Degradation Of Poly Research Articles

Comprehensive analysis reveals the differentiated influential mechanism of degradable poly (ε-caprolactone) and polybutylene succinate microplastics on nitrogen transformation in aerobic granular sludge systems

The escalating releasing of degradable microplastics (DMPs) into wastewater may pose a potential threat to biological nitrogen removal. However, whether and how different DMPs affect nitrogen transformations in aerobic granular sludge (AGS) systems remains unclear. This work therefore aimed to fill such knowledge gaps by employing poly (ε-caprolactone) (PCL) and polybutylene succinate (PBS) as the model microplastics. Results revealed that exposure to 0.5 and 5 mg/L DMPs did not remarkably affect the nitrogen removal. However, increasing DMPs concentration to 50 mg/L suppressed the nitrogen transformation, causing a significant degree of inhibition in total nitrogen removal efficiency, particularly in the PCL-exposure group (decreased by 2.0%–25.7%). The pronounced inhibitory effects were attributed to the more readily biodegradability of PCL compared to PBS, resulting in an enhanced release of microplastics that induced excessive production of reactive oxygen species and destruction of cytomembrane integrity. Consequently, the relative abundance of denitrifiers was decreased, leading to suppressed expression of the genes (e.g. narG) involved in nitrogen transformation. This was accompanied by a decline in enzyme activity (e.g. nitrate reductase) and electron transport system activity. The correlations among genes, microbes and environmental factors were reshaped by different DMPs, underlying the intrinsic mechanism for the deteriorated nitrogen removal. Overall, this study implies that compared to PBS microplastics, the accumulation of PCL microplastics in aquatic environments poses a more significant threat to biological treatment efficacy and global nitrogen cycling, thereby warranting increased attention.

Amphiphilic Poly(2-oxazoline)s with Glycine-Containing Hydrophobic Blocks Tailored for Panobinostat- and Imatinib-Loaded Micelles.

Aiming toward the development of tailored carrier materials for the cytostatics panobinostat and imatinib, an amphiphilic block copolymer composed of poly(2-ethyl-2-oxazoline) and a degradable poly(2-(3-phenylpropyl)-2-oxazoline) analogue (dPPhPrOx-b-PEtOx) was synthesized via a postpolymerization synthesis route based on reacylation of oxidized linear poly(ethylene imine). The obtained dPPhPrOx-b-PEtOx was found to readily self-assemble into well-defined micelles with a critical micelle concentration of 1μgmL-1. The incubation of HUVEC cells with the blank micelles revealed their excellent cytocompatibility (up to 2 mg mL-1), thus confirming the polymers' suitability for potential drug delivery application. Subsequently, the encapsulation of the two cytostatics, panobinostat and imatinib, into the dPPhPrOx-b-PEtOx micelles was successfully demonstrated (Dh ≈ 80 nm, PDI ≈ 0.16), whereby the well-defined nature of the micelle was maintained upon extended incubation at 37 °C (36 h) and storage at 4 °C (1 month). Labeling of the micelles with Alexa Fluor 594 and Alexa Fluor 647, which form a Förster resonance energy transfer (FRET) pair, indicated the stability of loaded micelles upon dilution until the CMC. Finally, the cytotoxicity of the loaded micelles was investigated against three different cell lines: Medulloblastoma cell lines ONS-76 and DAOY as well as the glioblastoma cell line U87MG. While the panobinostat-loaded micelles displayed similar cytotoxicity compared to the pure drug in the cell lines, imatinib-loaded micelles were found to be more potent compared to the pristine drug, as significantly higher cytotoxicity was observed across all three cell lines.

Long-term in vivo degradation and biocompatibility of degradable pHEMA hydrogels containing graphene oxide

Developing biocompatible, non-fouling and biodegradable hydrogels for blood-contacting devices remains a demanding challenge. Such materials should promote natural healing, prevent clotting, and undergo controlled degradation. This study evaluates the biocompatibility and biodegradation of degradable poly(2-hydroxyethyl methacrylate) (d-pHEMA) hydrogels with or without reinforcement with oxidized few-layer graphene (d-pHEMA/M5ox) in a long term implantation in rats, assessing non-desired side-effects (irritation, chronic toxicity, immune response).Subcutaneous implantation over 6 months revealed degradation of both hydrogels, despite slower for d-pHEMA/M5ox, with degradation products found in intracellular vesicles. No inflammation nor infection at implantation areas were observed, and no histopathological findings were detected in parenchymal organs. Immunohistochemistry confirmed d-pHEMA and d-pHEMA/M5ox highly anti-adhesiveness. Gene expression of macrophages markers revealed presence of both M1 and M2 macrophages at all timepoints. M1/M2 profile after 6 months reveals an anti-inflammatory environment, suggesting no chronic inflammation, as also demonstrated by cytokines (IL-α, TNF-α and IL-10) analysis.Overall, modification of pHEMA towards a degradable material was successfully achieved without evoking a loss of its inherent properties, specially its anti-adhesiveness and biocompatibility. Therefore, these hydrogels hold potential as blank-slate for further modifications that promote cellular adhesion/proliferation for tissue engineering applications, namely for designing blood contacting devices with different load bearing requirements. Statement of significanceBiocompatibility, tunable biodegradation kinetics, and suitable immune response with lack of chronic toxicity and irritation, are key features in degradable blood contact devices that demand long-term exposure. We herein evaluate the 6-month in vivo performance of a degradable and hemocompatible anti-adhesive hydrogel based in pHEMA, and its mechanically reinforced formulation with few-layer graphene oxide. This subcutaneous implantation in a rat model, shows gradual degradation with progressive changes in material morphology, and no evidence of local inflammation in surrounding tissue, neither signs of inflammation or adverse reactions in systemic organs, suggesting biocompatibility of degradation products.Such hydrogels exhibit great potential as a blank slate for tissue engineering applications, including for blood contact, where cues for specific cells can be incorporated.

Responses of lettuce (Lactuca sativa L.) growth and soil properties to conventional non-biodegradable and new biodegradable microplastics

Residual plastic films in soils are posing a potential threat to agricultural ecosystem. However, little is known about the impacts of microplastics (MPs) derived from biodegradable and non-biodegradable plastic films on plant-soil systems. Here, we carried out a pot experiment using soil-cultivated lettuce treated by two types of MPs, degradable poly(butylene adipate-co-terephthalate) (PBAT-MPs) and non-biodegradable polyethylene (PE-MPs). MPs resulted in different degrees of reduction in shoot biomass, chlorophyll content, photosynthetic parameters, and leaf contents of nitrogen (N), phosphorus (P), and potassium (K), accelerated accumulation of hydrogen peroxide and superoxide, and increased malondialdehyde content in lettuce leaves. Moreover, MPs obviously decreased contents of total N, nitrate, ammonium, and available K in soils, and increased available P, thus altering soil nutrient availability. MPs also significantly decreased proportions of macroaggregates, and decreased soil electrical conductivity and microbial activity. PBAT-MPs had significantly greater impacts on oxidative damage, photosynthetic rate, soil aggregation, microbial activity, and soil ammonium than those of PE-MPs. Our results suggested that MPs caused oxidative damages, nutrient uptake inhibition, soil properties alteration, ultimately leading to growth reduction, and PBAT-MPs exhibited stronger impacts. Therefore, it is urgent to further study the ecological effects of MPs, especially biodegradable MPs, on soil-plant systems.

Investigating the potential of degradable poly(vinyl acetate) copolymer microparticles for encapsulation and in vitro release studies

Poly(vinyl acetate) is a well-known polymer synthesized through the free radical polymerization of vinyl acetate (VAc) monomer. However, enhancing the degradability of this polymer is best achieved by copolymerizing cyclic ketene acetal (CKA) with VAc. Despite their potential, the practical use of these degradable polymers remains limited. Therefore, our study aimed to develop a sustainable technology encompassing the synthesis and application of poly(VAc-co-MDO), and environmental biodegradability of poly(vinyl alcohol (VA)). To achieve this, we synthesized a series of degradable copolymers, namely poly(VAc-co-MDO), via free radical ring-opening polymerization (rROP) of 2-methylene-1,3-dioxepane (MDO) with VAc. The number of degradable ester units in the polymer backbone was systematically controlled by varying the initial monomer feed compositions, resulting in a range of 8–85 mol%. To compare their properties, we also synthesized homopolymers, namely poly(VAc) and poly(MDO). Subsequently, we formulated the homo and copolymers into microparticles using the co-solvent evaporation method, which yielded spherical particles with a particle size distribution ranging from 5 to 10 µm. Furthermore, we demonstrated the applicability of these degradable copolymers, exemplified by a poly[VAc(0.92)-co-MDO(0.08)] with 8 mol% MDO in the polymer backbone, in an encapsulation modeling study using curcumin as the active molecule. Successful encapsulation of curcumin into degradable polymer particles was confirmed and quantified via HPLC analysis. The degradability of the copolymers was evaluated through accelerated alkali hydrolysis, resulting in the formation of oligomeric degradation products. Additionally, we investigated the environmental biodegradability of poly(VA-co-MDO) as a proof of concept, revealing a biodegradability of 89% within 28 days for this polymer consisting of 88 mol% poly(VA) and 12 mol% poly(MDO) in the backbone. Preparing stable formulation for applications and performing biodegradability tests for the copolymers or microparticles derived from random poly(VAc-co-MDO) was challenging due to the insolubility of the polymer or instability in the form of sedimentation of the microparticles in the inoculum. Hence, in order to achieve stable formulation, we synthesized random poly(VA-co-MDO) through the selective cleavage of chloroacetyl group (ClAc) from its precursor, poly(VClAc-co-MDO). This method was preferred because obtaining poly(VA-co-MDO) directly from poly(VAc-co-MDO) was hindered by significant ester backbone cleavage, even under mild conditions. Our research assumes significance in light of recent restrictions imposed by various chemical agencies on the use of non-degradable polymers and microparticles in formulations.

Exosome-loaded degradable polymeric microcapsules for the treatment of vitreoretinal diseases.

The therapeutic benefits of many cell types involve paracrine mechanisms. Inspired by the paracrine functions of exosomes and the sustained degradation properties of microcapsules, here we report the therapeutic benefits of exosome-loaded degradable poly(lactic-co-glycolic acid) microcapsules with micrometric pores for the treatment of vitreoretinal diseases. On intravitreal injection in a mouse model of retinal ischaemia-reperfusion injury, microcapsules encapsulating mouse mesenchymal-stem-cell-derived exosomes settled in the inferior vitreous cavity, released exosomes for over one month as they underwent degradation and led to the restoration of retinal thickness to nearly that of the healthy retina. In mice and non-human primates with primed mycobacterial uveitis, intravitreally injected microcapsules loaded with exosomes from monkey regulatory T cells resulted in a substantial reduction in the levels of inflammatory cells. The exosome-encapsulating microcapsules, which can be lyophilised, may offer alternative treatment options for vitreoretinal diseases.

Immunobiology of foreign body response to composite PLACL/gelatin electrospun nanofiber meshes with mesenchymal stem/stromal cells in a mouse model: Implications in pelvic floor tissue engineering and regeneration

Pelvic Organ Prolapse (POP) is a common gynaecological disorder where pelvic organs protrude into the vagina. While transvaginal mesh surgery using non-degradable polymers was a commonly accepted treatment for POP, it has been associated with high rates of adverse events such as mesh erosion, exposure and inflammation due to serious foreign body response and therefore banned from clinical use after regulatory mandates. This study proposes a tissue engineering strategy using uterine endometrium-derived mesenchymal stem/stromal cells (eMSC) delivered with degradable poly L-lactic acid-co-poly ε-caprolactone (PLACL) and gelatin (G) in form of a composite electrospun nanofibrous mesh (P + G nanomesh) and evaluates the immunomodulatory mechanism at the material interfaces. The study highlights the critical acute and chronic inflammatory markers along with remodelling factors that determine the mesh surgery outcome. We hypothesise that such a bioengineered construct enhances mesh integration and mitigates the Foreign Body Response (FBR) at the host interface associated with mesh complications. Our results show that eMSC-based nanomesh significantly increased 7 genes associated with ECM synthesis and cell adhesion including, Itgb1, Itgb2, Vcam1, Cd44, Cdh2, Tgfb1, Tgfbr1, 6 genes related to angiogenesis including Ang1, Ang2, Vegfa, Pdgfa, Serpin1, Cxcl12, and 5 genes associated with collagen remodelling Col1a1, Col3a1, Col6a1, Col6a2, Col4a5 at six weeks post-implantation. Our findings suggest that cell-based tissue-engineered constructs potentially mitigate the FBR response elicited by biomaterial implants. From a clinical perspective, this construct provides an alternative to current inadequacies in surgical outcomes by modulating the immune response, inducing angiogenesis and ECM synthesis during the acute and chronic phases of the FBR.

Rapid marine degradable poly(butylene oxalate) by introducing promotion building blocks

The design and development of high-performance marine-degradable plastics have long been considered a superior strategy to address marine plastic pollution. To achieve a balance between rapid marine degradability and high performance of polyester plastics, this work designed two series of poly(butylene oxalate) (PBOx) copolymers with intrinsic hydrolysis ability using poly(ethylene oxalate) (PEOx) and poly(glycolic acid) (PGA) as promotion building blocks. The synthesis process, crystallization properties, barrier performance, and mechanical properties of copolymers were comparatively investigated. Additionally, the marine degradability of copolymers received specific focus. The theoretical calculation demonstrated that the introduction of promotion blocks reduced the hydrolysis energy barrier of the copolymers. In general, the results revealed the advantages of PBEOx copolymer in satisfying practicality and better regulating marine degradability. The high gas barrier performance, suitable thermal properties, tunable mechanical properties, and rapid marine degradability endow the copolymer as a promising candidate toward sustainable and marine-degradable plastics.

There is no difference in the efficacy of anterior cruciate ligament reconstruction using autograft combined with or without ligament augmentation: a systematic review and meta-analysis.

This study aims to determine the efficacy of anterior cruciate ligament reconstruction (ACLR) using autograft combined with or without ligament augmentation. A computerized search of the databases was conducted, including PubMed, Web of Science, Embase, Scopus and the Cochrane Library. Only prospective or retrospective comparative studies with a minimum 2-year follow-up were considered for inclusion. Two independent reviewers performed data extraction and methodological quality assessment. A Mantel-Haenszel analysis was used for the pooling of results. Sensitivity analysis was performed to maintain the stability of results. The egger test was applied to assess the publication bias. Fourteen studies were included. The total cohort was 1353 patients (non-augmented group: 763 patients; augmented group: 590 patients). There were three Randomized Controlled Trials (RCTs, Level I), six retrospective comparative studies (Level III) and five case-control studies (Level III). The follow-up rate was ≥ 88% and the follow-up periods were ≥ 24months in all included studies. The augmented graft used to compare with autograft included the Ligament Augmentation Device (LAD), the Ligament Advanced Reinforcement System (LARS) artificial ligament, FiberTape, hamstring tendon allograft, degradable poly (urethane urea). No significant differences were observed between the augmented and non-augmented groups regarding postoperative patient-reported outcomes (PROs), including the International Knee Documentation Committee score, Lysholm score and Tegner score, knee laxity, including KT-1000, side-to-side difference, Lachman test and pivot shift and rate of graft failure. ACLR using autografts combined with ligament augmentation shows no advantages in PROs, knee laxity and graft failure rate compared with using autografts only. Level III. The research protocol was registered at the PROSPERO database (CRD42022324784).

Degradation of Poly(ε-caprolactone) Resorbable Multifilament Yarn under Physiological Conditions.

Poly(ε-caprolactone) (PCL) is a hydrophobic, resorbable aliphatic polymer recognized for its low tenacity and extensive elongation at break, making it a popular choice for fabricating biodegradable tissue engineering scaffolds. PCL's slow degradation rate typically results in a complete resorption period of 2 to 3 years. While numerous studies have examined the degradation of PCL in various forms such as films and webs, no study to date has investigated its physiological degradation in multifilament yarn form. In this study, we subjected PCL multifilament yarn samples to physiological conditions in phosphate-buffered saline (PBS) maintained at a consistent temperature of 37 ± 2 °C and agitated at 45 rpm for a period of 32 weeks. We retrieved samples at five different intervals to analyze the degradation profile of the multifilament yarn. This allowed us to estimate the complete resorption time and rate under these in vitro conditions. Over the 32-week period, the multifilament yarn's mass decreased by 4.8%, its elongation at break declined by 42%, the tenacity dropped by 40%, and the peak load at break fell by 46.5%. Based on these findings, we predict that a scaffold structure incorporating PCL multifilament yarn would undergo complete resorption in approximately 14 months under physiological conditions, such as in PBS solution at a pH of approximately 7 and a temperature of 37 °C.

Assessment of the effect of accelerated ultraviolet aging on mini‐PV modules encapsulated with different poly(ethylene‐co‐vinyl acetate) formulations

AbstractOne of the hindering issues for the long‐term reliability of the photovoltaic (PV) modules is the degradation of poly(ethylene‐co‐vinyl acetate) (PEVA)—a popular encapsulant material. As a globally accepted practice, PEVA is required to have the vinyl acetate (VA) content between 28–33% by weight for encapsulation application in the PV modules. Recent studies have indicated stability improvements in the bare encapsulant layer when the VA content is reduced up to 18%. However, effect of UV aging on the PEVA films encapsulated using these VA contents have not been studied at the module level. Therefore, in this work, we have fabricated mini‐modules containing PEVA films that contain 18, 24 or 33% VA content and have subsequently been subjected to UV aging (1000 hours at 340 nm wavelength and 65C). The assessment of the durability at both the mini‐module and materials level has been made using various characterization techniques such as current–voltage characteristics, adhesion strength measurement, fluorescence imaging and spectra, FTIR, Raman spectra, volume resistivity and TGA. YI for the free‐standing films of PEVA18, PEVA24 and PEVA33 after 1000 hours of UV aging was slightly less than the YI values for the corresponding laminated films of PEVAs in mini‐PV modules after similar hours of aging. This work shows for the first time that increasing the VA content in PEVA increases the fluorescence intensity and contour size in the encapsulated polymer after UV aging. FTIR analysis indicates deacetylation of PEVA33 which resulted in discoloration (increased ΔYI) and has adversely affected the adhesion strength and power output after UV aging. Compared to PEVA33, the modules containing PEVA18 and PEVA24 are resilient against UV aging for all the properties. Hence, this study recommends using PEVA with 24% VA content as an encapsulant as it presents best combination of the adhesion strength and the environmental stability.

Degradable PDA@PNIPAM-TA Nanocomposites for Temperature- and NIR light-Controlled Pesticide Release.

Controlled pesticide delivery systems offer many distinctive advantages over conventional pesticide formulations. In this work, degradable poly(N-isopropylacrylamide) (PNIPAM)-tannic acid (TA) microgels and multifunctional PDA@PNIPAM-TA nanocomposites were prepared in a high-gravity rotating packed bed reactor (RPB) for smart pesticide delivery and release. The as-prepared microgels and nanocomposites showed reversible temperature-dependent swelling/deswelling behavior and irreversible pH-induced degradation. A dynamic contact angle test suggested that the introduction of TA and PDA into the PNIPAM matrix could enhance foliar adhesion and deposition efficiency. The nanocomposites were further used for the encapsulation and delivery of imidacloprid (IMI) to protect it from rapid photolysis and improve its pest-control efficiency. Their thermoresponsive behavior as well as pesticide loading capacity could be tuned by tailoring the PNIPAM-TA shell thickness, which could be varied by the NIPAM amount. The release rate of IMI from the core/shell nanocomposites was positively correlated with environmental temperature and near-infrared (NIR) light, which was adaptive to the positive temperature-dependent toxicity correlation of IMI and the increasing trend of pests under high temperature. The cumulative release of IMI was 23.5% at 25 °C, while it was 81.2% at 40 °C after 24 h of incubation, and the release rate was greatly enhanced under NIR irradiation. The results indicated that the facile control of pesticide release could be realized by regulating environmental conditions. This work also provides an idea for using high-gravity technology to conveniently construct a smart, effective, and environmentally friendly pesticide delivery system for sustainable crop protection.

Three-Dimensional Printing of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] Biodegradable Scaffolds: Properties, In Vitro and In Vivo Evaluation.

The results of constructing 3D scaffolds from degradable poly(3-hydrosbutyrpate-co-3-hydroxyvalerate) using FDM technology and studying the structure, mechanical properties, biocompatibility in vitro, and osteoplastic properties in vivo are presented. In the process of obtaining granules, filaments, and scaffolds from the initial polymer material, a slight change in the crystallization and glass transition temperature and a noticeable decrease in molecular weight (by 40%) were registered. During the compression test, depending on the direction of load application (parallel or perpendicular to the layers of the scaffold), the 3D scaffolds had a Young's modulus of 207.52 ± 19.12 and 241.34 ± 7.62 MPa and compressive stress tensile strength of 19.45 ± 2.10 and 22.43 ± 1.89 MPa, respectively. SEM, fluorescent staining with DAPI, and calorimetric MTT tests showed the high biological compatibility of scaffolds and active colonization by NIH 3T3 fibroblasts, which retained their metabolic activity for a long time (up to 10 days). The osteoplastic properties of the 3D scaffolds were studied in the segmental osteotomy test on a model defect in the diaphyseal zone of the femur in domestic Landrace pigs. X-ray and histological analysis confirmed the formation of fully mature bone tissue and complete restoration of the defect in 150 days of observation. The results allow us to conclude that the constructed resorbable 3D scaffolds are promising for bone grafting.

Quantitative measurement of chain crosslink of poly(butylene succinate-co-terephthalate)(PBST) mulch film during degradation above the soil in cotton growth

Degradation of poly (butylene succinate-co-terephthalate) (PBST) mulch film in the vast cotton field in the dry and windy plain has been studied. The films within 3 months' use which were above the soil and far away from the plant were selected collected as they were under closely identical outdoor degradation conditions. In macro mechanical properties, the quick decay of the ductility was the most obvious change of the mulch film in outdoor use. The elongation at break in transverse direction (TD) decreased faster than that in machine direction (MD). From micro view, chemical groups are almost retained within 3 months, while three kinds of changes in the polymer chain have been observed: (a) most additives are lost after 1 month's use; (b) chain slightly hydrolysis, of which far less than 1 break per chain occurs at the end of the 3rd month; (c) chain crosslinks, of which there are ∼1.3, 4.1 and 5.2 crosslink points per chain in average after 1, 2 and 3 months' use. The chain crosslink of the PBST is considered to be the main reason for the big decrease of the mechanical property, especially the ductility of the film, and then the main reason for the large-scale breakage of the film during 1∼2 months in Xinjiang. UV screening agent which has a strong adhesion to the polymer should be considered to solve the mulch film problem in the dry and windy plain.

All-natural environmentally degradable poly (butylene terephthalate-co-caprolactone): A theoretical and experimental study of its degradation properties and mechanisms

The design and production of materials with excellent mechanical properties and biodegradability face significant challenges. Poly (butylene terephthalate-co-caprolactone) copolyesters (PBTCL) is obtained by modifying the engineering plastic polybutylene terephthalate (PBT) with a simple one-pot process using readily biodegradable ε-caprolactone (ε-CL). The material has mechanical properties comparable to those of commercial biodegradable copolyester PBAT. Besides, this copolyester exhibited remarkable degradability in natural environments such as soil and ocean, for example, PBTCL1.91 lost >40 % of its weight after 6 months of immersion in the Bohai Sea. The effect and diversity of specific microorganisms acting on degradation in the ocean were analyzed by 16 s rDNA gene sequencing. Theoretical calculations such as Fukui function and DFT, and experimental studies on water-soluble intermediates and residual matrixes produced after degradation, confirmed that the insertion CL units not only act as active sites themselves susceptible to hydrolysis reactions, but also promote the reactivity of ester bonds between aromatic segments. This work provides insight for the development of novel materials with high performance and environmental degradability.

Slow hydrogel matrix degradation enhances salivary gland mimetic phenotype.

We recently developed a salivary gland tissue mimetic (SGm), comprised of salivary gland cells encapsulated in matrix metalloproteinase (MMP)-degradable poly(ethylene glycol) hydrogels within arrays of ∼320 µm diameter spherical cavities molded in PDMS. The SGm provides a functional and physiologically relevant platform well-suited to high-throughput drug screening for radioprotective compounds. However, the utility of the SGm would benefit from improved retention of acinar cell phenotype and function. We hypothesized that tuning biochemical cues presented within the PEG hydrogel matrix would improve maintenance of acinar cell phenotype and function by mimicking the natural extracellular matrix microenvironment of the intact gland. Hydrogels formed using slower-degrading MMP-sensitive peptide crosslinkers showed >2-fold increase in sphere number formed at 48 h, increased expression of acinar cell markers, and more robust response to calcium stimulation by the secretory agonist, carbachol, with reduced SGm tissue cluster disruption and outgrowth during prolonged culture. The incorporation of adhesive peptides containing RGD or IKVAV improved calcium flux response to secretory agonists at 14 days of culture. Tuning the hydrogel matrix improved cell aggregation, and promoted acinar cell phenotype, and stability of the SGm over 14 days of culture. Furthermore, combining this matrix with optimized media conditions synergistically prolonged the retention of the acinar cell phenotype in SGm. STATEMENT OF SIGNIFICANCE: Salivary gland (SG) dysfunction occurs due to off-target radiation due to head and neck cancer treatments. Progress in understanding gland dysfunction and developing therapeutic strategies for the SG are hampered by the lack of in vitro models, as salivary gland cells rapidly lose critical secretory function within 24 hours in vitro. Herein, we identify properties of poly(ethylene glycol) hydrogel matrices that enhance the secretory phenotype of SG tissue mimetics within the previously-described SG-microbubble tissue chip environment. Combining slow-degrading hydrogels with media conditions optimized for secretory marker expression further enhanced functional secretory response and secretory marker expression.

Iron-Catalyzed Alkoxylation, Dehydrogenative-Polymerization and Tandem Hydrosilylative-Alkoxylation.

Alkoxylation, hydrosilylative-alkoxylation, and dehydrogenative-polymerization are some of the most widely used transformations in synthetic chemistry. However, these transformations are traditionally catalyzed by precious, and rare late-transition metals. Presented here is a molecularly defined iron complex that catalyzes alkoxylation, tandem hydrosilylative-alkoxylation, and dehydrogenative polymerization of silanes under mild conditions. The iron complex [Fe(CO)4(H)(SiPh3)] 1 catalyzes a direct Si-O coupling reaction between an array of silanes and alcohols to produce desired alkoxysilanes in excellent yield, with H2 as the only byproduct. The iron catalyst tolerates various functional groups and provides access to 20 alkoxysilanes, including essential molecules such as β-citronellol and cholesterol. Further, complex 1 catalyzes the polymerization of renewable diol and silane monomer to produce a renewable and degradable poly(isosorbide-silyl ether). Remarkably, complex 1 catalyzes a tandem hydrosilylative-alkoxylation of alkynes under mild conditions to yield unsaturated silyl ethers. The synthetic utility has been demonstrated by gram-scale alkoxylation and hydrosilylative-alkoxylation reactions.

Semiconducting Polymer Nanoporous Thin Films as a Tool to Regulate Intracellular ROS Balance in Endothelial Cells.

The design of soft and nanometer-scale photoelectrodes able to stimulate and promote the intracellular concentration of reactive oxygen species (ROS) is searched for redox medicine applications. In this work, we show semiconducting polymer porous thin films with an enhanced photoelectrochemical generation of ROS in human umbilical vein endothelial cells (HUVECs). To achieve that aim, we synthesized graft copolymers, made of poly(3-hexylthiophene) (P3HT) and degradable poly(lactic acid) (PLA) segments, P3HT-g-PLA. In a second step, the hydrolysis of sacrificial PLA leads to nanometer-scale porous P3HT thin films. The pore sizes in the nm regime (220-1200 nm) were controlled by the copolymer composition and the structural arrangement of the copolymers during the film formation, as determined by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The porous P3HT thin films showed enhanced photofaradaic behavior, generating a higher concentration of ROS in comparison to non-porous P3HT films, as determined by scanning electrochemical microscopy (SECM) measurements. The exogenous ROS production was able to modulate the intracellular ROS concentration in HUVECs at non-toxic levels, thus affecting the physiological functions of cells. Results presented in this work provide an important step forward in the development of new tools for precise, on-demand, and non-invasive modulation of intracellular ROS species and may be potentially extended to many other physiological or pathological cell models.

PVA free-radical diblock copolymer for nanoencapsulation with enhanced biodegradability in the environment

The synthesis of readily biodegradable amphiphilic polyvinyl alcohol diblock copolymers (poly(VA-b-MDO)) was achieved through the combination of radical ring-opening polymerization (rROP) and reversible addition-fragmentation chain-transfer (RAFT)-living radical polymerization using 2-methylene-1,3-dioxepane (MDO) and vinyl acetate (VAc) monomers in three steps. The chemistry features solvent-free conditions (bulk polymerization) and subsequent deprotection of the acetyl group under mild conditions. With this optimized method, various lengths of poly(VA) and poly(MDO) in poly(VA-b-MDO) were synthesized by controlling the molecular weight distribution of both blocks. The self-assembly of diblock copolymers to nanoparticles with narrow size distribution and subsequent encapsulation of personal care and pharma active ingredients (e.g., curcumin and fenofibrate) and their controlled release were investigated. In vitro release experiments demonstrated that encapsulated nanoparticles release the actives at a slow and consistent rate compared to free actives. Stability experiments showed that the particle size distribution and purity of curcumin and fenofibrate remained unchanged after being exposed to light for ten months. More importantly, our environmental biodegradability studies revealed that the degradable poly(VA-b-MDO) (6b), consisting of 35 mol% poly(VA) and 65 mol% poly (MDO) blocks, achieves a biodegradability of 78% in 28 days. This is owing to the higher mole ratio of degradable polyester units in the polymer backbone as compared to poly(VA-b-MDO) (6c), which contains 64 mol% poly(VA) and 36 mol% poly(MDO) blocks (33% in 28 days). Our results provide insights into the potential applicability of these polymers in personal care and pharmaceutical products where biodegradability is a crucial factor. By developing a sustainable methodology from synthesis to application, our work helps to harness the potential of biodegradable diblock copolymers in the consumer care and medical fields.

Degradation of poly(vinyl sulfone carbonate) in aqueous media

A cyclic vinyl sulfone carbonate monomer has previously been developed and used to prepare degradable polymers through ring-opening copolymerization with cyclic ester monomers such as L-lactide. The resulting polymers have the advantage of being functionalized by reaction of the pendant vinyl sulfone moiety. However, the hydrolytic susceptibility of repeating units of the vinyl sulfone carbonate was never examined. Herein, we demonstrate that block copolymers prepared with this monomer and using methoxy poly(ethylene glycol) and 4-arm poly(ethylene glycol) as initiators are readily hydrolysable in micelle form in pH 7.4 phosphate buffer, whereas non-water soluble poly(vinyl sulfone carbonate) is resistant to hydrolysis, exhibiting little mass loss over 32 weeks. A degradation mechanism was proposed for the block copolymer micelles wherein the backbone carbonate linkage is susceptible to nucleophile attack by a hydroxyl ion due to the metal ion coordinating with the pendant thioether-vinyl sulfone group allowing access of hydroxyl ions to the carbonyl carbon of the carbonate group. The non-water soluble poly(vinyl sulfone carbonate) is only very slowly hydrolyzed due to restricted water access to the polymer backbone. Further, the block copolymers remained hydrolytically degradable following reaction of the pendant vinyl sulfone. These findings should prove useful for the broader application of this monomer in developing functionalized biodegradable polymers.