Understanding the Interfacial Adhesion between Natural Silk and Polycaprolactone for Fabrication of Continuous Silk Biocomposites

The poor interfacial adhesion between silk fiber and polyester species remains a critical problem for the optimal mechanical performance of silk-reinforced polyester composites. Here, we investigated in quantitative terms the interfacial properties between natural silk fibers and polycaprolactone (PCL) at nano-, micro-, and macroscales and fabricated continuous silk-PCL composite filaments by melt extrusion and drawing processing of PCL melt at 100, 120, and 140 °C. Bombyx mori (Bm) silk, Antheraea pernyi (Ap) silk, and polyamide6 (PA6) fiber were compared to the composite with PCL. The Ap silk exhibited the highest surface energy, the best wettability, and the largest interfacial shear strength (IFSS) with PCL. The silk-PCL composite from the 120 °C melt processing displayed the highest tensile modulus, implying an optimal temperature for interfacial adhesion. The Raman imaging technique revealed in detail the nature of the physical fusion of the interface phase in these silk- and polyamide-reinforced PCL composites. This work is intended to lay a foundation for the design and processing of robust composites from continuous silk fibers and bioresorbable polyesters for potential structural biomaterials.

Preparation of a novel regenerated silk fibroin-based hydrogel for extrusion bioprinting

Three-dimensional (3D) bioprinting technology, allowing rapid prototyping and personalized customization, has received much attention in recent years, while regenerated silk fibroin (RSF) has also been widely investigated for its excellent biocompatibility, processibility, and comprehensive mechanical properties. However, due to the difficulty in curing RSF aqueous solution and the tendency of conformational transition of RSF chains under shearing, it is rather complicated to fabricate RSF-based materials with high mechanical strength through extrusion bioprinting. To solve this problem, a printable hydrogel with thixotropy was prepared from regenerated silk fibroin with high-molecular-weight (HMWRSF) combined with a small amount of hydroxypropyl methylcellulose (HPMC) in urea containing aqueous solution. It was found that the introduction of urea could not only vary the solid content of the hydrogel to benefit the mechanical properties of the 3D-bioprinted pre-cured hydrogels or 3D-bioprinted sponges, but also expand the "printable window" of this system. Indeed, the printability and rheological properties could be modulated by varying the solid content, the heating time, the urea/HMWRSF weight ratio, etc. Moreover, the microstructure of nanospheres stacked in these lyophilized 3D-bioprinted sponges was interesting to observe, which indicated the existence of microhydrogels and both "the reversible network" and "the irreversible network" in this HMWRSF-based pre-cured hydrogel. Like other HMWRSF materials fabricated in other ways, these 3D-bioprinted HMWRSF-based sponges exhibited good cytocompatibility for dental pulp mesenchymal stem cells. This work may inspire the design of functional HMWRSF-based materials by regulating the relationship between structure and properties.

Overall survival in the OlympiA phase III trial of adjuvant olaparib in patients with germline pathogenic variants in BRCA1/2 and high risk, early breast cancer

BACKGROUND

The randomized, double-blind OlympiA trial compared 1 year of the oral poly(adenosine diphosphate-ribose) polymerase inhibitor, olaparib, to matching placebo as adjuvant therapy for patients with pathogenic or likely pathogenic variants in germline BRCA1 or BRCA2 (gBRCA1/2pv) and high-risk, human epidermal growth factor receptor 2-negative, early breast cancer (EBC). The first pre-specified interim analysis (IA) previously demonstrated statistically significant improvement in invasive disease-free survival (IDFS) and distant disease-free survival (DDFS). The olaparib group had fewer deaths than the placebo group, but the difference did not reach statistical significance for overall survival (OS). We now report the pre-specified second IA of OS with updates of IDFS, DDFS, and safety.

PATIENTS AND METHODS

One thousand eight hundred and thirty-six patients were randomly assigned to olaparib or placebo following (neo)adjuvant chemotherapy, surgery, and radiation therapy if indicated. Endocrine therapy was given concurrently with study medication for hormone receptor-positive cancers. Statistical significance for OS at this IA required P < 0.015.

RESULTS

With a median follow-up of 3.5 years, the second IA of OS demonstrated significant improvement in the olaparib group relative to the placebo group [hazard ratio 0.68; 98.5% confidence interval (CI) 0.47-0.97; P = 0.009]. Four-year OS was 89.8% in the olaparib group and 86.4% in the placebo group (Δ 3.4%, 95% CI -0.1% to 6.8%). Four-year IDFS for the olaparib group versus placebo group was 82.7% versus 75.4% (Δ 7.3%, 95% CI 3.0% to 11.5%) and 4-year DDFS was 86.5% versus 79.1% (Δ 7.4%, 95% CI 3.6% to 11.3%), respectively. Subset analyses for OS, IDFS, and DDFS demonstrated benefit across major subgroups. No new safety signals were identified including no new cases of acute myeloid leukemia or myelodysplastic syndrome.

CONCLUSION

With 3.5 years of median follow-up, OlympiA demonstrates statistically significant improvement in OS with adjuvant olaparib compared with placebo for gBRCA1/2pv-associated EBC and maintained improvements in the previously reported, statistically significant endpoints of IDFS and DDFS with no new safety signals.

Final results of the global and Asia cohorts of KAMILLA, a phase IIIB safety trial of trastuzumab emtansine in patients with HER2-positive advanced breast cancer

Background

KAMILLA is a single-arm safety study of trastuzumab emtansine (T-DM1) in patients with human epidermal growth factor receptor 2 (HER2)-positive advanced breast cancer (BC; NCT01702571). We report the final analysis of cohort 2 (Asia) within the context of published cohort 1 (Global) findings.

Methods

Patients had HER2-positive, locally advanced, or metastatic BC progressing after chemotherapy and anti-HER2 therapy or ≤6 months after adjuvant therapy. The primary objective was to further evaluate T-DM1 (3.6 mg/kg, administered intravenously every 3 weeks) safety/tolerability, including the following adverse events of primary interest (AEPIs): grade ≥3 AEPIs (hepatic events, allergic reactions, thrombocytopenia, hemorrhage events), all grade ≥3 treatment-related AEs, and all-grade pneumonitis.

Results

KAMILLA enrolled 2185 patients (cohort 1, n = 2003; cohort 2, n = 182) as of 31 July 2019. Of these, 2002 and 181 per cohort were treated and included in the safety population. Approximately 70% of patients had two or more previous treatment lines in the metastatic setting. Median T-DM1 exposure was 5.6 and 5.0 months per cohort; median follow-up was 20.6 and 15.1 months. The overall AEPI rate was higher in cohort 2 (93/181; 51.4%) versus cohort 1 (462/2002; 23.1%), mostly driven by a higher grade ≥3 thrombocytopenia rate in cohort 2. In cohort 2, grade ≥3 thrombocytopenia was not associated with grade ≥3 hemorrhagic events and most (128/138) fully resolved. Grade ≥3 treatment-related AEPI rates were 18.4% (cohort 1) and 48.6% (cohort 2), the latter mainly due to thrombocytopenia. Any-grade pneumonitis rates were 1.0% and 2.2%. No new safety signals were identified. Median (95% confidence interval) progression-free survival was 6.8 months (5.8-7.6 months) and 5.7 months (5.5-7.0 months) in cohorts 1 and 2, respectively; median overall survival was 27.2 months (25.5-28.7 months) and 29.5 months (21.1 months to non-estimable). In both cohorts, median progression-free survival and overall survival decreased with increasing prior therapy lines.

Conclusions

Cohort 2 results aligned with previous findings in Asian patients, supporting the manageable safety profile and use of T-DM1 in advanced BC.

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KAMILLA safety results for cohorts 1 (global; n = 2002) and 2 (Asia; n = 181) aligned with results from prior T-DM1 mBC trials.

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The overall rate of adverse events of primary interest (AEPIs) was higher in cohort 2 (51.4%) versus cohort 1 (23.1%).

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The higher AEPI rate was mostly due to a higher grade ≥3 thrombocytopenia event rate in cohort 2, most of which resolved.

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Median PFS and OS were similar for both cohorts, and decreased with increasing prior therapy lines.

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The manageable safety profile and efficacy of T-DM1 further support its favorable benefit/risk balance.

Proteinic Artificial Skin with Molecularly Encoded Coloration

An ability to integrate adaptive coloration and tissue-like compositions, structures, as well as mechanical properties, and so forth into a material remains elusive. To address this problem, this work presents a solution whereby these features were integrated into a proteinic artificial skin through biomimetic design. In this artificial skin, silk fibroin was used to mimic the structural framework of the cytoskeleton due to its unique molecular network structure and outstanding and tunable mechanical properties. Meanwhile, a thermochromic filamentous network consisting of C₂₅-GAGAGAGY amphiphilic peptides was designed to mimic the functional tracks in the cytoskeleton, enabling its temperature-adaptive coloration ability. The interconnected linkage between the structural frame and functional units makes this artificial skin have stable structures, mechanical properties, and functions. The whole protein composition also makes this artificial skin essentially different from other existing color-tunable artificial skins, which are a combination of organic and inorganic compounds. Furthermore, because the protein composition is compatible with a range of dyes, the chromatic gamut of adaptive coloration of the developed artificial skin can be further expanded by color fusion. With the further inclusion of other functional units, such as photothermal and magnetothermal nanoparticles, the thermochromism of the artificial skin could be realized through sun exposure and alternating magnetic field modulation. With this diversity in color change pathways and stimulation mode, as well as the environmental friendliness of the material used, these artificial proteinic skins have promising applications as sensors in physiological monitoring, food preservation, and anti-counterfeiting.

Protein-inorganic hybrid porous scaffolds for bone tissue engineering

Porous scaffolds hold promise in the treatment of bone defects for bone tissue engineering due to their interconnected porous structure and suitable mechanical properties. Herein, LAPONITE® (LAP), which is able to promote osteogenic differentiation, was introduced into regenerated silk fibroin (RSF) porous scaffolds. Due to hydrogen bonding and electrostatic interactions between RSF and LAP, RSF/LAP 3D porous scaffolds were successfully prepared. The pore size, porosity, and mechanical properties of the RSF/LAP 3D porous scaffolds were modulated during the preparation process. Evaluation of the proliferation of bone marrow mesenchymal stem cells (BMSCs) on the RSF/LAP 3D porous scaffolds in vitro indicated that the addition of LAP improved the adhesion and proliferation of cells. Additionally, alkaline phosphatase activity and osteospecific gene expression analysis showed that the RSF/LAP 3D porous scaffolds enhanced the osteogenic differentiation of BMSCs compared to the pristine RSF porous scaffolds, especially with a higher LAP content. The subcutaneous implantation of the RSF/LAP 3D porous scaffolds in rats demonstrated good histocompatibility in vivo. Therefore, RSF/LAP 3D porous scaffolds with good biocompatibility and biodegradability have good application prospects in the field of bone tissue engineering.

Silk-Based Electrochemical Sensor for the Detection of Glucose in Sweat

The development of reliable glucose sensors for noninvasive monitoring is highly desirable and essential for diabetes detection. As a testing sample, sweat is voluminous and is easy to collect compared to blood. However, the application of sweat glucose sensors is generally limited because of their low stability and sensitivity compared to commercial glucometers. In this manuscript, a silk nanofibril (SNF)/reduced graphene oxide (RGO)/glucose oxidase (GOx) composite was developed as the working electrode of the sweat glucose sensor. The SNF/RGO/GOx composite was prepared via a facile two-step process, which involved the self-assembly of SNF from silk fibroin while reducing graphene oxide to RGO and immobilizing GOx on SNF. The SNF/RGO/GOx glucose sensor exhibited a low limit of detection (300 nM) and high sensitivity (18.0 μA/mM) in the sweat glucose range, covering both healthy people and diabetic patients (0-100 μM). Moreover, the SNF/RGO/GOx glucose sensors showed a long stability for at least 4 weeks. Finally, the SNF/RGO/GOx glucose sensor was applied to test the actual sweat samples from two volunteers and two sweating methods (by dry sauna and exercise). The results indicate the glucose data tested by the SNF/RGO/GOx glucose sensor were reliable, which correlated well to the data obtained from the commercial glucometer. Therefore, the SNF/RGO/GOx glucose sensor developed in this study may have a great potential for glucose control in personalized healthcare monitoring and chronic disease management.

Reconstruction of an orbital defect in rabbits using a silk fibroin-bone microparticle complex

OBJECTIVE

To construct a silk fibroin-bone microparticle composite based on a porous silk fibroin membrane and to study its feasibility as a material to reconstruct an orbital bone defect.

METHODS

A 3D porous silk fibroin membrane scaffold was constructed with a defined pore size and incorporated with bone microparticles from a New Zealand rabbit orbital bone defect. The silk fibroin-bone microparticle composite was then implanted into the orbital bone defect to promote osteogenesis along the surface of the porous silk fibroin membrane. The feasibility of constructing an ideal orbital defect repair material and the silk fibroin-bone micronucleus complex was evaluated by animal experiments, molecular biology, histomorphology, imaging, raw molecular mechanisms, and the biological behavior of the material in vivo.

RESULTS

The silk fibroin-bone microparticle composite promotes angiogenesis and osteogenesis to repair bone defects in vivo. Moreover, SF (silk fibroin)/BD (bone dust) complex promotes osteogenesis and angiogenesis by activating FGF2 (Fibroblast Growth Factor 2) and SF scaffolds can bind and restore FGF2.

CONCLUSION

Silk fibroin is biocompatible and the silk fibroin-bone microparticle complex successfully repaired orbital bone defects. Additionally, fibroblast growth factor expression around or within the remaining incompletely degraded silk fibroin materials was observed in vivo.

Mechanically and electrically biocompatible hydrogel ionotronic fibers for fabricating structurally stable implants and enabling noncontact physioelectrical modulation

Narrowing the mechanical and electrical mismatch between tissue and implantable microelectronics is essential for reducing immune responses and modulating physioelectrical signals. Nevertheless, the design of such implantable microelectronics remains a challenge due to the limited availability of suitable materials. Here, the fabrication of an electrically and mechanically biocompatible alginate hydrogel ionotronic fiber (AHIF) is reported, which is constructed by combing ionic chelation-assisted wet-spinning and mechanical training. The synergistic effects of these two processes allow the alginate to form a highly-oriented nanofibril and molecular network, with a hierarchical structure highly similar to that of natural fibers. These favourable structural features endow AHIF with tissue-mimicking mechanical characteristics, such as self-stiffening and soft tissue-like mechanical properties. In addition, tissue-like chemical components, i.e., biomacromolecules, Ca²⁺ ions, and water, endow AHIF with properties including biocompatibility and tissue-matching conductivity. These advantages bring light to the application of AHIFs in electrically-conductive implantable devices. As a prototype, an AHIF is designed to perform physioelectrical modulation through noncontact electromagnetic induction. Through experimental and machine learning optimizations, physioelectrical-like signals generated by the AHIF are used to identify the geometry and tension state of the implanted device in the body. Such an intelligent AHIF system has promising application prospects in bioelectronics, IntelliSense, and human-machine interactions.

Enhancement of the Mechanical Properties of Poly(lactic acid)/Epoxidized Soybean Oil Blends by the Addition of 3-Aminophenylboronic Acid

Here, the high-strength, high-ductility blends of poly(lactic acid) (PLA) with epoxidized soybean oil (ESO) and 3-aminophenylboronic acid (APBA) were successfully prepared via a melt-bending method. The effects of APBA addition on the mechanical and thermal properties, morphologies, and crystallization behavior of the blends were investigated. The results showed that the addition of APBA endowed the PLA/ESO/APBA blends with a good balance of strength and toughness. The yield strength of the PLA/ESO/APBA (90:10:3) blend was 70 MPa, which was 25% higher than that of the corresponding PLA/ESO blend without APBA (56 MPa), while its elongation at break reached 160%, which is greatly superior to that of pure PLA (6.5%). Scanning electron microscopy images showed that the incorporation of APBA significantly improved the compatibility between PLA and ESO, while gel permeation chromatography and rheological analysis suggested the occurrence of complex reactions between the three constituents, which improved the compatibility between PLA and ESO and enhanced the mechanical properties of the blends. Hence, the PLA/ESO/APBA blends possess great potential for application in the manufacture of environmentally friendly degradable plastics.

Robust Silk Protein Hydrogels Made by a Facile One-Step Method and Their Multiple Applications

Silk fibroin is a natural polymer that has various material forms and wide applications. Hydrogel is one of the most attractive silk materials because of its hydrophilicity, biocompatibility, and flexibility. However, its applications are still quite limited because they have a complicated preparation process and/or low mechanical strength. Herein, a simple way to prepare tough silk fibroin hydrogels via a solvent-exchange method is introduced. The degummed silk fiber was directly dissolved in a calcium chloride/formic acid solution and then water was used to replace the solvent. The silk fibroin hydrogel that was obtained using this facile method exhibited even better mechanical properties than most silk fibroin hydrogels that have been reported in the literature. Also, the silk fibroin hydrogel maintained biocompatibility that was as good as that prepared via other methods. Finally, the possibility of using this regenerated silk fibroin hydrogel as a multi-functional platform (such as a catalyst carrier, photothermal agent, and underwater adhesive) has been discussed. Therefore, such a natural, sustainable, robust, and good biocompatible silk fibroin hydrogel that is prepared by an improved method may have great potential for further applications.

Non-metallic T2-MRI agents based on conjugated polymers

Developing non-metallic contrast agents of clinically applied magnetic resonance imaging (MRI) is an alternative strategy to reduce the toxicity of heavy metal elements in current MRI agents. These non-metallic MRI agents usually generate contrasts by unpaired electrons, which are prone to be deactivated by in vivo radical scavenging pathways. Since the unpaired electrons in conjugated polymers exhibit satisfying stability for in vivo imaging, developing conjugated polymers based MRI agents may solve the in vivo stability problem of current non-metallic agents. However, MRI-active properties have not been reported in existing conjugated polymers yet. Herein we report on MRI-active conjugated polymer nanoparticles based on polypyrrole (PPy), which can be used for in vivo imaging. Our method not only introduce a kind of non-metallic MRI agents but extends the applications of conjugated polymers from optical imagings to MRI.

The toxicity of heavy metals for MRI contrast agents is an issue. Here, the authors report on the development of conjugated polymers nanoparticles based on paramagnetic polypyrrole to generate T2 MRI contrast effects by changing the interactions between polarons and water protons.

Animal protein-plant protein composite nanospheres for dual-drug loading and synergistic cancer therapy

The co-delivery of multiple drugs using one drug carrier is a viable strategy to optimize drug dosage and reduce the side effects in chemotherapy. Herein, a hydrophilic animal protein (silk fibroin) and a hydrophobic plant protein (zein) were selected for preparing a composite drug carrier. Adapting our previously developed method for the preparation of regenerated silk fibroin (RSF) nanospheres, we prepared RSF/zein nanospheres that displayed an interesting structure including a single central hole. The particle size of the RSF/zein nanospheres was regulated from 150 to 460 nm by varying the preparation conditions, implying that such a drug carrier is suitable for both intravenous administration and lymphatic chemotherapy. Two anti-cancer drugs with different target sites, paclitaxel (PTX) and curcumin (CUR), were selected for the preparation of dual-drug-loaded CUR/PTX@RSF/zein nanospheres. Both drugs achieved a high loading capacity in the RSF/zein nanospheres, i.e., 8.2% for PTX and 12.1% for CUR. Subsequently, the encapsulated PTX and CUR were released from the RSF/zein nanospheres in a sustained manner for at least 7 days. Importantly, these dual-drug-loaded RSF/zein nanospheres exhibited a considerable synergistic therapeutic effect, showing more efficient suppression of in vitro cancer cell growth than free PTX or CUR, a combination of free PTX and CUR, or single-drug-loaded nanospheres. Therefore, the CUR/PTX@RSF/zein nanospheres developed in this study hold great potential for combination chemotherapy in future clinical applications.

Acquiring structural and mechanical information of a fibrous network through deep learning

Fibrous networks play an essential role in the structure and properties of a variety of biological and engineered materials, such as cytoskeletons, protein filament-based hydrogels, and entangled or crosslinked polymer chains. Therefore, insight into the structural features of these fibrous networks and their constituent filaments is critical for discovering the structure-property-function relationships of these material systems. In this paper, a fibrous network-deep learning system (FN-DLS) is established to extract fibrous network structure information from atomic force microscopy images. FN-DLS accurately assesses the structural and mechanical characteristics of fibrous networks, such as contour length, number of nodes, persistence length, mesh size and fractal dimension. As an open-source system, FN-DLS is expected to serve a vast community of scientists working on very diverse disciplines and pave the way for new approaches on the study of biological and synthetic polymer and filament networks found in current applied and fundamental sciences.

Abstract ES5-1: Genomic and transcriptomic landscape of TNBC

Triple-negative breast cancer (TNBC) is highly heterogeneous. Due to the limited number of TNBCs that have been analyzed, molecular events driving subtypes and prognosis are not firmly established, and little is known regarding TNBC in non-Caucasian patients. Our findings advance the understanding of TNBC subtypes, subdivide the established transcriptome-based subtypes in search of more targeted therapeutic strategies, and offer potential insights to guide subtype-specific therapy. We further conducted a phase Ib/II subtyping-based and genomic biomarker guided umbrella trial to evaluate the efficacy of these targets. Objective response rate (ORR) of these 69 refractory metastatic TNBC patients was 29.0%, while the ORR of arm C (immunotherapy) was 52.6%. Still, genomic and transcriptomic-based target mining do not solve all the problems in TNBC treatment, for example the poor treatment efficacy in luminal androgen receptor (LAR) and basal-like immune-suppressed (BLIS) subtypes. Increasing the dimensions of omics to look for potential therapeutic targets would hopefully solve this problem.

Citation Format: Z Shao. Genomic and transcriptomic landscape of TNBC [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr ES5-1.

Increased risk of diabetes in cancer survivors: a pooled analysis of 13 population-based cohort studies

BACKGROUND

Diabetes is considered as an established risk factor for cancer development. However, the link between diabetes among cancer survivors remains inconclusive. The hypothesis of this study was to assess the hazard ratio (HR) of incidence of diabetes in cancer survivors compared with the HR in the general population.

PATIENTS AND METHODS

A comprehensive literature search was performed in PubMed, Embase, and the Cochrane Library from database inception to 15 December 2020 for population-based cohort studies. Summary effect estimates were combined using random-effects models. We also performed subgroup analyses to test sources of heterogeneity and the stability of the results stratified by various study and participant characteristics.

RESULTS

Thirteen population-based cohort studies involving 1 686 595 participants were analyzed. The HR for the development of diabetes in cancer survivors was 1.39 [95% confidence interval (CI) 1.29-1.50; I2 = 82.3%; P < 0.001] compared with that in noncancer controls, among which survivors of hematological, gynecologic, breast, colorectal and urinary tract cancer (all P < 0.05) showed consistent significant results, whereas no significant increased risk was observed for other cancer types. The effects were more prominent in populations of shorter cancer survival duration (<1 year) (HR 2.09, 95% CI 1.32-3.32; P = 0.009). Moreover, cancer survivors with a longer follow-up period (>10 years) had a relatively higher risk of diabetes (HR 1.54, 95% CI 1.34-1.77) than those with a shorter follow-up period.

CONCLUSIONS

In this large pooled analysis of population-based cohorts, evidence supports the hypothesis that the risk of developing diabetes is increased in cancer survivors compared with the general population. We should interpret the results with caution for considerable interstudy heterogeneity. However, health policy makers should take this as a challenge for the early prevention and effective intervention of diabetes.

Poly(vinyl alcohol) Hydrogels with Integrated Toughness, Conductivity, and Freezing Tolerance Based on Ionic Liquid/Water Binary Solvent Systems

In recent years, ionic conductive hydrogels have shown great potential for application in flexible sensors, energy storage devices, and actuators. However, developing facile and effective methods for fabricating such hydrogels remains a great challenge, especially for hydrogels that retain their properties in extreme environmental conditions, such as at subzero temperatures or storage in open-air conditions. Herein, a water-miscible ionic liquid (IL), such as 1-ethyl-3-methylimidazolium acetate (EMImAc), was introduced to form an IL/water binary solvent system for poly(vinyl alcohol) (PVA) to create ionic conductive PVA hydrogels. The physically crosslinked PVA/EMImAc/H₂O hydrogels showed better mechanical properties and transparency than the traditional PVA hydrogel prepared by the freeze-thaw method due to the formation of homogeneous and small PVA microcrystals in the EMImAc/H₂O binary solvent system. More importantly, the PVA/EMImAc/H₂O hydrogel exhibited significant anti-freezing and water-retaining properties because of the presence of the IL. The hydrogels remained flexible and conductive at temperatures as low as -50 °C and retained more than 90% of their weight after storage in open-air conditions for 2 weeks. In addition, the thermal stability of the hydrogel could be increased to 95 °C through the addition of Mg(II) ions. A multimodal sensor based on the PVA/EMImAc/H₂O/Mg(II) hydrogel showed high sensitivity and a quick response to changes in pressure, strain, and temperature, with both long-term stability and a wide working temperature range. This study may open a new route for the fabrication of functional PVA-based hydrogel electrolytes and provide a practical pathway for their use in multifunctional electronic and sensory device applications.

Crystallization, Mechanical, and Antimicrobial Properties of Diallyl Cyanuric Derivative-Grafted Polypropylene

A functional N-halamine precursor with double bonds, 1-3-diallyl-s-triazine-2,4,6-trione (DTT), was synthesized and grafted onto polypropylene using dicumyl peroxide (DCP) as an initiator via melt blending at 200 °C. The DTT content grafted onto the polypropylene (PP) backbone was depended on both DTT and DCP concentrations in feed. The crystallization temperature of PP increased from 116 °C (neat PP) to 123 °C (10% DTT) with the increasing DTT content. Meanwhile, the crystallization rate and relative crystallinity of PP were significantly increased after introduction of the N-halamine precursor. Moreover, the incorporation of DTT had partial compensation for the decreasing mechanical properties of polypropylene, which resulted from degradation. When the amount of added DTT reached up to 5%, the chlorinated DTT-modified PP sheets were able to kill 105-6 cfu/mL Escherichia coli (CMCC 44103) and Staphylococcus aureus (ATCC 6538) within 10 min. The DTT-modified PP with the regenerating antibacterial property may have great potential for application in packaging, filters, and hygienic products.

Synthesis of novel multi-hydroxyl N-halamine precursors based on barbituric acid and their applications in antibacterial poly(ethylene terephthalate) (PET) materials

Two novel multi-hydroxyl N-halamine precursors were successfully synthesized in a green and facile way via Knoevenagel condensation reaction between barbituric acid and an aldehyde (citral or cinnamaldehyde), followed by a hydroxylation reaction with hydrogen peroxide. 1H-NMR and FT-IR spectral analyses confirmed their formation. Through the melt-blending process, the multi-hydroxyl derivatives of barbituric acid were introduced via transesterification into poly(ethylene terephthalate) (PET) at 265 °C in a rheometer. The crystallization behaviors of the modified PET samples were investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and polarized optical microscopy (POM) analyses. The results showed that the crystallization temperature and crystallization rate of PET were significantly improved upon the introduction of the precursor. Meanwhile, the relative crystallinity of the modified PET samples increased with an increase in the dosage of the N-halamine precursor. After the treatment with sodium hypochlorite solution, the PET surfaces modified with N-halamine derivatives would impart powerful antibacterial properties and achieve 100% killing of Staphylococcus aureus (ATCC 6538) and Escherichia coli (CMCC44103) cells within 30 min. Therefore, the multi-hydroxyl N-halamine precursors exhibit great potential as bifunctional additives (nucleating and antibacterial agents) in the manufacturing of functional PET materials.

Mechanism of Mechanical Training-Induced Self-Reinforced Viscoelastic Behavior of Highly Hydrated Silk Materials

Mechanical training is an operation where a sample is cyclically stretched in a solvent. It is accepted as an effective strategy to strengthen and stiffen the highly hydrated silk materials (HHSMs). However, the detailed reinforcement mechanism of the process still remains to be understood. Herein, this process is studied by the integration of experimental characterization and theoretical analysis. The results from time-resolved Fourier transform infrared spectroscopy and real-time birefringent characterization reveal that the silk proteins rapidly formed a molecular cross-linking network (MCN) during the mechanical training. The cross-links were the β-sheet nanocrystals generated from the conformation transition of silk proteins. With the progress in mechanical training, these MCNs gradually remodeled to a highly oriented molecular network structure. The final structure of the silk proteins in HHSMs is highly similar to the structural organization of silk proteins in the natural animal silk. The training process significantly improved the mechanical strength and modulus of the material. With regards to the dynamic behavior of conformation transition and MCN orientation, the structural evaluation of silk proteins during mechanical training was divided into three distinct stages, namely, the MCN-forming stage, MCN-orienting stage, and oriented-MCN stage. Such division is in complete agreement with the three-stage viscoelastic behavior observed in the cyclic loading and unloading tests. Hence, a five-parameter viscoelastic model has been established to elucidate the structure-property relationship of these three stages. This work improves in-depth understanding of the fundamental issues related to structure-property relationships of HHSMs and thus provides inspiration and guidance in the design of soft silk functional materials.