Functional and biodegradable dendritic macromolecules with controlled architectures as nontoxic and efficient nanoscale gene vectors

Research Progress of Drug Delivery Systems Targeting the Kidneys

Chronic kidney disease (CKD) affects more than 10% of the global population, and its incidence is increasing, partially due to an increase in the prevalence of disease risk factors. Acute kidney injury (AKI) is an independent risk factor for CKD and end-stage renal disease (ESRD). The pathogenic mechanisms of CKD provide several potential targets for its treatment. However, due to off-target effects, conventional drugs for CKD typically require high doses to achieve adequate therapeutic effects, leading to long-term organ toxicity. Therefore, ideal treatments that completely cure the different types of kidney disease are rarely available. Several approaches for the drug targeting of the kidneys have been explored in drug delivery system research. Nanotechnology-based drug delivery systems have multiple merits, including good biocompatibility, suitable degradability, the ability to target lesion sites, and fewer non-specific systemic effects. In this review, the development, potential, and limitations of low-molecular-weight protein-lysozymes, polymer nanomaterials, and lipid-based nanocarriers as drug delivery platforms for treating AKI and CKD are summarized.

Peptide-based non-viral gene delivery: A comprehensive review of the advances and challenges

Gene therapy is the most effective treatment option for diseases, but its effectiveness is affected by the choice and design of gene carriers. The genes themselves have to pass through multiple barriers in order to enter the cell and therefore require additional vectors to carry them inside the cell. In gene therapy, peptides have unique properties and potential as gene carriers, which can effectively deliver genes into specific cells or tissues, protect genes from degradation, improve gene transfection efficiency, and enhance gene targeting and biological responsiveness. This paper reviews the research progress of peptides and their derivatives in the field of gene delivery recently, describes the obstacles encountered by foreign materials to enter the interior of the cell, and introduces the following classes of functional peptides that can carry materials into the interior of the cell, and assist in transmembrane translocation of carriers, thus breaking through endosomal traps to enable successful entry of genetic materials into the nucleus of the cell. The paper also discusses the combined application of peptide vectors with other vectors to enhance its transfection ability, explores current challenges encountered by peptide vectors, and looks forward to future developments in the field.

Novel inhalation therapy in pulmonary fibrosis: principles, applications and prospects

Pulmonary fibrosis (PF) threatens millions of people worldwide with its irreversible progression. Although the underlying pathogenesis of PF is not fully understood, there is evidence to suggest that the disease can be blocked at various stages. Inhalation therapy has been applied for lung diseases such as asthma and chronic obstructive pulmonary disease, and its application for treating PF is currently under consideration. New techniques in inhalation therapy, such as the application of microparticles and nanoparticles, traditional Chinese medicine monomers, gene therapy, inhibitors, or agonists of signaling pathways, extracellular vesicle interventions, and other specific drugs, are effective in treating PF. However, the safety and effectiveness of these therapeutic techniques are influenced by the properties of inhaled particles, biological and pathological barriers, and the type of inhalation device used. This review provides a comprehensive overview of the pharmacological, pharmaceutical, technical, preclinical, and clinical experimental aspects of novel inhalation therapy for treating PF and focus on therapeutic methods that significantly improve existing technologies or expand the range of drugs that can be administered via inhalation. Although inhalation therapy for PF has some limitations, the advantages are significant, and further research and innovation about new inhalation techniques and drugs are encouraged.

Intranasal G5-BGG/pDNA Vaccine Elicits Protective Systemic and Mucosal Immunity against SARS-CoV-2 by Transfecting Mucosal Dendritic Cells

Infectious disease pandemics, including the coronavirus disease 2019 pandemic, have heightened the demand for vaccines. Although parenteral vaccines induce robust systemic immunity, their effectiveness in respiratory mucosae is limited. Considering the crucial role of nasal-associated lymphoid tissue (NALT) in mucosal immune responses, in this study, the intranasal complex composed of G5-BGG and antigen-expressing plasmid DNA (pSP), named G5-BGG/pSP complex, is developed to activate NALT and to promote both systemic and mucosal immune defense. G5-BGG/pSP could traverse mucosal barriers and deliver DNA to the target cells because of its superior nasal retention and permeability characteristics. The intranasal G5-BGG/pSP complex elicits robust antigen-specific immune responses, such as the notable production of IgG antibody against several virus variants. More importantly, it induces elevated levels of antigen-specific IgA antibody and a significant expansion of the lung-resident T lymphocyte population. Notably, the intranasal G5-BGG/pSP complex results in antigen expression and maturation of dendritic cells in nasal mucosae. These findings exhibit the potential of G5-BGG, a novel cationic material, as an effective gene carrier for intranasal vaccines to obtain robust systemic and mucosal immunity.

MicroRNA therapeutics and nucleic acid nano-delivery systems in bacterial infection: a review

Bacteria that have worked with humans for thousands of years pose a major threat to human health even today, as drug resistance has become a prominent problem. Compared to conventional drug therapy, nucleic acid-based therapies are a promising and potential therapeutic strategy for diseases in which nucleic acids are delivered through a nucleic acid delivery system to regulate gene expression in specific cells, offering the possibility of curing intractable diseases that are difficult to treat at this stage. Among the many nucleic acid therapeutic ideas, microRNA, a class of small nucleic acids with special properties, has made great strides in biology and medicine in just over two decades, showing promise in preclinical drug development. In this review, we introduce recent advances in nucleic acid delivery systems and their clinical applications, highlighting the potential of nucleic acid therapies, especially miRNAs extracted from traditional herbs, in combination with the existing set of nucleic acid therapeutic systems, to potentially open up a new line of thought in the treatment of cancer, viruses, and especially bacterial infectious diseases.

Nanomaterials for photothermal cancer therapy

Cancer has emerged as a pressing global public health issue, and improving the effectiveness of cancer treatment remains one of the foremost challenges of modern medicine. The primary clinical methods of treating cancer, including surgery, chemotherapy and radiotherapy, inevitably result in some adverse effects on the body. However, the advent of photothermal therapy offers an alternative route for cancer treatment. Photothermal therapy relies on photothermal agents with photothermal conversion capability to eliminate tumors at high temperatures, which offers advantages of high precision and low toxicity. As nanomaterials increasingly play a pivotal role in tumor prevention and treatment, nanomaterial-based photothermal therapy has gained significant attention owing to its superior photothermal properties and tumor-killing abilities. In this review, we briefly summarize and introduce the applications of common organic photothermal conversion materials (e.g., cyanine-based nanomaterials, porphyrin-based nanomaterials, polymer-based nanomaterials, etc.) and inorganic photothermal conversion materials (e.g., noble metal nanomaterials, carbon-based nanomaterials, etc.) in tumor photothermal therapy in recent years. Finally, the problems of photothermal nanomaterials in antitumour therapy applications are discussed. It is believed that nanomaterial-based photothermal therapy will have good application prospects in tumor treatment in the future.

Nucleic acid drug vectors for diagnosis and treatment of brain diseases

Nucleic acid drugs have the advantages of rich target selection, simple in design, good and enduring effect. They have been demonstrated to have irreplaceable superiority in brain disease treatment, while vectors are a decisive factor in therapeutic efficacy. Strict physiological barriers, such as degradation and clearance in circulation, blood-brain barrier, cellular uptake, endosome/lysosome barriers, release, obstruct the delivery of nucleic acid drugs to the brain by the vectors. Nucleic acid drugs against a single target are inefficient in treating brain diseases of complex pathogenesis. Differences between individual patients lead to severe uncertainties in brain disease treatment with nucleic acid drugs. In this Review, we briefly summarize the classification of nucleic acid drugs. Next, we discuss physiological barriers during drug delivery and universal coping strategies and introduce the application methods of these universal strategies to nucleic acid drug vectors. Subsequently, we explore nucleic acid drug-based multidrug regimens for the combination treatment of brain diseases and the construction of the corresponding vectors. In the following, we address the feasibility of patient stratification and personalized therapy through diagnostic information from medical imaging and the manner of introducing contrast agents into vectors. Finally, we take a perspective on the future feasibility and remaining challenges of vector-based integrated diagnosis and gene therapy for brain diseases.

Advancements and Utilizations of Scaffolds in Tissue Engineering and Drug Delivery

The drug development process requires a thorough understanding of the scaffold and its three-dimensional structure. Scaffolding is a technique for tissue engineering and the formation of contemporary functioning tissues. Tissue engineering is sometimes referred to as regenerative medicine. They also ensure that drugs are delivered with precision. Information regarding scaffolding techniques, scaffolding kinds, and other relevant facts, such as 3D nanostructuring, are discussed in depth in this literature. They are specific and demonstrate localized action for a specific reason. Scaffold's acquisition nature and flexibility make it a new drug delivery technology with good availability and structural parameter management.

Mechanisms and challenges of nanocarriers as non-viral vectors of therapeutic genes for enhanced pulmonary delivery

With the rapid development of biopharmaceuticals and the outbreak of COVID-19, the world has ushered in a frenzy to develop gene therapy. Therefore, therapeutic genes have received enormous attention. However, due to the extreme instability and low intracellular gene expression of naked genes, specific vectors are required. Viral vectors are widely used attributed to their high transfection efficiency. However, due to the safety concerns of viral vectors, nanotechnology-based non-viral vectors have attracted extensive investigation. Still, issues of low transfection efficiency and poor tissue targeting of non-viral vectors need to be addressed. Especially, pulmonary gene delivery has obvious advantages for the treatment of inherited lung diseases, lung cancer, and viral pneumonia, which can not only enhance lung targeting and but also reduce enzymatic degradation. For systemic diseases therapy, pulmonary gene delivery can enhance vaccine efficacy via inducing not only cellular, humoral immunity but also mucosal immunity. This review provides a comprehensive overview of nanocarriers as non-viral vectors of therapeutic genes for enhanced pulmonary delivery. First of all, the characteristics and therapeutic mechanism of DNA, mRNA, and siRNA are provided. Thereafter, the advantages and challenges of pulmonary gene delivery in exerting local and systemic effects are discussed. Then, the inhalation dosage forms for nanoparticle-based drug delivery systems are introduced. Moreover, a series of materials used as nanocarriers for pulmonary gene delivery are presented, and the endosomal escape mechanisms of nanocarriers based on different materials are explored. The application of various non-viral vectors for pulmonary gene delivery are summarized in detail, with the perspectives of nano-vectors for pulmonary gene delivery.

Emerging innate biological properties of nano-drug delivery systems: A focus on PAMAM dendrimers and their clinical potential

Drug delivery systems or vectors are usually needed to improve the bioavailability and effectiveness of a drug through improving its pharmacokinetics/pharmacodynamics at an organ, tissue or cellular level. However, emerging technologies with sensitive readouts as well as a greater understanding of physiological/biological systems have revealed that polymeric drug delivery systems are not biologically inert but can have innate or intrinsic biological actions. In this article, we review the emerging multiple innate biological/toxicological properties of naked polyamidoamine (PAMAM) dendrimer delivery systems in the absence of any drug cargo and discuss their correlation with the defined physicochemical properties of PAMAMs in terms of molecular size (generation), architecture, surface charge and chemistry. Further, we assess whether any of the reported intrinsic biological actions of PAMAMs such as their antimicrobial activity or their ability to sequester glucose and modulate key protein interactions or cell signaling pathways, can be exploited clinically such as in the treatment of diabetes and its complications.

Agmatine-grafted bioreducible poly(l-lysine) for gene delivery with low cytotoxicity and high efficiency

Bioreducible cationic polymers have gained considerable attention in gene delivery due to their low cytotoxicity and high efficiency. In the present work, we reported a cationic polymer, poly(disulfide-l-lysine)-g-agmatine (denoted as SSL-AG), and evaluated its ability to transfer pEGFP-ZNF580 plasmid (pZNF580) into human umbilical vein endothelial cells (HUVECs). This SSL-AG polymeric carrier efficiently condensed pZNF580 into positively charged particles (<200 nm) through electrostatic interaction. This carrier also exhibited excellent buffering capacity in the physiological environment, good pDNA protection against enzymatic degradation and rapid pDNA release in a highly reducing environment mainly because of the responsive cleavage of disulfide bonds in the polymer backbone. The hemolysis assay and in vitro cytotoxicity assay suggested that the SSL-AG carrier and corresponding gene complexes possessed both good hemocompatibility and great cell viability in HUVECs. The cellular uptake of the SSL-AG/Cy5-oligonucleotide group was 3.6 times that of the poly(l-lysine)/Cy5-oligonucleotide group, and its mean fluorescence intensity value was even higher than that of the PEI 25 kDa/Cy5-oligonucleotide group. Further, the intracellular trafficking results demonstrated that the SSL-AG/Cy5-oligonucleotide complexes exhibited a high nucleus co-localization rate (CLR) value (36.0 ± 2.8%, 3.4 times that of the poly (l-lysine)/Cy5-oligonucleotide group, 1.6 times that of the poly(disulfide-l-lysine)-g-butylenediamine/Cy5-oligonucleotide group) at 24 h, while the endo/lysosomal CLR value was relatively low. This suggested that SSL-AG successfully delivered plasmid into HUVECs with high cellular uptake, rapid endosomal escape and efficient nuclear accumulation owing to the structural advantages of the bioreducible and agmatine groups. In vitro transfection assay also verified the enhanced transfection efficiency in the SSL-AG/pZNF580 group. Furthermore, the results of CCK-8, cell migration and in vitro/vivo angiogenesis assays revealed that pZNF580 delivered by SSL-AG could effectively enhance the proliferation, migration and vascularization of HUVECs. In a word, the SSL-AG polymer has great potential as a safe and efficient gene carrier for gene therapy.

Dendron-Functionalized Polyglutamate-Pyropheophorbide-a Conjugates as Nanomedicines for Breast Cancer Photodynamic Therapy

Photodynamic therapy (PDT) has shown its promise in the treatment of cancer. Herein, a dendron-functionalized polyglutamic acid (PGA) polymer (PG-L8G-Ppa-Dendron, PGPD) is synthesized and it is conjugated with pyropheophorbide-a (Ppa) for the first time to treat triple negative breast cancer (TNBC), whereas a linear polyglutamate-Ppa conjugate (PGP) is synthesized as a control. Compared to the linear counterpart, the glycosylated polymer-based PGPD with a dendritic structure has excellent solubility and it self-assembles to form uniform-sized nanoparticles. PGPD displays a highly effective PDT effect in the animal model, evidenced with effective induction of reactive oxygen species (ROS) production and cell apoptosis. This may be due to an enhanced efficiency in delivery and accumulation of Ppa by this glycosylated dendritic polymer at tumor sites. Therefore, PGPD can be a highly effective and biosafe nanoagent for PDT of TNBC.

Recent Advances in Preclinical Research Using PAMAM Dendrimers for Cancer Gene Therapy

Carriers of genetic material are divided into vectors of viral and non-viral origin. Viral carriers are already successfully used in experimental gene therapies, but despite advantages such as their high transfection efficiency and the wide knowledge of their practical potential, the remaining disadvantages, namely, their low capacity and complex manufacturing process, based on biological systems, are major limitations prior to their broad implementation in the clinical setting. The application of non-viral carriers in gene therapy is one of the available approaches. Poly(amidoamine) (PAMAM) dendrimers are repetitively branched, three-dimensional molecules, made of amide and amine subunits, possessing unique physiochemical properties. Surface and internal modifications improve their physicochemical properties, enabling the increase in cellular specificity and transfection efficiency and a reduction in cytotoxicity toward healthy cells. During the last 10 years of research on PAMAM dendrimers, three modification strategies have commonly been used: (1) surface modification with functional groups; (2) hybrid vector formation; (3) creation of supramolecular self-assemblies. This review describes and summarizes recent studies exploring the development of PAMAM dendrimers in anticancer gene therapies, evaluating the advantages and disadvantages of the modification approaches and the nanomedicine regulatory issues preventing their translation into the clinical setting, and highlighting important areas for further development and possible steps that seem promising in terms of development of PAMAM as a carrier of genetic material.

Supramolecular dendrimer-containing layer-by-layer nanoassemblies for bioapplications: current status and future prospects

This review provides a comprehensive and critical overview of the supramolecular dendrimer-containing multifunctional layer-by-layer nanoassemblies driven by a multitude of intermolecular interactions for biological and biomedical applications.

Click Synthesis of Size- and Shape-Tunable Star Polymers with Functional Macrocyclic Cores for Synergistic DNA Complexation and Delivery

The architectural perfection and multivalency of dendrimers have made them useful for biodelivery via peripheral functionalization and the adjustment of dendrimer generations. Modulation of the core-forming and internal matrix-forming structures offers virtually unlimited opportunities for further optimization, but only in a few cases this has been made compatible with strict diastereomeric purity over molecularly diverse series, low toxicity, and limited synthetic effort. Fully regular star polymers built on biocompatible macrocyclic platforms, such as hyperbranched cyclodextrins, offer advantages in terms of facile synthesis and flexible compositions, but core elaboration in terms of shape and function becomes problematic. Here we report the synthesis and characterization of star polymers consisting of functional trehalose-based macrocyclic cores (cyclotrehalans, CTs) and aminothiourea dendron arms, which can be efficiently synthesized from sequential click reactions of orthogonal monomers, display no cytotoxicity, and efficiently complex and deliver plasmid DNA in vitro and in vivo. When compared with some commercial cationic dendrimers or polymers, the new CT-scaffolded star polymers show better transfection efficiencies in several cell lines and structure-dependent cell selectivity patterns. Notably, the CT core could be predefined to exert Zn(II) complexing or molecular inclusion capabilities, which has been exploited to synergistically boost cell transfection by orders of magnitude and modulate the organ tropism in vivo.

Nanotoxicology of Dendrimers in the Mammalian Heart: ex vivo and in vivo Administration of G6 PAMAM Nanoparticles Impairs Recovery of Cardiac Function Following Ischemia-Reperfusion Injury

Aim

The effects of polyamidoamine (PAMAM) dendrimers on the mammalian heart are not completely understood. In this study, we have investigated the effects of a sixth-generation cationic dendrimer (G6 PAMAM) on cardiac function in control and diabetic rat hearts following ischemia-reperfusion (I/R) injury.

Methods

Isolated hearts from healthy non-diabetic (Ctr) male Wistar rats were subjected to ischemia and reperfusion (I/R). LV contractility and hemodynamics data were computed digitally whereas cardiac damage following I/R injury was assessed by measuring cardiac enzymes. For ex vivo acute exposure experiments, G6 PAMAM was administered during the first 10 mins of reperfusion in Ctr animals. In chronic in vivo studies, nondiabetic rats (Ctr) received either vehicle or daily i.p. injections of G6 PAMAM (40 mg/kg) for 4 weeks. Diabetic (D) animals received either vehicle or daily i.p. injections of G6 PAMAM (10, 20 or 40 mg/kg) for 4 weeks. The impact of G6 PAMAM on pacing-postconditioning (PPC) was also studied in Ctr and D rats.

Results

In ex vivo studies, acute administration of G6 PAMAM to isolated Ctr hearts during reperfusion dose-dependently impaired recovery of cardiac hemodynamics and vascular dynamics parameters following I/R injury. Chronic daily i.p. injections of G6 PAMAM significantly (P<0.01) impaired recovery of cardiac function following I/R injury in nondiabetic animals but this was not generally observed in diabetic animals except for CF which was impaired by about 50%. G6 PAMAM treatment completely blocked the protective effects of PPC in the Ctr animals.

Conclusion

Acute ex vivo or chronic in vivo treatment with naked G6 PAMAM dendrimer can significantly compromise recovery of non-diabetic hearts from I/R injury and can further negate the beneficial effects of PPC. Our findings are therefore extremely important in the nanotoxicological evaluation of G6 PAMAM dendrimers for potential clinical applications in physiological and pathological settings.

Application of new lysine-based peptide dendrimers D3K2 and D3G2 for gene delivery: Specific cytotoxicity to cancer cells and transfection in vitro

In order to enhance intracellular uptake and accumulation of therapeutic nucleic acids for improved gene therapy methods, numerous delivery vectors have been elaborated. Based on their origin, gene carriers are generally classified as viral or non-viral vectors. Due to their significantly reduced immunogenicity and highly optimized methods of synthesis, nanoparticles (especially those imitating natural biomolecules) constitute a promising alternative for virus-based delivery devices. Thus, we set out to develop innovative peptide dendrimers for clinical application as transfection agents and gene carriers. In the present work we describe the synthesis of two novel lysine-based dendritic macromolecules (D3K2 and D3G2) and their initial characterization for cytotoxicity/genotoxicity and transfection potential in two human cell line models: cervix adenocarcinoma (HeLa) and microvascular endothelial (HMEC-1). This approach allowed us to identify more cationic D3K2 as potent delivery agent, being able to increase intracellular accumulation of large nucleic acid molecules such as plasmids. Moreover, the dendrimers exhibited specific cytotoxicity towards cancer cell line without showing significant toxic effects on normal cells. These observations are promising prognosis for future clinical application of this type of nanoparticles.

Development of a safe and efficient gene delivery system based on a biodegradable tannic acid backbone

Finding a safe and efficient gene delivery vector is a major international challenge facing the development of gene therapy. Tannic acid (TA) is a natural cross-linker owing to its hydroxyl and carboxyl groups that can interact with biopolymers for different biomaterial design. In this work, three polyethyleneimine-modified TA polymers were prepared, and the polymers were characterized by FTIR, UV-vis, elemental analysis and ¹H NMR. The potential of PTAs as gene vector was studied in vitro, including DNA loading capacity, DNA protection ability and biocompatibility. In addition, the particle size, zeta potential, DNA encapsulation efficiency, cell uptake and transfection efficiency of the PTA-pDNA polyplexes were also studied. The results showed that PTA2k and PTA30k could completely condense DNA at N/P of 2, and PTA600 could only completely condense DNA at N/P of 50. The PTA/pDNA polyplexes could protect DNA from degrading by DNA enzymes and could be efficiently uptaked by cells. Biocompatibility assay showed that PTA had no significant cytotoxicity and effect on cell proliferation compared to PEI. At low N/P ratios of 1-4, PTA showed higher transfection efficiency than PEI, and the transfection efficiency increased with the increase of PEI molecular weight in PTA. At N/P of 3, PTA30k showed the highest transfection efficiency of 23.8%, while PEI30k showed only 6.7%. These results indicate that PTA is a promising candidate vector for safe and efficient gene delivery.

Evolution from Covalent to Self-Assembled PAMAM-Based Dendrimers as Nanovectors for siRNA Delivery in Cancer by Coupled In Silico-Experimental Studies. Part I: Covalent siRNA Nanocarriers

Small interfering RNAs (siRNAs) represent a new approach towards the inhibition of gene expression; as such, they have rapidly emerged as promising therapeutics for a plethora of important human pathologies including cancer, cardiovascular diseases, and other disorders of a genetic etiology. However, the clinical translation of RNA interference (RNAi) requires safe and efficient vectors for siRNA delivery into cells. Dendrimers are attractive nanovectors to serve this purpose, as they present a unique, well-defined architecture and exhibit cooperative and multivalent effects at the nanoscale. This short review presents a brief introduction to RNAi-based therapeutics, the advantages offered by dendrimers as siRNA nanocarriers, and the remarkable results we achieved with bio-inspired, structurally flexible covalent dendrimers. In the companion paper, we next report our recent efforts in designing, characterizing and testing a series of self-assembled amphiphilic dendrimers and their related structural alterations to achieve unprecedented efficient siRNA delivery both in vitro and in vivo.

Redox-sensitive, cholesterol-bearing PEGylated poly(propylene imine)-based dendrimersomes for drug and gene delivery to cancer cells

Stimuli-responsive nanocarriers have attracted increased attention as materials that can facilitate drug and gene delivery in cancer therapy. The present study reports the development of redox-sensitive dendrimersomes comprising disulfide-linked cholesterol-bearing PEGylated dendrimers, which can be used as drug and gene delivery systems. Two disulfide-linked cholesterol-bearing PEGylated generation 3 diaminobutyric polypropylenimine dendrimers have been successfully synthesized via an in situ two-step reaction. They were able to spontaneously self-assemble into stable, cationic, nanosized vesicles (or dendrimersomes) with lower critical aggregation concentration values for high-cholesterol-bearing vesicles. These dendrimersomes were able to entrap both hydrophilic and hydrophobic dyes, and they also showed a redox-responsive sustained release of the entrapped guests in the presence of a glutathione concentration similar to that of a cytosolic reducing environment. The high-cholesterol-bearing dendrimersomes were found to have a higher melting enthalpy, increased adsorption tendency on mica surface, entrapping ability for a larger amount of hydrophobic drugs, and increased resistance to redox-responsive environments in comparison with their low-cholesterol counterpart. In addition, both dendrimersomes were able to condense more than 85% of the DNA at all the tested ratios for the low-cholesterol vesicles, and at dendrimer : DNA weight ratios of 1 : 1 and higher for the high-cholesterol vesicles. These vesicles resulted in an enhanced cellular uptake of DNA, by up to 15-fold when compared with naked DNA with low-cholesterol vesicles. As a result, they increased the gene transfection on the PC-3 prostate cancer cell line, with the highest transfection being obtained with low-cholesterol vesicle complexes at a dendrimer : DNA weight ratio of 5 : 1 and high-cholesterol vesicle complexes at a dendrimer : DNA weight ratio of 10 : 1. These transfection levels were about 5-fold higher than those observed when treated with naked DNA. These cholesterol-bearing PEGylated dendrimer-based vesicles are, therefore, promising as redox-sensitive drugs and gene delivery systems for potential applications in combination cancer therapies.

SAHA (vorinostat) facilitates functional polymer-based gene transfection via upregulation of ROS and synergizes with TRAIL gene delivery for cancer therapy

Non-viral gene delivery is an attractive approach for the treatment of many diseases including cancer, benefiting from its safety and large-scale production concerns. However, the relatively low transfection efficacy compared with viral vectors restricts the clinical applications of non-viral gene vectors. Reactive oxygen species (ROS) triggered charge reversal polymers (named B-PDEAEA) presented improved transfection efficacy, because of fast release of plasmid DNA responding to enhanced oxidative stress in cancer cells. But inadequate dissociation can still occur owing to the insufficient intracellular ROS generation. Here, we report SAHA (vorinostat), which is a clinical histone deacetylase inhibitor and anticancer drug, induces the ROS accumulation in cancer cells, and facilitates the charge reversal process of B-PDEAEA and the cellular dissociation of the delivered gene from the vectors. As a result, SAHA remarkably increases the gene transfection efficacy in an ROS-dependent manner. Importantly, SAHA synergizes with B-PDEAEA mediated therapeutic gene TNF-related apoptosis-inducing ligand (TRAIL) delivery in inducing apoptosis of cancer cells. These findings support the first concept of improving the gene delivery efficacy of stimuli-responsive vectors through upregulating the cellular ROS via an FDA approved anticancer agent. Additionally, combination of SAHA and TRAIL gene therapy could be a potential strategy for cancer treatment.

Nanoparticle-mediated siRNA Gene-silencing in Adult Zebrafish Heart

Mammals have a very limited capacity to regenerate the heart after myocardial infarction. On the other hand, the adult zebrafish regenerates its heart after apex resection or cryoinjury, making it an important model organism for heart regeneration study. However, the lack of loss-of-function methods for adult organs has restricted insights into the mechanisms underlying heart regeneration. RNA interference via different delivery systems is a powerful tool for silencing genes in mammalian cells and model organisms. We have previously reported that siRNA-encapsulated nanoparticles successfully enter cells and result in a remarkable gene-specific knockdown in the regenerating adult zebrafish heart. Here, we present a simple, rapid, and efficient protocol for the dendrimer-mediated siRNA delivery and gene-silencing in the regenerating adult zebrafish heart. This method provides an alternative approach for determining gene functions in adult organs in zebrafish and can be extended to other model organisms as well.

Tailoring the Supramolecular Structure of Guanidinylated Pullulan toward Enhanced Genetic Photodynamic Therapy

In the progress of designing a gene carrier system, what is urgently needed is a balance of excellent safety and satisfactory efficiency. Herein, a straightforward and versatile synthesis of a cationic guanidine-decorated dendronized pullulan (OGG3P) for efficient genetic photodynamic therapy was proposed. OGG3P was able to block the mobility of DNA from a weight ratio of 2. However, G3P lacking guanidine residues could not block DNA migration until at a weight ratio of 15, revealing guanidination could facilitate DNA condensation via specific guanidinium-phosphate interactions. A zeta potential plateau (∼+23 mV) of OGG3P complexes indicated the nonionic hydrophilic hydroxyl groups in pullulan might neutralize the excessive detrimental cationic charges. There was no obvious cytotoxicity and hemolysis, but also enhancement of transfection efficiency with regard to OGG3P in comparison with that of native G3P in Hela and HEK293T cells. More importantly, we found that the uptake efficiency in Hela cells between OGG3P and G3P complexes was not markedly different. However, guanidination caused changes in uptake pathway and led to macropinocytosis pathway, which may be a crucial reason for improved transfection efficiency. After introducing a therapeutic pKillerRed-mem plasmid, OGG3P complexes achieved significantly enhanced KillerRed protein expression and ROS production under irradiation. ROS-induced cancer cells proliferation suppression was also confirmed. This study highlights the guanidine-decorated dendronized pullulan could emerge as a reliable nonviral gene carrier to specifically deliver therapeutic genes.

Cross-Linked and Biodegradable Polymeric System as a Safe Magnetic Resonance Imaging Contrast Agent

Owing to the low efficacy of clinically used small-molecule gadolinium (Gd)-based magnetic resonance imaging (MRI) agents, we designed and explored biodegradable macromolecular conjugates as MRI contrast agents. The linear polymeric structure and core-cross-linked formulation possessed different characteristics and features, so we prepared and comparatively studied the two kinds of Gd-based N-(2-hydroxypropyl) methacrylamide (HPMA) polymeric systems (the core-cross-linked pHPMA-DOTA-Gd and the linear one) using the clinical agent diethylene-triamine pentaacetic acid-Gd(III) (DTPA-Gd) as a control. This study was aimed to find the optimal polymeric formulation as a biocompatible and efficient MRI contrast agent. The high molecular weight (MW, 181 kDa) and core-cross-linked copolymer was obtained via the cross-linked block linear copolymer and could be degraded to low-MW segments (29 kDa) in the presence of glutathione (GSH) and cleaned from the body. Both core-cross-linked and linear pHPMA-DOTA-Gd copolymers displayed 2-3-fold increased relaxivity (r₁ value) than that of DTPA-Gd. Animal studies demonstrated that two kinds of macromolecular systems led to much longer blood circulation time, higher tumor accumulation, and much higher signal intensity compared with the linear and clinical ones. Finally, in vivo and in vitro toxicity studies indicated that the two macromolecular agents had great biocompatibility. Therefore, we performed preliminary but important studies on the Gd-based HPMA polymeric systems as biocompatible and efficient MRI contrast agents and found that the biodegradable core-cross-linked pHPMA-DOTA-Gd copolymer might have greater benefits for the foreground.

Enzyme-Sensitive and Amphiphilic PEGylated Dendrimer-Paclitaxel Prodrug-Based Nanoparticles for Enhanced Stability and Anticancer Efficacy

In this study, we prepared a smart polymeric vehicle for the hydrophobic drug paclitaxel (PTX) that allowed a maximum steady-state circulation and a fast intracellular release in tumors. PTX was linked to the Janus PEGylated (PEG = poly(ethylene glycol)) peptide dendrimer via an enzyme-sensitive linker glycylphenylalanylleucylglycine tetrapeptide by efficient click reaction, resulting in Janus dendritic prodrug with 20.9% PTX content. The prodrug self-assembled into nanoscale particles with appropriate nanosizes, compact morphology, and negative surface charge. In addition to high stability during circulation, as demonstrated by protein adsorption assays and drug release studies in the cancer's intracellular environment, the nanoparticles were able to quickly release the drug intact in its original molecular structure, as verified via high-performance liquid chromatography and mass spectrometry analyses. Compared to free PTX, the enzyme-responsive feature of nanoparticles promoted higher cytotoxicity against 4T1 cancer cells and much lower cytotoxicity against normal cells. The nanoparticles accumulated in the tumor and were retained for an extended period of time, as confirmed by fluorescence imaging. Therefore, these nanoparticles exhibited significantly enhanced antitumor efficiency in the 4T1 breast cancer model as indicated by the observed inhibition of angiogenesis and proliferation as well as induction of apoptosis. Moreover, the nanoparticles reduced the occurrence of side effects, particularly dose-limited toxicities, as monitored by body weight and hematological features. Hence, our Janus PEGylated dendrimer-PTX prodrug-based nanoparticles may potentially serve as nanoscale vehicles for breast cancer therapy.

Stimuli-responsive dendrimers in drug delivery

Dendrimers have shown great promise as carriers in drug delivery due to their unique structures and superior properties. However, the precise control of payload release from a dendrimer matrix still presents a great challenge. Stimuli-responsive dendrimers that release payloads in response to a specific trigger could offer distinct clinical advantages over those dendrimers that release payloads passively. These smart polymers are designed to specifically release their payloads at targeted regions or at constant release profiles for specific therapies. They represent an attractive alternative to targeted dendrimers and enable dendrimer-based therapeutics to be more effective, more convenient, and much safer. The wide range of stimuli, either endogenous (acid, enzyme, and redox potentials) or exogenous (light, ultrasound, and temperature change), allows great flexibility in the design of stimuli-responsive dendrimers. In this review article, we will highlight recent advances and opportunities in the development of stimuli-responsive dendrimers for the treatment of various diseases, with emphasis on cancer. Specifically, the applications of stimuli-responsive dendrimers in drug delivery as well as their mechanisms are intensively reviewed.

Dendritic chitosan as a magnetic and biocompatible nanocarrier for the simultaneous delivery of doxorubicin and methotrexate to MCF-7 cell line

A novel smart, biocompatible, and pH-responsive magnetic highly branched chitosan was synthesized efficiently for use in dual-anticancer drug delivery systems.

Tailoring the dendrimer core for efficient gene delivery

Dendrimers have been widely used as non-viral gene vectors due to well-defined chemical structures, high density of cationic charges and ease of surface modification. Although a large number of studies have reported the important roles of dendrimer architecture, component, generation and surface functionality in gene delivery, the effect of dendrimer core on this issue still remains unclear. Recent literatures suggest that a slight alternation in dendrimer core has a profound effect in the transfection efficacy and biocompatibility. In this review, we will discuss the transfection mechanism of dendrimers with different types of cores in respect of flexibility, hydrophobicity and functionality. We hope to open a possibility of designing efficient dendrimers for gene delivery by choosing a proper dendrimer core.

STATEMENT OF SIGNIFICANCE

As a branch of researches on dendrimers and dendritic polymers, the design of biocompatible and high efficient polymeric gene carriers has attracted increasing attentions during these years. Although the effect of dendrimer generation, species, architecture and surface functionality on gene delivery have been widely reported, the effect of dendrimer core on this issue still remains unclear. Recent literatures suggest that a minor variation on the dendrimer core has a profound effect in the transfection efficacy and biocompatibility. This critical review summarized the dendrimers with different types of cores and discussed the transfection mechanism with particular focus on the flexibility, hydrophobicity, and functionality. It is hoped to provide a new insight to design efficient and safe dendrimer-based gene vectors by choosing a proper core. To the best of our knowledge, this is the first review on the effect of dendrimer core on gene delivery. The findings obtained in this filed are of central importance in the design of efficient polymeric gene vectors. This article will appeal a wide readership such as physical chemist, dendrimer chemist, biological chemist, pharmaceutical scientist, and biomaterial researchers. We hope that this review article can be published by Acta Biomaterialia, a top journal that publishes important reviews in the field of biomaterials science.

Impact of PAMAM delivery systems on signal transduction pathways in vivo: Modulation of ERK1/2 and p38 MAP kinase signaling in the normal and diabetic kidney

The in vivo impact of two generation 6 cationic polyamidoamine (PAMAM) dendrimers on cellular signaling via extracellular-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38 MAPK), as well as their relationship to epidermal growth factor receptor (EGFR), were studied in the normal and/or diabetic rat kidney. A single 10mg/kg/i.p administration of Polyfect (PF; with an intact branching architecture) or Superfect (SF; with a fragmented branching architecture) modulated renal ERK1/2 and p38 MAPK phosphorylation in a dendrimer-specific and animal model-dependent manner. AG1478 treatment (a selective EGFR inhibitor) confirmed that renal ERK1/2 and p38 MAPK signaling was downstream of EGFR. Surprisingly, both PAMAMs induced hyperphosphorylation of ERK1/2 and p38 MAPK (at 1 or 5mg/kg) despite inhibiting EGFR phosphorylation in the diabetic kidney. PAMAMs did not alter renal morphology but their effects on p38 MAPK and EGFR phosphorylation were reversed by ex vivo treatment of kidneys with the anti-oxidant, Tempol. Thus, PAMAMs can intrinsically modulate signaling of mitogen-activated protein kinases (MAPKs) depending on the type of dendrimer (fragmented vs intact branching architecture) and animal model (normal vs diabetic) used and likely occurs via an EGFR-independent and oxidative-stress dependent mechanism. These findings might have important toxicological implications for PAMAM-based delivery systems.

A supramolecular approach to improve the gene transfection efficacy of dendrimers

Cyanuric acid is able to form complementary hydrogen bonds with melamine. Here, the specific recognition between cyanuric acid and melamine is used to significantly improve the gene transfection efficacy of low generation dendrimers via a supramolecular approach.

Hyperbranched polyphosphates: synthesis, functionalization and biomedical applications

Hyperbranched polyphosphates (HBPPs) are newly emerged polymeric biomaterials with repeating phosphate bonds in a highly branched framework over the past 5 years. Due to the integration of the advantages of both hyperbranched polymers and polyphosphates, HBPPs are versatile in chemical structure, flexible in physicochemical properties, water soluble, biocompatible and biodegradable in biological features. On the basis of their excellent water solubility, biocompatibility, biodegradability and potential functionalization as well as their simple preparation in one-pot synthesis, HBPPs have fascinating biomedical applications, especially for drug delivery. In this tutorial review, the recent advances of HBPPs are summarized. HBPPs with different topological structures and various functionalities were synthesized via adjusting the side group of cyclic phosphate monomers, which have shown promising biomedical applications, for example, using as a macromolecular anticancer agent and constructing advanced drug delivery systems, including site-specific delivery systems, self-delivery systems, and stimuli-responsive delivery systems. Such progress may promote the further development of interdisciplinary research between polymer chemistry, material science and biomedicine.

Biocompatible polymeric nanocomplexes as an intracellular stimuli-sensitive prodrug for type-2 diabetes combination therapy

Combination therapy is usually considered as a promising strategy owing to its advantages such as reduced doses, minimized side effects and improved therapeutic efficiency in a variety of diseases including diabetes. Here we synthesized a new highly intracellular stimuli-sensitive chitosan-graft-metformin (CS-MET) prodrug by imine reaction between oxidative chitosan and metformin for type 2 diabetes (T2D) therapy. Hypothetically, CS-MET functions dually as an anti-diabetes prodrug as well as a gene delivery vector without superfluous materials. CS-MET formed nanocomplexes with therapeutic gene through electrostatic interactions and entered cells by Organic Cation Transporter (OCT)-independent endocytosis. The incorporation of metformin into chitosan has been found to increase endosomal escape via the proton sponge effect. When vector carrying a short-hairpin RNA (shRNA) silencing sterol regulatory element-binding protein (SREBP), a major transcription factor involved in de novo lipogenisis, it reduced the SREBP mRNA and proteins efficiently. Furthermore, by intraperitoneal injection, CS-MET/shSREBP nanocomplexes effectively knocked down SREBP in livers of western-type diet (WD)-induced obese C57BL/6J mice, markedly reversed insulin resistance and alleviated the fatty liver phenotype without obvious toxic effects. Thus we were able to show that the intracellular stimuli-sensitive CS-MET prodrug renders a potential platform to increase the anti-diabetes activity with synergistic enhancement of gene therapy.

Polymers modified with double-tailed fluorous compounds for efficient DNA and siRNA delivery

Cationic polymers are widely used as gene carriers, however, these polymers are usually associated with low transfection efficacy and non-negligible toxicity. Fluorination on polymers significantly improves their performances in gene delivery, but a high density of fluorous chains must be conjugated on a single polymer. Here we present a new strategy to construct fluorinated polymers with minimal fluorous chains for efficient DNA and siRNA delivery. A double-tailed fluorous compound 2-chloro-4,6-bis[(perfluorohexyl)propyloxy]-1,3,5-triazine (CBT) was conjugated on dendrimers of different generations and low molecular weight polyethylenimine via a facile synthesis. The yielding products with average numbers of 1-2 conjugated CBT moieties showed much improved EGFP and luciferase transfection efficacy compared to unmodified polymers. In addition, these polymers show high siRNA delivery efficacy on different cell lines. Among the synthesized polymers, generation 1 (G1) dendrimer modified with an average number of 1.9 CBT moieties (G1-CBT1.9) shows the highest efficacy when delivering both DNA and siRNA and its efficacy approaches that of Lipofectamine 2000. G1-CBT1.9 also shows efficient gene silencing in vivo. All of the CBT-modified polymers exhibit minimal toxicity on the cells at their optimal transfection conditions. This study provides a new strategy to design efficient fluorous polymers for DNA and siRNA delivery.

Cationic Polyamidoamine Dendrimers as Modulators of EGFR Signaling In Vitro and In Vivo

Cationic polyamidoamine (PAMAM) dendrimers are branch-like spherical polymers being investigated for a variety of applications in nanomedicine including nucleic acid drug delivery. Emerging evidence suggests they exhibit intrinsic biological and toxicological effects but little is known of their interactions with signal transduction pathways. We previously showed that the activated (fragmented) generation (G) 6 PAMAM dendrimer, Superfect (SF), stimulated epidermal growth factor receptor (EGFR) tyrosine kinase signaling-an important signaling cascade that regulates cell growth, survival and apoptosis- in cultured human embryonic kidney (HEK 293) cells. Here, we firstly studied the in vitro effects of Polyfect (PF), a non-activated (intact) G6 PAMAM dendrimer, on EGFR tyrosine kinase signaling via extracellular-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) in cultured HEK 293 cells and then compared the in vivo effects of a single administration (10mg/kg i.p) of PF or SF on EGFR signaling in the kidneys of normal and diabetic male Wistar rats. Polyfect exhibited a dose- and time-dependent inhibition of EGFR, ERK1/2 and p38 MAPK phosphorylation in HEK-293 cells similar to AG1478, a selective EGFR inhibitor. Administration of dendrimers to non-diabetic or diabetic animals for 24h showed that PF inhibited whereas SF stimulated EGFR phosphorylation in the kidneys of both sets of animals. PF-mediated inhibition of EGFR phosphorylation as well as SF or PF-mediated apoptosis in HEK 293 cells could be significantly reversed by co-treatment with antioxidants such as tempol implying that both these effects involved an oxidative stress-dependent mechanism. These results show for the first time that SF and PF PAMAM dendrimers can differentially modulate the important EGFR signal transduction pathway in vivo and may represent a novel class of EGFR modulators. These findings could have important clinical implications for the use of PAMAM dendrimers in nanomedicine.

Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications

This review highlights the recent developments of surface modification and endothelialization of biomaterials in vascular tissue engineering applications.