Polymer Patches Research Articles

Digital Image Correlation Measurement of the Deformation and Failure in PBX Brazilian Discs Reinforced with CFRP Patches

AbstractPolymer‐bonded explosive (PBX) is a mechanical weak link in weapons systems. PBX is susceptible to cracking owing to its brittle nature, which seriously threatens the security and reliability of the weapons system. In this work, a novel strengthening method making use of a carbon fibre reinforced polymer (CFRP) patch was adopted to enhance the mechanical performance of the PBX. Brazilian compression tests were conducted on the unreinforced, locally reinforced, and fully reinforced PBX discs to elucidate the strengthening mechanism of the patch. Digital image correlation was employed to characterise the deformation and failure processes of the discs during the full testing period. The results showed that failure of the PBX was caused by initiation and extension of the deformation that localises within the regions near the loading positions. The CFRP patches provided the benefits of load transfer and deformation confinement, which alleviated stress concentration in the disc. Consequently, collapse of the patched discs was delayed, and the load‐carrying ability was improved. The findings of this study may deepen our understanding of PBX failure behaviours, and further the performance optimisation of weapons systems.

Formulation and evaluation of transdermal patches of an Antifungal drug

Background: Bioavailability of Terbinafine HCl tablets as a result of the first-pass metabolism is approximately 40%.A single oral dose of 250mg Terbinafine results in a peak plasma concentration (Cmax) of 0.83μg/ml within 2h of administration. The absorption of half-life is 0.8h and the distribution half- life is 4.6 h. This Originates the Transdermal drug delivery as an alternative route of administration for such drugs which can bypass the hepatic first-pass metabolism. Objective: The objective of the present study was to compare the release effect of Terbinafine HCl from different polymeric (natural and synthetic) patches prepared using different permeation enhancers (natural and synthetic) and varying concentrations. The best polymer and permeation enhancer was selected based on the release of the drug from the patches. Materials and Methods: Polymers such as HPMC, Chitosan, and Glycerin was used as a plasticizer. Enhancers used were Eucalyptus oil and Dimethyl Sulfoxide. Transdermal patches were prepared by using the solvent casting technique. FTIR was studied to estimate the incompatibility. Patches were evaluated for physicochemical Characteristics like thickness, weight variation, folding endurance, moisture loss, moisture absorption, drug content, and In-vitro diffusion studies. Results: The results obtained showed no physical-chemical incompatibility between the drug and the polymers. HPMC was found to be a suitable polymer compared to Chitosan in preparation of transdermal patches. From the evaluation of patches, DMSO appears acceptable permeation enhancer compared to Eucalyptus oil as a natural origin. F19 containing 20% of DMSO was considered as the best formulation for the transdermal delivery of TH. Conclusion: Transdermal patches were successfully prepared for TH and their evaluation studies of each dosage form revealed that topically applied TH patch possess immense potential to control the release rate of medicament to improve the bioavailability as well as patient compliance.

Antibiofilm Effects of Macrolide Loaded Microneedle Patches: Prospects in Healing Infected Wounds.

The aim of this study was to fabricate polymeric microneedles, loaded with macrolides (erythromycin, azithromycin), using hyaluronic acid and polyvinyl pyrollidone. These microneedles were fabricated using a vacuum micromolding technique. The integrity of the microneedle patches was studied by recording their morphologic features, folding endurance, swelling and micro-piercing. Physicochemical characteristics were studied by differential scanning calorimetry, thermogravimetric analysis and fourier transform infrared spectroscopy. In-vitro drug release, antibiofilm and effect of microneedle patch on wound healing were also studied to confirm the efficacy of the formulations. Formulated patches displayed acceptable folding endurance (>100) and uniform distribution of microneedles (10 × 10) that can penetrate parafilm. Differential scanning calorimetry results depict a decrease in the crystallinity of macrolides following their incorporation in to a polymer matrix. Percentage release of azithromycin and erythromycin from the polymeric patch formulations (over 30min) was 90% and 63% respectively. Broadly, the zone of bacterial growth inhibition follows the same order for Staphylococcus aureus, Escherichia coli and Salmonella enterica. After 5days of treatment with azithromycin patches, the wound healing was complete and skin structure (e.g. hair follicles and dermis) was regenerated. It was concluded that azithromycin loaded microneedle patches can be used to treat biofilms in the infected wounds.

Self-assembly of a layered two-dimensional molecularly woven fabric.

Fabrics-materials consisting of layers of woven fibres-are some of the most important materials in everyday life1. Previous nanoscale weaves2-16 include isotropic crystalline covalent organic frameworks12-14 that feature rigid helical strands interlaced in all three dimensions, rather than the two-dimensional17,18 layers of flexible woven strands that give conventional textiles their characteristic flexibility, thinness, anisotropic strength and porosity. A supramolecular two-dimensional kagome weave15 and a single-layer, surface-supported, interwoven two-dimensional polymer16 have also been reported. The direct, bottom-up assembly of molecular building blocks into linear organic polymer chains woven in two dimensions has been proposed on a number of occasions19-23, but has not previously been achieved. Here we demonstrate that by using an anion and metal ion template, woven molecular 'tiles' can be tessellated into a material consisting of alternating aliphatic and aromatic segmented polymer strands, interwoven within discrete layers. Connections between slowly precipitating pre-woven grids, followed by the removal of the ion template, result in a wholly organic molecular material that forms as stacks and clusters of thin sheets-each sheet up to hundreds of micrometres long and wide but only about four nanometres thick-in which warp and weft single-chain polymer strands remain associated through periodic mechanical entanglements within each sheet. Atomic force microscopy and scanning electron microscopy show clusters and, occasionally, isolated individual sheets that, following demetallation, have slid apart from others with which they were stacked during the tessellation and polymerization process. The layered two-dimensional molecularly woven material has long-range order, is birefringent, is twice as stiff as the constituent linear polymer, and delaminates and tears along well-defined lines in the manner of a macroscopic textile. When incorporated into a polymer-supported membrane, it acts as a net, slowing the passage of large ions while letting smaller ions through.

In situ manipulation of van der Waals heterostructures for twistronics.

In van der Waals heterostructures, electronic bands of two-dimensional (2D) materials, their nontrivial topology, and electron-electron interactions can be markedly changed by a moiré pattern induced by twist angles between different layers. This process is referred to as twistronics, where the tuning of twist angle can be realized through mechanical manipulation of 2D materials. Here, we demonstrate an experimental technique that can achieve in situ dynamical rotation and manipulation of 2D materials in van der Waals heterostructures. Using this technique, we fabricated heterostructures where graphene is perfectly aligned with both top and bottom encapsulating layers of hexagonal boron nitride. Our technique enables twisted 2D material systems in one single stack with dynamically tunable optical, mechanical, and electronic properties.

Synthesis and Characterization of Polyaniline-Chitosan Patches with Enhanced Stability in Physiological Conditions.

Electroconductive polymeric patches are being developed in the hope to interface with the electroresponsive tissues. For these constructs, conjugated polymers are considered as conductive components for their electroactive nature. Conversely, the clinical applications of these conductive polymeric patches are limited due to their short operational time, a decrease in their electroactivity occurs with the passage of time. This paper reports on the polymerization of aniline on prefabricated chitosan films on microscopic glass slides in the presence of sodium phytate. The strong chelation among sodium phytate, aniline and chitosan led to the formation of electoconductive polymeric patch. We assume that immobilization of sodium phytate in the polymeric patch helps to prevent electric deterioration, extend its electronic stability and reduce sheet resistance. The patch oxidized after three weeks (21 days) of incubation in phosphate buffer (pH 7.4 as physiological medium). This feasible fabrication technique set the foundation to design electronically stable, conjugated polymer-based patches, by providing a robust system of conduction that could be used with electroactive tissues such as cardiac muscles at the interface.

Design and fabrication of polycaprolactone/gelatin composite scaffolds for diaphragmatic muscle reconstruction.

Diaphragmatic wall defects caused by congenital disorders or disease remain a major challenge for physicians worldwide. Polymeric patches have been extensively explored within research laboratories and the clinic for soft tissue and diaphragm reconstruction. However, patch usage may be associated with allergic reaction, infection, granulation, and recurrence of the hernia. In this study, we designed and fabricated a porous scaffold using a combination of 3D printing and freeze-drying techniques. A 3D printed polycaprolactone (PCL) mesh was used to reinforcegelatin scaffolds, representing an advantage over previously reported examples since it provides mechanical strength and flexibility. In vitro studies showed that adherent cells were anchorage-dependent and grew as a monolayer attached to the scaffolds. Microscopic observations indicated better cell attachments for the scaffolds with higher gelatin content as compared with the PCL control samples. Tensile testing demonstrated the mechanical strength of samples was significantly greater than adult diaphragm tissue. The biocompatibility of the specimens was investigated in vivo using a subcutaneous implantation method in Bagg albino adult mice for 20 days, with the results indicating superior cellular behavior and attachment on scaffolds containing gelatin in comparison to pure PCL scaffolds, suggesting that the porous PCL/gelatin scaffolds have potential as biodegradable and flexible constructs for diaphragm reconstruction.

DNA Self-Assembly Mediated by Programmable Soft-Patchy Interactions.

Adding shape and interaction anisotropy to a colloidal particle offers exquisitely tunable routes to engineer a rich assortment of complex-architected structures. Inspired by the hierarchical self-assembly concept with block copolymers and DNA liquid crystals and exploiting the unique assembly properties of DNA, we report here the construction and self-assembly of DNA-based soft-patchy anisotropic particles with a high degree of modularity in the system's design. By programmable positioning of thermoresponsive polymeric patches on the backbone of a stiff DNA duplex with linear and star-shaped architecture, we reversibly drive the DNA from a disordered ensemble to a diverse array of long-range ordered multidimensional nanostructures with tunable lattice spacing, ranging from lamellar to bicontinuous double-gyroid and double-diamond cubic morphologies, through the alteration of temperature. Our results demonstrate that the proposed hierarchical self-assembly strategy can be applied to any kind of DNA nanoarchitecture, highlighting the design principles for integration of self-assembly concepts from the physics of liquid crystals, block copolymers, and patchy colloids into the continuously growing interdisciplinary research field of structural DNA nanotechnology.

Intraoral slow-releasing polymeric patches containing sodium fluoride and chlorhexidine: Development and evaluation

Intraoral slow-releasing polymeric patches containing sodium fluoride and chlorhexidine: Development and evaluation

Growth factor loaded in situ photocrosslinkable poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/gelatin methacryloyl hybrid patch for diabetic wound healing

Management of chronic diabetic ulcers remains as a major challenge in healthcare which requires extensive multidisciplinary approaches to ensure wound protection, management of excess wound exudates and promoting healing. Developing wound healing patches that can act as a protective barrier and support healing is highly needed to manage chronic diabetic ulcers. In order to boost the wound healing potential of patch material, bioactive agents such as growth factors can be used. Porous membranes made of nanofibers generated using electrospinning have potential for application as wound coverage matrices. However, electrospun membranes produced from several biodegradable polymers are hydrophobic and cannot manage the excess exudates produced by chronic wounds. Gelatin-methacryloyl (GelMA) hydrogels absorb excess exudates and provide an optimal biological environment for the healing wound. Epidermal growth factor (EGF) promotes cell migration, angiogenesis and overall wound healing. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) membranes provide microbial, thermal and mechanical barrier properties to the wound healing patch. Herein, we developed a biodegradable polymeric patch based on the combination of mechanically stable electrospun PHBV, GelMA hydrogel and EGF for promoting diabetic wound healing. In vitro and in vivo studies were carried out to evaluate the effect of developed patches on cell proliferation, cell migration, angiogenesis and wound healing. Our results showed that EGF loaded patches can promote the migration and proliferation of multiple types of cells (keratinocytes, fibroblasts and endothelial cells) and enhance angiogenesis. In situ development of the patch and subsequent in vivo wound healing study in diabetic rats showed that EGF loaded patches provide rapid healing compared to control wounds. Interestingly, 100 ng EGF per cm2 of the patches was enough to provide favourable cellular response, angiogenesis and rapid diabetic wound healing. Overall results indicate that EGF loaded PHBV-GelMA hybrid patch could be a promising approach to promote diabetic wound healing.

A novel treatment strategy for preterm birth: Intra-vaginal progesterone-loaded fibrous patches.

Progesterone-loaded poly(lactic) acid fibrous polymeric patches were produced using electrospinning and pressurized gyration for intra-vaginal application to prevent preterm birth. The patches were intravaginally inserted into rats in the final week of their pregnancy, equivalent to the third trimester of human pregnancy. Maintenance tocolysis with progesterone-loaded patches was elucidated by recording the contractile response of uterine smooth muscle to noradrenaline in pregnant rats. Both progesterone-loaded patches indicated similar results from release and thermal studies, however, patches obtained by electrospinning had smaller average diameters and more uniform dispersion compared to pressurized gyration. Patches obtained by pressurized gyration had better results in production yield and tensile strength than electrospinning; thereby pressurized gyration is better suited for scaled-up production. The patches did not affect cell attachment, viability, and proliferation on Vero cells negatively. Consequently, progesterone-loaded patches are a novel and successful treatment strategy for preventing preterm birth.

Effects of composite patching on cyclic crack tip deformation of cracked pinned metallic joints

ABSTRACT Advanced composite patching has been used to rehabilitate cracked structures. In this work, the effects of bonded carbon fiber-reinforced polymer (CFRP) patch on reducing the crack tip driving forces, namely J-integral, crack tip plastic zone, and crack tip opening displacement, of a crack emanating from a fastener hole, under cyclic loading, was studied. The number of CFRP layers, the orientation of the fiber with respect to the direction of the path of the crack, and the pinned joint configurations are the main parameters studied in this research. A three-dimensional finite element model was employed in this work, using ABAQUS. The double-sided CFRP patch-repaired pinned joint is simulated in order to study crack retardation behavior under two different combinations of loading, i.e. Modes I and II. The results of the study show that the stiffness of the cracked pinned joint is increased by using a CFRP composite patch. The reduction in the J-integral ranged from 25% to 45%, depending on the length of the crack and the mode of the crack. Moreover, the monotonic and cyclic crack tip plastic zones decreased by 5% to 45%, depending on the length of the crack.

Abstract 396: 3d-Engineered Aligned Co-axial Nanofibrous Cardiac Patch for Drug Screening and Cardiac Repair Applications

Introduction: Recent studies have demonstrated the great potential of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) for testing the efficacy of various cardiac drugs. Additionally, studies have shown that the hiPSC-CMs grown in a 3D environment express better physiological characteristics than 2D cultures. The convergence of polymeric cardiac patch technology with hiPSC-CMs has opened up innovative ways for generating biomimetic 3D cardiac tissues. Hypothesis: The central hypothesis of this study was to develop a 3D cardiac tissue model for pharmacological testing of various cardiac drugs on a 3D nanofibrous aligned co-axial cardiac patch. Methods: A co-axial (Co-A) PCL-gelatin aligned nanofibrous patch was fabricated using the electrospinning technique and its mechanical properties were assessed using Universal Test Machine. Then, the hiPSC-CMs were cultured on this Co-A patch for 2 weeks and the LDH assay was performed to determine the cell viability. The functionality of the cardiac patch was determined by an assessment of calcium cycling in hiPSC-CMs. Further, particle image velocimetry (PIV) and microelectrode array (MEA) was used to evaluate the physiological functionality of the cardiac patch in response to various cardiac drugs. Results: Our studies showed that the mean diameter and thickness of aligned Co-A nanofibrous patch was 578±184 nm and 115±11 μm respectively, while its tensile strength was 0.780 ± 0.098 MPa. Further, confocal imaging confirmed the core-shell structure of the Co-A patches with a core diameter of 2.21 ± 0.50 μm. Additionally, The hiPSC-CMs cultured on these aligned Co-A patches showed an aligned morphology and expressed Troponin-T, GATA4, α-sarcomeric actinin, and connexin-43. The hiPSC-CMs seeded on a 3D scaffold showed efficient calcium cycling properties, which were similar to the hiPSC-CMs cultured in 2D scaffold. Furthermore, PIV and MEA analysis showed that hiPSC-CMs cultured in 2D and 3D showed a similar response to various cardiac drugs, isoproterenol, verapamil and E4031. Conclusions: Overall, this study demonstrated a successful fabrication of aligned Co-A nanofibrous cardiac patch and its evaluation as a 3D cardiac tissue model in-vitro, which could be applied towards drug screening, toxicity studies and cardiac repair applications for ischemic heart disease.

Ionic liquid-mediated delivery of insulin to buccal mucosa

Buccal drug delivery offers a potential non-invasive means of delivering therapeutics to patients. Despite the promise, the feasibility of transporting proteins and peptides into systemic circulation from buccal administration remains a daunting challenge. Here, we report the fabrication of a biodegradable polymeric patch for buccal delivery of insulin using chitosan as the mucoadhesive matrix and ionic liquids (ILs)/deep eutectic solvent (DES) as the transport facilitator. Insulin is mixed with ILs/DES made from Choline and Geranic acid (CAGE) to form a viscoelastic CAGE gel and sandwiched between two layers of a biodegradable polymer. The rheological properties of the CAGE gel were dominated by the elastic modulus and suggested a solid-like viscoelastic behavior. CAGE induced a 7-fold increase in the cumulative insulin transport across the ex vivo porcine buccal tissue (~26% of loaded insulin) which was also confirmed by confocal microscopy. The CAGE/insulin patches placed in the rat buccal pouch in vivo lowered blood glucose levels in a dose-dependent manner (up to 50% drop recorded) with no obvious tissue damage at the application site. The pharmacokinetic performance of the delivered insulin indicated a sustained profile as serum insulin levels plateaued after 3 h for the duration of study. The safety and efficacy of the polymeric patch using insulin as a model drug holds significant promise as a platform technology to deliver injectables through the buccal route.

Electroconductive Graphene-Containing Polymeric Patch: A Promising Platform for Future Cardiac Repair.

Myocardial infarction (MI) is one of the leading causes of death worldwide. The complications associated with MI can lead to the formation of nonconductive fibrous scar tissues. Despite the great improvement in electroconductive biomaterials to increase the physiological function of bio-engineered cardiac tissues in vivo, there are still several challenges in creating a suitable scaffold with appropriate mechanical and electrical properties. In the current study, a highly hydrophilic fibrous scaffold composed of polycaprolactone/chitosan/polypyrrole (PCP) and combined with functionalized graphene, to provide superior conductivity and a stronger mechanical cardiopatch, is presented. The PCP/graphene (PCPG) patches were optimized to show mechanical and conductive properties close to the native myocardium. Also, the engineered patches showed strong capability as a drug delivery system. Heparin, an anticoagulant drug, was loaded within the fibrous patches, and the adsorption of the bovine serum albumin (BSA) protein was evaluated. The optimized cardiopatch shows great potential to be used to provide mechanical support and restore electromechanical coupling at the site of MI to maintain a normal cardiac function.

Novel targeted and sustained drug delivery therapy for localized pancreatic cancer: Validation in porcine models and minimally invasive surgical feasibility in human cadavers.

e16747 Background: As systemic therapy improves, control of localized pancreatic adenocarcinoma (PDAC) remains a major challenge. Up to 40% of patients present with locally advanced and borderline resectable tumors, for whom enhanced local downsizing of disease could improve resection rates and survival. PanTher is developing a locally targeted drug delivery product (PTM-101) to treat localized PDAC by directly delivering chemotherapy to the primary tumor. PTM-101 is a bioresorbable polymeric patch containing paclitaxel surgically placed onto the tumor. It biodegrades, resulting in sustained localized release of drug. In murine orthotopic patient-derived xenograft models a 60% increase in OS and inhibition of metastasis was achieved after single treatment. Here we validate and de-risk PTM-101 implantation in standard OR settings in large animals and human cadavers to prepare for a phase 1 study. Methods: We conducted two 30-day studies in porcine models to assess safety, toxicity and biodistribution. Parameters included body weights, hematology, urinalyses, drug levels in the blood and at the implantation site and histomorphologic evaluation. To validate the feasibility of minimally invasive surgical insertion, we conducted a follow-up study in three human cadavers. In each case, PTM-101 was laparoscopically placed directly on the pancreas. Results: We surgically implanted PTM-101 without complications and our approach ensures localized drug delivery with extreme control of drug biodistribution. Importantly, no detectable levels of drug were present in the blood any time during the 30-day treatment, confirming our targeted delivery. PTM-101 was consistently and effectively placed during a minimally invasive surgery without substantial increase in procedure time. PTM-101 conforms fully to pancreatic tissue, allowing for close contact with the intended tissue for drug delivery, and can cover the areas of the pancreas where critical involvements of tumors with vasculature are commonly found. Conclusions: By changing the route of administration to target just the area of interest, PTM-101 can increase the amount of drug reaching the tumor with the aim to enhance therapeutic efficacy. This could open the door to clinically relevant applications in PDAC patients: (i)pre-operatively as neoadjuvant treatment to control progression and downsize locally advanced and borderline anatomy to improve resectability; or (ii)post-resection to reduce the rate of local recurrence.

Drug Delivery is Key to Treatment

A prototype polymer patch capable of performing the same role as actual heart tissue could be a gamechanger.

Tissue Engineered Esophageal Patch by Mesenchymal Stromal Cells: Optimization of Electrospun Patch Engineering.

Aim of work was to locate a simple, reproducible protocol for uniform seeding and optimal cellularization of biodegradable patch minimizing the risk of structural damages of patch and its contamination in long-term culture. Two seeding procedures are exploited, namely static seeding procedures on biodegradable and biocompatible patches incubated as free floating (floating conditions) or supported by CellCrownTM insert (fixed conditions) and engineered by porcine bone marrow MSCs (p-MSCs). Scaffold prototypes having specific structural features with regard to pore size, pore orientation, porosity, and pore distribution were produced using two different techniques, such as temperature-induced precipitation method and electrospinning technology. The investigation on different prototypes allowed achieving several implementations in terms of cell distribution uniformity, seeding efficiency, and cellularization timing. The cell seeding protocol in stating conditions demonstrated to be the most suitable method, as these conditions successfully improved the cellularization of polymeric patches. Furthermore, the investigation provided interesting information on patches’ stability in physiological simulating experimental conditions. Considering the in vitro results, it can be stated that the in vitro protocol proposed for patches cellularization is suitable to achieve homogeneous and complete cellularizations of patch. Moreover, the protocol turned out to be simple, repeatable, and reproducible.

Reinforcement of Notched PBX Simulant Beams with CFRP Patches-Experimental Study

Strength degradation induced by geometrical discontinuities is a primary cause of structural failure for polymer bonded explosive (PBX). To restore structural integrity and extend service life, reinforcement of weakened PBX structures is urgently demanded. In the present work, carbon fiber reinforced polymer (CFRP) patches are employed to notched PBX simulant beams. By using digital image correlation (DIC) technique, the influences of CFRP patches on mechanical behavior of the beams under bending load are explored. Results show that the CFRP patches endows the beams with increased strength and stiffness. Due to the load-sharing and deformation-confining of the patches, stress concentration at the notch is relieved, and crack propagation in PBX simulant matrix is prevented. These discoveries may provide important enlightment for the reinforcement and repair of the weakened PBX structures, and in addition, provide basis to the potential application of CFRP patches in energetic materials.

Development and Characterization of an Anisotropic Biomimetic Polymeric Patch to Improve the Durability of Surgical Heart Valve Repair

Objective: Patches currently used for valve repair have suboptimal mechanical and biocompatibility performance. We hypothesize that a biostable “biomimetic” patch that replicates the three-layer ar...