The Effect of Fluid Shear Stress on the In Vitro Release Kinetics of Sirolimus from PLGA Films

DendriPep Nanocoats: Substrate-Agnostic, Self-Assembling Constructs with Shear-Controlled Thickness and Permeability

This study investigates the self-assembly of hybrid poly(amidoamine)-peptide dendrimers (DendriPeps) into shear-responsive vesicle-like structures with nanometric thickness, called "Nanocoats", that are capable of encapsulating nano- and microscale particles. To assess the material-agnostic coating power of DendriPeps, we tested the formation of Nanocoats on a variety of synthetic and biological substrates, including polystyrene nanoparticles, poly(N-isopropylacrylamide) microgels, gallium-indium liquid metal nanodroplets, and bacteriophages and lentiviruses. Specifically, we utilized spectroscopic and microscopic techniques to monitor the reversible assembly of Nanocoats on the surface of the particles upon controlling the shear stress of the surrounding aqueous phase. Furthermore, we evaluated the use of Nanocoats as a glue mediating the formation of particle clusters, whose size, in terms of the number of particles and coating thickness, can be dynamically controlled by adjusting the shear stress. Finally, we harnessed the reconfigurability of DendriPep Nanocoats to develop vectors for the shear-controlled delivery of a bioactive payload. To that end, we achieved the controlled release of the antibacterial peptide polymyxin B from DendriPep-coated microgels by applying shear stresses of 0.5-1 Pa. These results demonstrate the potential of DendriPeps to develop reconfigurable systems for biomedical applications that leverage localized shear gradients.

Control and interplay of scaffold-biomolecule interactions applied to cartilage tissue engineering

Cartilage tissue engineering based on the combination of biomaterials, adult or stem cells and bioactive factors is a challenging approach for regenerative medicine with the aim of achieving the formation of a functional neotissue stable in the long term. Various 3D scaffolds have been developed to mimic the extracellular matrix environment and promote cartilage repair. In addition, bioactive factors have been extensively employed to induce and maintain the cartilage phenotype. However, the spatiotemporal control of bioactive factor release remains critical for maximizing the regenerative potential of multipotent cells, such as mesenchymal stromal cells (MSCs), and achieving efficient chondrogenesis and sustained tissue homeostasis, which are essential for the repair of hyaline cartilage. Despite advances, the effective delivery of bioactive factors is limited by challenges such as insufficient retention at the site of injury and the loss of therapeutic efficacy due to uncontrolled drug release. These limitations have prompted research on biomolecule-scaffold interactions to develop advanced delivery systems that provide sustained release and controlled bioavailability of biological factors, thereby improving therapeutic outcomes. This review focuses specifically on biomaterials (natural, hybrid and synthetic) and biomolecules (molecules, proteins, nucleic acids) of interest for cartilage engineering. Herein, we review in detail the approaches developed to maintain the biomolecules in scaffolds and control their release, based on their chemical nature and structure, through steric, non-covalent and/or covalent interactions, with a view to their application in cartilage repair.

Effect of extracellular matrix stiffness on efficacy of Dapagliflozin for diabetic cardiomyopathy

BACKGROUND

Extracellular matrix (ECM) stiffness is closely related to the progress of diabetic cardiomyopathy (DCM) and the response of treatment of DCM to anti-diabetic drugs. Dapagliflozin (Dapa) has been proven to have cardio-protective efficacy for diabetes and listed as the first-line drug to treat heart failure. But the regulatory relationship between ECM stiffness and treatment efficacy of Dapa remains elusive.

MATERIALS AND METHODS

This work investigated the effect of ECM stiffness on DCM progression and Dapa efficacy using both in vivo DCM rat model and in vitro myocardial cell model with high glucose injury. First, through DCM rat models with various levels of myocardial injury and administration with Dapa treatment for four weeks, the levels of myocardial injury, myocardial oxidative stress, expressions of AT1R (a mechanical signal protein) and the stiffness of myocardial tissues were obtained. Then for mimicking the stiffness of myocardial tissues at early and late stages of DCM, we constructed cell models through culturing H9c2 myocardial cells on the polyacrylamide gels with two stiffness and exposed to a high glucose level and without/with Dapa intervention. The cell viability, reactive oxygen species (ROS) levels and expressions of mechanical signal sensitive proteins were obtained.

RESULTS

The DCM progression is accompanied by the increased myocardial tissue stiffness, which can synergistically exacerbate myocardial cell injury with high glucose. Dapa can improve the ECM stiffness-induced DCM progression and its efficacy on DCM is more pronounced on the soft ECM, which is related to the regulation pathway of AT1R-FAK-NOX2. Besides, Dapa can inhibit the expression of the ECM-induced integrin β1, but without significant impact on piezo 1.

CONCLUSIONS

Our study found the regulation and effect of biomechanics in the DCM progression and on the Dapa efficacy on DCM, providing the new insights for the DCM treatment. Additionally, our work showed the better clinical prognosis of DCM under early Dapa intervention.

Dynamic investigation of zein-based degradable and hemocompatible coatings for drug-eluting stents: a microfluidic approach

Biodegradable stent coatings have shown great potential in terms of delivering drugs to a damaged vessel wall, and their release profiles are key elements governing the overall performance of drug-eluting stents (DESs). However, release and degradation kinetics are usually not tested under simulated physiological conditions or in dynamic environments, both essential aspects in the design of novel DESs. To bridge this gap, fused silica-based microfluidic systems, with either round or square channel cross-sections, were designed to mimic the microenvironment of a stented vessel. In particular, we fabricated and characterized microfluidic chips based on customizable channels, which were spray-coated with a naturally-derived, rutin-loaded zein solution, to perform a comprehensive study under flow conditions. Dynamic assays after 6 hours showed how the degradation of the zein matrix was affected by the cross-sectional conformation (∼69% vs. ∼61%, square and round channel, respectively) and the simulated blood fluid components (∼55%, round channel with a more viscous solution). The released amount of rutin was ∼81% vs. ∼77% and ∼78% vs. ∼74% from the square and round channels, using the less and more viscous blood-simulated fluids, respectively. Fitting the drug release data to Korsmeyer-Peppas and first-order mathematical models provided further insight into the mechanism of rutin release and coating behavior under flowing conditions. More importantly, whole blood tests with our newly developed microfluidic platforms confirmed the hemocompatibility of our zein-based coating. In detail, in-flow and static studies on the blood cell behavior showed a significant reduction of platelet adhesion (∼73%) and activation (∼93%) compared to the stainless-steel substrate, confirming the benefits of using such naturally-derived coatings to avoid clogging. Overall, our microfluidic designs can provide a key practical tool for assessing polymer degradation and drug release from degradable matrices under flowing conditions, thus aiding future studies on the development of hemocompatible, controlled-release coatings for DESs.

Effect of Extracellular Matrix Stiffness on Candesartan Efficacy in Anti-Fibrosis and Antioxidation

Myocardial fibrosis progression and imbalanced redox state are closely associated with increased extracellular matrix (ECM) stiffness. Candesartan (CAN), an angiotensin II (Ang II) receptor inhibitor, has shown promising anti-fibrosis and antioxidant efficacy in previous cardiovascular disease studies. However, the effect of ECM stiffness on CAN efficacy remains elusive. In this study, we constructed rat models with three different degrees of myocardial fibrosis and treated them with CAN, and then characterized the stiffness, cardiac function, and NADPH oxidase-2 (NOX2) expression of the myocardial tissues. Based on the obtained stiffness of myocardial tissues, we used polyacrylamide (PA) gels with three different stiffness to mimic the ECM stiffness of cardiac fibroblasts (CFs) at the early, middle, and late stages of myocardial fibrosis as the cell culture substrates and then constructed CFs mechanical microenvironment models. We studied the effects of PA gel stiffness on the migration, proliferation, and activation of CFs without and with CAN treatment, and characterized the reactive oxygen species (ROS) and glutathione (GSH) levels of CFs using fluorometry and scanning electrochemical microscopy (SECM). We found that CAN has the best amelioration efficacy in the cardiac function and NOX2 levels in rats with medium-stiffness myocardial tissue, and the most obvious anti-fibrosis and antioxidant efficacy in CFs on the medium-stiffness PA gels. Our work proves the effect of ECM stiffness on CAN efficacy in myocardial anti-fibrosis and antioxidants for the first time, and the results demonstrate that the effect of ECM stiffness on drug efficacy should also be considered in the treatment of cardiovascular diseases.

An Overview of In Vitro Drug Release Methods for Drug-Eluting Stents

The drug release profile of drug-eluting stents (DESs) is affected by a number of factors, including the formulation, design, and physicochemical properties of the utilized material. DES has been around for twenty years and despite its widespread clinical use, and efficacy in lowering the rate of target lesion restenosis, it still requires additional development to reduce side effects and provide long-term clinical stability. Unfortunately, for analyzing these implants, there is still no globally accepted in vitro test method. This is owing to the stent's complexity as well as the dynamic arterial compartments of the blood and vascular wall. The former is the source of numerous biological, chemical, and physical mechanisms that are more commonly observed in tissue, lumen, and DES. As a result, universalizing bio-relevant apparatus, suitable for liberation testing of such complex implants is difficult. This article aims to provide a comprehensive review of the methods used for in vitro release testing of DESs. Aspects related to the correlation of the release profiles in the cases of in vitro and in vivo are also addressed.

Sirolimus Release from Biodegradable Polymers for Coronary Stent Application: A Review

Drug-eluting stents (DESs) are commonly used for the treatment of coronary artery disease. The evolution of the drug-eluting layer on the surface of the metal stent plays an important role in DES functionality. Here, the use of biodegradable polymers has emerged as an attractive strategy because it minimizes the occurrence of late thrombosis after stent implantation. Furthermore, understanding the drug-release behavior of DESs is also important for improving the safety and efficacy of stent treatments. Drug release from biodegradable polymers has attracted extensive research attention because biodegradable polymers with different properties show different drug-release behaviors. Molecular weight, composition, glass transition temperature, crystallinity, and the degradation rate are important properties affecting the behavior of polymers. Sirolimus is a conventional anti-proliferation drug and is the most widely used drug in DESs. Sirolimus-release behavior affects endothelialization and thrombosis formation after DES implantation. In this review, we focus on sirolimus release from biodegradable polymers, including synthetic and natural polymers widely used in the medical field. We hope this review will provide valuable up-to-date information on this subject and contribute to the further development of safe and efficient DESs.

Design Challenges in Polymeric Scaffolds for Tissue Engineering

Numerous surgical procedures are daily performed worldwide to replace and repair damaged tissue. Tissue engineering is the field devoted to the regeneration of damaged tissue through the incorporation of cells in biocompatible and biodegradable porous constructs, known as scaffolds. The scaffolds act as host biomaterials of the incubating cells, guiding their attachment, growth, differentiation, proliferation, phenotype, and migration for the development of new tissue. Furthermore, cellular behavior and fate are bound to the biodegradation of the scaffold during tissue generation. This article provides a critical appraisal of how key biomaterial scaffold parameters, such as structure architecture, biochemistry, mechanical behavior, and biodegradability, impart the needed morphological, structural, and biochemical cues for eliciting cell behavior in various tissue engineering applications. Particular emphasis is given on specific scaffold attributes pertaining to skin and brain tissue generation, where further progress is needed (skin) or the research is at a relatively primitive stage (brain), and the enumeration of some of the most important challenges regarding scaffold constructs for tissue engineering.

Biomimetic clotrimazole-loaded PLGA films with enhanced adhesiveness for controlled drug release

Biomimetic adhesive surfaces have a number of potential applications in the pharmaceutical and biomedical fields. Fabrication techniques must be adapted to biocompatible and biodegradable materials required for controlled drug release applications. In this study biomimetic adhesive poly(lactic-co-glycolic acid) (PLGA) films loaded with different concentrations of clotrimazole (CTZ) were prepared without combining other adhesive excipients as a controlled release system for potential local oral drug delivery. The films were fully characterized from morphological point of view, and CTZ-loaded biomimetic films exhibited adequate surface pH values, high drug encapsulation efficiency, and loading content. The adhesion strength of the obtained films was significantly higher compared to a flat film reference under different contact conditions. Thermal analysis indicated a decrease of drug crystallinity upon incorporation into PLGA films. The in vitro release of CTZ from PLGA biomimetic films was tested in simulated saliva, and it exhibited an initial burst release, accompanied by a sustained release phase over 10 days. Finally, the mucoadhesive properties of the obtained films was studied using agar/mucin plate as a representative mucosal substrate, and the results demonstrated superior mucoadhesion potential of CTZ-loaded biomimetic film in comparison to its flat counterpart. Having demonstrated the ability to load CTZ into PLGA biomimetic films with enhanced adhesion capacity, the potential use in local oral drug delivery applications warrants further in vitro and in vivo investigations.

Smart Drug Release from Medical Devices

Medical devices are becoming key players on health monitoring and treatment. Advances in materials science and electronics have paved the way to the design of advanced wearable, insertable, and implantable medical devices suitable for the prevention and cure of diseases and the physical or functional replacement of damaged tissues or organs. However, intimate and prolonged contact of the medical devices with the human body increases the risks of adverse foreign-body reactions and biofilm formation. Drugs can be included in/on the medical device not only to minimize the risks but also to improve the therapeutic outcomes. Drug-eluting medical devices can deliver the drug in the place where it is needed using lower doses and avoiding systemic effects. Drug-device combination products that release the drug following preestablished rates have already demonstrated their clinical relevance. The aim of this mini-review is to bring attention to medical devices that can actively regulate drug release as a function of tiny changes in their environment, caused by the pathology itself, microorganisms adhesion or some external events. Thus, endowing medical devices with stimuli-responsiveness should allow for precise, on-demand, regulated release of the ancillary drugs to expand the therapeutic performance of the medical device and also should serve as a first step to offer personalized solutions to each patient. Main sections deal with smart drug-eluting medical devices that are sensitive to infection-related stimuli, natural healing processes, mechanical forces, electric fields, ultrasound, near-infrared radiation, or chemicals such as vitamin C.