PLCL/SF/NGF nerve conduit loaded with RGD-TA-PPY hydrogel promotes regeneration of sciatic nerve defects in rats through PI3K/AKT signalling pathways.

Peripheral nerve defect are common clinical problem caused by trauma or other diseases, often leading to the loss of sensory and motor function in patients. Autologous nerve transplantation has been the gold standard for repairing peripheral nerve defects, but its clinical application is limited due to insufficient donor tissue. In recent years, the application of tissue engineering methods to synthesize nerve conduits for treating peripheral nerve defect has become a current research focus. This study introduces a novel approach for treating peripheral nerve defects using a tissue-engineered PLCL/SF/NGF@TA-PPy-RGD conduit. The conduit was fabricated by combining electrospun PLCL/SF with an NGF-loaded conductive TA-PPy-RGD gel. The gel, synthesized from RGD-modified tannic acid (TA) and polypyrrole (PPy), provides growth anchor points for nerve cells. In vitro results showed that this hybrid conduit could enhance PC12 cell proliferation, migration, and reduce apoptosis under oxidative stress. Furthermore, the conduit activated the PI3K/AKT signalling pathway in PC12 cells. In a rat model of sciatic nerve defect, the PLCL/SF/NGF@TA-PPy-RGD conduit significantly improved motor function, gastrocnemius muscle function, and myelin sheath axon thickness, comparable to autologous nerve transplantation. It also promoted angiogenesis around the nerve defect. This study suggests that PLCL/SF/NGF@TA-PPy-RGD conduits provide a conducive environment for nerve regeneration, offering a new strategy for peripheral nerve defect treatment, this study provided theoretical basis and new strategies for the research and treatment of peripheral nerve defect.

Structural Consequences of Introducing Bioactive Domains to Designer ß-Sheet Peptide Self-Assemblies.

We applied solid- and solution-state nuclear magnetic resonance spectroscopy to examine the structure of multidomain peptides composed of self-assembling ß-sheet domains linked to bioactive domains. Bioactive domains can be selected to stimulate specific biological responses (e.g., via receptor binding), while the ß-sheets provide the desirable nanoscale properties. Although previous work has established the efficacy of multidomain peptides, molecular-level characterization is lacking. The bioactive domains are intended to remain solvent-accessible without being incorporated into the ß-sheet structure. We tested for three possible anticipated molecular-level consequences of introducing bioactive domains to ß-sheet-forming peptides: (1) the bioactive domain has no effect on the self-assembling peptide structure; (2) the bioactive domain is incorporated into the ß-sheet nanofiber; and (3) the bioactive domain interferes with self-assembly such that nanofibers are not formed. The peptides involved in this study incorporated self-assembling domains based on the (SL)6 motif and bioactive domains including a VEGF-A mimic (QK), an IGF-mimic (IGF-1c), and a de novo SARS-CoV-2 binding peptide (SBP3). We observed all three of the anticipated outcomes from our examination of peptides, illustrating the unintended structural effects that could adversely affect the desired biofunctionality and biomaterial properties of the resulting peptide hydrogel. This work is the first attempt to evaluate the structural effects of incorporating bioactive domains into a set of peptides unified by a similar self-assembling peptide domain. These structural insights reveal unmet challenges in the design of highly tunable bioactive self-assembling peptide hydrogels.

Thin-Film Composite Membrane Compaction: Exploring the Interplay among Support Compressive Modulus, Structural Characteristics, and Overall Transport Efficiency.

Water scarcity has driven the demand for water production from unconventional sources and the reuse of industrial wastewater. Pressure-driven membranes, notably thin-film composite (TFC) membranes, stand as energy-efficient alternatives to the water scarcity challenge and various wastewater treatments. While pressure drives solvent movement, it concurrently triggers membrane compaction and flux deterioration. This necessitates a profound comprehension of the intricate interplay among compressive modulus, structural properties, and transport efficacy amid the compaction process. In this study, we present an all-encompassing compaction model for TFC membranes, applying authentic structural and mechanical variables, achieved by coupling viscoelasticity with Monte Carlo flux calculations based on the resistance-in-series model. Through validation against experimental data for multiple commercial membranes, we evaluated the influence of diverse physical parameters. We find that support polymers with a higher compressive modulus (lower compliance), supports with higher densities of "finger-like" pores, and "sponge-like" pores with optimum void fractions will be preferred to mitigate compaction. More importantly, we uncover a trade-off correlation between steady-state permeability and the modulus for identical support polymers displaying varying porosities. This model holds the potential as a valuable guide in shaping the design and optimization for further TFC applications and extending its utility to biological scaffolds and hydrogels with thin-film coatings in tissue engineering.

Preoperative vascular surgery model using a single polymer tough hydrogel with controllable elastic moduli.

Materials used in organ mimics for medial simulation and education require tissue-like softness, toughness, and hydration to give clinicians and students accurate tactile feedback. However, there is a lack of materials that satisfy these requirements. Herein, we demonstrate that a stretchable and tough polyacrylamide hydrogel is useful to build organ mimics that match softness, crack growth resistance, and interstitial water of real organs. Varying the acrylamide concentration between 29 or 62% w/w with a molar ratio between cross-linker and acrylamide of 1 : 10 800 resulted in a fracture energy around ∼2000 J m-2. More interestingly, this tough gel permitted variation of the elastic modulus from 8 to 62 kPa, which matches the softness of brain to vascular and muscle tissue. According to the rheological frequency sweep, the tough polyacrylamide hydrogels had a greatly decreased number of flow units, indicating that when deformed, stress was dispersed over a greater area. We propose that such molecular dissipation results from the increased number of entangled polymers between distant covalent cross-links. The gel was able to undergo various manipulations including stretching, puncture, delivery through a syringe tip, and suturing, thus enabling the use of the gel as a blood vessel model for microsurgery simulation.

A new natural drying method for food packaging and preservation using biopolymer-based dehydration film.

A new method for the drying of beef and chicken meats at low temperatures (4 °C) was developed by using a composite film based on sodium carboxymethyl cellulose-gum Arabic (SG) with anthocyanins from Cinnamomum camphora fruit peel (ANC.P, 0, 1, 1.5 and 2%). After incorporation of ANC.P into SG, the physicochemical properties, morphological characteristics, melting, molecular, antioxidant and antimicrobial properties of the resulting dehydration films were improved. Film-dried beef and chicken slices showed higher values of dehydration ratio on day 6 (54.58% and 72.06%, respectively) compared with the control samples without film (4.55% and 7.04%, respectively). Results showed that SG-ANC.P film-dried meats exhibited more stable pH and color, higher rehydration rate, better sensory quality and microbial growth inhibition compared with SG film-dried samples and control samples, in which control samples showed the highest total viable count values (6.02 and 5.16 log CFU/mL for beef and chicken, respectively) during storage.

3D Printing of Biocompatible Shape-Memory Double Network Hydrogels.

Shape-memory hydrogels can be fixed to an arbitrary temporary shape and recover their permanent shape under appropriate stimulus conditions. Their shape-memory behavior and biocompatible mechanical and chemical properties impart them with many biomedical applications. However, like most hydrogels, traditional shape-memory hydrogels suffer from intrinsic brittleness due to the network inhomogeneity and high water content. In the past, the double network (DN) scheme has been proved a robust method to improve the mechanical performance of hydrogels. Although 3D printing of DN hydrogels has been realized before, 3D printable shape-memory DN hydrogels have not been achieved so far. In this work, we propose a one-pot method for printing a biocompatible shape-memory DN hydrogel via fused deposition method. The two networks incorporated to the hydrogel ink are polyacrylamide (PAAm) and gelatin. The PAAm network is covalently cross-linked and responsible for the permanent shape, while the gelatin network has thermoreversible cross-links and responsible for fixing the temporary shape. The DN hydrogel shows 3 to 7 times higher fracture toughness than a single network gelatin or PAAm hydrogel and can be fixed to 300% of its original length under tension and 10% of its original thickness under compression. The ink compositions are tuned for optimal printing quality and shape-memory performance. The robust mechanical integrity and dramatic shape transformation capability of the 3D-printed shape-memory DN hydrogel will open-up new potential applications in transformative medical robots and self-deployable devices.

Tunability of liquid-infused silicone materials for biointerfaces.

The ability to control the properties of bio-inspired liquid-infused surfaces is of interest in a wide range of applications. Liquid layers created using oil-infused polydimethylsiloxane elastomers offer a potentially simple way of accomplishing this goal through the adjustment of parameters such as curing agent ratio and oil viscosity. In this work, the effect of tuning these compositional parameters on the properties of the infused polymer are investigated, including infusion dynamics, stiffness, longevity in the face of continuous liquid overlayer removal, and resistance to bacterial adhesion. It is found that that curing agent concentration appears to have the greatest impact on the functionality of the system, with a lower base-to-curing agent ratio resulting in both increased longevity and improved resistance to adhesion by Escherichia coli. A demonstration of how these findings may be implemented to introduce patterned wettability to the surface of the infused polymers is presented by controlling the spatial arrangement of bacteria. These results demonstrate a new degree of control over immobilized liquid layers and will facilitate their use in future applications.

Degradable and biocompatible hydrogels bearing a hindered urea bond.

A hindered urea bond (HUB), recently reported as a new type of dynamic chemical bond, can be facilely constructed by mixing an isocyanate and a hindered amine. Here, we report the use of the HUB in the design of degradable hydrogel materials for applications of stem cell encapsulation and delivery. Polyethyleneglycol (PEG) diamine was end-capped with a HUB and an allyl group in a one-pot synthesis. The resulting polymer was cross-linked to form a hydrogel under UV with the addition of a 4-arm PEG thiol and a photoinitiator. The degradation properties of the hydrogels were confirmed with NMR, GPC, weight loss, and protein release studies. We found that the degradation kinetics is dependent on the size of the N-substituents, and the one with the tert-butyl group shows complete degradation within 2 days. The new hydrogel materials were also demonstrated to be biocompatible with hMSCs, and the cell release kinetics can be facilely tuned over 5 days.

Micropatterned Hydrogel Surface with High-Aspect-Ratio Features for Cell Guidance and Tissue Growth.

Surface topography has been introduced as a new tool to coordinate cell selection, growth, morphology, and differentiation. The materials explored so far for making such structural surfaces are mostly rigid and impermeable. Hydrogel, on the other hand, was proved a better synthetic media for cell culture because of its biocompatibility, softness, and high permeability. Herein, we fabricated a poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel substrate with high-aspect-ratio surface microfeatures. Such structural surface could effectively guide the orientation and shape of human mesenchymal stem cells (HMSCs). Notably, on the flat hydrogel surface, cells rounded up, whereas on the microplate patterned hydrogel surface, cells elongated and aligned along the direction parallel to the plates. The microplates were 2 µm thick, 20 µm tall, and 10-50 µm wide. The interplate spacing was 5-15 µm, and the intercolumn spacing was 5 µm. The elongation of cell body was more pronounced on the patterns with narrower interplate spacing and wider plates. The cells behaved like soft solid. The competition between surface energy and elastic energy defined the shape of the cells on the structured surfaces. The soft permeable hydrogel scaffold with surface structures was also demonstrated as being viable for long-term cell culture, and could be used to generate interconnected tissues with finely tuned cell morphology and alignment across a few centimeter sizes.