Dilution-stable PAMAM G1-grafted polyrotaxane supermolecules deliver gene into cells through a caveolae-dependent pathway

A cationic cyclodextrin derivative-lipid hybrid nanoparticles for gene delivery effectively promotes stability and transfection efficiency

Genetic medicines hold great promise for treatment of a number of diseases, however, the development of effective gene delivery carrier is still a challenge. The commonly used gene carrier liposomes and cationic polymers have limited their clinical application due to their respective disadvantages. Lipid-polymer hybrid nanoparticles (LHNPs) are novel drug delivery system which exhibit complementary characteristics of both polymeric nanoparticles and liposomes. In this account, we developed the α-cyclodextrin conjugated generation-2 polyamidoamine dendrimers-lipids hybrid nanoparticles (CDG2-LHNPs) for gene delivery. The pDNA/CDG2-LHNPs was stable during 15 days storage period both at 4 °C, 25 °C and 37 °C, whereas the particle size of pDNA/CDG2 and pDNA/liposomes dramatically increased after storage at 4 °C for 8 h. CDG2-LHNPs showed significantly superior transfection efficiencies compared to either CDG2 or liposomes. The mechanism of high transfection efficiency of pDNA/CDG2-LHNPs was further explored using pharmacological inhibitors chlorpromazine, filipin and cytochalasion D. The result demonstrated that cell uptake of pDNA/CDG2-LHNPs was mediated by clathrin-mediated endocytosis (CME), caveolae-mediated endocytosis (CvME) and macropinocytosis together. pDNA/CDG2-LHNPs were more likely be taken up by cells through C_VME, which avoided lysosomal degradation to a large extent. Moreover, the liposome component of pDNA/CDG2-LHNPs increased its cell uptake efficiency, and the CDG2 polymer component increased its proton buffer capacity, so the hybrid nanoparticles taken up by CME could also successfully escape from the lysosome. This CDG2-LHNPs with stability and high transfection efficiency overcome the shortcomings of liposomes and polymers applied separately, and has great potential for gene drug delivery.

Development of a multi-arm polyrotaxanes modified mesoporous silica-coated gold nanoplatform for protecting endothelial progenitor cells against high glucose environment

Recent study reported that endothelial progenitor cells (EPCs) have potential to treat diabetic macroangiopathy. High glucose environment of diabetes can affect the adhesion of EPCs by decreasing the expression of CXC chemokine receptor 4 (CXCR4) and affect the proliferation of EPCs by decreasing the expression of miR-126. The results showed that the cytotoxicity of GNR@MSNs@PEI to EPCs was significantly lower than PEI; the temperature of GNR@MSNs@PEI solution can be controlled between 38-40°C under 808 nm laser irradiation. 25.67 µg of pcDNA3.1-GFP-CXCR4 and 5.36 µg of FITC-miR-126 could be loaded in 1 mg of GNR@MSNs@PEI; GNR@MSNs@PEI has gene transfection almost the same as Lipofectamine 3000. Subsequent in vitro studies showed that pcDNA3.1-GFP-CXCR4 and miR-126 loaded GNR@MSNs@PEI can significantly increase the adhesion and proliferation and decrease the apoptosis of EPCs treated with high glucose under 808 nm laser irradiation. In conclusion, nano-carriers (GNR@MSNs@PEI) with high pcDNA3.1-CXCR4 and miR-126 loading capacity, high biocompatibility, well cell internalization, and controllable release ability were constructed to transfer CXCR4 expression plasmid (pcDNA3.1-CXCR4) and miR-126 into EPCs efficiently. Further in vitro studies indicated that pcDNA3.1-CXCR4 and miR-126-loaded GNR@MSNs@PEI could protect EPCs against high glucose-induced injury.

Endocytosis in cellular uptake of drug delivery vectors: Molecular aspects in drug development

Drug delivery vectors are widely applied to increase drug efficacy while reducing the side effects and potential toxicity of a drug. They allow for patient-tailored therapy, dose titration, and therapeutic drug monitoring. A major part of drug delivery systems makes use of large nanocarriers: liposomes or virus-like particles (VLPs). These systems allow for a relatively large amount of cargo with good stability of vectors, and they offer multiple options for targeting vectors in vivo. Here we discuss endocytic pathways that are available for drug delivery by large nanocarriers. We focus on molecular aspects of the process, including an overview of potential molecular targets for studies of drug delivery vectors and for future solutions allowing targeted drug delivery.

A review on core-shell structured unimolecular nanoparticles for biomedical applications

Polymeric unimolecular nanoparticles (NPs) exhibiting a core-shell structure and formed by a single multi-arm molecule containing only covalent bonds have attracted increasing attention for numerous biomedical applications. This unique single-molecular architecture provides the unimolecular NP with superior stability both in vitro and in vivo, a high drug loading capacity, as well as versatile surface chemistry, thereby making it a desirable nanoplatform for therapeutic and diagnostic applications. In this review, we surveyed the architecture of various types of polymeric unimolecular NPs, including water-dispersible unimolecular micelles and water-soluble unimolecular NPs used for the delivery of hydrophobic and hydrophilic agents, respectively, as well as their diverse biomedical applications. Future opportunities and challenges of unimolecular NPs were also briefly discussed.

Supramolecular Pharmaceutical Sciences: A Novel Concept Combining Pharmaceutical Sciences and Supramolecular Chemistry with a Focus on Cyclodextrin-Based Supermolecules

Supramolecular chemistry is an extremely useful and important domain for understanding pharmaceutical sciences because various physiological reactions and drug activities are based on supramolecular chemistry. However, it is not a major domain in the pharmaceutical field. In this review, we propose a new concept in pharmaceutical sciences termed "supramolecular pharmaceutical sciences," which combines pharmaceutical sciences and supramolecular chemistry. This concept could be useful for developing new ideas, methods, hypotheses, strategies, materials, and mechanisms in pharmaceutical sciences. Herein, we focus on cyclodextrin (CyD)-based supermolecules, because CyDs have been used not only as pharmaceutical excipients or active pharmaceutical ingredients but also as components of supermolecules.

Design and application of cationic amphiphilic β-cyclodextrin derivatives as gene delivery vectors

The nano self-assembly profiles of amphiphilic gene delivery vectors could improve the density of local cationic head groups to promote their DNA condensation capability and enhance the interaction between cell membrane and hydrophobic tails, thus increasing cellular uptake and gene transfection. In this paper, two series of cationic amphiphilic β-cyclodextrin (β-CD) derivatives were designed and synthesized by using 6-mono-OTs-β-CD (1) as the precursor to construct amphiphilic gene vectors with different building blocks in a selective and controlled manner. The effect of different type and degree of cationic head groups on transfection and the endocytic mechanism of β-CD derivatives/DNA nanocomplexes were also investigated. The results demonstrated that the designed β-cyclodextrin derivatives were able to compact DNA to form stable nanocomplexes and exhibited low cytotoxicity. Among them, PEI-1 with PEI head group showed enhanced transfection activity, significantly higher than commercially available agent PEI25000 especially in the presence of serum, showing potential application prospects in clinical trials. Moreover, the endocytic uptake mechanism involved in the gene transfection of PEI-1 was mainly through caveolae-mediated endocytosis, which could avoid the lysosomal degradation of loaded gene, and had great importance for improving gene transfection activity.

Versatile Functionalization of Polysaccharides via Polymer Grafts: From Design to Biomedical Applications

Because of their biocompatibility, biodegradability, and unique bioactive properties, polysaccharides have been recognized and directly applied as excellent candidates for various biomedical applications. In order to introduce more functionalities onto polysaccharides, various modification methods were applied to improve the physical-chemical and biochemical properties. Grafting polysaccharides with functional polymers with limited reaction sites maximizes the structural integrity. To the best of our knowledge, great efforts have been made by scientists across the world, including our research group, to explore different strategies for the synthesis and design of controllable polymer-grafted polysaccharides. By the application of some reasonable strategies, a series of polymer-grafted polysaccharides with satisfactory biocharacteristics were obtained. The first strategy involves facile modification of polysaccharides with living radical polymerization (LRP). Functionalized polysaccharides with diverse grafts can be flexibly and effectively achieved. The introduced grafts include cationic components for nuclei acid delivery, PEGylated and zwitterionic moieties for shielding effects, and functional species for bioimaging applications as well as bioresponsive drug release applications. The second synthetic model refers to biodegradable polymer-grafted polysaccharides prepared by ring-opening polymerization (ROP). Inspired by pathways to introduce initiation sites onto polysaccharides, the use of amine-functionalized polysaccharides was explored in-depth to trigger ROP of amino acids. A series of poly(amino acid)-grafted polysaccharides with advanced structures (including linear, star-shaped, and comb-shaped copolymers) were developed to study and optimize the structural effects. In addition, biodegradable polyester-grafted polysaccharides were prepared and utilized for drug delivery. Another emerging strategy was to design polysaccharide-based assemblies with supramolecular structures. A variety of assembly techniques using non-covalent interactions were established to construct different types of polysaccharide-based assemblies with various bioapplications. On the basis of these strategies, polymer-grafted polysaccharides with controllable functions were reported to be well-suited for different kinds of biomedical applications. The exciting results were obtained from both in vitro and in vivo models. Viewing the rapid growth of this field, the present Account will update the concepts, trends, perspectives, and applications of functionalized polysaccharides, guiding and inspiring researchers to explore new polysaccharide-based systems for wider applications.

Highly stable polyglutamate derivatives/siRNA polyplex efficiently down-relegate survivin expression and augment the efficacy of cisplatin

RNA interfere (RNAi)-based technology holds great promise in cancer treatment. The use of small interfering RNA (siRNA), however, is hampered by its low delivery efficiency in vivo when they are diluted in blood biofluids and in the presence of serum and salt. In this study, we developed the polyglutamate derivative polymer brush, poly(ethyleneglycol) monomethyl ether-b-polyglutamate-g-spermine (mPEG-b-PG-g-spermine, PPGS), which could efficiently deliver survivin-siRNA under ultra-high dilution and in the presence of salt (NaCl 150mM) and serum (10% FBS), most likely due to its PEG-shelled polymer brush structure. On the contrary, aggregation occurred when PEI/siRNA polyplex dispersed in saline and serum-containing media and PEI polyplex dissociated after making a 256-fold dilution. PPGS/si-survivin polyplex exhibited high cellular uptake efficiency and efficiently down-regulated the expression of survivin mRNA in the cisplatin-resistance of non-small cell human lung adenocarcinoma (A549/DDP) cells in the presence of serum. However, either PEI polyplex or Lipofectmine 2000 complex was unstable in serum and salt-containing media and at high dilution rates, which resulted in their dramatical decrease of cellular uptake and gene-silencing efficiency in these conditions. The PPGS/si-survivin polyplex also exhibited synergistic effects of killing the cancer cells by combination treatment with cisplatin. Therefore, the PPGS gene carrier showed great potential in systemic siRNA delivery, and its combination with chemotherapeutic drug is promising in treating drug resistant cancers.

Clustering Small Dendrimers into Nanoaggregates for Efficient DNA and siRNA Delivery with Minimal Toxicity

Cationic dendrimers are widely used as nonviral gene vectors, however, current gene materials based on dendrimers are either little effective or too toxic on the transfected cells. Here, a facile strategy is presented to prepare high efficient dendrimers with low transfection toxicity. Small dendrimers with 2 nm are clustered into nanoaggregates (≈100 nm) via phenylboronic acid modification and the self-assembled materials enable efficient DNA and siRNA delivery on several cell lines. The clustered nanostructures can disassemble into small dendrimers in acidic conditions thus exerting significantly less toxicity on the transfected cells. Further structure-function relationship studies reveal that both the phenyl group and boronic acid group play essential roles in the self-assembly and gene delivery processes. The transfection efficacy of phenylboronic acid-modified dendrimers can be down-regulated by blocking the boronic acid groups on dendrimers with diols or degrading the groups with hydrogen peroxide. This study provides a facile strategy in the development of efficient and biocompatible gene vectors based on low molecular weight polymers and clearly demonstrates the structure-function relationship of phenylboronic acid-modified polymers in gene delivery.

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.

Reducible polyrotaxane-based pseudo-comb polycations via consecutive ATRP processes for gene delivery

Supramolecular cyclodextrin polyrotaxane (PR) has attracted much attention due to their unique flexible properties. In this work, the reducible PR-based cationic block copolymer (SS-PR) was prepared via ATRP of DMAEMA based on the self-assembled pseudo-PR. A series of pseudo-comb polycations (SS-PR-pDM) with different molecular weights were subsequently produced via two-step ATRP of DMAEMA by using bromoisobutylryl-functionalized SS-PR as the macroinitiator. Incorporation of disulfide linkages in the backbone of PR permits the SS-PR and pseudo-comb SS-PR-pDM to be readily disassembled upon reductive stimuli. SS-PR-pDM exhibited the enhanced pDNA-condensing ability and similarly low toxicity compared with SS-PR. Meanwhile, SS-PR-pDM displayed higher cell internalization rates (88% for SS-PR-pDM3 vs. 77% for SS-PR) and luciferase gene transfection efficiency. The percentages of the EGFP-positive HeLa cells mediated by SS-PR-pDM3 and SS-PR were 44% and 22%, respectively. Furthermore, the favorable property of the pseudo-comb SS-PR-pDM benefited pDNA entering the nucleus. The present work demonstrates that properly grafting cationic side chains from reducible PR backbones via consecutive ATRP processes was one effective means to produce new PR-based supramolecular polycations.

STATEMENT OF SIGNIFICANCE

Supramolecular cyclodextrin polyrotaxanes (PR) had been attracted much attention due to their unique flexible properties. In this work, two kinds of bioreducible PR-based polycations were synthesized via consecutive ATRP processes for gene delivery. The bioreducible PR-based cationic block copolymer (SS-PR) was prepared via ATRP of DMAEMA based on the self-assembled pseudopolyrotaxane of α-cyclodextrins (α-CD) with a disulfide-linked bromoisobutylryl-terminated PEG. Then, a series of pseudo-comb polycations (SS-PR-pDM) with different molecular weights were subsequently produced by using SS-PR-Br macroinitiators via step-two ATRP of DMAEMA. Incorporation of disulfide linkages in bromoisobutylryl-terminated PEG permits the SS-PR and pseudo-comb SS-PR-pDM to be readily disassembled upon reductive stimuli, contributing to gene delivery efficiency. SS-PR-pDM displayed higher cell internalization and gene transfection efficiency. In addtion, the favorable property of the pseudo-comb SS-PR-pDM benefited pDNA entering the nucleus. The present work demonstrates that properly grafting pDMAEMA side chains from bioreducible polyrotaxane backbones via consecutive ATPR processes was one effective means to produce new PR-based supramolecular polycations.

Nanocomplexes from RGD-modified generation 1.0 polyamidoamine based copolymers used for intravascular gene release to prevent restenosis

Aim: To validate the efficacy of nanocomplexes from RGD-modified polyamidoamine (PAMAM G1) copolymer for prevention of restenosis. Materials & methods: Generation 1.0 polyamidoamine (PAMAM G1)-based copolymers (PGP) and RGD modified PGP (PGP-RGD) were synthesized and its properties were evaluated. Intravascular VEGF165 release tests were performed. Results: The PGP-RGD1 (2.6% grafting rate) exhibited lower cytotoxicity and larger combining ability with pDNA. The complexes had sizes of 80–160 nm and zeta potentials of 3–20 mV. Transfection efficiency of PGP-RGD1 complexes in human umbilical vein endothelial cells was larger than that of PGP complexes. Patency and expression level of artery in PGP-RGD1 group were higher than that in saline group. Conclusion: PGP-RGD1 will be a promising targeted gene vector.

Endothelial cell-targeted pVEGF165 polyplex plays a pivotal role in inhibiting intimal thickening after vascular injury

Upregulation of vascular endothelial growth factor (VEGF) expression can inhibit intimal thickening after vascular injury. However, the lack of efficient gene delivery systems leads to insufficient VEGF expression, which prevents its application in gene therapy. In the present study, to improve the delivery of the plasmid vector with the VEGF gene (pVEGF165) to the injured vessel wall, we explored the potentially important difference between endothelial cell-targeted and nontargeted polymeric carriers. The αvβ3 integrin is overexpressed on activated endothelial cells but not on normal quiescent vessels. In this study, CDG2-cRGD, synthesized by conjugating an αvβ3 integrin-binding cyclic arginylglycylaspartic acid (cRGD) peptide with the Generation 2 polycation polyamidoamine (PAMAMG2)-g-cyclodextrin (termed as CDG2), was developed as a targetable carrier. It was observed that the specific integrin-ligand interactions greatly enhanced cellular internalization of CDG2-cRGD in human umbilical vein endothelial cells (HUVECs), which are notoriously difficult to transfect. Consequently, HUVECs were found to show remarkably high levels of VEGF165 expression induced by the CDG2-cRGD polyplex. Interestingly, VEGF165 overexpression in vivo was more complex than that in vitro, and in vivo assays demonstrated that the stimulus response to balloon injury in arteries could obviously upregulate VEGF165 expression in the saline-treated group, although it was not enough to prevent intimal thickening. In gene-transfected groups, intravascular delivery of pVEGF165 with the CDG2-cRGD polyplex into rabbits after vascular injury resulted in a significant inhibition of intimal thickening at 4 weeks, whereas the low therapeutic efficacy in the nontargeted CDG2-treated group was only comparable to that in the saline-treated group. It is becoming clear that the conflicting results of VEGF165 gene therapy in two gene-transfected groups are reflective of the pivotal role of the cRGD-conjugated carriers in achieving the beneficial therapeutic effects of vascular gene therapy.

Synthesis of taurine-fluorescein conjugate and evaluation of its retina-targeted efficiency in vitro

In this work, retinal penetration of fluorescein was achieved in vitro by covalent attachment of taurine to fluorescein, yielding the F–Tau conjugate. Nuclear magnetic resonance (NMR) and high resolution mass spectrometry (HRMS) were used to confirm the successful synthesis of F–Tau. The cellular uptake of F–Tau in adult retinal pigment epithelial cells (ARPE-19) and human retinal microvascular endothelial cells (hRMECs) was visualized via confocal scanning microscopy. The results indicated an improvement of solubility and a reduction of logP of F–Tau compared with fluorescein. As compared with fluorescein, F–Tau showed little toxicity, and was retained longer by cells in uptake experiments. F–Tau also displayed higher transepithelial permeabilities than fluorescein in ARPE-19 and hRMECs monolayer cells (P<0.05). These results showed that taurine may be a useful ligand for targeting small-molecule hydrophobic pharmaceuticals into the retina.

Potential of caveolae in the therapy of cardiovascular and neurological diseases

Caveolae are membrane micro-domains enriched in cholesterol, sphingolipids and caveolins, which are transmembrane proteins with a hairpin-like structure. Caveolae participate in receptor-mediated trafficking of cell surface receptors and receptor-mediated signaling. Furthermore, caveolae participate in clathrin-independent endocytosis of membrane receptors. On the one hand, caveolins are involved in vascular and cardiac dysfunction. Also, neurological abnormalities in caveolin-1 knockout mice and a link between caveolin-1 gene haplotypes and neurodegenerative diseases have been reported. The aim of this article is to present the rationale for considering caveolae as potential targets in cardiovascular and neurological diseases.