The development of bioresorbable composite polymeric implants with high mechanical strength

Maglev-fabricated long and biodegradable stent for interventional treatment of peripheral vessels

While chronic limb-threatening ischemia is a serious peripheral artery disease, the lack of an appropriate stent significantly limits the potential of interventional treatment. In spite of much progress in coronary stents, little is towards peripheral stents, which are expected to be both long and biodegradable and thus require a breakthrough in core techniques. Herein, we develop a long and biodegradable stent with a length of up to 118 mm based on a metal-polymer composite material. To achieve a well-prepared homogeneous coating on a long stent during ultrasonic spraying, a magnetic levitation is employed. In vivo degradation of the stent is investigated in rabbit abdominal aorta/iliac arteries, and its preclinical safety is evaluated in canine infrapopliteal arteries. First-in-man implantation of the stent is carried out in the below-the-knee artery. The 13 months' follow-ups demonstrate the feasibility of the long and biodegradable stent in clinical applications.

Evolution of Musculoskeletal Electronics

The musculoskeletal system, constituting the largest human physiological system, plays a critical role in providing structural support to the body, facilitating intricate movements, and safeguarding internal organs. By virtue of advancements in revolutionized materials and devices, particularly in the realms of motion capture, health monitoring, and postoperative rehabilitation, "musculoskeletal electronics" has actually emerged as an infancy area, but has not yet been explicitly proposed. In this review, the concept of musculoskeletal electronics is elucidated, and the evolution history, representative progress, and key strategies of the involved materials and state-of-the-art devices are summarized. Therefore, the fundamentals of musculoskeletal electronics and key functionality categories are introduced. Subsequently, recent advances in musculoskeletal electronics are presented from the perspectives of "in vitro" to "in vivo" signal detection, interactive modulation, and therapeutic interventions for healing and recovery. Additionally, nine strategy avenues for the development of advanced musculoskeletal electronic materials and devices are proposed. Finally, concise summaries and perspectives are proposed to highlight the directions that deserve focused attention in this booming field.

Development of 3D Printed Biodegradable, Entirely X-ray Visible Stents for Rabbit Carotid Artery Implantation

Biodegradable stents are considered a promising strategy for the endovascular treatment of cerebrovascular diseases. The visualization of biodegradable stents is of significance during the implantation and long-term follow-up. Endowing biodegradable stents with X-ray radiopacity can overcome the weakness of intrinsic radioparency of polymers. Hence, this work focuses on the development of an entirely X-ray visible biodegradable stent (PCL-KIO3) composed of polycaprolactone (PCL) and potassium iodate via physical blending and 3D printing. The in vitro results show that the introduction of potassium iodate makes the 3D-printed PCL stents visualizable under X-ray. So far, there is inadequate study about polymeric stent visualization in vivo. Therefore, PCL-KIO3 stents are implanted into the rabbit carotid artery to evaluate the biosafety and visibility performance. During stent deployment, the visualization of the PCL-KIO3 stent effectively helps to understand the position and dilation status of stents. At 6-month follow-up, the PCL-KIO3 stent could still be observed under X-ray and maintains excellent vessel patency. To sum up, this study demonstrates that PCL-KIO3 stent may provide a robust strategy for biodegradable stent visualization.

Application of Artificial Intelligence in Tissue Engineering

Tissue engineering, a crucial approach in medical research and clinical applications, aims to regenerate damaged organs. By combining stem cells, biochemical factors, and biomaterials, it encounters challenges in designing complex 3D structures. Artificial intelligence (AI) enhances tissue engineering through computational modeling, biomaterial design, cell culture optimization, and personalized medicine. This review explores AI applications in organ tissue engineering (bone, heart, nerve, skin, cartilage), employing various machine learning (ML) algorithms for data analysis, prediction, and optimization. Each section discusses common ML algorithms and specific applications, emphasizing the potential and challenges in advancing regenerative therapies.

Modified Theoretical Model Predicts Radial Support Capacity of Polymer Braided Stents

BACKGROUND AND OBJECTIVE

Self-expanding polymer braided stents are expected to replace metallic stents in the treatment of Peripheral Arterial Disease, which seriously endangers human health. To restore the patency of blocked peripheral arteries with different properties and functions, the radial supporting capacity of the stent should be considered corresponding to the vessel. A theoretical model can be established as an effective method to study the radial supporting capacity of the stent which can shorten the stent design cycle and realize the customization of the stent according to lesion site. However, the classical model developed by Jedwab and Clerc of radial force is only limited to metallic braided stents, and the predictions for polymer braided stents are deviated.

METHODS

In this paper, based on the limitation of the J&C model for polymer braided stents, a modified radial force model for polymer braided stents was proposed, which considered the friction between monofilaments and the torsion of the monofilaments. And the modified model was verified by radial force tests of polymer braided stents with different structures and monofilaments.

RESULTS

Compared with the J&C model, the proposed modified model has better predictability for the radial force of polymer braided stents that prepared with different braided structure and polymer monofilaments. The root mean squared error of modified model is 0.041±0.026, while that of the J&C model is 0.246±0.111.

CONCLUSIONS

For polymer braided stents, the friction between the polymer monofilaments and the torsion of the monofilaments during the radial compression cannot be ignored. The radial force prediction accuracy of the modified model considering these factors was significantly improved. This work provides a research basis on the theoretical model of polymer braided stents, and improves the feasibility of rapid personalized customization of polymer braided stents.

Antioxidant and Trilayered Electrospun Small-Diameter Vascular Grafts Maintain Patency and Promote Endothelialisation in Rat Femoral Artery

Vascular grafts with a small diameter encounter inadequate patency as a result of intimal hyperplasia development. In the current study, trilayered electrospun small-diameter vascular grafts (PU-PGACL + GA) were fabricated using a poly(glycolic acid) and poly(caprolactone) blend as the middle layer and antioxidant polyurethane with gallic acid as the innermost and outermost layers. The scaffolds exhibited good biocompatibility and mechanical properties, as evidenced by their 6 MPa elastic modulus, 4 N suture retention strength, and 2500 mmHg burst pressure. Additionally, these electrospun grafts attenuated cellular oxidative stress and demonstrated minimal hemolysis (less than 1%). As a proof-of-concept, the preclinical evaluation of the grafts was carried out in the femoral artery of rodents, where the conduits demonstrated satisfactory patency. After 35 days of implantation, ultrasound imaging depicted adequate blood flow through the grafts, and the computed vessel diameter and histological staining showed no significant stenosis issue. Immunohistochemical analysis confirmed matrix deposition (38% collagen I and 16% elastin) and cell infiltration (42% for endothelial cells and 55% for smooth muscle cells) in the explanted grafts. Therefore, PU-PGACL + GA showed characteristics of a clinically relevant small-diameter vascular graft, facilitating re-endothelialization while preserving the anticoagulant properties of the synthetic blood vessels.

4D printed hydrogel scaffold with swelling-stiffening properties and programmable deformation for minimally invasive implantation

The power of three-dimensional printing in designing personalized scaffolds with precise dimensions and properties is well-known. However, minimally invasive implantation of complex scaffolds is still challenging. Here, we develop amphiphilic dynamic thermoset polyurethanes catering for multi-material four-dimensional printing to fabricate supportive scaffolds with body temperature-triggered shape memory and water-triggered programmable deformation. Shape memory effect enables the two-dimensional printed pattern to be fixed into temporary one-dimensional shape, facilitating transcatheter delivery. Upon implantation, the body temperature triggers shape recovery of the one-dimensional shape to its original two-dimensional pattern. After swelling, the hydrated pattern undergoes programmable morphing into the desired three-dimensional structure because of swelling mismatch. The structure exhibits unusual soft-to-stiff transition due to the water-driven microphase separation formed between hydrophilic and hydrophobic chain segments. The integration of shape memory, programmable deformability, and swelling-stiffening properties makes the developed dynamic thermoset polyurethanes promising supportive void-filling scaffold materials for minimally invasive implantation.

Tough and Water-Resistant Bioelastomers with Active-Controllable Degradation Rates

Biodegradable electronic devices have gained significant traction in modern medical applications. These devices are generally desired to have a long enough working lifetime for stable operation and allow for active control over their degradation rates after usage. However, current biodegradable materials used as encapsulations or substrates for these devices are challenging to meet the two requirements due to the constraints of inadequate water resistance, poor mechanical properties, and passive degradation characteristics. Herein, we develop a novel biodegradable elastomer named POC-SS-Res by introducing disulfide linkage and resveratrol (Res) into poly(1,8-octanediol-co-citrate) (POC). Compared to POC, POC-SS-Res exhibits good water resistance and excellent mechanical properties in PBS, providing effective protection for devices. At the same time, POC-SS-Res offers the unique advantage of an active-controllable degradation rate, and its degradation products express low biotoxicity. Good biocompatibility of POC-SS-Res is also demonstrated. Bioelectronic components encapsulated with POC-SS-Res have an obvious prolongation of working lifetime in PBS compared to that encapsulated with POC, and its degradation rate can be actively controlled by the addition of glutathione (GSH).

Highly Elastic, Bioresorbable Polymeric Materials for Stretchable, Transient Electronic Systems

Substrates or encapsulants in soft and stretchable formats are key components for transient, bioresorbable electronic systems; however, elastomeric polymers with desired mechanical and biochemical properties are very limited compared to non-transient counterparts. Here, we introduce a bioresorbable elastomer, poly(glycolide-co-ε-caprolactone) (PGCL), that contains excellent material properties including high elongation-at-break (< 1300%), resilience and toughness, and tunable dissolution behaviors. Exploitation of PGCLs as polymer matrices, in combination with conducing polymers, yields stretchable, conductive composites for degradable interconnects, sensors, and actuators, which can reliably function under external strains. Integration of device components with wireless modules demonstrates elastic, transient electronic suture system with on-demand drug delivery for rapid recovery of post-surgical wounds in soft, time-dynamic tissues.

Hybrid interpenetrating network of polyester coronary stent with tunable biodegradation and mechanical properties

Poly(l-lactide) (PLLA) is an important candidate raw material of the next-generation biodegradable stent for percutaneous coronary intervention, yet how to make a polyester stent with sufficient mechanical strength and relatively fast biodegradation gets to be a dilemma. Herein, we put forward a hybrid interpenetrating network (H-IPN) strategy to resolve this dilemma. As such, we synthesize a multi-functional biodegradable macromer of star-like poly(d,l-lactide-co-ɛ-caprolactone) with six acrylate end groups, and photoinitiate it, after mixing with linear PLLA homopolymer, to trigger the free radical polymerization. The resultant crosslinked polymer blend is different from the classic semi-interpenetrating network, and partial chemical crosslinking occurs between the linear polymer and the macromer network. Combined with the tube blow molding and the postprocessing laser cutting, we fabricate a semi-crosslinked-polyester biodegradable coronary stent composed of H-IPN, which includes a physical network of polyester spherulites and a chemical crosslinking network of copolyester macromers and a part of homopolymers. Compared with the currently main-stream PLLA stent in research, this H-IPN stent realizes a higher and more appropriate biodegradation rate while maintaining sufficient radial strength. A series of polymer chemistry, polymer physics, polymer processing, and in vitro and in vivo biological assessments of medical devices have been made to examine the H-IPN material. The interventional implanting of the H-IPN stent into aorta abdominalis of rabbits and the follow-ups to 12 months have confirmed the safety and effectiveness.

Recent Progress in Advanced Polyester Elastomers for Tissue Engineering and Bioelectronics

Polyester elastomers are highly flexible and elastic materials that have demonstrated considerable potential in various biomedical applications including cardiac, vascular, neural, and bone tissue engineering and bioelectronics. Polyesters are desirable candidates for future commercial implants due to their biocompatibility, biodegradability, tunable mechanical properties, and facile synthesis and fabrication methods. The incorporation of bioactive components further improves the therapeutic effects of polyester elastomers in biomedical applications. In this review, novel structural modification methods that contribute to outstanding mechanical behaviors of polyester elastomers are discussed. Recent advances in the application of polyester elastomers in tissue engineering and bioelectronics are outlined and analyzed. A prospective of the future research and development on polyester elastomers is also provided.

Advances in Fabrication Technologies for the Development of Next-Generation Cardiovascular Stents

Coronary artery disease is the most prevalent cardiovascular disease, claiming millions of lives annually around the world. The current treatment includes surgically inserting a tubular construct, called a stent, inside arteries to restore blood flow. However, due to lack of patient-specific design, the commercial products cannot be used with different vessel anatomies. In this review, we have summarized the drawbacks in existing commercial metal stents which face problems of restenosis and inflammatory responses, owing to the development of neointimal hyperplasia. Further, we have highlighted the fabrication of stents using biodegradable polymers, which can circumvent most of the existing limitations. In this regard, we elaborated on the utilization of new fabrication methodologies based on additive manufacturing such as three-dimensional printing to design patient-specific stents. Finally, we have discussed the functionalization of these stent surfaces with suitable bioactive molecules which can prove to enhance their properties in preventing thrombosis and better healing of injured blood vessel lining.

Investigation on Filaments for 3D Printing of Nasal Septum Cartilage Implant

Septoplasty is a widely used method in treating deviated septum. Although it is successfully implemented, there are problems with excessive bleeding, septal perforation, or infections. The use of anatomically shaped implants could help overcome these problems. This paper focuses on assessing the possibility of the usage of a nasal septum cartilage implant 3D printed from various market-available filaments. Five different types of laments were used, two of which claim to be suitable for medical use. A combination of modeling, mechanical (bending, compression), structural (FTIR), thermal (DSC, MFR), surface (contact angle), microscopic (optical), degradation (2 M HCl, 5 M NaOH, and 0.01 M PBS), printability, and cell viability (MTT) analyses allowed us to assess the suitability of materials for manufacturing implants. Bioflex had the most applicable properties among the tested materials, but despite the overall good performance, cell viability studies showed toxicity of the material in MTT test. The results of the study show that selected filaments were not suitable for nasal cartilage implants. The poor cell viability of Bioflex could be improved by surface modification. Further research on biocompatible elastic materials for 3D printing is needed either by the synthesis of new materials or by modifying existing ones.

Manipulation of porous poly(l-lactide-co-ε-caprolactone) microcarriers via microfluidics for C2C12 expansion

The growth and repair of skeletal muscle are due in part to activation of muscle precursor cells, commonly known as satellite cells or myoblasts. In order to acquire enough cells for neoskeletal muscle regeneration, it is urgent to develop microcarriers for skeletal myoblasts proliferation with a considerable efficiency. The current study was thus proposed to develop a microfluidic technology to manufacture porous poly(l-lactide-co-ε-caprolactone) (PLCL) microcarriers of high uniformity, and porosity was manipulated via camphene to suit the proliferation of C2C12 cells. A co-flow capillary microfluidic device was first designed to obtain PLCL microcarriers with different porosity. The attachment and proliferation of C2C12 cells on these microcarriers were evaluated and the differentiation potential of expanded cells were verified. The obtained porous microcarriers were all uniform in size with a high mono-dispersity (CV < 5 %). The content of camphene rendered effects on the size, porosity, and pore size of microcarriers, and porous structure addition produced a softening of their mechanical properties. The one of 10 % camphene (PM-10) exhibited the superior expansion for C2C12 cells with the number of cells after 5 days of culture reached 9.53 times of the adherent cells on the first day. The expanded cells from PM-10 still retained excellent myogenic differentiation performance as the expressions of MYOD, Desmin and MYH2 were intensively enhanced. Hence, the current developed porous PLCL microcarriers could offer as a promising type of substrates not only for in vitro muscular precursor cells expansion without compromising any multipotency but also have the potential as injectable constructs to mediate muscle regeneration.

Biodegradable Block Poly(ester amine)s with Pendant Hydroxyl Groups for Biomedical Applications

The article presents the results of the synthesis and characteristics of the amphiphilic block terpolymers, built of a hydrophilic polyesteramine block, and hydrophobic blocks made of lactidyl and glycolidyl units. These terpolymers were obtained during the copolymerization of L-lactide with glycolide carried out in the presence of previously produced macroinitiators with protected amine and hydroxyl groups. The terpolymers were prepared to produce a biodegradable and biocompatible material containing active hydroxyl and/or amino groups, with strong antibacterial properties and high surface wettability by water. The control of the reaction course, the process of deprotection of functional groups, and the properties of the obtained terpolymers were made based on 1H NMR, FTIR, GPC, and DSC tests. Terpolymers differed in the content of amino and hydroxyl groups. The values of average molecular mass oscillated from about 5000 g/mol to less than 15,000 g/mol. Depending on the length of the hydrophilic block and its composition, the value of the contact angle ranged from 50° to 20°. The terpolymers containing amino groups, capable of forming strong intra- and intermolecular bonds, show a high degree of crystallinity. The endotherm responsible for the melting of L-lactidyl semicrystalline regions appeared in the range from about 90 °C to close to 170 °C, with a heat of fusion from about 15 J/mol to over 60 J/mol.

Focus on the crucial deformation region to adjust the comprehensive performance of poly (L-lactic acid) stent

The fully biodegradable polymer stent is considered as the fourth-generation vascular implant with good biocompatibility and long-term therapeutic potential. It has attracted much attention because it overcomes the disadvantage of the permanently implanted metal stent. However, compared with the metal stent, its mechanical properties are slightly inferior, which is an urgent problem. Based on previous studies, fully biodegradable polymer stents are prone to experience cracks and damage in large deformation region during the crimping and expansion process. The large deformation region is mainly located at the ring bend of the stent. We supposed that these damages are the leading causes of weakening the mechanical performance of polymer stents and are mainly affected by the crucial deformation region. For this purpose, this work studies the relationship between different crucial deformation regions and the mechanical performance of the polymer stent. Firstly, the volume of the crucial deformation region is improved by increasing the ring width. Although the radial strength of the stent is enhanced with the increase in ring width, the radial stiffness also increases, and correspondingly, the flexibility of the stent decreases. To obtain acceptable comprehensive mechanical performance, two types of slotting design in critical deformation region were proposed. The proposed slotted stent with a bulge has sufficient radial strength and low radial stiffness, having a good radial support capacity and flexibility. In other words, the proposed stent has improved the radial support without sacrificing flexibility. Overall, different crucial deformation regions cause different degrees of damage to the stent during crimping and expansion, which affects the mechanical properties of the stent. Reasonable structural design of the crucial deformation region is the key to adjust the comprehensive performance of the stent.

A hazardous boundary of Poly(L-lactic acid) braided stent design: Limited elastic deformability of polymer materials

Poly (L-lactic acid) (PLLA) braided stents, which are expected to replace metal stents, are promising in peripheral vascular therapy due to their superior biocompatibility. Although various design ideas have been proposed and investigated on metal stents, few researches are related to the design theory of PLLA braided stent. In this article, mechanical performance of PLLA braided stents with different parameters was systematically evaluated, and a design theory based on material properties was proposed. Different from metal materials, the risk of filament deformation beyond elastic zone should be evaluated and controlled in PLLA stent design. The findings were obtained through combination study of experiments and simulations. Design parameters, including pitch angle and stent diameter, played a crucial role in mechanical performance of PLLA braided stent. The deformation of PLLA stents with larger pitch angles and stent diameters was in elastic zone and thus presented better mechanical performance with satisfactory resilience. This work could provide meaningful suggestions for preparing bioresorbable braided stents with suitable design parameters.

Novel Self-expanding Shape-Memory Bioresorbable Peripheral Stent Displays Efficient Delivery, Accelerated Resorption, and Low Luminal Loss in a Porcine Model

OBJECTIVE AND DESIGN

The search for improved stenting technologies to treat peripheral artery disease is trending toward biodegradable self-expanding shape-memory stents that, as of now, still suffer from the acute trade-off between deliverability and luminal stability: Higher deliverability leads to lower lumen stability, vessel recoil, and stent breakage. This study was aimed at the development and testing of a self-expanding bioresorbable poly(l,l-lactide-co-ε-caprolactone) stent that was designed to produce confident self-expansion after efficient crimping, as well as quick bioresorption, and sufficient radial force.

MATERIALS AND METHODS

Bench tests were employed to measure shape-memory properties, radial force, and hydrolytic degradation of the stent. The porcine model was employed to study deliverability, lumen stability, biocompatibility, and stent integrity. A total of 32 stents were implanted in the iliac arteries of 16 pigs with 15 to 180 day follow-up periods. The stented vessels were studied by angiography and histological evaluation.

RESULTS

Recovery of the diameter of the stent due to shape-memory effect was equal to 90.6% after 6Fr crimping and storage in refrigeration for 1 week. Radial force measured after storage was equal to 0.7 N/mm. Technical success of implantation in pigs (after the delivery implemented by pusher) was 94%. At 180 days, no implanted stents were found to be fragmented: All of the devices remained at the site of implantation with no stent migration and all stents retained their luminal support. Only moderate inflammation and neoepithelialization were detected by histological assessment at 60, 90, 120, and 180 days. Lumen loss at 180 days was less than 25% of the vessel diameter.

CONCLUSIONS

The stent with the mechanical and chemical properties described in this study may present the optimal solution of the trade-off between deliverability and luminal stability that is necessary for designing the next generation stent for endovascular therapy of peripheral arterial disease.

The Advancement of Biodegradable Polyesters as Delivery Systems for Camptothecin and Its Analogues-A Status Report

Camptothecin (CPT) has demonstrated antitumor activity in lung, ovarian, breast, pancreas, and stomach cancers. However, this drug, like many other potent anticancer agents, is extremely water-insoluble. Furthermore, pharmacology studies have revealed that prolonged schedules must be administered continuously. For these reasons, several of its water-soluble analogues, prodrugs, and macromolecular conjugates have been synthesized, and various formulation approaches have been investigated. Biodegradable polyesters have gained popularity in cancer treatment in recent years. A number of biodegradable polymeric drug delivery systems (DDSs), designed for localized and systemic administration of therapeutic agents, as well as tumor-targeting macromolecules, have entered clinical trials, demonstrating the importance of biodegradable polyesters in cancer therapy. Biodegradable polyester-based DDSs have the potential to deliver the payload to the target while also increasing drug availability at intended site. The systemic toxicity and serious side-effects associated with conventional cancer therapies can be significantly reduced with targeted polymeric systems. This review elaborates on the use of biodegradable polyesters in the delivery of CPT and its analogues. The design of various DDSs based on biodegradable polyesters has been described, with the drug either adsorbed on the polymer's surface or encapsulated within its macrostructure, as well as those in which a hydrolyzed chemical bond is formed between the active substance and the polymer chain. The data related to the type of DDSs, the kind of linkage, and the details of in vitro and in vivo studies are included.

Development of sand-plastic composites as floor tiles using silica sand and recycled thermoplastics: a sustainable approach for cleaner production

Strict environmental concerns, depleting natural recourses, and rising demand for building construction materials have promoted scientific research toward alternative building materials. This research supports the idea of sustainability and a circular economy via the utilization of waste to produce value-added products. The research explored the potential of waste plastics and silica sand for developing thermoplastic composite as floor tiles. The samples were characterized by water absorption, compressive strength, flexural strength, and sliding wear. The morphological analysis of the sand-plastic interfaces was covered under the umbrella of this study. The maximum compressive and flexural strength were found to be 46.20 N/mm2 and 6.24 N/mm2, respectively, with the minimum water absorption and sliding wear rate of 0.039% and 0.143 × 10-8 kg/m, respectively. The study suggests the workability of the developed floor tiles in non-traffic areas of public places. Thus, the study provides a green building material through recycling waste plastics for sustainable development.

A Review of Microinjection Moulding of Polymeric Micro Devices

Polymeric micro devices are gaining huge market potential in broad areas of medical devices, diagnostic devices, drug delivery, and optical applications. Current research is focusing on developing functional polymeric micro devices on a mass-production scale. Microinjection moulding is a promising technique suitable for fabricating polymeric micro devices. This review aims to summarise the primary achievements that have been achieved in various aspects of microinjection moulding of polymer micro devices, consisting of micro parts and micro surface structures. The relationships of the machine, process, rheology, tooling, micro/nanoscale replication, morphology, properties, and typical applications are reviewed in detail. Finally, a conclusion and challenges are highlighted.

Digital Light 3D Printed Bioresorbable and NIR-Responsive Devices with Photothermal and Shape-Memory Functions

Digital light processing (DLP) 3D printing is a promising technique for the rapid manufacturing of customized medical devices with high precision. To be successfully translated to a clinical setting, challenges in the development of suitable photopolymerizable materials have yet to be overcome. Besides biocompatibility, it is often desirable for the printed devices to be biodegradable, elastic, and with a therapeutic function. Here, a multifunctional DLP printed material system based on the composite of gold nanorods and polyester copolymer is reported. The material demonstrates robust near-infrared (NIR) responsiveness, allowing rapid and stable photothermal effect leading to the time-dependent cell death. NIR light-triggerable shape transformation is demonstrated, resulting in a facilitated insertion and expansion of DLP printed stent ex vivo. The proposed strategy opens a promising avenue for the design of multifunctional therapeutic devices based on nanoparticle-polymer composites.

Evaluation of resistance to radial cyclic loads of poly(L-lactic acid) braided stents with different braiding angles

Poly(L-lactic acid) (PLLA) braided stents have superior biocompatibility and flexibility, substituting metal stents in peripheral blood vessels. However, the radial supporting capacity of PLLA braided stent should be improved to bear the dynamic load from the peripheral artery. This paper evaluated the radial support performance of PLLA braided stents with different braiding angles after the radial cyclic loads test. The results indicate that braiding angle of stents is an important parameter affecting its ability to resist radial cyclic loads. The stent with a smaller braiding angle has better initial radial support but insufficient durability, while the stent with a larger braiding angle could maintain adequate radial support and suitable ability to resist radial cyclic loads. The theoretical analysis, verified by observing the surface morphology of filament crossover points, found that filaments of the stents with smaller braiding angles have more significant axial displacement and axial rotation angle during radial compression, which made the friction phenomenon more intense and led to insufficient ability to resist radial cyclic loads. This study could provide a meaningful idea for preparing biodegradable braided stents with suitable ability to resist radial cyclic loads.

Amphiphilic Crosslinked Four-Armed Poly(lactic-co-glycolide) Electrospun Membranes for Enhancing Cell Adhesion

Common poly(lactide-co-glycolide) (i-PLGA) has emerged as a biodegradable and biocompatible material in tissue engineering. However, the poor hydrophilicity and elasticity of i-PLGA lead to its limited application in tissue engineering. To this end, an amphiphilic crosslinked four-armed poly(lactic-co-glycolide) was prepared. First, four-armed PLGA (4A-PLGA) was synthesized by polymerizing l-lactide (LA) and glycolide (GA) with pentaerythritol as the initiator. Then, the hydrophilic polymer poly(glutamate propylene ester) (PGPE) was prepared through the esterification of glutamic acid and 1,2-propanediol. The hydrophilic 4A-PLGA-PGPE was finally synthesized through the condensation reaction of 4A-PLGA and PGPE with the aid of triphosgene. 4A-PLGA-PGPE was then used to prepare amphiphilic membranes by electrospinning. It was demonstrated that the mechanical properties and biocompatibility of 4A-PLGA were improved after the introduction of PGPE. Furthermore, the introduction of glutamate improved the hydrophilicity of 4A-PLGA, thus effectively promoting cell entry and adhesion, which makes the electrospun 4A-PLGA-PGPE membranes promising for tissue engineering.

Progress in the drug encapsulation of poly(lactic-co-glycolic acid) and folate-decorated poly(ethylene glycol)-poly(lactic-co-glycolic acid) conjugates for selective cancer treatment

Poly(lactic-co-glycolic acid) (PLGA) is a US Food and Drug Administration (FDA)-approved polymer used in humans in the forms of resorbable sutures, drug carriers, and bone regeneration materials. Recently, PLGA-based conjugates have been extensively investigated for cancer, which is the second leading cause of death globally. This article presents an account of the literature on PLGA-based conjugates, focusing on their chemistries, biological activity, and functions as targeted drug carriers or sustained drug controllers for common cancers (e.g., breast, prostate, and lung cancers). The preparation and drug encapsulation of PLGA nanoparticles and folate-decorated poly(ethylene glycol)-poly(lactic-co-glycolic acid) (FA-PEG-PLGA) conjugates are discussed, along with several representative examples. Particularly, the reactions used for preparing drug-conjugated PLGA and FA-PEG-PLGA are emphasized, with the associated chemistries involved in the formation of structures and their biocompatibility with internal organs. This review provides a deeper understanding of the constituents and interactions of PLGA-conjugated materials to ensure successful conjugation in PLGA material design and the subsequent biomedical applications.

Different properties of poly(L-lactic acid) monofilaments and its corresponding braided springs after constrained and unconstrained annealing

Thermal annealing is widely applied to enhance the mechanical performance of PLLA monofilaments, which brings in a variety of expected strengths through different constrained methods. In this work, samples with constrained and unconstrained annealing process were both prepared and characterized, including mechanical performance, surface morphology, radial supporting performance and axial flexibility. Experimental results revealed that the monofilaments under constrained annealing showed higher elastic modulus with 6.4 GPa, which were higher than those without any constraint. While the maximal elongation at break with 51.11% were observed in unconstrained annealed monofilaments. Few changes were presented in the molecular weight between the two types of samples. Moreover, the springs under constrained annealing inhibited the most reliable radial supporting performance with higher radial compression force and chronic outward force, 0.665 N/mm and 0.14 N respectively. However, unconstrained annealing springs showed better flexibility with 0.178 N bending stiffness and 1.58 N maximum bending force. These results suggested that filaments and springs with various properties can be obtained under different annealing conditions.

Water-Triggered Stiffening of Shape-Memory Polyurethanes Composed of Hard Backbone Dangling PEG Soft Segments

Shape-memory polymers (SMPs) induced by heat or water are commonly used candidates for biomedical applications. Shape recovery inevitably leads to a dramatic decrease of Young's modulus due to the enhanced flexibility of polymer chains at the transition temperature. Herein, the principle of phase-transition-induced stiffening of shape-memory metallic alloys (SMAs) is introduced to the design of molecular structures for shape-memory polyurethane (SMPUs), featuring all-hard segments composed of main chains that are attached with poly(ethylene glycol) (PEG) dangling side chains. Different from conventional SMPs, they achieve a soft-to-stiff transition when shape recovers. The stiffening process is driven by water-triggered segmental rearrangement due to the incompatibility between the hard segments and the soft PEG segments. Upon hydration, the extent of microphase separation is enhanced and the hard domains are transformed to a more continuous morphology to realize more effective stress transfer. Meanwhile, such segmental rearrangement facilitates the shape-recovery process in the hydrated state despite the final increased glass transition temperature (T_g ). This work represents a novel paradigm of simultaneously integrating balanced mechanics, shape-memory property, and biocompatibility for SMPUs as materials for minimally invasive surgery such as endoluminal stents.

A review on femoropopliteal arterial deformation during daily lives and nickel-titanium stent properties

The increasing number of studies on the behaviour of stent placement in recent decades provides a clear understanding of peripheral artery disease (PAD). The severe mechanical loads (axial tension and compression, bending, radial compression and torsion) deformation of the femoropopliteal artery (FPA) is responsible for the highest failure rate of permanent nickel-titanium (Nitinol) stents. Therefore, the purpose of this article is to review research papers that examined the deformation of the natural load environment of FPA, the properties of Nitinol and mechanical considerations. In conclusion, a better understanding of mechanical behaviour for FPA Nitinol stents contributes to increased mechanical performance and fatigue-life.

3D printed elastomers with Sylgard-184-like mechanical properties and tuneable degradability

The 3D printing of biodegradable elastomers with high mechanical strength is of great interest for personalized medicine, but rather challenging. In this study, we propose a dual-polymer resin formulation for digital light processing of biodegradable elastomers with tailorable mechanical properties comparable to those of Sylgard-184.

Synergistically Promoting Bone Regeneration by Icariin-Incorporated Porous Microcarriers and Decellularized Extracellular Matrix Derived From Bone Marrow Mesenchymal Stem Cells

Multifunctionality has becoming essential for bone tissue engineering materials, such as drug release. In this study, icariin (ICA)-incorporated poly(glycolide-co-caprolactone) (PGCL) porous microcarriers were fabricated and then coated with decellularized extracellular matrix (dECM) which was derived from bone marrow mesenchymal stem cells (BMSC). The porous structure was generated due to the soluble gelatin within the microcarriers. The initial released ICA in microcarriers regulated osteogenic ECM production by BMSCs during ECM formation. The dECM could further synergistically enhance the migration and osteogenic differentiation of BMSCs together with ICA as indicated by the transwell migration assay, ALP and ARS staining, as well as gene and protein expression. Furthermore, in vivo results also showed that dECM and ICA exhibited excellent synergistic effects in repairing rat calvarial defects. These findings suggest that the porous microcarriers loaded with ICA and dECM coatings have great potential in the field of bone tissue engineering.

A ready-to-use, thermoresponsive, and extended-release delivery system for the paranasal sinuses

A drug delivery system for the paranasal sinuses consisting of a freeze-dried thermoresponsive hydrogel with degradable microspheres, called FD-TEMPS (Freeze Dried-Thermogel, Extended-release Microsphere-based delivery to the Paranasal Sinuses), was developed. Glass transition temperatures (Tg') of the maximally freeze concentrated solutions consisting of poly(N-isopropylacrylamide) (pNIPAAm) and polyethylene glycol (PEG) were determined by differential scanning calorimetry, which informed optimization of the thermogel formulation. By replacing low molecular weight (MW) PEG (200 Da) with a higher MW PEG (2000 Da), the resulting freeze-dried gel exhibited a brittle texture, porous structure, and low residual moisture (< 3% measured by thermal gravimetric analysis). When combined with poly(lactic-co-glycolic acid) microspheres (PLGA MSs) and freeze dried, the complete system (FD-TEMPS) exhibited enhanced shelf-stability. Specifically, the smooth, spherical morphology of the MSs and initial release kinetics were maintained following 6 weeks of storage under ambient conditions. Furthermore, FD-TEMPS remained in place after application to a simulated mucosal surface, suggesting that it could be more uniformly distributed along the sinonasal mucosa in vivo. Freeze drying enables this delivery system to be stored as a ready-to-use product for better ease of clinical translation without compromising the thermoresponsive or sustained release characteristics that would enable local delivery of therapeutics to the sinonasal mucosa.

Implantable system for chronotherapy

Diurnal variation in enzymes, hormones, and other biological mediators has long been recognized in mammalian physiology. Developments in pharmacobiology over the past few decades have shown that timing drug delivery can enhance drug efficacy. Here, we report the development of a battery-free, refillable, subcutaneous, and trocar-compatible implantable system that facilitates chronotherapy by enabling tight control over the timing of drug administration in response to external mechanical actuation. The external wearable system is coupled to a mobile app to facilitate control over dosing time. Using this system, we show the efficacy of bromocriptine on glycemic control in a diabetic rat model. We also demonstrate that antihypertensives can be delivered through this device, which could have clinical applications given the recognized diurnal variation of hypertension-related complications. We anticipate that implants capable of chronotherapy will have a substantial impact on our capacity to enhance treatment effectiveness for a broad range of chronic conditions.

Electronic Drugs: Spatial and Temporal Medical Treatment of Human Diseases

Recent advances in diagnostics and medicines emphasize the spatial and temporal aspects of monitoring and treating diseases. However, conventional therapeutics, including oral administration and injection, have difficulties meeting these aspects due to physiological and technological limitations, such as long-term implantation and a narrow therapeutic window. As an innovative approach to overcome these limitations, electronic devices known as electronic drugs (e-drugs) have been developed to monitor real-time body signals and deliver specific treatments to targeted tissues or organs. For example, ingestible and patch-type e-drugs could detect changes in biomarkers at the target sites, including the gastrointestinal (GI) tract and the skin, and deliver therapeutics to enhance healing in a spatiotemporal manner. However, medical treatments often require invasive surgical procedures and implantation of medical equipment for either short or long-term use. Therefore, approaches that could minimize implantation-associated side effects, such as inflammation and scar tissue formation, while maintaining high functionality of e-drugs, are highly needed. Herein, the importance of the spatial and temporal aspects of medical treatment is thoroughly reviewed along with how e-drugs use cutting-edge technological innovations to deal with unresolved medical challenges. Furthermore, diverse uses of e-drugs in clinical applications and the future perspectives of e-drugs are discussed.

Vascular Tissue Engineering: Challenges and Requirements for an Ideal Large Scale Blood Vessel

Since the emergence of regenerative medicine and tissue engineering more than half a century ago, one obstacle has persisted: the in vitro creation of large-scale vascular tissue (>1 cm³) to meet the clinical needs of viable tissue grafts but also for biological research applications. Considerable advancements in biofabrication have been made since Weinberg and Bell, in 1986, created the first blood vessel from collagen, endothelial cells, smooth muscle cells and fibroblasts. The synergistic combination of advances in fabrication methods, availability of cell source, biomaterials formulation and vascular tissue development, promises new strategies for the creation of autologous blood vessels, recapitulating biological functions, structural functions, but also the mechanical functions of a native blood vessel. In this review, the main technological advancements in bio-fabrication are discussed with a particular highlights on 3D bioprinting technologies. The choice of the main biomaterials and cell sources, the use of dynamic maturation systems such as bioreactors and the associated clinical trials will be detailed. The remaining challenges in this complex engineering field will finally be discussed.

Preparation of a Cage-Type Polyglycolic Acid/Collagen Nanofiber Blend with Improved Surface Wettability and Handling Properties for Potential Biomedical Applications

Electrospun biobased polymeric nanofiber blends are widely used as biomaterials for different applications, such as tissue engineering and cell adhesion; however, their surface wettability and handling require further improvements for their practical utilization in the assistance of surgical operations. Therefore, Polyglycolic acid (PGA) and collagen-based nanofibers with three different ratios (40:60, 50:50 and 60:40) were prepared using the electrospinning method, and their surface wettability was improved using ozonation and plasma (nitrogen) treatment. The effect on the wettability and the morphology of pristine and blended PGA and collagen nanofibers was assessed using the WCA test and SEM, respectively. It was observed that PGA/collagen with the ratio 60:40 was the optimal blend, which resulted in nanofibers with easy handling and bead-free morphology that could maintain their structural integrity even after the surface treatments, imparting hydrophilicity on the surface, which can be advantageous for cell adhesion applications. Additionally, a cage-type collector was used during the electrospinning process to provide better handling properties to (PGA/collagen 60:40) blend. The resultant nanofiber mat was then incorporated with activated poly (α,β-malic acid) to improve its surface hydrophilicity. The chemical composition of PGA/collagen 60:40 was assessed using FTIR spectroscopy, supported by Raman spectroscopy.

Long-acting implantable corticosteroid matrix for chronic rhinosinusitis: Results of LANTERN Phase 2 randomized controlled study

Background

Topical steroids are first‐line treatment for chronic rhinosinusitis (CRS), but fail to provide adequate symptom control for all patients. Designed for medical treatment failures, LYR‐210 is an implantable matrix that locally elutes mometasone furoate to inflamed sinonasal tissue for up to 24 weeks in CRS patients. In an open‐label phase 1 study, LYR‐210 demonstrated clinically relevant improvement in the 22‐item Sino‐Nasal Outcome Test (SNOT‐22). Safety and efficacy of LYR‐210 in CRS were evaluated in the LANTERN Phase 2 study.

Methods

Sixty‐seven surgically naive adult CRS patients who were inadequately controlled by previous medical management and seeking an alternative treatment enrolled in a multicenter, blinded, controlled, dose‐ranging study. Patients had moderate‐to‐severe disease based on SNOT‐22 and composite 7‐day average scores of the 4 cardinal CRS symptoms (4CS), with diagnosis confirmed by nasal endoscopy and magnetic resonance imaging. Patients were randomized (1:1:1) to saline irrigation–only control or bilateral in‐office administration of LYR‐210 (2500 μg) or LYR‐210 (7500 μg). Safety and efficacy were evaluated over 24 weeks.

Results

Both LYR‐210 doses were safe and well‐tolerated over the 24‐week treatment period. LYR‐210 demonstrated rapid and durable dose‐dependent symptom improvement based on 4CS and SNOT‐22, with LYR‐210 (7500 μg) achieving statistical significance as early as 8 weeks and out to 24 weeks compared with control. LYR‐210 (7500 μg) reduced rescue treatment use and radiographic ethmoid opacification at week 24.

Conclusions

LYR‐210 is the first implantable sinonasal treatment to achieve up to 24 weeks of benefit from a single administration in surgically naive CRS patients with and without nasal polyps.

Development of a polycaprolactone/poly(p-dioxanone) bioresorbable stent with mechanically self-reinforced structure for congenital heart disease treatment

Recent progress in bioresorbable stents (BRSs) has provided a promising alternative for treating coronary artery disease. However, there is still lack of BRSs with satisfied compression and degradation performance for pediatric patients with congenital heart disease, leading to suboptimal therapy effects. Here, we developed a mechanically self-reinforced composite bioresorbable stent (cBRS) for congenital heart disease application. The cBRS consisted of poly(p-dioxanone) monofilaments and polycaprolactone/poly(p-dioxanone) core-shell composite yarns. Interlacing points in cBRS structure were partially bonded, offering the cBRS with significantly higher compression force compared to typical braids and remained good compliance. The suitable degradation profile of the cBRS can possibly preserve vascular remodeling and healing process. In addition, the controllable structural organization provides a method to customize the performance of the cBRS by altering the proportion of different components in the braids. The in vivo results suggested the cBRS supported the vessel wall similar to that of metallic stent. In both abdominal aorta and iliac artery of porcine, cBRS was entirely endothelialized within 1 month and maintained target vessels with good patency in the 12-month follow-up. The in vivo degradation profile of the cBRS is consistent with static degradation results in vitro. It is also demonstrated that there is minimal impact of pulsatile pressure of blood flow and variation of radial force on the degradation rate of the cBRS. Moreover, the lumen of cBRS implanted vessels were enlarged after 6 months, and significantly larger than the vessels implanted with metallic stent in 12 months.

Drug Release and Pharmacokinetic Evaluation of Novel Implantable Mometasone Furoate Matrices in Rabbit Maxillary Sinuses

BACKGROUND

Intranasal corticosteroid sprays (INCSs) used to treat chronic rhinosinusitis are suboptimal due to limited penetration into the middle meatus, rapid clearance, and poor patient compliance. A bioresorbable drug matrix, developed with the XTreo^TM drug delivery platform, may overcome the limitations of INCS by providing continuous dosing over several months.

OBJECTIVE

To evaluate the in vitro drug release and in vivo pharmacokinetics of novel mometasone furoate (MF) matrices in a rabbit dorsal maxillary osteotomy model.

METHODS

XTreo^TM matrices were formulated to consistently elute MF for up to 6 months. Matrices were surgically placed bilaterally into the maxillary sinuses of New Zealand White (NZW) rabbits. Tissue and plasma MF concentrations were measured to assess the in vivo drug delivery. The in vivo and in vitro drug release kinetics of the matrices were quantified and compared to those of rabbits receiving daily Nasonex^® MF nasal sprays.

RESULTS

XTreo^TM matrices self-expanded upon deployment to conform to the irregular geometry of the maxillary sinus cavities in the NZW rabbits. Sustained release of MF was demonstrated in vitro and in vivo for 2 MF matrices of distinct release durations and an in vitro-in vivo correlation was established. Therapeutic levels of MF in local tissues were measured throughout the intended dosing durations. In contrast to the variable peaks and troughs of daily nasal sprays, sustained dosing via a single administration of MF matrices was confirmed by quantifiable plasma MF concentrations over the intended dosing duration.

CONCLUSION

The XTreo^TM MF matrices provided targeted and efficient dosing to local sinus tissues that was superior to INCS. Sustained drug release was confirmed both in vitro and in vivo. The novel XTreo^TM technology may provide precisely tuned, long-lasting drug delivery to sinus tissues with a single treatment.

A machine learning-based multiscale model to predict bone formation in scaffolds

Computational modeling methods combined with non-invasive imaging technologies have exhibited great potential and unique opportunities to model new bone formation in scaffold tissue engineering, offering an effective alternate and viable complement to laborious and time-consuming in vivo studies. However, existing numerical approaches are still highly demanding computationally in such multiscale problems. To tackle this challenge, we propose a machine learning (ML)-based approach to predict bone ingrowth outcomes in bulk tissue scaffolds. The proposed in silico procedure is developed by correlating with a dedicated longitudinal (12-month) animal study on scaffold treatment of a major segmental defect in sheep tibia. Comparison of the ML-based time-dependent prediction of bone ingrowth with the conventional multilevel finite element (FE2) model demonstrates satisfactory accuracy and efficiency. The ML-based modeling approach provides an effective means for predicting in vivo bone tissue regeneration in a subject-specific scaffolding system.