments, Cloacamonales and Thermotogales were enriched under anaerobic sludge conditions, while Clostridiales, Gemmatales, Phycisphaerales, and Chlamydiales were the most enriched under aerobic seawater conditions.

Biocomposite thermoplastic polyurethanes containing evolved bacterial spores as living fillers to facilitate polymer disintegration.

The field of hybrid engineered living materials seeks to pair living organisms with synthetic materials to generate biocomposite materials with augmented function since living systems can provide highly-programmable and complex behavior. Engineered living materials have typically been fabricated using techniques in benign aqueous environments, limiting their application. In this work, biocomposite fabrication is demonstrated in which spores from polymer-degrading bacteria are incorporated into a thermoplastic polyurethane using high-temperature melt extrusion. Bacteria are engineered using adaptive laboratory evolution to improve their heat tolerance to ensure nearly complete cell survivability during manufacturing at 135 °C. Furthermore, the overall tensile properties of spore-filled thermoplastic polyurethanes are substantially improved, resulting in a significant improvement in toughness. The biocomposites facilitate disintegration in compost in the absence of a microbe-rich environment. Finally, embedded spores demonstrate a rationally programmed function, expressing green fluorescent protein. This research provides a scalable method to fabricate advanced biocomposite materials in industrially-compatible processes.

A Biologically Degradable and BioseniaticTM Feedstock for the High-Quality 3D Printing of Anatomical Models.

A Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) -based filament was evaluated as an alternative feedstock for Fused Deposition Modeling (FDM) of instructional and clinical medical specimens. PHBHHx-based prints of domestic cat vertebrae, skull bone, and an aortic arch cast were found comparable to conventional materials. PHBHHx-based filament and extrudate samples were evaluated for biological degradability, to meet the BioseniaticTM standard, defined by the University of Georgia New Materials Institute. Both samples achieved more than 90% mineralization within 32 days in industrial composting conditions.

DOAC Dosing Discordance Using Different Estimates of Kidney Function and Outcomes.

Direct oral anticoagulants (DOACs) are indicated for the prevention of stroke in nonvalvular atrial fibrillation. Although Food and Drug Administration labeling for DOACs uses estimated creatinine clearance according to the Cockcroft-Gault (C-G) equation, estimated glomerular filtration rate according to the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is often reported. The objectives of this study were to evaluate DOAC dosing discordance and to determine whether discordance based on various estimates of kidney function is associated with bleeding or thromboembolism. The study was an institutional review board approved retrospective analysis of patients at UPMC Presbyterian Hospital from January 1, 2010, to December 12, 2016. Data were obtained through electronic medical records. Adults who received a medication charge for rivaroxaban or dabigatran, had a diagnosis code for atrial fibrillation, and had a serum creatinine within 3 days of DOAC initiation were included. Doses were considered discordant if the calculated dose based on CKD-EPI did not match the patient's dose during index admission, if dosed correctly using C-G. Association of discordance with dabigatran, rivaroxaban, and clinical outcomes was determined using odds ratios and 95% confidence intervals. Rivaroxaban discordance was present among 49 of the 644 (8%) patients who were dosed correctly with C-G. Dabigatran discordance was present among 17 of the 590 (3%) patients who were dosed correctly. Discordance with rivaroxaban was found to increase the risk of thromboembolism when using CKD-EPI (odds ratio, 2.83; 95% CI, 1.02-7.79, P = .045) versus C-G. Our findings emphasize the need to dose DOACs, specifically rivaroxaban, appropriately in patients with nonvalvular atrial fibrillation.

Fully Synthetic Heparan Sulfate-Based Neural Tissue Construct That Maintains the Undifferentiated State of Neural Stem Cells.

Heparin and heparan sulfate (HS) are attractive components for constructing biomaterials due to their ability to recruit and regulate the activity of growth factors. The structural and functional heterogeneity of naturally derived heparin and HS is, however, an impediment for the preparation of biomaterials for regenerative medicine. To address this problem, we have prepared hydrogels modified by well-defined synthetic HS-derived disaccharides. Human induced pluripotent cell-derived neural stem cells (HIP-NSCs) encapsulated in a polyethylene glycol-based hydrogel modified by a pendent HS disaccharide that is a known ligand for fibroblast growth factor-2 (FGF-2) exhibited a significant increase in proliferation and self-renewal. This observation is important because evidence is emerging that undifferentiated stems cells can yield significant therapeutic benefits via their paracrine signaling mechanisms. Our data indicate that the HS disaccharide protects FGF-2, which has a very short biological half-live, from degradation. It is anticipated that, by careful selection of a synthetic HS oligosaccharide, it will be possible to control retention and release of specific growth factor, which in turn will provide control over cell fate.

Evidence for the Phospholipid Sponge Effect as the Biocidal Mechanism in Surface-Bound Polyquaternary Ammonium Coatings with Variable Cross-Linking Density.

Poly quaternary "-oniums" derived from polyethylenimine (PEI), poly(vinyl-N-alkylpyridinium), or chitosan belong to a class of cationic polymers that are efficient antimicrobial agents. When dissolved in solution, the positively charged polycations are able to displace the divalent cations of the cellular phospholipid bilayer and disrupt the ionic cross-links and structural integrity of the membrane. However, when immobilized to a surface where confinement limits diffusion, poly -oniums still show excellent antimicrobial activity, which implies a different biocidal mode of action. Recently, a proposed mechanism, named phospholipid sponge effect, suggested that surface-bound polycationic networks are capable of recruiting negatively charged phospholipids out of the bacterial cell membrane and sequestering them within the polymer matrix.1 However, there has been insufficient evidence to support this hypothesis. In this study, a surface-bound N,N-dodecyl methyl-co-N,N-methylbenzophenone methyl quaternary PEI (DMBQPEI) was prepared to verify the phospholipid sponge effect. By tuning the irradiation time, the cross-linking densities of surface-bound DMBQPEI films were mediated. The modulus of films was measured by PeakForce Quantitative Nanomechanical Mapping (QNM) to indicate the cross-linking density variation with increasing irradiation time. A negative correlation between the film cross-linking density and the absorption of a negatively charged phospholipid (DPhPG) was observed, but no such correlations were observed with a neutral phospholipid (DPhPC), which strongly supported the action of anionic phospholipid suction proposed in the lipid sponge effect. Moreover, the killing efficiency toward S. aureus and E. coli was inversely affected by the cross-linking density of the films, providing evidence for the phospholipid sponge effect. The relationship between killing efficiency and film cross-linking density is discussed.

Surface Grafted Antimicrobial Polymer Networks with High Abrasion Resistance.

In this work, we have investigated a quaternary ammonium compound that exhibits excellent antimicrobial activity and can be permanently grafted to substrates containing C-H bonds to form a durable polymeric film within 1 min. The compound consists of a biocidal component, dodecyl-alkylated quaternary ammonium, and a benzophenone moiety that, under mild UV irradiation, generates a densely cross-linked network and covalently attaches to a variety of substrates, including plastics, fabrics, and alkyl-modified glass surfaces. The surface attachment is 1 order of magnitude faster than that of previously reported benzophenone-associated cross-linkers, due to the electron-withdrawing effect of quaternary ammonium on the benzophenone chromophore. The modified surfaces are nonleaching and exhibit contact-killing and highly effective antimicrobial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) using cell count and live/dead staining methods. The charged ammonium group also promotes photoreaction efficiency with respect to network robustness, leading to a thin film that can sustain high shear forces and abrasion when compared to commercially available silane-based quaternary ammonium compounds. The biocidal activity is also retained after exposure to mechanical stress and abrasion.