Regulation of sequential release of growth factors using bilayer polymeric nanoparticles for cardiac tissue engineering

Biomaterials / bioinks and extrusion bioprinting

Bioinks are formulations of biomaterials and living cells, sometimes with growth factors or other biomolecules, while extrusion bioprinting is an emerging technique to apply or deposit these bioinks or biomaterial solutions to create three-dimensional (3D) constructs with architectures and mechanical/biological properties that mimic those of native human tissue or organs. Printed constructs have found wide applications in tissue engineering for repairing or treating tissue/organ injuries, as well as in vitro tissue modelling for testing or validating newly developed therapeutics and vaccines prior to their use in humans. Successful printing of constructs and their subsequent applications rely on the properties of the formulated bioinks, including the rheological, mechanical, and biological properties, as well as the printing process. This article critically reviews the latest developments in bioinks and biomaterial solutions for extrusion bioprinting, focusing on bioink synthesis and characterization, as well as the influence of bioink properties on the printing process. Key issues and challenges are also discussed along with recommendations for future research.

Sulfonated Thermoresponsive Injectable Gel for Sequential Release of Therapeutic Proteins to Protect Cardiac Function after Myocardial Infarction

Myocardial infarction causes cardiomyocyte death and persistent inflammatory responses, which generate adverse pathological remodeling. Delivering therapeutic proteins from injectable materials in a controlled-release manner may present an effective biomedical approach for treating this disease. A thermoresponsive injectable gel composed of chitosan, conjugated with poly(N-isopropylacrylamide) and sulfonate groups, was developed for spatiotemporal protein delivery to protect cardiac function after myocardial infarction. The thermoresponsive gel delivered vascular endothelial growth factor (VEGF), interleukin-10 (IL-10), and platelet-derived growth factor (PDGF) in a sequential and sustained manner in vitro. An acute myocardial infarction mouse model was used to evaluate polymer biocompatibility and to determine therapeutic effects from the delivery system on cardiac function. Immunohistochemistry showed biocompatibility of the hydrogel, while the controlled delivery of the proteins reduced macrophage infiltration and increased vascularization. Echocardiography showed an improvement in ejection fraction and fractional shortening after injecting the thermal gel and proteins. A factorial design of experimental study was implemented to optimize the delivery system for the best combination and doses of proteins for further increasing stable vascularization and reducing inflammation using a subcutaneous injection mouse model. The results showed that VEGF, IL-10, and FGF-2 demonstrated significant contributions toward promoting long-term vascularization, while PDGF's effect was minimal.

Novel trends, challenges and new perspectives for enamel repair and regeneration to treat dental defects

Dental enamel is the hardest tissue in the human body, providing external protection for the tooth against masticatory forces, temperature changes and chemical stimuli. Once enamel is damaged/altered by genetic defects, dental caries, trauma, and/or dental wear, it cannot repair itself due to the loss of enamel producing cells following the tooth eruption. The current restorative dental materials are unable to replicate physico-mechanical, esthetic features and crystal structures of the native enamel. Thus, development of alternative approaches to repair and regenerate enamel defects is much needed but remains challenging due to the structural and functional complexities involved. This review paper summarizes the clinical aspects to be taken into consideration for the development of optimal therapeutic approaches to tackle dental enamel defects. It also provides a comprehensive overview of the emerging acellular and cellular approaches proposed for enamel remineralization and regeneration. Acellular approaches aim to artificially synthesize or re-mineralize enamel, whereas cell-based strategies aim to mimic the natural process of enamel development given that epithelial cells can be stimulated to produce enamel postnatally during the adult life. The key issues and current challenges are also discussed here, along with new perspectives for future research to advance the field of regenerative dentistry.

Applications of nanoparticles in cardiovascular imaging and therapeutics

Cardiovascular disease (CVD) is a major health problem afflicting millions of people worldwide. Early detection methods are lacking, and current therapies have significant limitations. Recently, there has been a surge in the number of studies investigating the utilisation of nanoparticles in cardiovascular imaging and therapy. With respect to cardiovascular imaging, previous studies have looked at the role of nanoparticles in thrombus formation, angiogenesis, blood pool and stem cell imaging. Whereas, with respect to therapy, nanoparticles have been studied for delivering drugs and nucleic acids, specifically to the site of interest; in the context of cardiac regeneration; and its potential in refining current therapy guidelines for CVD management. This review aims to extensively summarise the studies that have been conducted investigating the role of nanoparticles in different aspects of cardiovascular imaging and therapy.

Acute myocardial infarction therapy: in vitro and in vivo evaluation of atrial natriuretic peptide and triphenylphosphonium dual ligands modified, baicalin-loaded nanoparticulate system

Background

Myocardial infarction (MI) is one of the most common ischemic heart diseases. It is very essential to explore new types of cardioprotective drugs delivery systems in this area.

Objective

The aim of the present study was to investigate the protective effect of baicalin (BA) and puerarin (PU) against acute MI rat models. BA and PU co-loaded nanoparticulate system were developed to improve bioavailability of the drugs, to prolong retention time in vivo and to enhance the protective effect.

Methods

In the present study, ANP and TPP contained ligands were synthesized. ANP/TPP-BN-LPNs were prepared and its physico-chemical properties were evaluated. The MI therapy efficiency of ANP/TPP-BN-LPNs was assessed in rats after intravenous injection. Single ligand contained LPNs, no ligand contained LPNs, and BN solution formulations were also prepared and used for the comparison.

Results

ANP/TPP-BN-LPNs were uniform and spheroidal particles. The size of ANP/TPP-BN-LPNs was 98.5 ± 2.9 nm, with a zeta potential of –19.5 ± 1.9 mV. The dual ligands modified LPNs exhibited significantly improved therapeutic efficiency compared with the single ligand modified LPNs and other systems. In vivo infarct therapy studies in rats proved that ANP/TPP-BN-LPNs were a promising system for efficient delivery of cardiovascular drugs for the treatment of cardiovascular diseases.

Conclusions

ANP/TPP-BN-LPNs could be used as a long-circulating and heart-targeting drug delivery system.

Tissues with Patterned Vessels or Protein Release Induce Vascular Chemotaxis in an In Vitro Platform

Engineered tissues designed for translational applications in regenerative medicine require vascular networks to deliver oxygen and nutrients rapidly to the implanted cells. A limiting factor of in vivo translation is the rapid and successful inosculation, or connection, of host and implanted vascular networks and subsequent perfusion of the implant. An approach gaining favor in vascular tissue engineering is to provide instructive cues from the engineered tissue to enhance host vascular penetration and connection with the implant. Here, we use a novel in vitro platform based on the aortic ring assay to evaluate the impact of patterned, endothelialized vessels or growth factor release from engineered constructs on preinosculative vascular cell outgrowth from surrogate host tissue in a controlled, defined environment, and introduce robust tools for evaluating vascular morphogenesis and chemotaxis. We demonstrate the creation of engineered vessels at the arteriole scale, which develop basement membrane, exhibit tight junctions, and actively sprout into the surrounding bulk hydrogel. Vessel-containing constructs are co-cultured adjacent to rodent aortic rings, and the resulting heterocellular outgrowth is quantified. Cells originating from the aortic ring migrate preferentially toward constructs containing engineered vessels with 1.5-fold faster outgrowth kinetics, 2.5-fold increased cellular density, and 1.6-fold greater network formation versus control (no endothelial cells and growth factor-reduced culture medium). Growth factor release from constructs with nonendothelialized channels and in reduced factor medium equivalently stimulates sustained vascular outgrowth distance, cellular density, and network formation, akin to engineered vessels in endothelial growth medium 2 (EGM-2) medium. In conclusion, we show that three-dimensional endothelialized patterned vessels or growth factor release stimulate a robust, host-derived vascular cell chemotactic response at early time points critical for instructive angiogenic cues. Further, we developed robust, unbiased tools to quantify metrics of vascular morphogenesis and preinosculative heterocellular outgrowth from rat aortic rings and demonstrated the utility of our complex, controlled environment, heterocellular in vitro platform. Impact statement Using a novel in vitro platform, we show that engineered constructs with patterned vessels or angiogenic growth factor release, two methods of instructing host revascularization responses, equivalently improve early host-derived vascular outgrowth. Our platform leverages the aortic ring assay in a tissue engineering context to study preinosculative vascular cell chemotaxis from surrogate host vascular cells in response to paracrine cues from co-cultured engineered tissues using robust, open-source quantification tools. Our accessible and flexible platform enables translationally focused studies in revascularization using implantable therapeutics containing prepatterned vessels with greater environmental control than in vivo studies to advance vascular tissue engineering.

De novo Drug Delivery Modalities for Treating Damaged Hearts: Current Challenges and Emerging Solutions

Cardiovascular disease (CVD) is the leading cause of mortality, resulting in approximately one-third of deaths worldwide. Among CVD, acute myocardial infarctions (MI) is the leading cause of death. Current treatment modalities for treating CVD have improved over the years, but the demand for new and innovative therapies has been on the rise. The field of nanomedicine and nanotechnology has opened a new paradigm for treating damaged hearts by providing improved drug delivery methods, specifically targeting injured areas of the myocardium. With the advent of innovative biomaterials, newer therapeutics such as growth factors, stem cells, and exosomes have been successfully delivered to the injured myocardial tissue, promoting improvement in cardiac function. This review focuses on three major drug delivery modalities: nanoparticles, microspheres, and hydrogels, and their potential for treating damaged hearts following an MI.

Investigation of human adipose stem cell-derived nanoparticles as a biomimetic carrier for intracellular drug delivery

Prevailing drug delivery strategies rely on the use of synthetic nanocarriers like metal nanoparticles and polymeric liposomes to control the release of therapeutics in a safe and efficacious manner. Despite their high efficiency in encapsulating drugs, these systems exhibit low to moderate biocompatibility, low cellular uptake, and sub-optimal targeting capabilities. Conversely, cell-derived nanoparticles (CDNs) have emerged as a promising alternative to these artificial drug delivery carriers for achieving safer clinical outcomes. In this study, we have generated CDNs from human adipose-derived stem cells (hASCs) using a high-yield fabrication strategy. Briefly, hASCs were subjected to a cell-shearing approach that entails passing the cells through an array of filters, along with serial centrifugations to eliminate intracellular contents. Ultimately, the fragmented parent cell membrane self-assembles to form the CDNs. This strategy successfully converted 80% of the plasma membrane into the novel nanocarriers with an average hydrodynamic diameter of 100 nm. Stability analysis confirmed that the formulated nanocarriers are stable for over 3 weeks, making them a potent candidate for long-term therapies. To demonstrate their potential in drug delivery, we encapsulated trehalose, a cell-impermeable sugar molecule, into the CDNs via an extrusion loading technique. Drug-loaded CDNs were effectively internalized into human umbilical vein endothelial cells (HUVECs) and hASCs, without inducing any significant cytotoxicity. Overall, the findings of this study establish the potential of hASC-derived CDNs as customizable biomimetic nanocarriers for drug delivery and other translational medicine applications.

Bioprinting for combating infectious diseases

Infectious diseases have the ability to impact health on a global scale, as is being demonstrated by the current coronavirus disease 2019 (COVID-19) pandemic. The strenuous circumstances related to this global health crisis have been highlighting the challenges faced by the biomedical field in combating infectious diseases. Notably, printing technologies have advanced rapidly over the last decades, allowing for the incorporation of living cells in the printing process (or bioprinting) to create constructs that are able to serve as in vitro tissue or virus-disease models in combating infectious diseases. This paper describes applications of bioprinting in addressing the challenges faced in combating infectious diseases, with a specific focus on in vitro modelling and on development of therapeutic agents and vaccines. Integration of these technologies may allow for a more efficient and effective response to current and future pandemics.

Cardiomyocyte Induction and Regeneration for Myocardial Infarction Treatment: Cell Sources and Administration Strategies

Occlusion of coronary artery and subsequent damage or death of myocardium can lead to myocardial infarction (MI) and even heart failure-one of the leading causes of deaths world wide. Notably, myocardium has extremely limited regeneration potential due to the loss or death of cardiomyocytes (i.e., the cells of which the myocardium is comprised) upon MI. A variety of stem cells and stem cell-derived cardiovascular cells, in situ cardiac fibroblasts and endogenous proliferative epicardium, have been exploited to provide renewable cellular sources to treat injured myocardium. Also, different strategies, including direct injection of cell suspensions, bioactive molecules, or cell-incorporated biomaterials, and implantation of artificial cardiac scaffolds (e.g., cell sheets and cardiac patches), have been developed to deliver renewable cells and/or bioactive molecules to the MI site for the myocardium regeneration. This article briefly surveys cell sources and delivery strategies, along with biomaterials and their processing techniques, developed for MI treatment. Key issues and challenges, as well as recommendations for future research, are also discussed.

Nanoengineering in Cardiac Regeneration: Looking Back and Going Forward

To deliver on the promise of cardiac regeneration, an integration process between an emerging field, nanomedicine, and a more consolidated one, tissue engineering, has begun. Our work aims at summarizing some of the most relevant prevailing cases of nanotechnological approaches applied to tissue engineering with a specific interest in cardiac regenerative medicine, as well as delineating some of the most compelling forthcoming orientations. Specifically, this review starts with a brief statement on the relevant clinical need, and then debates how nanotechnology can be combined with tissue engineering in the scope of mimicking a complex tissue like the myocardium and its natural extracellular matrix (ECM). The interaction of relevant stem, precursor, and differentiated cardiac cells with nanoengineered scaffolds is thoroughly presented. Another correspondingly relevant area of experimental study enclosing both nanotechnology and cardiac regeneration, e.g., nanoparticle applications in cardiac tissue engineering, is also discussed.

Use of Nanoparticles in Tissue Engineering and Regenerative Medicine

Advances in nanoparticle (NP) production and demand for control over nanoscale systems have had significant impact on tissue engineering and regenerative medicine (TERM). NPs with low toxicity, contrasting agent properties, tailorable characteristics, targeted/stimuli-response delivery potential, and precise control over behavior (via external stimuli such as magnetic fields) have made it possible their use for improving engineered tissues and overcoming obstacles in TERM. Functional tissue and organ replacements require a high degree of spatial and temporal control over the biological events and also their real-time monitoring. Presentation and local delivery of bioactive (growth factors, chemokines, inhibitors, cytokines, genes etc.) and contrast agents in a controlled manner are important implements to exert control over and monitor the engineered tissues. This need resulted in utilization of NP based systems in tissue engineering scaffolds for delivery of multiple growth factors, for providing contrast for imaging and also for controlling properties of the scaffolds. Depending on the application, materials, as polymers, metals, ceramics and their different composites can be utilized for production of NPs. In this review, we will cover the use of NP systems in TERM and also provide an outlook for future potential use of such systems.

Materials Science and Design Principles of Growth Factor Delivery Systems in Tissue Engineering and Regenerative Medicine

Growth factors (GFs) are signaling molecules that direct cell development by providing biochemical cues for stem cell proliferation, migration, and differentiation. GFs play a key role in tissue regeneration, but one major limitation of GF-based therapies is dosage-related adverse effects. Additionally, the clinical applications and efficacy of GFs are significantly affected by the efficiency of delivery systems and other pharmacokinetic factors. Hence, it is crucial to design delivery systems that provide optimal activity, stability, and tunable delivery for GFs. Understanding the physicochemical properties of the GFs and the biomaterials utilized for the development of biomimetic GF delivery systems is critical for GF-based regeneration. Many different delivery systems have been developed to achieve tunable delivery kinetics for single or multiple GFs. The identification of ideal biomaterials with tunable properties for spatiotemporal delivery of GFs is still challenging. This review characterizes the types, properties, and functions of GFs, the materials science of widely used biomaterials, and various GF loading strategies to comprehensively summarize the current delivery systems for tunable spatiotemporal delivery of GFs aimed for tissue regeneration applications. This review concludes by discussing fundamental design principles for GF delivery vehicles based on the interactive physicochemical properties of the proteins and biomaterials.

Engineered circulatory scaffolds for building cardiac tissue

Heart failure (HF) is the terminal state of cardiovascular disease (CVD), leading numerous patients to death every year. Cardiac tissue engineering is a multidisciplinary field of creating functional cardiac patches in vitro to promote cardiac function after transplantation onto damaged zone, giving the hope for patients with end-stage HF. However, the limited thickness of cardiac patches results in the graft failure of survival and function due to insufficient blood supply. To date, prevascularized cardiac tissue, with the use of circulatory scaffolds, holds the promise to be inosculated and perfused with host vasculature to eventually promote cardiac pumping function. Circulatory scaffolds play its role to provide oxygen and nutrients and take metabolic wastes away, and achieve anastomosis with host vasculature in vivo. Of worth note, heart-on-a-chip based on circulatory scaffolds now has been considered as a valuable unit to broaden the research for building cardiac tissue. In this review, we will present recent different strategies to engineer circulatory scaffolds for building cardiac tissue with microvasculature, followed by its current state and future direction.

Integrated approaches to spatiotemporally directing angiogenesis in host and engineered tissues

The field of tissue engineering has turned towards biomimicry to solve the problem of tissue oxygenation and nutrient/waste exchange through the development of vasculature. Induction of angiogenesis and subsequent development of a vascular bed in engineered tissues is actively being pursued through combinations of physical and chemical cues, notably through the presentation of topographies and growth factors. Presenting angiogenic signals in a spatiotemporal fashion is beginning to generate improved vascular networks, which will allow for the creation of large and dense engineered tissues. This review provides a brief background on the cells, mechanisms, and molecules driving vascular development (including angiogenesis), followed by how biomaterials and growth factors can be used to direct vessel formation and maturation. Techniques to accomplish spatiotemporal control of vascularization include incorporation or encapsulation of growth factors, topographical engineering, and 3D bioprinting. The vascularization of engineered tissues and their application in angiogenic therapy in vivo is reviewed herein with an emphasis on the most densely vascularized tissue of the human body - the heart.

STATEMENT OF SIGNIFICANCE

Vascularization is vital to wound healing and tissue regeneration, and development of hierarchical networks enables efficient nutrient transfer. In tissue engineering, vascularization is necessary to support physiologically dense engineered tissues, and thus the field seeks to induce vascular formation using biomaterials and chemical signals to provide appropriate, pro-angiogenic signals for cells. This review critically examines the materials and techniques used to generate scaffolds with spatiotemporal cues to direct vascularization in engineered and host tissues in vitro and in vivo. Assessment of the field's progress is intended to inspire vascular applications across all forms of tissue engineering with a specific focus on highlighting the nuances of cardiac tissue engineering for the greater regenerative medicine community.

Tissue Engineering to Improve Immature Testicular Tissue and Cell Transplantation Outcomes: One Step Closer to Fertility Restoration for Prepubertal Boys Exposed to Gonadotoxic Treatments

Despite their important contribution to the cure of both oncological and benign diseases, gonadotoxic therapies present the risk of a severe impairment of fertility. Sperm cryopreservation is not an option to preserve prepubertal boys’ reproductive potential, as their seminiferous tubules only contain spermatogonial stem cells (as diploid precursors of spermatozoa). Cryobanking of human immature testicular tissue (ITT) prior to gonadotoxic therapies is an accepted practice. Evaluation of cryopreserved ITT using xenotransplantation in nude mice showed the survival of a limited proportion of spermatogonia and their ability to proliferate and initiate differentiation. However, complete spermatogenesis could not be achieved in the mouse model. Loss of germ cells after ITT grafting points to the need to optimize the transplantation technique. Tissue engineering, a new branch of science that aims at improving cellular environment using scaffolds and molecules administration, might be an approach for further progress. In this review, after summarizing the lessons learned from human prepubertal testicular germ cells or tissue xenotransplantation experiments, we will focus on the benefits that might be gathered using bioengineering techniques to enhance transplantation outcomes by optimizing early tissue graft revascularization, protecting cells from toxic insults linked to ischemic injury and exploring strategies to promote cellular differentiation.

Aggregation Behavior of Nano-Silica in Polyvinyl Alcohol/Polyacrylamide Hydrogels Based on Dissipative Particle Dynamics

Due to the aggregation behavior of nano-silica in aqueous solution, the use of nano-silica without surface modification for synthesizing hydrogels is still a challenging task. This paper presents our study on the use of dissipative particle dynamics simulations to discover the aggregation behavior of nano-silica in polyvinyl alcohol (PVA)/polyacrylamide (PAM) blended hydrogels. By simulations, we aimed at investigating the effects of such factors as nano-silica content, polymer component ratio, temperature and shear rate on the aggregation behavior of nano-silica in terms of the mesoscopic morphologies and the relative concentration distribution functions. Our results reveal that the dispersion of nano-silica is seen if the nano-silica content is increased to 1.5%, and the aggregation of nano-silica becomes noticeable in blended hydrogels with an increase in the nano-silica content. This finding agrees well with the experimental results obtained by means of scanning electron microscopy. Furthermore, it is also found that the dispersion of nano-silica becomes more uniform with an increase in PAM content, temperature and shear rate. These findings greatly enrich our understanding of the aggregation behavior of nano-silica in PVA/PAM blended hydrogels.

Bioprinting Pattern-Dependent Electrical/Mechanical Behavior of Cardiac Alginate Implants: Characterization and Ex Vivo Phase-Contrast Microtomography Assessment

Three-dimensional (3D)-bioprinting techniques may be used to modulate electrical/mechanical properties and porosity of hydrogel constructs for fabrication of suitable cardiac implants. Notably, characterization of these properties after implantation remains a challenge, raising the need for the development of novel quantitative imaging techniques for monitoring hydrogel implant behavior in situ. This study aims at (i) assessing the influence of hydrogel bioprinting patterns on electrical/mechanical behavior of cardiac implants based on a 3D-printing technique and (ii) investigating the potential of synchrotron X-ray phase-contrast imaging computed tomography (PCI-CT) for estimating elastic modulus/impedance/porosity and microstructural features of 3D-printed cardiac implants in situ via an ex vivo study. Alginate laden with human coronary artery endothelial cells was bioprinted layer by layer, forming cardiac constructs with varying architectures. The elastic modulus, impedance, porosity, and other structural features, along with the cell viability and degradation of printed implants were examined in vitro over 25 days. Two selected cardiac constructs were surgically implanted onto the myocardium of rats and 10 days later, the rat hearts with implants were imaged ex vivo by means of PCI-CT at varying X-ray energies and CT-scan times. The elastic modulus/impedance, porosity, and structural features of the implant were inferred from the PCI-CT images by using statistical models and compared with measured values. The printing patterns had significant effects on implant porosity, elastic modulus, and impedance. A particular 3D-printing pattern with an interstrand distance of 900 μm and strand alignment angle of 0/45/90/135° provided relatively higher stiffness and electrical conductivity with a suitable porosity, maintaining high cell viability over 7 days. The X-ray photon energy of 30-33 keV utilizing a CT-scan time of 1-1.2 h resulted in a low-dose PCI-CT, which provided a good visibility of the low-X-ray absorbent alginate implants. After 10 days postimplantation, the PCI-CT provided a reasonably accurate estimation of implant strand thickness and alignment, pore size and interconnectivity, porosity, elastic modulus, and impedance, which were consistent with our measurements. Findings from this study suggest that 3D-printing patterns can be used to modulate electrical/mechanical behavior of alginate implants, and PCI-CT can be potentially used as a 3D quantitative imaging tool for assessing structural and electrical/mechanical behavior of hydrogel cardiac implants in small animal models.

Potential of propagation-based synchrotron X-ray phase-contrast computed tomography for cardiac tissue engineering

Hydrogel-based cardiac tissue engineering offers great promise for myocardial infarction repair. The ability to visualize engineered systems in vivo in animal models is desired to monitor the performance of cardiac constructs. However, due to the low density and weak X-ray attenuation of hydrogels, conventional radiography and micro-computed tomography are unable to visualize the hydrogel cardiac constructs upon their implantation, thus limiting their use in animal systems. This paper presents a study on the optimization of synchrotron X-ray propagation-based phase-contrast imaging computed tomography (PCI-CT) for three-dimensional (3D) visualization and assessment of the hydrogel cardiac patches. First, alginate hydrogel was 3D-printed into cardiac patches, with the pores filled by fibrin. The hydrogel patches were then surgically implanted on rat hearts. A week after surgery, the hearts including patches were excised and embedded in a soft-tissue-mimicking gel for imaging by using PCI-CT at an X-ray energy of 25 keV. During imaging, the sample-to-detector distances, CT-scan time and the region of interest (ROI) were varied and examined for their effects on both imaging quality and radiation dose. The results showed that phase-retrieved PCI-CT images provided edge-enhancement fringes at a sample-to-detector distance of 147 cm that enabled visualization of anatomical and microstructural features of the myocardium and the implanted patch in the tissue-mimicking gel. For visualization of these features, PCI-CT offered a significantly higher performance than the dual absorption-phase and clinical magnetic resonance (3 T) imaging techniques. Furthermore, by reducing the total CT-scan time and ROI, PCI-CT was examined for lowering the effective dose, meanwhile without much loss of imaging quality. In effect, the higher soft tissue contrast and low-dose potential of PCI-CT has been used along with an acceptable overall animal dose to achieve the high spatial resolution needed for cardiac implant visualization. As a result, PCI-CT at the identified imaging parameters offers great potential for 3D assessment of microstructural features of hydrogel cardiac patches.

Delivery of growth factor-based therapeutics in vascular diseases: Challenges and strategies

Either cardiovascular or peripheral vascular diseases have become the major cause of morbidity and mortality worldwide. Recently, growth factors therapeutics, whatever administrated in form of exogenous growth factors or their relevant genes have been discovered to be an effective strategy for the prevention and therapy of vascular diseases, because of their promoting angiogenesis. Besides, as an alternative, stem cell-based therapy has been also developed in view of their paracrine-mediated effect or ability of differentiation toward angiogenesis-related cells under assistance of growth factors. Despite of being specific and potent, no matter growth factors or stem cells-based therapy, their full clinical transformation is limited from bench to bedside. In this review, the potential choices of therapeutic modes based on types of different growth factors or stem cells were firstly summarized for vascular diseases. The confronted various challenges such as lack of non-invasive delivery method, the physiochemical challenge, the short half-life time, and poor cell survival, were carefully analyzed for these therapeutic modes. Various strategies to overcome these limitations are put forward from the perspective of drug delivery. The expertised design of a suitable delivery form will undoubtedly provide valuable insight into their clinical application in the regenerative medicine.

Computational nanomedicine for mechanistic elucidation of bilayer nanoparticle-mediated release for tissue engineering

Aim: Temporal control of growth-factor release from nanoparticles is essential to many tissue engineering applications, yet remains a challenge due to its complicated behavior. The interplay between nanoparticle characteristics and release mechanisms can be captured using computational models. This study aims to develop two novel models to represent the release of bilayer nanoparticles. Materials & methods: Bilayer nanoparticles were prepared and characterized experimentally. ‘Local volume averaging’ and ‘Geno-Mechanistic’ models were developed and validated with experiments, and then used to identify critical release parameters and elucidate the release mechanisms. Results: Models presented an agreement with experimental data and successfully estimated transport/degradation parameters, which were closely associated with nanoparticle polymer mass ratio and crystallinity. Models suggested that despite relatively rapid core degradation, shell predominantly controlled overall release patterns. Conclusion: The developed models and computational frameworks offer a great potential for optimizing/tuning bilayer polymeric nanoparticles for tissue engineering applications.

RGD modified and PEGylated lipid nanoparticles loaded with puerarin: Formulation, characterization and protective effects on acute myocardial ischemia model

CONTEXT

Puerarin has been widely used as a therapeutic agent for the treatment of cardiovascular diseases. However, its rapid elimination half-life in plasma and poor water solubility limits its clinical efficacy.

OBJECTIVE

RGD modified and PEGylated solid lipid nanoparticles loaded with puerarin (RGD/PEG-PUE-SLN) were developed to improve bioavailability of PUE, to prolong retention time in vivo and to enhance its protective effect on acute myocardial ischemia model.

METHODS

In the present study, RGD-PEG-DSPE was synthesized. RGD/PEG-PUE-SLN were prepared by the solvent evaporation method with some modifications. The physicochemical properties of NPs were characterized, the pharmacokinetics, biodistribution, pharmacodynamic behavior of RGD/PEG-PUE-SLN were evaluated in acute MI rats.

RESULTS

The mean diameter, zeta potential, entrapment efficiency and drug loading capacity for RGD/PEG-PUE-SLN were observed as 110.5nm, -26.2mV, 85.7% and 16.5% respectively. PUE from RGD/PEG-PUE-SLN exhibited sustained drug release with a burst release during the initial 12h and a followed sustained release. Pharmacokinetics results indicated that AUC increased from 52.93 (μg/mLh) for free PUE to 176.5 (μg/mLh) for RGD/PEG-PUE-SLN. Similarly, T_1/2 increased from 0.73h for free PUE to 2.62h for RGD/PEG-PUE-SLN. RGD/PEG-PUE-SLN exhibited higher drug concentration in the heart and plasma compared with other PUE formulations. It can be clearly seen that the infarct size of RGD/PEG-PUE-SLN is the lowest among all the formulation.

CONCLUSION

We conclude that RGD modified and PEGylated SLN are promising candidate delivery vehicles for cardioprotective drugs in treatment of myocardial infarction.