Block copolymer micelles for delivery of gene and related compounds

Synthesis and Biological Properties of Porphyrin-Containing Polymeric Micelles with Different Sizes

To understand the size effect of polymeric micelles on their biological properties, such as cellular uptake, biodistribution, tumor accumulation, and so on, we prepared a series of doxorubicin (DOX)-loaded protoporphyrin (PP)-poly(ε-caprolactone) (PCL)-poly(ethylene glycol) (PEG) micelles with different diameters (40, 70, 100, and 130 nm). The incorporation of the protoporphyrin moiety enhanced the stability of the micelles and provided luminescent capability that is useful in the investigation of the cellular uptake of the micelles by fluorescence imaging. The biodistributions of the micelles in mice bearing tumors were evaluated by near-infrared fluorescence imaging and DOX concentration measurements in different tissues. The in vitro and in vivo investigations demonstrated the pronounced dependence of the cellular uptake, biodistribution, and antitumor effectiveness of the micelles on their size.

Rod-to-Globule Transition of pDNA/PEG-Poly(l-Lysine) Polyplex Micelles Induced by a Collapsed Balance Between DNA Rigidity and PEG Crowdedness

The role of poly(ethylene-glycol) (PEG) in rod-shaped polyplex micelle structures, having a characteristic core of folded plasmid DNA (pDNA) and a shell of tethered PEG chains, is investigated using PEG-detachable polyplex micelles. Rod shapes undergo change to compacted globule shapes by removal of PEG from polyplex micelles prepared from block copolymer with acid-labile linkage between PEG and poly(l-lysine) (PLys) through exposure to acidic milieu. This structural change supports the previous investigation on the rod shapes that PEG shell prevents the DNA structure from being globule shaped as the most favored structure in minimizing surface area. Noteworthy, despite the PEG is continuously depleted, the structural change does not occur in gradual shortening manner but the rod shapes keep their length unchanged and abruptly transform into globule shapes. Analysis of PEG density reveals the transition occurred when tethered PEG of rod shapes has decreased to a critical crowdedness, i.e., discontacted with neighboring PEG, which eventually illuminates another contribution, rigidity of DNA packaged as bundle in the rod shapes, in addition to the steric repulsion of PEG, in sustaining rod shapes. This investigation affirms significant role of PEG and also DNA rigidity as bundle in the formation of rod-shaped structures enduring the quest of compaction of charge-neutralized DNA in the polyplex micelles.

Co-delivery of drugs and plasmid DNA for cancer therapy

Cancer is an extremely complex disease involving multiple signaling pathways that enable tumor cells to evade programmed cell death, thus making cancer treatment extremely challenging. The use of combination therapy involving both gene therapy and chemotherapy has resulted in enhanced anti-cancer effects and has become an increasingly important strategy in medicine. This review will cover important design parameters that are incorporated into delivery systems for the co-administration of drug and plasmid-based nucleic acids (pDNA and shRNA), with particular emphasis on polymers as delivery materials. The unique challenges faced by co-delivery systems and the strategies to overcome such barriers will be discussed. In addition, the advantages and disadvantages of combination therapy using separate carrier systems versus the use of a single carrier will be evaluated. Finally, future perspectives in the design of novel platforms for the combined delivery of drugs and genes will be presented.

Small-Angle Neutron Scattering Studies on the Multilamellae Formed by Mixing Lamella-Forming Cationic Diblock Copolymers with Lipids and Their Interaction with DNA

We demonstrate that the lamella-forming polystyrene-block-poly(N-methyl-4-vinylpyridinium iodine) (PS-b-P4VPQ), with similar sizes of the PS and P4VPQ blocks, can be dispersed in the aqueous solutions by forming lipid/PS-b-P4VPQ multilamellae. Using small-angle neutron scattering (SANS) and 1,2-dipalmitoyl-d62-sn-glycero-3-phosphocholine (d62-DPPC) in D2O, a broad correlation peak is found in the scattering profile that signifies the formation of the loosely ordered d62-DPPC/PS-b-P4VPQ multilamellae. The thicknesses of the hydrophobic and hydrophilic layers of the d62-DPPC/PS-b-P4VPQ multilamellae are close to the PS layer and the condensed brush layer thicknesses as determined from previous neutron reflectometry studies on the PS-b-P4VPQ monolayer at the air-water interface. Such well-dispersed d62-DPPC/PS-b-P4VPQ multilamellae are capable of forming multilamellae with DNA in aqueous solution. It is found that the encapsulation of DNA in the hydrophilic layer of the d62-DPPC/PS-b-P4VPQ multilamellae slightly increases the thickness of the hydrophilic layer. Adding CaCl2 can enhance the DNA adsorption in the hydrophilic brush layer, and it is similar to that observed in the neutron reflectometry study of the DNA adsorption by the PS-b-P4VPQ monolayer.

A High-Throughput Platform for Formulating and Screening Multifunctional Nanoparticles Capable of Simultaneous Delivery of Genes and Transcription Factors

Simultaneous delivery of multiple genes and proteins (e.g., transcription factors; TFs) is an emerging issue surrounding therapeutic research due to their ability to regulate cellular circuitry. Current gene and protein delivery strategies, however, are based on slow batch synthesis, which is ineffective, poorly controlled, and incapable of simultaneous delivery of both genes and proteins with synergistic functions. Consequently, advances in this field have been limited to in vitro studies. Here, by integrating microfluidic technologies with a supramolecular synthetic strategy, we present a high-throughput approach for formulating and screening multifunctional supramolecular nanoparticles (MFSNPs) self-assembled from a collection of functional modules to achieve simultaneous delivery of one gene and TF with unprecedented efficiency both in vitro and in vivo. We envision that this new approach could open a new avenue for immunotherapy, stem cell reprogramming, and other therapeutic applications.

Polyplex Micelles with Double-Protective Compartments of Hydrophilic Shell and Thermoswitchable Palisade of Poly(oxazoline)-Based Block Copolymers for Promoted Gene Transfection

Improving the stability of polyplex micelles under physiological conditions is a critical issue for promoting gene transfection efficiencies. To this end, hydrophobic palisade was installed between the inner core of packaged plasmid DNA (pDNA) and the hydrophilic shell of polyplex micelles using a triblock copolymer consisting of hydrophilic poly(2-ethyl-2-oxazoline), thermoswitchable amphiphilic poly(2-n-propyl-2-oxazoline) (PnPrOx) and cationic poly(L-lysine). The two-step preparation procedure, mixing the triblock copolymer with pDNA below the lower critical solution temperature (LCST) of PnPrOx, followed by incubation above the LCST to form a hydrophobic palisade of the collapsed PnPrOx segment, induced the formation of spatially aligned hydrophilic-hydrophobic double-protected polyplex micelles. The prepared polyplex micelles exhibited significant tolerance against attacks from nuclease and polyanions compared to those without hydrophobic palisades, thereby promoting gene transfection. These results corroborated the utility of amphiphilic poly(oxazoline) as a molecular thermal switch to improve the stability of polyplex gene carriers relevant for physiological applications.

Polymer-based vehicles for therapeutic peptide delivery

During the last decades increasing attention has been paid to peptides as potential therapeutics. However, clinical applications of peptide drugs suffer from susceptibility to degradation, rather short circulation half-life, limited ability to cross physiological barriers and potential immunogenicity. These challenges can be addressed by using polymeric materials as peptide delivery systems, owing to their versatile structures and properties. A number of polymer-based vehicles have been developed to stabilize the peptides and to control their release rates. Unfortunately, no single polymer or formulation strategy has been considered ideal for all types of peptide drugs. In this review, currently used and potential polymer-based systems for the peptide delivery will be discussed.

Host-Guest Interaction-Based Self-Engineering of Nano-Sized Vesicles for Co-Delivery of Genes and Anticancer Drugs

On the basis of host-guest interactions, this study reported a kind of linear-hyperbranched supramolecular amphiphile and its assembled vesicles for the combined achievement of drug encapsulation and DNA delivery. Amine-attached β-cyclodextrin-centered hyperbranched polyglycerol and linear adamantane-terminated octadecane were arranged to spontaneously interlink together and then self-assemble into nanoscale vesicles. As the model of a hydrophilic agent, DOX·HCl was demonstrated to be readily loaded into the hollow cavity of the vesicles. The drug release pattern could be controlled by adjusting the environmental acidity, favoring the intracellularly fast drug liberation in response to the cellular lysosomal microenvironment. The nanovesicles displayed superior serum-tolerant transgene ability and significantly lower cytotoxicity compared to those of PEI25K, the gold standard of gene delivery vectors. The drug-loaded nanovesicle can co-deliver DNA payloads into cells and allow the preferable accumulation of two payloads in nuclei. The drug encapsulation was found to have little influence on the transfection. This co-delivery vehicle presents a good example of rational design of cationic supramolecular vesicles for stimulus-responsive drug/DNA transport.

Real-time vascular imaging and photodynamic therapy efficacy with micelle-nanocarrier delivery of chlorin e6 to the microenvironment of melanoma

BACKGROUND

Strategies combining anti-vascular therapy and vascular imaging may facilitate the prediction of early response and outcome in cancer treatment.

OBJECTIVE

The aim of this study was to investigate the relationship between the tumor-associated vasculature in melanoma and to develop an approach for melanoma treatment by utilizing the free form and micelle form of the photosensitizer (PS) chlorin e6 in photodynamic therapy (PDT).

METHODS

Green fluorescence protein (GFP) expressing B16-F10 melanoma cells were implanted into the mouse ear dermis. Ce6 in free form or in micelle form was administered via the tail vein. An OV100 imaging system was used to record the red fluorescence of Ce6 to obtain real-time vascular images in the GFP tumor.

RESULTS

Compared to free Ce6, Ce6 linked to the micelle-nanocarrier depicted a much clearer vascular image and had an effective vascular destruction by PDT. Micelle Ce6 was localized in lysosomes and in the endoplasmic reticulum of cultured endothelial cells, implying an active endocytosis of the nano-carrier.

CONCLUSION

Micelle Ce6 can serve as a bifunctional PS for vascular imaging and PDT, which facilitates its delivery in the tumor microenvironment.

Bioresponsive polymer-based nucleic acid carriers

Nucleic acid carriers need to possess multifunctionality for overcoming biological barriers, such as the stable encapsulation of nucleic acids in extracellular milieu, internalization by target cells, controlled intracellular distribution, and release of nucleic acids at the target site of action. To fulfill these stepwise functionalities, "bioresponsive" polymers that can alter their structure responding to site-specific biological signals are highly useful. Notably, pH, redox potential, and enzymatic activities vary along with microenvironments in the body, and thus, the responsiveness to these signals enables to construct nucleic acid carriers with programmed functionalities. This chapter describes the design of bioresponsive polymers that respond to various biological microenvironments for smart nucleic acids delivery.

Polymeric micelles and nanoemulsions as drug carriers: Therapeutic efficacy, toxicity, and drug resistance

The manuscript reports the side-by-side comparison of therapeutic properties of polymeric micelles and nanoemulsions generated from micelles. The effect of the structure of a hydrophobic block of block copolymer on the therapeutic efficacy, tumor recurrence, and development of drug resistance was studied in pancreatic tumor bearing mice. Mice were treated with paclitaxel (PTX) loaded poly(ethylene oxide)-co-polylactide micelles or corresponding perfluorocarbon nanoemulsions. Two structures of the polylactide block differing in a physical state of micelle cores or corresponding nanodroplet shells were compared. Poly(ethylene oxide)-co-poly(d,l-lactide) (PEG-PDLA) formed micelles with elastic amorphous cores while poly(ethylene oxide)-co-poly(l-lactide) (PEG-PLLA) formed micelles with solid crystalline cores. Micelles and nanoemulsions stabilized with PEG-PDLA copolymer manifested higher therapeutic efficacy than those formed with PEG-PLLA copolymer studied earlier. Better performance of PEG-PDLA micelles and nanodroplets was attributed to the elastic physical state of micelle cores (or droplet shells) allowing adequate rate of drug release via drug diffusion and/or copolymer biodegradation. The biodegradation of PEG-PDLA stabilized nanoemulsions was monitored by the ultrasonography of nanodroplets injected directly into the tumor; the PEG-PDLA stabilized nanodroplets disappeared from the injection site within 48h. In contrast, nanodroplets stabilized with PEG-PLLA copolymer were preserved at the injection site for weeks and months indicating extremely slow biodegradation of solid PLLA blocks. Multiple injections of PTX-loaded PEG-PDLA micelles or nanoemulsions to pancreatic tumor bearing mice resulted in complete tumor resolution. Two of ten tumors treated with either PEG-PDLA micellar or nanoemulsion formulation recurred after the completion of treatment but proved sensitive to the second treatment cycle indicating that drug resistance has not been developed. This is in contrast to the treatment with PEG-PLLA micelles or nanoemulsions where all resolved tumors quickly recurred after the completion of treatment and proved resistant to the repeated treatment. The prevention of drug resistance in tumors treated with PEG-PDLA stabilized formulations was attributed to the presence and preventive effect of copolymer unimers that were in equilibrium with PEG-PDLA micelles. PEG-PDLA stabilized nanoemulsions manifested lower hematological toxicity than corresponding micelles suggesting higher drug retention in circulation. Summarizing, micelles with elastic cores appear preferable to those with solid cores as drug carriers. Micelles with elastic cores and corresponding nanoemulsions both manifest high therapeutic efficacy, with nanoemulsions exerting lower systemic toxicity than micelles. The presence of a small fraction of micelles with elastic cores in nanoemulsion formulations is desirable for prevention of the development of drug resistance.

Photodynamic therapy: one step ahead with self-assembled nanoparticles

Photodynamic therapy (PDT) is a promising treatment modality for cancer with possible advantages over current treatment alternatives. It involves combination of light and a photosensitizer (PS), which is activated by absorption of specific wavelength light and creates local tissue damage through generation of reactive oxygen species (ROS) that induce a cascade of cellular and molecular events. However, as of today, PDT is still in need of improvement and nanotechnology may play a role. PDT frequently employs PS with molecular structures that are highly hydrophobic, water insoluble and prone to aggregation. Aggregation of PS leads to reduced ROS generation and thus lowers the PDT activity. Some PS such as 5-aminolevulinic acid (ALA) cannot penetrate through the stratum corneum of the skin and systemic administration is not an option due to frequently encountered side effects. Therefore PS are often encapsulated or conjugated in/on nano-drug delivery vehicles to allow them to be better taken up by cells and to more selectively deliver them to tumors or other target tissues. Several nano-drug delivery vehicles including liposomes, fullerosomes and nanocells have been tested and reviewed. Here we cover non-liposomal self-assembled nanoparticles consisting of polymeric micelles including block co-polymers, polymeric micelles, dendrimers and porphysomes.

CREDVW-Linked Polymeric Micelles As a Targeting Gene Transfer Vector for Selective Transfection and Proliferation of Endothelial Cells

Nowadays, gene transfer technology has been widely used to promote endothelialization of artificial vascular grafts. However, the lack of gene vectors with low cytotoxicity and targeting function still remains a pressing challenge. Herein, polyethylenimine (PEI, 1.8 kDa or 10 kDa) was conjugated to an amphiphilic and biodegradable diblock copolymer poly(ethylene glycol)-b-poly(lactide-co-glycolide) (mPEG-b-PLGA) to prepare mPEG-b-PLGA-g-PEI copolymers with the aim to develop gene vectors with low cytotoxicity while high transfection efficiency. The micelles were prepared from mPEG-b-PLGA-g-PEI copolymers by self-assembly method. Furthermore, Cys-Arg-Glu-Asp-Val-Trp (CREDVW) peptide was linked to micelle surface to enable the micelles with special recognition for endothelial cells (ECs). In addition, pEGFP-ZNF580 plasmids were condensed into these CREDVW-linked micelles to enhance the proliferation of ECs. These CREDVW-linked micelle/pEGFP-ZNF580 complexes exhibited low cytotoxicity by MTT assay. The cell transfection results demonstrated that pEGFP-ZNF580 could be transferred into ECs efficiently by these micelles. The results of Western blot analysis showed that the relative ZNF580 protein level in transfected ECs increased to 76.9%. The rapid migration of transfected ECs can be verified by wound healing assay. These results indicated that CREDVW-linked micelles could be a suitable gene transfer vector with low cytotoxicity and high transfection efficiency, which has great potential for rapid endothelialization of artificial blood vessels.

Nanoparticles complexed with gene vectors to promote proliferation of human vascular endothelial cells

Amphiphilic block copolymers containing biodegradable hydrophobic segments of depsipeptide based copolymers have been synthesized and explored as gene carriers for enhancing proliferation of endothelial cells in vitro. These polymers form nanoparticles (NPs) with positive charges on their surface, which could condense recombinant plasmids of enhanced green fluorescent protein plasmid and ZNF580 gene (pEGFP-ZNF580) and protect them against DNase I. ZNF580 gene is efficiently transported into EA.hy926 cells to promote their proliferation, whereby the transfection efficiency of NPs/pEGFP-ZNF580 is approximately similar to that of Lipofectamine 2000. These results indicate that the NPs might have potential as a carrier for pEGFP-ZNF580, which could support endothelialization of cardiovascular implants.

Biochemical characterization of the interactions between doxorubicin and lipidic GM1 micelles with or without paclitaxel loading

Doxorubicin (Dox) is an anthracycline anticancer drug with high water solubility, whose use is limited primarily due to significant side effects. In this study it is shown that Dox interacts with monosialoglycosphingolipid (GM1) ganglioside micelles primarily through hydrophobic interactions independent of pH and ionic strength. In addition, Dox can be incorporated even into GM1 micelles already containing highly hydrophobic paclitaxel (Ptx). However, it was not possible to incorporate Ptx into Dox-containing GM1 micelles, suggesting that Dox could be occupying a more external position in the micelles. This result is in agreement with a higher hydrolysis of Dox than of Ptx when micelles were incubated at alkaline pH. The loading of Dox into GM1 micelles was observed over a broad range of temperature (4°C–55°C). Furthermore, Dox-loaded micelles were stable in aqueous solutions exhibiting no aggregation or precipitation for up to 2 months when kept at 4°C–25°C and even after freeze–thawing cycles. Upon exposure to blood components, Dox-containing micelles were observed to interact with human serum albumin. However, the amount of human serum albumin that ended up being associated to the micelles was inversely related to the amount of Dox, suggesting that both could share their binding sites. In vitro studies on Hep2 cells showed that the cellular uptake and cytotoxic activity of Dox and Ptx from the micellar complexes were similar to those of the free form of these drugs, even when the micelle was covered with albumin. These results support the idea of the existence of different nano-domains in a single micelle and the fact that this micellar model could be used as a platform for loading and delivering hydrophobic and hydrophilic active pharmaceutical ingredients.

Inorganic nanovectors for nucleic acid delivery

Nucleic acids show immense potential to treat cancer, acquired immune deficiency syndrome, neurological diseases and other incurable human diseases. Upon systemic administration, they encounter a series of barriers and hence barely reach the site of action, the cell. Intracellular delivery of nucleic acids is facilitated by nanovectors, both viral and non-viral. A major advantage of non-viral vectors over viral vectors is safety. Nanovectors evaluated specifically for nucleic acid delivery include polyplexes, lipoplexes and other cationic carrier-based vectors. However, more recently there is an increased interest in inorganic nanovectors for nucleic acid delivery. Nevertheless, there is no comprehensive review on the subject. The present review would cover in detail specific properties and types of inorganic nanovectors, their preparation techniques and various biomedical applications as therapeutics, diagnostics and theranostics. Future prospects are also suggested.

Nanocarrier-mediated co-delivery of chemotherapeutic drugs and gene agents for cancer treatment

The efficacy of chemotherapeutic drug in cancer treatment is often hampered by drug resistance of tumor cells, which is usually caused by abnormal gene expression. RNA interference mediated by siRNA and miRNA can selectively knock down the carcinogenic genes by targeting specific mRNAs. Therefore, combining chemotherapeutic drugs with gene agents could be a promising strategy for cancer therapy. Due to poor stability and solubility associated with gene agents and drugs, suitable protective carriers are needed and have been widely researched for the co-delivery. In this review, we summarize the most commonly used nanocarriers for co-delivery of chemotherapeutic drugs and gene agents, as well as the advances in co-delivery systems.

Ternary polyplex micelles with PEG shells and intermediate barrier to complexed DNA cores for efficient systemic gene delivery

Simultaneous achievement of prolonged retention in blood circulation and efficient gene transfection activity in target tissues has always been a major challenge hindering in vivo applications of nonviral gene vectors via systemic administration. Herein, we constructed novel rod-shaped ternary polyplex micelles (TPMs) via complexation between the mixed block copolymers of poly(ethylene glycol)-b-poly{N'-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} (PEG-b-PAsp(DET)) and poly(N-isopropylacrylamide)-b-PAsp(DET) (PNIPAM-b-PAsp(DET)) and plasmid DNA (pDNA) at room temperature, exhibiting distinct temperature-responsive formation of a hydrophobic intermediate layer between PEG shells and pDNA cores through facile temperature increase from room temperature to body temperature (~37 °C). As compared with binary polyplex micelles of PEG-b-PAsp(DET) (BPMs), TPMs were confirmed to condense pDNA into a more compact structure, which achieved enhanced tolerability to nuclease digestion and strong counter polyanion exchange. In vitro gene transfection results demonstrated TPMs exhibiting enhanced gene transfection efficiency due to efficient cellular uptake and endosomal escape. Moreover, in vivo performance evaluation after intravenous injection confirmed that TPMs achieved significantly prolonged blood circulation, high tumor accumulation, and promoted gene expression in tumor tissue. Moreover, TPMs loading therapeutic pDNA encoding an anti-angiogenic protein remarkably suppressed tumor growth following intravenous injection into H22 tumor-bearing mice. These results suggest TPMs with PEG shells and facilely engineered intermediate barrier to inner complexed pDNA have great potentials as systemic nonviral gene vectors for cancer gene therapy.

Glutathione- and pH-responsive nonporous silica prodrug nanoparticles for controlled release and cancer therapy

A myriad of drug delivery systems such as liposomes, micelles, polymers and inorganic nanoparticles (NPs) have been developed for cancer therapy. Very few of them, however, have the ability to integrate multiple functionalities such as specific delivery, high circulation stability, controllable release and good biocompatibility and biodegradability in a single system to improve the therapeutic efficacy. Herein, we report two types of stimuli-responsive nonporous silica prodrug NPs towards this goal for controlled release of anticancer drugs and efficient combinatorial cancer therapy. As a proof of concept, anticancer drugs camptothecin (CPT) and doxorubicin (DOX) were covalently encapsulated into silica matrices through glutathione (GSH)-responsive disulfide and pH-responsive hydrazone bonds, respectively, resulting in NPs with sizes tunable in the range of 50-200 nm. Both silica prodrug NPs showed stimuli-responsive controlled release upon exposure to a GSH-rich or acidic environment, resulting in improved anticancer efficacy. Notably, two prodrug NPs simultaneously taken up by HeLa cells showed a remarkable combinatorial efficacy compared to free drug pairs. These results suggest that the stimuli-responsive silica prodrug NPs are promising anticancer drug carriers for efficient cancer therapy.

Complete dissociation and reassembly behavior as studied by using poly(ethylene glycol)-block-poly(glutamate sodium) and kanamycin A

Kanamycin A, an amino modified sugar, can interact with poly(ethylene glycol)-block-poly(glutamate sodium) (PEG114-PGlu64) via electrostatic interactions (with PGlu) and hydrogen bonding (with PEG). The interplay of these two forces determines the assembly process and the resulting structure. In deionized water, kanamycin A and PEG114-PGlu64 form a spherical structure at [+]/[-] = 3.5. This structure dissociates instantly and completely in the presence of 30 mM NaCl. However, a new structure is reassembled in about 2 hours. A similar phenomenon is observed when the buffer pH is increased from 7.8 to 8.3. We attribute the distinct dissociation/reassembly process to the reestablishment of the balance between electrostatic interactions and hydrogen bonding. The dissociation/reassembly process in response to environmental changes offers a novel approach to release the loaded cargo in a controlled manner.

Gene therapy for nucleus pulposus regeneration by heme oxygenase-1 plasmid DNA carried by mixed polyplex micelles with thermo-responsive heterogeneous coronas

Safe and high-efficiency gene therapy for nucleus pulposus (NP) regeneration was urgently desired to treat disc degeneration-associated diseases. In this work, an efficient nonviral cationic block copolymer gene delivery system was used to deliver therapeutic plasmid DNA (pDNA), which was prepared via complexation between the mixed cationic block copolymers, poly(ethylene glycol)-block-poly{N-[N-(2-aminoethyl)-2-aminoehtyl]aspartamide} [PEG-b-PAsp(DET)] and poly(N-isopropylacrylamide)-block-PAsp(DET) [PNIPAM-b-PAsp(DET)], and pDNA at 25 °C. The mixed polyplex micelles (MPMs) containing heterogeneous coronas with hydrophobic and hydrophilic microdomains coexisting could be obtained upon heating from 25 to 37 °C, which showed high tolerability against nuclease and strong resistance towards protein adsorption. The gene transfection efficiency of MPMs in NP cells was significantly higher than that of regular polyplex micelles prepared from sole block copolymer of PEG-b-PAsp(DET) (SPMs) in in vitro and in vivo evaluation due to the synergistic effect of improved colloidal stability and low cytotoxicity. High expression of heme oxygenase-1 (HO-1) in NP cells transfected by MPMs loading HO-1 pDNA significantly decreased the expression activity of matrix metalloproteinases 3 (MMP-3) and cyclo-oxygenase-2 (COX-2) induced by interleukin-1β (IL-1β), and simultaneously increased the NP phenotype-associated genes such as aggrecan, type II collagen, and SOX-9. Moreover, the therapeutic effects of MPMs loading pDNA were tested to treat disc degeneration induced by stab injury. The results demonstrated that administration of HO-1 pDNA carried by MPMs in rat tail discs apparently reduced inflammatory responses induced by need stab and increased glycosaminoglycan (GAG) content, finally achieving better therapeutic efficacy as compared with SPMs. Consequently, MPMs loading HO-1 pDNA were demonstrated to be potential as a safe and high-efficiency nonviral gene delivery system for retarding or regenerating the degenerative discs.

Nanoparticle hardness controls the internalization pathway for drug delivery

Nanoparticle (NP)-based drug delivery systems offer fundamental advantages over current therapeutic agents that commonly display a longer circulation time, lower toxicity, specific targeted release, and greater bioavailability. For successful NP-based drug delivery it is essential that the drug-carrying nanocarriers can be internalized by the target cells and transported to specific sites, and the inefficient internalization of nanocarriers is often one of the major sources for drug resistance. In this work, we use the dissipative particle dynamics simulation to investigate the effect of NP hardness on their internalization efficiency. Three simplified models of NP platforms for drug delivery, including polymeric NP, liposome and solid NP, are designed here to represent increasing nanocarrier hardness. Simulation results indicate that NP hardness controls the internalization pathway for drug delivery. Rigid NPs can enter the cell by a pathway of endocytosis, whereas for soft NPs the endocytosis process can be inhibited or frustrated due to wrapping-induced shape deformation and non-uniform ligand distribution. Instead, soft NPs tend to find one of three penetration pathways to enter the cell membrane via rearranging their hydrophobic and hydrophilic segments. Finally, we show that the interaction between nanocarriers and drug molecules is also essential for effective drug delivery.

DC3-decorated polyplexes for targeted gene delivery into dendritic cells

Dendritic cells (DCs) are a family of specialized antigen presenting cells (APCs) that detect antigens and initiate a wide spectrum of immune responses against them. These characteristics make them promising candidates for immunotherapy manipulations. In this study we designed and synthesized DC-targeted block copolymers composed of linear polyethylenimine (PEI) conjugated to hydrophilic polyethylene glycol (PEG) installed with a DC-targeting peptide (DC3, primary sequence FYPSYHSTPQRP). Two different conjugation procedures (basic and modified) were employed to synthesize the DC3-PEG-b-PEI and the control SCRM-PEG-b-PEI (with a scrambled DC3 peptide sequence) by one-pot synthesis, in two steps. In the first, basic conjugation procedure, PEG with N-hydroxysuccinimide (NHS) ester and maleimide (MAL) groups (NHS-PEG-MAL, 3.5 kDa) was first coupled to linear PEI (25 kDa) via the NHS group to yield the intermediate MAL-PEG-b-PEI, that was then conjugated to N-terminus-cysteine harboring peptides DC3 or SCRM via the MAL double bond to yield the final DC3-PEG-b-PEI or SCRM-PEG-b-PEI copolymers, respectively. In the second, modified conjugation procedure, Fmoc-cysteine harboring DC3 or SCRM peptides were first conjugated to NHS-PEG-MAL via the MAL group followed by coupling to linear PEI via the NHS functional group. Fmoc cleavage yielded the same final product as in the basic procedure. The modified conjugation procedure was capable of yielding block copolymers richer with peptides, as determined by (1)H NMR analysis. Self-assembly of DC3-PEG-b-PEI copolymers and DNA molecules yielded nanosized polyion complexes (polyplexes), with lower surface charge and limited cytotoxicity when compared to the PEI building block. Significant transfection efficiency of the DC-targeted polyplexes by murine dendritic DC2.4 cells was observed only in DC3-PEG-b-PEI/DNA polyplexes synthesized by the modified conjugation procedure. These polyplexes, with higher peptide-load, showed greater transfection capability in DC2.4 cells relative to the control nontargeted SCRM-PEG-b-PEI/DNA polyplexes, but not in endothelial cells. The transfection efficiency was comparable to or higher than that of the PEI/DNA positive control. The results indicate that PEGylated-PEI polyplexes show significant transfection efficiency into DCs when decorated with DC3 peptide, and are attractive candidates for immunotherapy via DCs.

Brain delivery of small interfering ribonucleic acid and drugs through intranasal administration with nano-sized polymer micelles

Recently, the development of effective strategies for enhancing drug delivery to the brain has been a topic of great interest in both clinical and pharmaceutical fields. In this review, we summarize our studies evaluating nose-to-brain delivery of drugs and small interfering ribonucleic acids in combination with cell-penetrating peptide-modified polymer micelles. Our findings show that the use of polymer micelles with surface modification with Tat peptide in the intranasal administration enables the non-invasive delivery of therapeutic agents to the brain by increasing the transfer of the administered drug or small interfering ribonucleic acid to the central nervous system from the nasal cavity.

Synthesis and evaluation of the targeted binding of RGD-containing PEGylated-PEI/DNA polyplex micelles as radiotracers for a tumor-targeting imaging probe

Polyplex micelles with pEGFP and RGD-modified poly(ethylene glycol)-grafted polyethylenimine (E[c(RGDyK)]₂-PEG-g-PEI) and were labeled with ^99mTc for the in vivo study as proficient probes for molecular imaging.

Interaction between calf thymus DNA and cationic bottle-brush copolymers: equilibrium and stopped-flow kinetic studies

Polyplex formation betweenctDNA and PEGylated cationic bottle-brush copolymers: PEG influences the DNA compaction behavior and the kinetics of polyplex formation.

Porphyrin-containing amphiphilic block copolymers for photodynamic therapy

Amphiphilic PNIPAM-b-PTPPC6MA block copolymers as promising photosensitizers for photodynamic therapy (PDT) constructed using porphyrin-containing monomers via RAFT polymerization.

Core cross-linked polyphosphoester micelles with folate-targeted and acid-cleavable features for pH-triggered drug delivery

Novel folate-conjugated acid-cleavable core cross-linked polyphosphoester micelles have been prepared and used for pH and enzyme-triggered delivery of doxorubicin.

Fast in situ generated ɛ-polylysine-poly (ethylene glycol) hydrogels as tissue adhesives and hemostatic materials using an enzyme-catalyzed method

In this study, novel bio-inspired in situ hydrogels as tissue adhesives and hemostatic materials were designed and prepared based on ɛ-polylysine-grafted poly(ethylene glycol) and tyramine via enzymatic cross-linking. The enzymatic cross-linked method enabled fast gelation within seconds, which facilitated its therapeutic applications. By changing the cross-linking conditions, the storage modulus of the hydrogels could be tunable and the mechanical strength influenced the tissue adhesiveness of the hydrogels. Besides, the hydrogels showed fine network structures with appropriate pore sizes, which were thought to be a contributing factor to the strong adhesiveness. Benefiting from the strong mechanical properties and fine network structures, the ɛ-polylysine-grafted poly(ethylene glycol) and tyramine hydrogels exhibited superior wound-healing and hemostatic ability compared to conventional and commercially available medical materials. Moreover, indirect cytotoxicity assessment indicated that the ɛ-polylysine-grafted poly(ethylene glycol) and tyramine hydrogels were nontoxic to the L929 cell. These results demonstrated that the enzymatic cross-linked in situ ɛ-polylysine hydrogels hold high potential for tissue sealants and hemostatic materials.

Enhanced gene expression promoted by hybrid magnetic/cationic block copolymer micelles

We report on novel gene delivery vector systems based on hybrid polymer-magnetic micelles. The hybrid micelles were prepared by codissolution of hydrophobically surface modified iron oxide and amphiphilic polystyrene-b-poly(quaternized 2-vinylpyridine) block copolymer (PS-b-P2QVP) in organic solvent. After extensive dialysis against water, micelles with positively charged hydrophilic corona of PQVP and hydrophobic PS core were prepared, in which magnetic nanoparticles were randomly distributed. The hybrid micelles were used to form complexes with linear (salmon sperm, 2000 bp, corresponding to M(w) of 1.32 × 10(6) Da) and plasmid (pEGFP-N1, 4730 bp, corresponding to M(w) of 3.12 × 10(6) Da) DNA. The resulting magnetopolyplexes of phosphate:amine (P/N) ratios in the 0.05-20 range were characterized by light scattering, ζ-potential measurements, and transmission electron microscopy as well as cytotoxicity and gel retardation assays. The investigated systems displayed a narrow size distribution, particle dimensions below 360 nm, whereas their ζ-potential values varied from positive to negative depending of the P/N ratio. The resulting vector nanosystems exhibited low toxicity. They were able to introduce pEGFP-N1 molecules into the cells. The application of a magnetic field markedly boosted the transgene expression efficiency of the magnetopolyplexes, which was even superior to those of commercial transfectants such as Lipofectamine and dendritic polyethylenimine.

Intraperitoneal administration of a tumor-associated antigen SART3, CD40L, and GM-CSF gene-loaded polyplex micelle elicits a vaccine effect in mouse tumor models

Polyplex micelles have demonstrated biocompatibility and achieve efficient gene transfection in vivo. Here, we investigated a polyplex micelle encapsulating genes encoding the tumor-associated antigen squamous cell carcinoma antigen recognized by T cells-3 (SART3), adjuvant CD40L, and granulocyte macrophage colony-stimulating factor (GM-CSF) as a DNA vaccine platform in mouse tumor models with different types of major histocompatibility antigen complex (MHC). Intraperitoneally administrated polyplex micelles were predominantly found in the lymph nodes, spleen, and liver. Compared with mock controls, the triple gene vaccine significantly prolonged the survival of mice harboring peritoneal dissemination of CT26 colorectal cancer cells, of which long-term surviving mice showed complete rejection when re-challenged with CT26 tumors. Moreover, the DNA vaccine inhibited the growth and metastasis of subcutaneous CT26 and Lewis lung tumors in BALB/c and C57BL/6 mice, respectively, which represent different MHC haplotypes. The DNA vaccine highly stimulated both cytotoxic T lymphocyte and natural killer cell activities, and increased the infiltration of CD11c⁺ DCs and CD4⁺/CD8a⁺ T cells into tumors. Depletion of CD4⁺ or CD8a⁺ T cells by neutralizing antibodies deteriorated the anti-tumor efficacy of the DNA vaccine. In conclusion, a SART3/CD40L+GM-CSF gene-loaded polyplex micelle can be applied as a novel vaccine platform to elicit tumor rejection immunity regardless of the recipient MHC haplotype.

Drastic stabilization of parallel DNA hybridizations by a polylysine comb-type copolymer with hydrophilic graft chain

Electrostatic interactions play a major role in protein-DNA interactions. As a model system of a cationic protein, herein we focused on a comb-type copolymer of a polycation backbone and dextran side chains, poly(L-lysine)-graft-dextran (PLL-g-Dex), which has been reported to form soluble interpolyelectrolyte complexes with DNA strands. We investigated the effects of PLL-g-Dex on the conformation and thermodynamics of DNA oligonucleotides forming various secondary structures. Thermodynamic analysis of the DNA structures showed that the parallel conformations involved in both DNA duplexes and triplexes were significantly and specifically stabilized by PLL-g-Dex. On the basis of thermodynamic parameters, it was further possible to design DNA switches that undergo structural transition responding to PLL-g-Dex from an antiparallel duplex to a parallel triplex even with mismatches in the third strand hybridization. These results suggest that polycationic molecules are able to induce structural polymorphism of DNA oligonucleotides, because of the conformation-selective stabilization effects.