Aiming for the heart: targeted delivery of drugs to diseased cardiac tissue

Fillable Magnetic Microrobots for Drug Delivery to Cardiac Tissues In Vitro

Many cardiac diseases, such as arrhythmia or cardiogenic shock, cause irregular beating patterns that must be regulated to prevent disease progression toward heart failure. Treatments can include invasive surgery or high systemic drug dosages, which lack precision, localization, and control. Drug delivery systems (DDSs) that can deliver cargo to the cardiac injury site could address these unmet clinical challenges. Here, a microrobotic DDS that can be mobilized to specific sites via magnetic control is presented. This DDS incorporates an internal chamber that can protect drug cargo. Furthermore, the DDS contains a tunable thermosensitive sealing layer that gradually degrades upon exposure to body temperature, enabling prolonged drug release. Once loaded with the small molecule drug norepinephrine, this microrobotic DDS modulated beating frequency in induced pluripotent stem-cell derived cardiomyocytes (iPSC-CMs) in a dose-dependent manner, thus simulating drug delivery to cardiac cells in vitro. The DDS also navigates several maze-like structures seeded with cardiomyocytes to demonstrate precise locomotion under a rotating low-intensity magnetic field and on-site drug delivery. This work demonstrates the utility of a magnetically actuating DDS for precise, localized, and controlled drug delivery which is of interest for a myriad of future opportunities such as in treating cardiac diseases.

Efficient drug delivery potential and antimicrobial activity of biocompatible hydrogels of dextrin/Na-alginate/PVA

Ceftriaxone sodium belongs to the third-generation cephalosporin group and is used intramuscular and intravenous route as a broad-spectrum antibiotic. This research aims to prepare biocompatible hydrogels for targeted delivery of ceftriaxone sodium by parental route. Different proportions of polymers (natural and synthetic) in the presence of cross-linker were synthesized by solvent casting method. Ceftriaxone sodium was loaded in hydrogels in different concentrations and its drug release behavior was evaluated along with swelling and biodegradation analysis. The characterization of hydrogel was done by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) to analyze surface morphology and functional groups involved in the formation of dextrin/Na-alginate/PVA hydrogels loaded with the drug. Thermogravimetric analysis (TGA) was confirmed by thermal stability and degradation pattern of loaded and unloaded hydrogels. The drug-loaded samples presented promising antimicrobial activity against S. aureus and P. multocida and their cytotoxic nature was also studied. Drug release analysis using simulated intestinal fluid (SIF) and phosphate buffer saline(PBS) for the circulatory system shows the consistent release of the drug. The findings unveiled the development of a biocompatible and innovative hydrogel, which has potential advantages for biomedical application, particularly in enhancing the therapeutic efficacy of ceftriaxone sodium drug.

Delivery of triptolide: a combination of traditional Chinese medicine and nanomedicine

As a natural product with various biological activities, triptolide (TP) has been reported in anti-inflammatory, anti-tumor and anti-autoimmune studies. However, the narrow therapeutic window, poor water solubility, and fast metabolism limit its wide clinical application. To reduce its adverse effects and enhance its efficacy, research and design of targeted drug delivery systems (TDDS) based on nanomaterials is one of the most viable strategies at present. This review summarizes the reports and studies of TDDS combined with TP in recent years, including passive and active targeting of drug delivery systems, and specific delivery system strategies such as polymeric micelles, solid lipid nanoparticles, liposomes, and stimulus-responsive polymer nanoparticles. The reviewed literature presented herein indicates that TDDS is a multifunctional and efficient method for the delivery of TP. In addition, the advantages and disadvantages of TDDS are sorted out, aiming to provide reference for the combination of traditional Chinese medicine and advanced nano drug delivery systems (NDDS) in the future.

Regenerative strategies for the consequences of myocardial infarction: Chronological indication and upcoming visions

Heart muscle injury and an elevated troponin level signify myocardial infarction (MI), which may result in defective and uncoordinated segments, reduced cardiac output, and ultimately, death. Physicians apply thrombolytic therapy, coronary artery bypass graft (CABG) surgery, or percutaneous coronary intervention (PCI) to recanalize and restore blood flow to the coronary arteries, albeit they were not convincingly able to solve the heart problems. Thus, researchers aim to introduce novel substitutional therapies for regenerating and functionalizing damaged cardiac tissue based on engineering concepts. Cell-based engineering approaches, utilizing biomaterials, gene, drug, growth factor delivery systems, and tissue engineering are the most leading studies in the field of heart regeneration. Also, understanding the primary cause of MI and thus selecting the most efficient treatment method can be enhanced by preparing microdevices so-called heart-on-a-chip. In this regard, microfluidic approaches can be used as diagnostic platforms or drug screening in cardiac disease treatment. Additionally, bioprinting technique with whole organ 3D printing of human heart with major vessels, cardiomyocytes and endothelial cells can be an ideal goal for cardiac tissue engineering and remarkable achievement in near future. Consequently, this review discusses the different aspects, advancements, and challenges of the mentioned methods with presenting the advantages and disadvantages, chronological indications, and application prospects of various novel therapeutic approaches.

Targeted Drug Delivery - From Magic Bullet to Nanomedicine: Principles, Challenges, and Future Perspectives

Nanomedicine is an advanced version of Paul Ehrlich's "magic bullet" concept. Targeted drug delivery is a system of specifying the drug moiety directly into its targeted body area (organ, cellular, and subcellular level of specific tissue) to overcome the aspecific toxic effect of conventional drug delivery, thereby reducing the amount of drug required for therapeutic efficacy. To achieve this objective, the magic bullet concept was developed and pushed scientists to investigate for more than a century, leading to the envisioning of different nanometer-sized devices - today's nanomedicine. Different carrier systems are being used and investigated, which include colloidal (vesicular and multiparticulate) carriers, polymers, and cellular/subcellular systems. This review addresses the need for and advantages of targeting, with its basic principles, strategies, and carrier systems. Recent advances, challenges, and future perspectives are also highlighted.

Bioscaffold-based study of glioblastoma cell behavior and drug delivery for tumor therapy

Glioblastoma multiforme (GBM) is a severe form of brain cancer with an average five-year survival rate of 6.7%. Current treatment strategies include surgical resection of the tumor area and lining the lesion site with therapeutics, which offer only a moderate impact on increasing survival rates. Drug-testing models based on the monolayer cell culture method may partially explain the lack of advancement in effective GBM treatment, because this model is limited in its ability to show heterogeneous cell-cell and cell-environment interactions as tumor cells in the in vivo state. The development of bioscaffold-based culture models is an important improvement in GBM research, preclinical trials, and targeted drug testing, through better mimicking of the heterogeneity of tumor environmental conditions. A major hurdle towards better GBM outcomes is in delivering medication across the blood-brain barrier (BBB), which normally prevents the crossing of materials into the treatment site. The delivery of therapeutics using bioscaffolds is a potential means of overcoming the BBB and could potentially facilitate long-lasting drug release. A number of natural and synthetic materials have been studied for their biodegradability, toxicity, distribution, and pharmaceutical stability, which are needed to determine the overall effectiveness and safety of glioblastoma treatment. This review summarizes advancements in the research of bioscaffold-based GBM cell growth systems and the potential of using bioscaffolds as a carrier for drug delivery.

MRI-based molecular imaging of epicardium-derived stromal cells (EpiSC) by peptide-mediated active targeting

After myocardial infarction (MI), epicardial cells reactivate their embryonic program, proliferate and migrate into the damaged tissue to differentiate into fibroblasts, endothelial cells and, if adequately stimulated, to cardiomyocytes. Targeting epicardium-derived stromal cells (EpiSC) by specific ligands might enable the direct imaging of EpiSCs after MI to better understand their biology, but also may permit the cell-specific delivery of small molecules to improve the post-MI healing process. Therefore, the aim of this study was to identify specific peptides by phage display screening to enable EpiSC specific cargo delivery by active targeting. To this end, we utilized a sequential panning of a phage library on cultured rat EpiSCs and then subtracted phage that nonspecifically bound blood immune cells. EpiSC specific phage were analyzed by deep sequencing and bioinformatics analysis to identify a total of 78 300 ± 31 900 different, EpiSC-specific, peptide insertion sequences. Flow cytometry of the five most highly abundant peptides (EP1, -2, -3, -7 or EP9) showed strong binding to EpiSCs but not to blood immune cells. The best binding properties were found for EP9 which was further studied by surface plasmon resonance (SPR). SPR revealed rapid and stable association of EpiSCs with EP9. As a negative control, THP-1 monocytes did not associate with EP9. Coupling of EP9 to perfluorocarbon nanoemulsions (PFCs) resulted in the efficient delivery of ¹⁹F cargo to EpiSCs and enabled their visualization by ¹⁹F MRI. Moreover, active targeting of EpiSCs by EP9-labelled PFCs was able to outcompete the strong phagocytic uptake of PFCs by circulating monocytes. In summary, we have identified a 7-mer peptide, (EP9) that binds to EpiSCs with high affinity and specificity. This peptide can be used to deliver small molecule cargos such as contrast agents to permit future in vivo tracking of EpiSCs by molecular imaging and to transfer small pharmaceutical molecules to modulate the biological activity of EpiSCs.

Nucleic Acid Aptamers as a Potential Nucleus Targeted Drug Delivery System

BACKGROUND

Nucleus targeted drug delivery provides several opportunities for the treatment of fatal diseases such as cancer. However, the complex nucleocytoplasmic barriers pose significant challenges for delivering a drug directly and efficiently into the nucleus. Aptamers representing singlestranded DNA and RNA qualify as next-generation highly advanced and personalized medicinal agents that successfully inhibit the expression of certain proteins; possess extraordinary gene-expression for manoeuvring the diseased cell's fate with negligible toxicity. In addition, the precisely directed aptamers to the site of action present a tremendous potential to reach the nucleus by escaping the ensuing barriers to exhibit a better drug activity and gene expression.

OBJECTIVE

This review epigrammatically highlights the significance of targeted drug delivery and presents a comprehensive description of the principal barriers faced by the nucleus targeted drug delivery paradigm and ensuing complexities thereof. Eventually, the progress of nucleus targeting with nucleic acid aptamers and success achieved so far have also been reviewed.

METHODS

Systematic literature search was conducted of research published to date in the field of nucleic acid aptamers.

CONCLUSION

The review specifically points out the contribution of individual aptamers as the nucleustargeting agent rather than aptamers in conjugated form.

Coating and Functionalization Strategies for Nanogels and Nanoparticles for Selective Drug Delivery

Drug delivery is a fascinating research field with several development opportunities. Great attention is now focused on colloidal systems, nanoparticles, and nanogels and on the possibility of modifying them in order to obtain precise targeted drug delivery systems. The aim of this review is to give an overview of the main available surface functionalization and coating strategies that can be adopted in order to modify the selectivity of the nanoparticles in the delivery process and obtain a final system with great targeted drug delivery ability. We also highlight the most important fields of application of these kinds of delivery systems and we propose a comparison between the advantages and disadvantages of the described functionalization strategies.

Toll-Like Receptors and Relevant Emerging Therapeutics with Reference to Delivery Methods

The built-in innate immunity in the human body combats various diseases and their causative agents. One of the components of this system is Toll-like receptors (TLRs), which recognize structurally conserved molecules derived from microbes and/or endogenous molecules. Nonetheless, under certain conditions, these TLRs become hypofunctional or hyperfunctional, thus leading to a disease-like condition because their normal activity is compromised. In this regard, various small-molecule drugs and recombinant therapeutic proteins have been developed to treat the relevant diseases, such as rheumatoid arthritis, psoriatic arthritis, Crohn’s disease, systemic lupus erythematosus, and allergy. Some drugs for these diseases have been clinically approved; however, their efficacy can be enhanced by conventional or targeted drug delivery systems. Certain delivery vehicles such as liposomes, hydrogels, nanoparticles, dendrimers, or cyclodextrins can be employed to enhance the targeted drug delivery. This review summarizes the TLR signaling pathway, associated diseases and their treatments, and the ways to efficiently deliver the drugs to a target site.

Extracellular Vesicles in Cardiovascular Diseases: Alternative Biomarker Sources, Therapeutic Agents, and Drug Delivery Carriers

Cardiovascular diseases (CVD) represent the leading cause of morbidity and mortality globally. The emerging role of extracellular vesicles (EVs) in intercellular communication has stimulated renewed interest in exploring the potential application of EVs as tools for diagnosis, prognosis, and therapy in CVD. The ubiquitous nature of EVs in biological fluids presents a technological advantage compared to current diagnostic tools by virtue of their notable stability. EV contents, such as proteins and microRNAs, represent specific signatures of cellular activation or injury. This feature positions EVs as an alternative source of biomarkers. Furthermore, their intrinsic activity and immunomodulatory properties offer EVs unique opportunities to act as therapeutic agents per se or to serve as drug delivery carriers by acting as miniaturized vehicles incorporating bioactive molecules. In this article, we aim to review the recent advances and applications of EV-based biomarkers and therapeutics. In addition, the potential of EVs as a drug delivery and theranostic platform for CVD will also be discussed.

Effect of Molecular Weight on Sonoporation-Mediated Uptake in Human Cells

Ultrasound-induced microbubble destruction can enhance drug delivery to cells. The molecular weight of therapeutic compounds varies significantly (from <1 kDa for small molecule drugs, to 7-15 kDa for siRNAs/miRNAs, to >1000 kDa for DNA plasmids). Therefore, the objective of this study was to determine the relationship between uptake efficiency and molecular weight using equal molar concentrations. Uptake efficiency of fluorescent compounds with different molecular weights (0.3, 10 and 2000 kDa) was explored in vitro using human cardiac mesenchymal cells and breast cancer cells exposed to microbubbles and 2.5-MHz ultrasound pulses. Uptake by viable cells was quantified using flow cytometry. After correction for the fluorescence yield of each compound, there was a significant size-dependent difference in fluorescence intensity, indicating an inverse relationship between size and uptake efficiency. These results suggest that diffusion of therapeutic compounds across permeabilized cell membranes may be an important mechanism for ultrasound-mediated drug delivery.

Targeting regenerative exosomes to myocardial infarction using cardiac homing peptide

Rationale: Cardiac stem cell-derived exosomes have been demonstrated to promote cardiac regeneration following myocardial infarction in preclinical studies. Recent studies have used intramyocardial injection in order to concentrate exosomes in the infarct. Though effective in a research setting, this method is not clinically appealing due to its invasive nature. We propose the use of a targeting peptide, cardiac homing peptide (CHP), to target intravenously-infused exosomes to the infarcted heart. Methods: Exosomes were conjugated with CHP through a DOPE-NHS linker. Ex vivo targeting was analyzed by incubating organ sections with the CHP exosomes and analyzing with fluorescence microscopy. In vitro assays were performed on neonatal rat cardiomyocytes and H9C2 cells. For the animal study, we utilized an ischemia/reperfusion rat model. Animals were treated with either saline, scramble peptide exosomes, or CHP exosomes 24 h after surgery. Echocardiography was performed 4 h after surgery and 21 d after surgery. At 21 d, animals were sacrificed, and organs were collected for analysis. Results: By conjugating the exosomes with CHP, we demonstrate increased retention of the exosomes within heart sections ex vivo and in vitro with neonatal rat cardiomyocytes. In vitro studies showed improved viability, reduced apoptosis and increased exosome uptake when using CHP-XOs. Using an animal model of ischemia/reperfusion injury, we measured the heart function, infarct size, cellular proliferation, and angiogenesis, with improved outcomes with the CHP exosomes. Conclusions: Our results demonstrate a novel method for increasing delivery of for treatment of myocardial infarction. By targeting exosomes to the infarcted heart, there was a significant improvement in outcomes with reduced fibrosis and scar size, and increased cellular proliferation and angiogenesis.

Continuous-Flow Production of Injectable Liposomes via a Microfluidic Approach

Injectable liposomes are characterized by a suitable size and unique lipid mixtures, which require time-consuming and nonstraightforward production processes. The complexity of the manufacturing methods may affect liposome solubility, the phase transition temperatures of the membranes, the average particle size, and the associated particle size distribution, with a possible impact on the drug encapsulation and release. By leveraging the precise steady-state control over the mixing of miscible liquids and a highly efficient heat transfer, microfluidic technology has proved to be an effective and direct methodology to produce liposomes. This approach results particularly efficient in reducing the number of the sizing steps, when compared to standard industrial methods. Here, Microfluidic Hydrodynamic Focusing chips were produced and used to form liposomes upon tuning experimental parameters such as lipids concentration and Flow-Rate-Ratios (FRRs). Although modelling evidenced the dependence of the laminar flow on the geometric constraints and the FRR conditions, for the specific formulation investigated in this study, the lipids concentration was identified as the primary factor influencing the size of the liposomes and their polydispersity index. This was attributed to a predominance of the bending elasticity modulus over the vesiculation index in the lipid mixture used. Eventually, liposomes of injectable size were produced using microfluidic one-pot synthesis in continuous flow.

Hepatic toxicity assessment of cationic liposome exposure in healthy and chronic alcohol fed mice

The utilisation of nanoparticles as the means of targeted delivery of therapeutics and/or imaging agents could greatly enhance the specific transport of biologically active payloads to target tissues while avoiding or reducing undesired side-effects. To allow for this to become a reality, the question of potential toxicological effects needs to be addressed. In the present investigation, a cationic liposome with prospective for medical applications was constructed and thoroughly assessed for any material-induced hepatic adverse effects in vivo − in healthy and alcoholic hepatic disease models and in vitro − (HepG2 cells). The data demonstrated that intravenous injection of liposomes did not cause any significant in vivo hepatic toxicity (inflammation, alterations in blood parameters, anti-oxidant depletion, acute phase response and histopathology) at doses of 200 μg per mouse in either healthy or chronically alcohol fed mice. Additionally, the in vitro material-induced adverse effects (cytotoxicity, inflammation or albumin secretion) were all also minimal. The data from this study demonstrated that the intravenous injection of cationic liposomes does not cause hepatic toxicity. This investigation is important as it investigates the toxicity of a nano-sized material in a model of alcoholic hepatic disease in vitro and in vivo. This is an area of research in the field of nanotoxicology that is currently almost entirely overlooked.

Drug Target Protein-Protein Interaction Networks: A Systematic Perspective

The identification and validation of drug targets are crucial in biomedical research and many studies have been conducted on analyzing drug target features for getting a better understanding on principles of their mechanisms. But most of them are based on either strong biological hypotheses or the chemical and physical properties of those targets separately. In this paper, we investigated three main ways to understand the functional biomolecules based on the topological features of drug targets. There are no significant differences between targets and common proteins in the protein-protein interactions network, indicating the drug targets are neither hub proteins which are dominant nor the bridge proteins. According to some special topological structures of the drug targets, there are significant differences between known targets and other proteins. Furthermore, the drug targets mainly belong to three typical communities based on their modularity. These topological features are helpful to understand how the drug targets work in the PPI network. Particularly, it is an alternative way to predict potential targets or extract nontargets to test a new drug target efficiently and economically. By this way, a drug target's homologue set containing 102 potential target proteins is predicted in the paper.

Paclitaxel/hydroxyapatite composite coatings on titanium alloy for biomedical applications

In order to reduce the side effects of chemotherapy, target therapies have been spotlighted. In this study, paclitaxel, the drug for cancer treatment, is electrochemically deposited on Ti alloy as vascular stents for the tumor localized therapy by sustaining drug releasing to achieve the cancer cells apoptosis or the prevention of cancer metastasis. In the experiment, cathodic polarization tests coupled with electrochemical reactions were analyzed to speculate the deposition mechanism, and the field emission scanning electron microscope (FESEM), focused ion beam (FIB) system and Fourier transform infrared spectroscopy (FTIR) to observe the surface morphology and analyze constituent elements. A spectrophotometer (UV visible spectrometer) was used to measure drug loading and release. Finally, MTT Assay was carried out to analyze the cell viability for drug efficacy. It is concluded that paclitaxel can be successfully deposited on the titanium alloy by electrochemical method. Besides, the post-hydroxyapatite coated specimen with high porosity can enhance the drug loading from 395±95μg/cm² to 572±99μg/cm², a lower burst release in the first day, a higher sustaining release rate in a month, and the more complete drug release. All results indicate that the paclitaxel/hydroxyapatite composite coating by the electrochemical deposition method is much more effective and promising.

A VEGF delivery system targeting MI improves angiogenesis and cardiac function based on the tropism of MSCs and layer-by-layer self-assembly

Myocardial infarction (MI) is a serious ischemic condition affecting many individuals around the world. Vascular endothelial growth factor (VEGF) is considered a promising factor for enhancing cardiac function by promoting angiogenesis. However, the lack of a suitable method of VEGF delivery to the MI area is a serious challenge. In this study, we screened a suitable delivery carrier with favorable biocompatibility that targeted the MI area using the strategy of an inherent structure derived from the body and that was based on characteristics of the MI. Mesenchymal stem cells (MSCs) are important infiltrating cells that are derived from blood and have an inherent tropism for the MI zone. We hypothesized that VEGF-encapsulated MSCs targeting MI tissue could improve cardiac function by angiogenesis based on the tropism of the MSCs to the MI area. We first developed VEGF-encapsulated MSCs using self-assembled gelatin and alginate polyelectrolytes to improve angiogenesis and cardiac function. In vitro, the results showed that VEGF-encapsulated MSCs had a sustained release of VEGF and tropism to SDF-1. In vivo, VEGF-encapsulated MSCs migrated to the MI area, enhanced cardiac function, perfused the infarcted area and promoted angiogenesis. These preclinical findings suggest that VEGF-loaded layer-by-layer self-assembled encapsulated MSCs may be a promising and minimally invasive therapy for treating MI. Furthermore, other drugs loaded to layer-by-layer self-assembled encapsulated MSCs may be promising therapies for treating other diseases.

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.

Recent development of biotin conjugation in biological imaging, sensing, and target delivery

Despite encouraging results from preliminary studies of anticancer therapies, the lack of tumor specificity remains an important issue in the modern pharmaceutical industry. New findings indicate that biotin or biotin-conjugates could be favorably assimilated by tumor cells that over-express biotin-selective transporters. Furthermore, biotin can form stable complexes with avidin and its bacterial counterpart streptavidin. The strong bridging between avidin and biotin moieties on other molecules is a proven adaptable tool with broad biological applications. Under these circumstances, a biotin moiety is certainly an attractive choice for live-cell imaging, biosensing, and target delivery.

Nanoparticle drug delivery systems and their use in cardiac tissue therapy

Cardiovascular diseases make up one of the main causes of death today, with myocardial infarction and ischemic heart disease contributing a large share of the deaths reported. With mainstream clinical therapy focusing on palliative medicine following myocardial infarction, the structural changes that occur in the diseased heart will eventually lead to end-stage heart failure. Heart transplantation remains the only gold standard of cure but a shortage in donor organs pose a major problem that led to clinicians and researchers looking into alternative strategies for cardiac repair. This review will examine some alternative methods of treatment using chemokines and drugs carried by nanoparticles as drug delivering agents for the purposes of treating myocardial infarction through the promotion of revascularization. We will also provide an overview of existing studies involving such nanoparticulate drug delivery systems, their reported efficacy and the challenges facing their translation into ubiquitous clinical use.

Myocardial Delivery of Lipidoid Nanoparticle Carrying modRNA Induces Rapid and Transient Expression

Nanoparticle-based delivery of nucleotides offers an alternative to viral vectors for gene therapy. We report highly efficient in vivo delivery of modified mRNA (modRNA) to rat and pig myocardium using formulated lipidoid nanoparticles (FLNP). Direct myocardial injection of FLNP containing 1-10 μg eGFPmodRNA in the rat (n = 3 per group) showed dose-dependent enhanced green fluorescent protein (eGFP) mRNA levels in heart tissue 20 hours after injection, over 60-fold higher than for naked modRNA. Off-target expression, including lung, liver, and spleen, was <10% of that in heart. Expression kinetics after injecting 5 μg FLNP/eGFPmodRNA showed robust expression at 6 hours that reduced by half at 48 hours and was barely detectable at 2 weeks. Intracoronary administration of 10 μg FLNP/eGFPmodRNA also proved successful, although cardiac expression of eGFP mRNA at 20 hours was lower than direct injection, and off-target expression was correspondingly higher. Findings were confirmed in a pilot study in pigs using direct myocardial injection as well as percutaneous intracoronary delivery, in healthy and myocardial infarction models, achieving expression throughout the ventricular wall. Fluorescence microscopy revealed GFP-positive cardiomyocytes in treated hearts. This nanoparticle-enabled approach for highly efficient, rapid and short-term mRNA expression in the heart offers new opportunities to optimize gene therapies for enhancing cardiac function and regeneration.

Targeting delivery of Radix Ophiopogonis polysaccharide to ischemic/reperfused rat myocardium by long-circulating macromolecular and liposomal carriers

Drug delivery to ischemic myocardium is an enormous challenge. This work aimed to characterize cardiac delivery behaviors of mono-polyethylene glycosylated (PEGylated) conjugates and long-circulating liposomes (L-Lps) with Radix Ophiopogonis polysaccharide (ROP) as drug. The results showed that compared to native ROP, 32-, 52-, and 45-fold increases in blood half-life were achieved by 20-kDa PEG mono-modified ROP (P_20k-R), 40-kDa PEG mono-modified ROP (P_40k-R), and ROP-loaded L-Lp, respectively. With comparable blood pharmacokinetics, ROP-loaded L-Lp showed both significantly higher targeting efficacy and drug exposure in infarcted myocardium than P_40k-R. With regard to P_20k-R, both its targeting efficacy and its level in infarcted myocardium at 3 hours postdose were comparable to P_40k-R, but its level in blood and myocardium reduced obviously faster. As a whole, the results indicate that both loading in L-Lps and mono-PEGylation are effective in targeting drug to ischemic myocardium, but the former appears to induce stronger effects.

Advanced targeted nanomedicine

Targeted drug delivery has been the major topic in drug formulation and delivery. As nanomedicine emerges to create nano scale therapeutics and diagnostics, it is still essential to embed targeting capability to these novel systems to make them useful. Here we discuss various targeting approaches for delivery of therapeutic and diagnostic nano materials in view of search for more universal methods to target diseased tissues. Many diseases are accompanied with hypoxia and acidosis. Coating nanoparticles with pH Low Insertion Peptides (pHLIPs) increases efficiency of targeting acidic diseased tissues. It has been showing promising results to create future nanotheranostics for cancer and other diseases which are dominating in the present world.

Controlled delivery of stromal derived factor-1α from poly lactic-co-glycolic acid core-shell particles to recruit mesenchymal stem cells for cardiac regeneration

Stromal derived factor-1α (SDF-1α) has shown promising results in treatment of myocardial infarction (MI), via recruitment of endogenous stem cells into the injured myocardium. However, the bioactivity of this susceptible signalling chemokine is reduced significantly during the common fabrication processes of drug delivery systems, due to the exposure to organic-aqueous interfaces or elevated temperature. In this study, we developed a novel SDF-1α delivery system using coaxial electrospraying, the technique which enables fabrication of core-shell particles with minimized contact of organic-aqueous phases. The SDF-1α incorporated PLGA particles exhibited distinct core-shell structure, confirmed by transmission electron microscopy (TEM). Controlled release of SDF-1α was obtained for at least 40days, and the release rate was tailored by co-encapsulation of bovine serum albumin (BSA) into the core of the particles. The SDF-1α released from PLGA/SDF-1α and PLGA/BSA-SDF-1α particles retained its chemotactic activity, and enhanced the number of migrated mesenchymal stem cells (MSCs) by 38% and 54%, respectively, compared to basal medium used as the control. Moreover, both SDF-1α and BSA supported the proliferation of MSCs within 3days of cell culture. The SDF-1α incorporated core-shell particles developed by electrospraying technique, can be effectively employed as injectable drug delivery system for in situ cardiac regeneration.

Increased cardiac distribution of mono-PEGylated Radix Ophiopogonis polysaccharide in both myocardial infarction and ischemia/reperfusion rats

Although PEGylation plays an important role in drug delivery, knowledge about the distribution behavior of PEGylated drugs in ischemic myocardia is rather limited compared to nanoparticles. This work therefore aims to characterize the targeting behavior of the anti-myocardial ischemic mono-PEGylated conjugates of Radix Ophiopogonis polysaccharide (ROP) in two clinically relevant animal models, ie, the myocardial infarction (MI) model and the ischemia/reperfusion (IR) model. To determine the effect of the molecular size of conjugates, two representative conjugates (20- and 40-kDa polyethylene glycol mono-modified ROPs), with hydrodynamic size being approximately and somewhat beyond 10 nm, respectively, were studied in parallel at three time points postdose after a method for determining them quantitatively in biosamples was established. The results showed that the cardiac distribution of the two conjugates was significantly enhanced in both MI and IR rats due to the enhanced permeability and retention effect induced by ischemia. In general, the cardiac targeting efficacy of the conjugates in MI and IR rats was approximately 2; however, different changing in targeting efficacy with time was observed between MI and IR rats and also between the conjugates. Although the enhanced permeability and retention effect-based targeting efficacy for mono-PEGylated ROPs was not high, they, as dissolved macromolecules, are prone to diffusion in the cardiac interstitium space, and thus, facilitate the drug to reach perfusion-deficient and nonperfused areas. These findings are helpful in choosing the cardiac targeting strategy.

Personalized medicine in hematology - A landmark from bench to bed

Personalized medicine is the cornerstone of medical practice. It tailors treatments for specific conditions of an affected individual. The borders of personalized medicine are defined by limitations in technology and our understanding of biology, physiology and pathology of various conditions. Current advances in technology have provided physicians with the tools to investigate the molecular makeup of the disease. Translating these molecular make-ups to actionable targets has led to the development of small molecular inhibitors. Also, detailed understanding of genetic makeup has allowed us to develop prognostic markers, better known as companion diagnostics. Current attempts in the development of drug delivery systems offer the opportunity of delivering specific inhibitors to affected cells in an attempt to reduce the unwanted side effects of drugs.

Targeted delivery of vascular endothelial growth factor improves stem cell therapy in a rat myocardial infarction model

Rebuilding of infarcted myocardium by mesenchymal stem cells (MSCs) has not been successful because of poor cell survival due in part to insufficient blood supply after myocardial infarction (MI). We hypothesize that targeted delivery of vascular endothelial growth factor (VEGF) to MI can help regenerate vasculature in support of MSC therapy in a rat model of MI. VEGF-encapsulated immunoliposomes targeting overexpressed P-selectin in MI tissue were infused by tail vein immediately after MI. One week later, MSCs were injected intramyocardially. The cardiac function loss was moderated slightly by targeted delivery of VEGF or MSC treatment. Targeted VEGF+MSC combination treatment showed highest attenuation in cardiac function loss. The combination treatment also increased blood vessel density (80%) and decreased collagen content in post-MI tissue (33%). Engraftment of MSCs in the combination treatment group was significantly increased and the engrafted cells contributed to the restoration of blood vessels.

FROM THE CLINICAL EDITOR

VEGF immunoliposomes targeting myocardial infarction tissue resulted in significantly higher attenuation of cardiac function loss when used in combination with mesenchymal stem cells. MSCs were previously found to have poor ability to restore cardiac tissue, likely as a result of poor blood supply in the affected areas. This new method counterbalances that weakness by the known effects of VEGF, as demonstrated in a rat model.

Heart regeneration: opportunities and challenges for drug discovery with novel chemical and therapeutic methods or agents

Following a heart attack, more than a billion cardiac muscle cells (cardiomyocytes) can be killed, leading to heart failure and sudden death. Much research in this area is now focused on the regeneration of heart tissue through differentiation of stem cells, proliferation of existing cardiomyocytes and cardiac progenitor cells, and reprogramming of fibroblasts into cardiomyocytes. Different chemical modalities (i.e. methods or agents), ranging from small molecules and RNA approaches (including both microRNA and anti-microRNA) to modified peptides and proteins, are showing potential to meet this medical need. In this Review, we outline the recent advances in these areas and describe both the modality and progress, including novel screening strategies to identify hits, and the upcoming challenges and opportunities to develop these hits into pharmaceuticals, at which chemistry plays a key role.

A fast pH-switchable and self-healing supramolecular hydrogel carrier for guided, local catheter injection in the infarcted myocardium

Minimally invasive intervention strategies after myocardial infarction use state-of-the-art catheter systems that are able to combine mapping of the infarcted area with precise, local injection of drugs. To this end, catheter delivery of drugs that are not immediately pumped out of the heart is still challenging, and requires a carrier matrix that in the solution state can be injected through a long catheter, and instantaneously gelates at the site of injection. To address this unmet need, a pH-switchable supramolecular hydrogel is developed. The supramolecular hydrogel is switched into a liquid at pH > 8.5, with a viscosity low enough to enable passage through a 1-m long catheter while rapidly forming a hydrogel in contact with tissue. The hydrogel has self-healing properties taking care of adjustment to the injection site. Growth factors are delivered from the hydrogel thereby clearly showing a reduction of infarct scar in a pig myocardial infarction model.

Protein engineering for cardiovascular therapeutics: untapped potential for cardiac repair

A number of new and innovative approaches for repairing damaged myocardium are currently undergoing investigation, with several encouraging results. In addition to the progression of stem cell-based approaches and gene therapy/silencing methods, evidence continues to emerge that protein therapeutics may be used to directly promote cardiac repair and even regeneration. However, proteins are often limited in their therapeutic potential by short local half-lives and insufficient bioavailability and bioactivity, and many academic laboratories studying cardiovascular diseases are more comfortable with molecular and cellular biology than with protein biochemistry. Protein engineering has been used broadly to overcome weaknesses traditionally associated with protein therapeutics and has the potential to specifically enhance the efficacy of molecules for cardiac repair. However, protein engineering as a strategy has not yet been used in the development of cardiovascular therapeutics to the degree that it has been used in other fields. In this review, we discuss the role of engineered proteins in cardiovascular therapies to date. Further, we address the promise of applying emerging protein engineering technologies to cardiovascular medicine and the barriers that must be overcome to enable the ultimate success of this approach.

pH (low) insertion peptide (pHLIP) targets ischemic myocardium

The pH (low) insertion peptide (pHLIP) family enables targeting of cells in tissues with low extracellular pH. Here, we show that ischemic myocardium is targeted, potentially opening a new route to diagnosis and therapy. The experiments were performed using two murine ischemia models: regional ischemia induced by coronary artery occlusion and global low-flow ischemia in isolated hearts. In both models, pH-sensitive pHLIPs [wild type (WT) and Var7] or WT-pHLIP-coated liposomes bind ischemic but not normal regions of myocardium, whereas pH-insensitive, kVar7, and liposomes coated with PEG showed no preference. pHLIP did not influence either the mechanical or the electrical activity of ischemic myocardium. In contrast to other known targeting strategies, the pHLIP-based binding does not require severe myocardial damage. Thus, pHLIP could be used for delivery of pharmaceutical agents or imaging probes to the myocardial regions undergoing brief restrictions of blood supply that do not induce irreversible changes in myocytes.

PEGylation for drug delivery to ischemic myocardium: pharmacokinetics and cardiac distribution of poly(ethylene glycol)s in mice with normal and ischemic myocardium

PEGylation now plays an important role in drug delivery and is considered as the method of choice for improving the pharmacokinetics and stability of parenteral agents. However, its application in treating cardiac diseases is still limited. To guide the design of PEGylation for drug delivery to ischemic myocardium, the effects of the molecular weight of PEG and the myocardial ischemic conditions on PEG levels in plasma and myocardium were studied in this work following intravenous administration of fluorescein isothiocyanate-labeled 20- and 40-kDa mPEGs to mice with normal and ischemic myocardium. The results show that myocardial ischemia caused some consistent changes in pharmacokinetic parameters of mPEGs. Due to the enhanced permeability and retention (EPR) effect caused by ischemia, the distribution of 20- and 40-kDa mPEGs in ischemic hearts was approximately 1.47- and 1.92-fold higher than that in normal hearts, respectively. Under the same heart condition (either normal or ischemic), the cardiac AUC(0.5-24h)s of the two mPEGs were comparable, although their plasma AUCs differed by nearly 4-fold; however, a smoother cardiac level-time profile was achieved by 40-kDa mPEG. This study addressed the relative importance of the EPR effect of ischemic zones and the molecular size of PEG in cardiac drug delivery, which is believed to be helpful for macromolecular drug design.