Hydrolytic Degradation Research Articles

Investigation of chemical, physical and mechanical properties of hybrid chitosan-silica based coatings for aluminium substrate

This paper describes the development and characterization of eco-friendly hybrid coatings using chitosan and tetraethoxysilane (TEOS) through sol-gel processing onto aluminium substrates.Firstly, we investigated the impact of curing temperatures and the addition of a coupling agent (VTMS) on various physical and chemical properties to determine the optimal composition, to achieve crack-free and uniform films.Chemical and physical properties were assessed via FTIR spectroscopy and SEM imaging, while surface wettability was analyzed through water contact angle measurements, and hydrolitic degradation tests were also performed. Since the mechanical strength of bonding is important for protective coatings, the mechanical characterization of optimized films was conducted by pin-on-disk and scratch tests to understand their elastic-plastic and adhesive behaviour. Finally, the antibacterial properties were also studied and discussed.The results indicate that an annealing temperature of 100 °C and the incorporation of vinyltrimethoxysilane (VTMS) as a coupling agent are essential for producing homogeneous, stable coatings with excellent hydrolytic degradation resistance. The addition of VTMS effectively addresses common challenges associated with hybrid sol-gel coatings, including cracking, porosity, and poor substrate adhesion. Subsequent investigations revealed that both the presence and concentration of chitosan within the hybrid sol-gel coatings significantly enhance mechanical resistance, water resistance, and friction reduction. A strong correlation between increased coating hydrophobicity and decreased coefficient of friction confirms the intrinsic lubricity of chitosan-silica sol-gel coatings. These coatings also exhibit antibacterial properties compared to both the uncoated aluminium substrate and pure silane coatings. Overall, these findings underscore the multifunctional benefits of chitosan-containing hybrid coatings, positioning them as a promising sustainable, transparent, self-lubricating, and water-resistant coating solution for anodized aluminium substrates.

Accelerated hydrolytic degradation of poly(l-lactide) by blending with poly(ether-block-amide)

A continuing challenge in the most common biodegradable polyester of poly(l-lactide) (PLLA) is to improve the degradation rate in the environment, though it has been widely used in packaging and medical applications. In this study, PLLA/poly(ether-block-amide) (PEBA) blends are prepared by melt blending to investigate the effect of PEBA component on the phase morphology, thermal behavior, mechanical properties, and hydrolytic degradation of the blends. The incorporation of PEBA component is beneficial to the improved toughness and increased water absorption of the blends, and accelerated hydrolytic degradation of PLLA. The blend exhibits the optimal mechanical and hydrolytic degradation properties when the blend mass ratio of PLLA/PEBA is 80/20. The toughness of the blend is increased by 390 % compared to that of pure PLLA. After being hydrolyzed at 58 °C for 240 h, the water absorption, the mass loss and the decrease of molecular weight of the blend is increased by 138 %, 160 % and 40 %, respectively, indicating faster hydrolytic degradation rate of the blend than that of pure PLLA. Furthermore, the accelerated hydrolytic degradation mechanism of PLLA in the blend is revealed. The amorphous region of PLLA is hydrolyzed initially at the phase interface of the blend, and subsequently the crystalline structure of PLLA is degraded. The hydrolysis process causes a change in the relative content of crystalline regions in the system, resulting in an increase in crystallinity of PLLA first and then decrease. These findings provide a new strategy for the design of novel degradable PLLA materials for practical applications.

(Bio)degradable Biochar Composites of PLA/P(3HB-co-4HB) Commercial Blend for Sustainable Future-Study on Degradation and Electrostatic Properties.

Interesting alternatives to expensive biodegradable polymers are their composites with natural fillers. The addition of biochar to a blend of poly(lactic acid) (PLA) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) was studied, and the resulting materials were evaluated for their properties and changes during degradation. Introducing biochar as a filler brought a noticeable improvement in electrostatic properties. Surface resistivity decreased from 3.80 × 1012 for the sample without biochar to 1.32 × 1012 for the sample with 30% filler content. Degradation tests revealed distinct differences in the degradation profile for composites due to the presence of filler. Composites with a lower biochar content displayed curling crack edges during hydrolytic degradation, and when the filler content reached 20 wt%, PLA loss accelerated. This study suggests that biochar-based composites have potential to be used as sustainable materials with improved properties.

Hydrolysis kinetics of self-degradable diverters for well stimulation

Self-degradable diverters have gained increased popularity in well stimulation as an environmentally friendly and robust fluid diversion technology. As of now, limited data and conflicting information exist in the literature regarding the hydrolytic degradation rates of diverters under field-representative conditions, and knowing these rates is crucial for optimizing well stimulation designs. In this work, we systematically measured the degradation rates of commercial self-degradable diverters in aqueous solutions spanning a wide solution pH range of 0.3–13.6 and a wide temperature range of 60–110 °C. We first demonstrated that existing bottle degradation test protocols might return misleading results due to the alteration of solution pH by degradation products, and we developed a more reliable experimental protocol using buffer solutions instead. Using this procedure, we found that as the solution pH increased, the hydrolysis rate of diverters first decreased and then increased, with a minimal degradation rate at around pH = 4. Elevated temperatures yielded faster hydrolysis. The collected kinetic data fit reasonably well to a published kinetic model that was originally developed for pure polylactic acid in deionized water, with an R2 value over 0.98 for all pH and temperature conditions. This comparison suggests that the model can be more widely applied to describe the degradation kinetics of commercial diverters over broad temperature and pH ranges. The test protocol, experimental data, and kinetic analysis in this work provide important guidance on improving the efficiency of fluid diversion and well stimulation operations.

Degradation of high concentrations of commercial polylactide packaging on food waste composting in pilot-scale test

The increasing use of synthetic biodegradable polymers, such as aliphatic polyesters, has led to a greater need to understand their behavior in an end-of-life scenario as food packaging materials. The aim of this work was to investigate the effect on composting of high to 10 wt% concentration of commercial polylactide packaging in food waste during a 98-day pilot-scale test. Members of the genera Bacillus, Geobacillus, Caldibacillus, Compostibacillus, Novibacillus, Planifilum and Aeribacillus accounted for 77 % of the bacterial community at the initial stage. Significant fragmentation of the polylactide packaging was observed after 14 days, and the appearance of low-molecular weight (approximately 5.4 kDa) hydrolytic degradation products led to an increase in biodiversity and a prolongation of the thermophilic stage by 12 days. The results obtained show the possibility of efficient disposal of food waste with high concentration of polylactide packaging under industrial composting conditions.

Biobased rubber toughened poly(lactic acid) blend for sustainable packaging films: The role of optical purity of poly(lactic acid)

AbstractThis study investigates the novel effect of poly(lactic acid) (PLA) optical purity on PLA/liquid natural rubber (LNR) blend films fabricated by solution casting. An investigation was conducted to examine how different levels of PLA optical purity affect the mechanical, structural, morphological, thermal, and barrier properties of PLA/LNR films. Infrared spectroscopy analysis revealed that the D‐isomer content of PLA significantly affected the chemical interactions between the LNR and PLA. The favorable chemical interaction between the LNR and PLA with a high D‐isomer content also increased the elongation at break by 300%. Morphological investigations proved that the chemical interaction also improved the dispersion and reduced the size of the LNR droplets formed in the PLA matrix. Notably, while low D‐isomer PLA blends showed decreased crystallinity (Xc) upon LNR addition, high D‐isomer PLA blends exhibited increased Xc by 460%, leading to a 42% increase in oxygen transmission rate. Additionally, hydrolytic degradation of high D‐isomer PLA increased by 259% with increasing LNR content. Overall, optical purity of PLA plays an important role in determining the properties of PLA blends.

Monothiolactide, a New Monomer for the Synthesis of Recyclable, Alternating Ester-Thioester Polymers.

Aliphatic polyesters and polythioesters are very interesting alternatives for current fossil-based and degradation-resistant plastics, due to their high (bio)degradability and (chemical) recyclability potential. Two important examples include polylactide (PLD), currently leading the synthetic bioplastics market, and its sulfur analog polythiolactide (PTLD). Both polymers can be made by ring-opening polymerization (ROP) of their corresponding (thio)dilactones, lactide (LD) and thiolactide (TLD) respectively. In this work, the benefits of esters and thioesters were combined in one material by the successful catalytic synthesis and ROP of monothiolactide (MTL), an unprecedented monomer containing half a LD and half a TLD structural unit. MTL can be obtained by a simple direct condensation of biobased lactic acid and thiolactic acid aided by Brønsted acid catalysis. The novel, but simple monomer showed to be easily polymerized with triethylamine to materials containing alternating lactic and thiolactic ester units with a very high molar mass. The lower stability of MTL (vs. TLD) resulted in improved ROP thermodynamics, while also fast and controllable polymerization kinetics were observed. The new polymers feature a good chemical recycling and hydrolytic degradation potential with important improvements compared to PTLD and PLD. Finally, a successful co-polymerization with commercial LD was shown, paving the way towards industrialization.

Antibiotic Removal by Three Promising Microalgae Strains: Biotic, Abiotic Routes, and Response Mechanisms

Microalgae represent an alternative to conventional wastewater treatment, potentially improving antibiotic removal and offering a solution to combat the spread of antimicrobial resistance. Through batch assays, this study investigates the routes for antibiotic removal using three strains (Chlamydomonas acidophila, Auxhenochlorella protothecoides and Tetradesmus obliquus). Using mixtures of ciprofloxacin, clarithromycin, erythromycin, metronidazole, ofloxacin, sulfamethoxazole, and trimethoprim at concentrations simulating wastewater composition, it also assesses antibiotic effects on microalgae physiology. The three strains primarily removed antibiotics through rapid biosorption, achieving up to 91.5% removal for specific ones like ciprofloxacin. T. obliquus and C. acidophila showed efficacy, with total removals of 37.2% and 49.3%, respectively. Over time, A. protothecoides demonstrated the highest active removal efficiency, eliminating 22.1% of total antibiotics, with a notable 67.6% removal for sulfamethoxazole. Abiotic degradation through hydrolysis and photolysis contributed to ciprofloxacin, ofloxacin, clarithromycin, and erythromycin removal (34.7% to 96.7%), showing pH-dependent photolysis. However, algae induced a shading effect, reducing the photolytic and hydrolytic degradation of specific antibiotics. T. obliquus and C. acidophila were inhibited by antibiotics, whereas A. protothecoides showed a 30.6% growth rate increase. The stimulatory effect was also observed for the nutrient removal, with A. protothecoides showing a 46.6% increase in ammonium removal and a 44.8% increase in phosphate removal with antibiotics. Additionally, antioxidant activities remained stable, except for a notable increase in peroxidase activity for A. protothecoides and T. obliquus. The study confirms efficient antibiotic removal and stimulatory responses in the three algal strains, indicating their potential for wastewater treatment and combating antimicrobial resistance.

Generation of Microplastics from Biodegradable Packaging Films Based on PLA, PBS and Their Blend in Freshwater and Seawater.

Biodegradable polymers and their blends have been advised as an eco-sustainable solution; however, the generation of microplastics (MPs) from their degradation in aquatic environments is still not fully grasped. In this study, we investigated the formation of bio-microplastics (BMPs) and the changes in the physicochemical properties of blown packaging films based on polylactic acid (PLA), polybutylene succinate (PBS) and a PBS/PLA 70/30 wt% blend after degradation in different aquatic media. The tests were carried out in two temperature/light conditions to simulate degradation in either warm water, under sunlight exposure (named Warm and Light-W&L), and cold deep water (named Cold and Dark-C&D). The pH changes in the aqueous environments were evaluated, while the formed BMPs were analyzed for their size and shape alongside with variations in polymer crystallinity, surface and mechanical properties. In W&L conditions, for all the films, the hydrolytic degradation led to the reorganization of the polymer crystalline phases, strong embrittlement and an increase in hydrophilicity. The PBS/PLA 70/30 blend exhibited increased resistance to degradation with respect to the neat PLA and PBS films. In C&D conditions, no microparticles were observed up to 12 weeks of degradation.

Analysis of omarigliptin forced degradation products by ultra-fast liquid chromatography, mass spectrometry, and in vitro toxicity assay.

Omarigliptin (OMG) is an antidiabetic drug indicated for the treatment of type 2 diabetes mellitus. Forced degradation studies are practical experiments to evaluate the stability of drugs and to establish degradation profiles. Herein, we present the investigation of the degradation products (DPs) of OMG formed under various stress conditions. OMG was subjected to hydrolytic (alkaline and acidic), oxidative, thermal, and photolytic forced degradation. A stability-indicating ultra-fast liquid chromatography method was applied to separate and quantify OMG and its DPs. Five DPs were adequately separated and detected in less than 6 min, while other published methods detected four DPs. MS was applied to identify and obtain information on the structural elucidation of the DPs. Three m/z DPs confirmed previously published research, and two novel DPs were described in this paper. The toxicity of OMG and its DPs were investigated for the first time using in vitro cytotoxicity assays, and the sample under oxidative conditions presented significant cytotoxicity. Based on the results from forced degradation studies, OMG was found to be labile to hydrolysis, oxidation, photolytic, and thermal stress conditions. The results of this study contribute to the quality control and stability profile of OMG.

Sequentially crosslinked collagen‐based hydrogel to form a semi‐interpenetrating network for enhanced stability to hydrolytic degradation and electrochemical properties

Sequentially crosslinked collagen‐based hydrogel to form a semi‐interpenetrating network for enhanced stability to hydrolytic degradation and electrochemical properties

Development of polyvinyl alcohol nanofiber scaffolds loaded with flaxseed extract for bone regeneration: phytochemicals, cell proliferation, adhesion, and osteogenic gene expression.

Introduction: Bone tissue engineering seeks innovative materials that support cell growth and regeneration. Electrospun nanofibers, with their high surface area and tunable properties, serve as promising scaffolds. This study explores the incorporation of flaxseed extract, rich in polyphenolic compounds, into polyvinyl alcohol (PVA) nanofibers to improve their application in bone tissue engineering. Methods: High-performance liquid chromatography (HPLC) identified ten key compounds in flaxseed extract, including polyphenolic acids and flavonoids. PVA nanofibers were fabricated with 30 wt.% flaxseed extract (P70/E30) via electrospinning. We optimized characteristics like diameter, hydrophilicity, swelling behavior, and hydrolytic degradation. MG-63 osteoblast cultures were used to assess scaffold efficacy through cell adhesion, proliferation, viability (MTT assay), and differentiation. RT-qPCR measured expression of osteogenic genes RUNX2, COL1A1, and OCN. Results: Flaxseed extract increased nanofiber diameter from 252nm (pure PVA) to 435nm (P70/E30). P70/E30 nanofibers showed higher cell viability (102.6% vs. 74.5% for pure PVA), although adhesion decreased (151 vs. 206 cells/section). Notably, P70/E30 enhanced osteoblast differentiation, significantly upregulating RUNX2, COL1A1, and OCN genes. Discussion: Flaxseed extract incorporation into PVA nanofibers enhances bone tissue engineering by boosting osteoblast proliferation and differentiation, despite reduced adhesion. These properties suggest P70/E30's potential for regenerative medicine, emphasizing scaffold optimization for biomedical applications.

Acid Hydrolytic Degradation Profiling of Ezetimibe: Identification, Isolation, and Structural Elucidation of Its Degradants

ABSTRACTEzetimibe (EZE) is a dyslipidemic agent used to treat hyperlipidemia along with statins and diet changes. To ascertain the drug's degradation profile, stress tests were conducted on it in accordance with International Council for Harmonization recommendations. An ultrahigh‐performance liquid chromatography–mass spectrometry method was developed and validated for the identification and quantification of EZE and its degradants. Using preparative high‐performance liquid chromatography, all impurities were isolated, and their structures were characterized thoroughly using advanced spectral techniques. The drug was relatively stable in basic, peroxide, photolytic, and thermal conditions; however, five degradants were observed in acid degradation. Among the five degradants, three degradation products eluted as Peak‐1, Peak‐2, and Peak‐3 which were found to be novel impurities that were not reported previously. However, the remaining two impurities were identified as Peak‐4 and Peak‐5, despite the insufficient information available. The present study has focused on the isolation of these five acid degradation products and the structural confirmation of these degradants by highly efficient spectral techniques. Moreover, the possible degradation mechanism of the azetidinone ring in the presence of acid has been explained, which might be helpful in determining the quality and purity of EZE and similar pharmaceutical compounds.

Developing double-crosslinking 3D printed hydrogels for bone tissue engineering

Bone defects are one of the main causes of disability worldwide. Due to the disadvantages associated with autografts, the latest advances have been focused on tissue regeneration approaches that use injectable hydrogels or 3D printed hydrogel-based structures that could refill appropriately the bone gap area without the need for external fixatives, leading to bone formation in the long term. Injectable hydrogels could be applied in extrusion-based 3D printing as inks; in this sense, double-crosslinking hydrogels appear as ideal candidates. In this work, injectable and printable double crosslinkable hydrogels based on oxidized xanthan gum (XGox) and methacrylate polyaspartylhydrazide (PAHy-MA) were produced. The formation of dynamic hydrazone bonds, occurring between aldehyde groups on the polysaccharide backbone and hydrazine moieties of PAHy-MA, induced an instant gelation, conferring, also, injectability and self-healing properties to the hydrogels. The presence of methacrylic moieties on the synthetic polymer allowed further crosslinking upon UV irradiation that stabilized the hydrogel shape and mitigated its susceptibility to hydrolytic degradation. Obtained hydrogels showed pseudoplastic behaviour and good recovery of viscoelastic properties over time. The physicochemical and rheological characterization highlighted increased stability and higher viscoelastic moduli after photo-crosslinking. The hydrogels also showed good printability, cytocompatibility and the early formation of a bone-like matrix when osteosarcoma-derived cells (MG-63) were cultured in the scaffolds for 21 days, with an increased collagen I deposition, mineralization and the expression of characteristic osteogenic markers.

Intrinsic Permanent Shape Reconfigurable Semicrystalline Biopolyester Thermoset.

Catalyst-free, volatile organic solvent (VOC)-free synthesis of biobased cross-linked polymers is an important sustainable feature in polyesterification. To date, these polyesters have been extensively studied for their fundamental sustainability across various uses. The ultimate potential sustainability for these materials, however, is constrained to static structural parts due to their intractable rigid three-dimensional (3D) network. Here, we reveal intrinsic dynamic exchangeable bonds within this type of cross-linked semicrystalline network, poly(1,8-octanediol-co-1,12-docanedioate-co-citrate) (PODDC), enabling permanent shape reconfigurability. Annealing at slightly above melting-transition temperature (Tm) allows for shape reconfigurability up to nine times, comparable in performance to the existing bond-exchange systems. No reagents are involved from synthesis to shape reconfiguration, suggesting an exciting feature exhibited by this sustainable cross-linked material without the need for further chemical modification. We further extend this benefit of reconfigurability to enable flexible shape design in a smart shape-memory polymer (SMP), showing it as one of its potential applications. After its applications, it can undergo hydrolytic degradation. We envision that such multifaceted sustainability for the material will attract interest in environmentally friendly applications such as fabricating external part of soft robots and shape-morphing devices with reduced environmental impact.

Biodegradable and biocompatible nonisocyanate polyurethanes synthesized from bio-derived precursors

Despite the enormous use of polyurethanes (PUs) in multiple aspects of modern lifestyle, the industrial scale manufacturing of PUs uses toxic chemicals like isocyanates, phosgene till today. In addition, the non-biodegradability and non-biocompatibility of PUs and their debris are serious cause of concerns for the environment. To deal with these challenges, in the current work, a new approach is reported in which bio-derived non-isocyanate polyurethanes were synthesized by exploiting viable amino acid-based diamines and biscyclocarbonates from sebacoyl chloride and diglycerol derivatives in a readily doable process. The newly designed polyhydroxyurethanes (PHUs) exhibited remarkable biodegradability and biocompatibility (cell viability) in comparison with commercial diamine based PHUs. A series of PHUs were synthesized in bulk and solvent free green synthetic route by polycondensing library of amino acids (such as glycine, alanine, valine, and isoleucine etc.) based diamines consisting of varying alkyl chain lengths and biscyclocarbonates like sebacic biscyclocarbonate and diglycerol biscyclocarbonate etc. All the synthesized PHUs were thoroughly characterised by IR, NMR and HRMS spectroscopic techniques. The impact of chain length and molecular structure of the synthesized PHUs were also evaluated using DSC, TGA, SEC, water contact angle measurements and hydrolytic degradation studies. The molar masses of the PHUs obtained from the SEC analysis are in the range of ∼17,000–24,000 Da. The current study demonstrated that amino acids is one of the major degradation products and are biocompatible in in-vitro conditions. The PHUs and their degradable products showed excellent cell viability when studied in HEK293T cells that were carried out using microgram to milligram concentration of PHUs. The outcome of this work in comparison to conventional PHUs and polyurethanes clearly demonstrated good biocompatibility and hence drawing attention to potential applications in bio-adhesives, bio-implants, drug delivery, and green coatings etc. in the near future.

An Advanced Solvent for the Caustic-Side Solvent Extraction of Cesium from Nuclear Waste: Comparing Lipophilic Guanidines for Improved Hydrolytic Stability

ABSTRACT An advanced solvent has been developed for application in the extraction of cesium from alkaline nuclear waste. Four lipophilic guanidines have been compared to arrive at a more hydrolysis-resistant suppressor component of the solvent. Plans call for deployment of the Next-Generation Caustic Side-Solvent Extraction (NG-CSSX) process at industrial scale for separation of radioactive Cs-137 from the legacy salt waste stored at the US Department of Energy Savannah River Site (SRS). In the solvent used in NG-CSSX, an alkyl guanidine “suppressor” component facilitates efficient stripping of the loaded cesium from the solvent. However, as typical of guanidine compounds, the suppressor previously used in the NG-CSSX solvent, N,N‘,N’’-tri(3,7-dimethyloctyl)guanidine (TiDG), suffers from hydrolytic degradation under process conditions. Recently, the sterically hindered alkyl guanidine N,N’-dicyclohexyl-N’’-(10-nonadecyl)guanidine (DCNDG) has been found to offer 8 to 44 times greater hydrolysis resistance than TiDG. Here, the process performance characteristics of the NG-CSSX solvent incorporating DCNDG are determined in comparison with TiDG and two other guanidine suppressors. The solvent has been adjusted in density to accommodate use in the SRS Salt Waste Processing Facility and tested under aggressive bench-scale conditions intended to increase plant throughput. Experiments include the effect of ageing at normal and off-normal temperatures of the distribution of Cs+ through the NG-CSSX process, the fate and effects of guanidine degradation products, suppressor capacity, coalescence times for aqueous-solvent dispersions, tendency for emulsification, third-phase formation, and degree of protonation of the guanidine in stripping. While the chosen structures of the four compared guanidines mainly effect differences in stability, subtle differences in other system properties such as emulsion formation and suppressor capacity provide insight into the function of this important solvent component. In comparison with TiDG and two other guanidines, DCNDG provides greatly increased stability while not compromising the excellent functional properties of the NG-CSSX solvent.

Differentiation between Hydrolytic and Thermo-Oxidative Degradation of Poly(lactic acid) and Poly(lactic acid)/Starch Composites in Warm and Humid Environments.

For the application of poly(lactic acid) (PLA) and PLA/starch composites in technical components such as toys, it is essential to know their degradation behavior under relevant application conditions in a hydrothermal environment. For this purpose, composites made from PLA and native potato starch were produced using twin-screw extruders and then processed into test specimens, which were then subjected to various one-week ageing processes with varying temperatures (23, 50, 70, 90 °C) and humidity levels (10, 50, 75, 90%). This was followed by mechanical characterization (tensile test) and identification of degradation using Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), and Nuclear Magnetic Resonance spectroscopy (NMR). With increasing temperature and humidity, there was a clear degradation of the PLA, which could be reduced or slowed down by adding 50 wt.% starch, due to increased crystallinity. Hydrolysis was identified as the main degradation mechanism for PLA and PLA/starch composites, especially above the glass transition temperature, with thermo-oxidative degradation also playing a subordinate role. Both hydrolytic degradation and thermo-oxidative degradation led to a reduction in mechanical properties such as tensile strength.

Intraoral ageing of aligners and attachments: Adverse effects on clinical efficiency and release of biologically-active compounds.

The clinical application of aligners is accompanied by the ageing of the polymer appliances and the attachments used, which may result in inefficiency in reaching the predicted range of tooth movement, and release of compounds and microplastics in the oral cavity as a result of the friction, wear and attrition of the aligner and composite attachment. The purpose of this review is to present the mechanism and effects of in vivo ageing; describe the hydrolytic degradation of aligners and enzymatic degradation of composite attachments; examine the ageing pattern of aligners in vivo, under actual clinical scenarios; and identify a link to the discrepancy between predicted and actual clinical outcome. Lastly, strategies to deal with three potentially critical issues associated with the use of aligners, namely the necessity of weekly renewal, the dissimilar mechanical properties of aligner and attachment resulting in wear and plastic deformation of the aligner, and the development of integuments and biofilms with microbial colonization of the appliance, are discussed.

Enhanced Degradability of Thiol-Ene Composites through the Inclusion of Isosorbide-Based Polycarbonates.

Open reduction internal fixation metal plates and screws remain the established standard-of-care for complex fracture fixation. They, however, have drawbacks such as limited customization, soft-tissue adhesions, and a lack of degradation. Bone cements and composites are being developed as alternative fixation techniques in order to overcome these issues. One such composite is a strong, stiff, and shapeable hydroxyapatite-containing material consisting of 1,3,5-triazine-2,4,6-trione (TATO) monomers, which cures through high energy visible light-induced thiol-ene coupling (TEC) chemistry. Previous human cadaver and in vivo studies have shown that patches of this composite provide sufficient fixation for healing bone fractures; however, the composite lacks degradability. To promote degradation through hydrolysis, new allyl-functionalized isosorbide-based polycarbonates have been added into the composite formulation, and their impact has been evaluated. Three polycarbonates with allyl functionalities, located at the termini (aPC1 and aPC2) or in the backbone (aPC3), were synthesized. Composites containing 1, 3, and 5 wt % of aPCs 1-3 were formulated and evaluated with regard to mechanical properties, water absorption, hydrolytic degradation, and cytotoxicity. Allyl-functionalized polycaprolactone (aPCL) was synthesized and used as a comparison. When integrated into the composite, aPC3 significantly impacted the material's properties, with the 5 wt % aPC3 formulation showing a significant increase in degradation of 469%, relative to the formulation not containing any aPCs after 8 weeks' immersion in PBS, along with a modest decrease in modulus of 28% to 4.01 (0.3) GPa. Osteosyntheses combining the aPC3 3 and 5 wt % formulations with screws on synthetic bones with ostectomies matched or outperformed the ones made with the previously studied neat composite with regard to bending stiffness and strength in four-point monotonic bending before and after immersion in PBS. The favorable mechanical properties, increased degradation, and nontoxic characteristics of the materials present aPC3 as a promising additive for the TATO composite formulations. This combination resulted in stiff composites with long-term degradation that are suitable for bone fracture repair.