Contribution of hydrophobic/hydrophilic modification on cationic chains of poly(ε-caprolactone)-graft-poly(dimethylamino ethylmethacrylate) amphiphilic co-polymer in gene delivery

Smart Multistage "Trojan Horse"-Inspired Bovine Serum Albumin-Coated Liposomes for Enhancing Tumor Penetration and Antitumor Efficacy

Poor antitumor drug penetration into tumor tissues is a global challenge in clinical cancer treatment. Here, we reported a smart multistage "Trojan Horse"-inspired bovine serum albumin (BSA)-coated liposome (HBM), including the mimics of capsid and secondary BSA-coated polymeric nanoparticles (NPs) for enhancing tumor penetration and antitumor efficacy. These drug-loaded polymeric NPs possess a capsid-like component, a well-distributed nanostructure (size: 190.1 ± 4.98 nm, PDI: 0.259), and an excellent drug loading content (15.85 ± 1.36%). Meaningfully, after the smart multistage BSA-coated liposome targeted the tumor tissue, the mimics of capsid were "taken off" under the condition of tumor-specific enzymes, releasing "Heart" BSA-modified secondary NPs to increase the ability to penetrate tumor cells for enhancing antitumor efficacy. As expected, the HBM efficiently achieves high drug penetration into PAN02 tumor cells. Moreover, compared to free DOX and HM (HBM without BSA) NPs, DOX/HBM NPs exhibited the strongest tumor penetration and the highest cytotoxicity against PAN02 tumor cells both in vitro (IC50 = 0.141 μg/mL) and in vivo. This smart multistage "Trojan Horse"-inspired BSA-coated liposome should provide a new hathpace for further development of polymeric NPs in clinical treatment.

Dendrimers as nanoscale vectors: Unlocking the bars of cancer therapy

Chemotherapy is the first choice in the treatment of cancer and is always preferred to other approaches such as radiation and surgery, but it has never met the need of patients for a safe and effective drug. Therefore, new advances in cancer treatment are now needed to reduce the side effects and burdens associated with chemotherapy for cancer patients. Targeted treatment using nanotechnology are now being actively explored as they could effectively deliver therapeutic agents to tumor cells without affecting normal cells. Dendrimers are promising nanocarriers with distinct physiochemical properties that have received considerable attention in cancer therapy studies, which is partly due to the numerous functional groups on their surface. In this review, we discuss the progress of different types of dendrimers as delivery systems in cancer therapy, focusing on the challenges, opportunities, and functionalities of the polymeric molecules. The paper also reviews the various role of dendrimers in their entry into cells via endocytosis, as well as the molecular and inflammatory pathways in cancer. In addition, various dendrimers-based drug delivery (e.g., pH-responsive, enzyme-responsive, redox-responsive, thermo-responsive, etc.) and lipid-, amino acid-, polymer- and nanoparticle-based modifications for gene delivery, as well as co-delivery of drugs and genes in cancer therapy with dendrimers, are presented. Finally, biosafety concerns and issues hindering the transition of dendrimers from research to the clinic are discussed to shed light on their clinical applications.

Random Copolymers of Lysine and Isoleucine for Efficient mRNA Delivery

Messenger RNA (mRNA) is currently of great interest as a new category of therapeutic agent, which could be used for prevention or treatment of various diseases. For this mRNA requires effective delivery systems that will protect it from degradation, as well as allow cellular uptake and mRNA release. Random poly(lysine-co-isoleucine) polypeptides were synthesized and investigated as possible carriers for mRNA delivery. The polypeptides obtained under lysine:isoleucine monomer ratio equal to 80/20 were shown to give polyplexes with smaller size, positive ζ-potential and more than 90% encapsulation efficacy. The phase inversion method was proposed as best way for encapsulation of mRNA into polyplexes, which are based on obtained amphiphilic copolymers. These copolymers showed efficacy in protection of bound mRNA towards ribonuclease and lower toxicity as compared to lysine homopolymer. The poly(lysine-co-isoleucine) polypeptides showed greater than poly(ethyleneimine) efficacy as vectors for transfection of cells with green fluorescent protein and firefly luciferase encoding mRNAs. This allows us to consider obtained copolymers as promising candidates for mRNA delivery applications.

Multiresponsive Microgels: Toward an Independent Tuning of Swelling and Surface Properties

Dual-responsive poly-(N-isopropylacrylamide) (PNIPAM) microgels surface-functionalized with polyethylene glycol (PEG) or poly-2-dimethylaminoethyl methacrylate (PDMAEMA) were developed to enable the swelling behavior and surface properties of the microgels to be tuned independently. The thermo-triggered swelling and pH-triggered surface properties of the microgels were investigated in aqueous suspensions using dynamic light scattering and on substrates using the surface forces apparatus. Grafting polymer chains on the microgel surface did not impede the thermo-triggered swelling behavior of the microgels in suspensions and immobilized on substrates. An unprecedented decoupling of the swelling behavior and surface properties could be obtained. More particularly, the thermo-triggered swelling behavior of the PNIPAM underlying microstructure could be tuned below and above the phase transition temperature with no change in the surface potential and adhesion provided by the surface non-responsive PEG.

Construction of Inflammatory Directed Polymer Micelles and Its Application in Acute Lung Injury

Currently, there is no specific treatment for acute lung injury (ALI) in clinical practice. In order to efficiently and accurately treat ALI, the advantages of cationic carriers were combined to accelerate the cell uptake. Polycaprolactone-polyethylene glycol carrier (PCL-PEG-COOH, PPC) with good biocompatibility, polycaprolactone-polyethylmethacrylate cationic carrier (PCL-PDMAEMA, PCD), and polycaprolactone-polyethylene glycol carrier connected with high-affinity targeting peptide (Esbp) targeting inflammatory endothelial cells (PCL-PEG-Esbp, PPE) were used to construct the high-molecular polymer micelles (PCD/PPC/PPE). The particle size of the prepared DEX-loaded micelles was 130 ± 4.41 nm, and the Zeta potential was 28.3 ± 0.76 mV. The CMC value of the prepared polymer micelles was 0.643 μg/mL, and it was not easy to depolymerize in the blood circulation. Only about 40% DXM was released from the drug-loaded polymer micelles after 12 h compared with free DXM, indicating that the micelle material had a certain sustained-release performance in vitro release experiments. The safe concentration range of polymer was determined by biocompatibility test. It was recommended that the concentration of polymer micelles should not exceed 0.40 mg/mL to obtain a good compatibility in organisms. The results of cytotoxicity measurement showed that when the content of PCD increased to 50%, the concentration of blank micelles should not exceed 500 μg/mL and the concentration of DXM-loaded micelles should not be higher than 100 μg/mL. It was proved in the cell uptake experiment that the cation carrier of the micelles accelerated the cell uptake. The targeting ability of the targeted micelle group was higher compared with the non-targeted micelle group (P < 0.01, **). Meanwhile, the targeting ability of the non-targeted micelle group was higher compared with the free group (P < 0.001, ***). The targeting ability of the non-targeted micelle group was about 2.30 times and the targeted micelle group was about 3.16 times larger than that of the free group. It was also proved in the in vivo targeting experiments that the targeted micelles had a good targeting ability. The results of in vivo imaging of mice showed that the DXM of the micelle group gathered more in the lungs, and the micelle group had a better targeting ability compared with the free DID group. The order of lung targeting intensity was targeted micelles > non-targeted micelles >> free DID group. The targeting ability of polypeptide Esbp to ALI was confirmed. In conclusion, the prepared PCD/PPC/PPE polymer micelles had obvious in vitro and in vivo targeting ability and good biocompatibility. They could be used as a new targeted delivery system for the treatment of ALI in the future.

Annexin V-Conjugated Mixed Micelles as a Potential Drug Delivery System for Targeted Thrombolysis

To alleviate the hemorrhagic side effect of thrombolysis therapy, a thrombus targeted drug delivery system based on the specific affinity of Annexin V to phosphatidylserine exposed on the membrane surface of activated platelet was developed. The amphiphilic and biodegradable biomaterial, polycaprolactone-block-poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-hydroxyethyl methacrylate) (PCL-b-PDMAEMA-b-PHEMA (PCDH)) triblock polymer, was synthesized via ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP) to use as the nanocarriers of thrombolytic drug. In order to conjugate Annexin V to the polymer, PCDH was modified by succinic anhydride via ring-opening reaction to introduce the carboxyl group (PCDH-COOH). After preparation of PCDH/PCDH-COOH (9/1, m/m) mixed micelles, Annexin V was coupled with the micelles using carbodiimide chemistry. The blood clot lysis assay in vitro confirmed that lumbrokinase-loaded targeted micelles (LKTM) had stronger thrombolysis potency than free lumbrokinase (LK) and LK-loaded nontargeted micelles (LKM, P < 0.05). In vivo thrombolytic assay, multispectral, optoacoustic tomography (MSOT) was used to assess the target ability of LKTM. The results of MSOT images indicated the fluorescence intensity of the LKTM group located in the blood clot position were significantly stronger than the LKM group. A 5 mm of carotid artery containing blood clot was cut out 24 h later after administration to assess the degree of thrombolysis. The results of thrombolytic assay in vivo were consistent with the assay in vitro, which the differences between LK, LKM, and LKTM groups were both statistically significant. All the results of thrombolysis assays above proved that the capacity of thrombolysis in the LKTM group was optimal. It suggested that Annexin V-conjugated micelles will be a potential drug delivery system for targeted thrombolysis.

Influence of Block versus Random Monomer Distribution on the Cellular Uptake of Hydrophilic Copolymers

The use of polymers has revolutionized the field of drug delivery in the past two decades. Properties such as polymer size, charge, hydrophilicity, or branching have all been shown to play an important role in the cellular internalization of polymeric systems. In contrast, the fundamental impact of monomer distribution on the resulting biological properties of copolymers remains poorly studied and is always only investigated for biologically active self-assembling polymeric systems. Here, we explore the fundamental influence of monomer distribution on the cellular uptake of nonaggregating and biologically passive copolymers. Reversible addition-fragmentation chain-transfer (RAFT) polymerization was used to prepare precisely defined copolymers of three hydrophilic acrylamide monomers. The cellular internalization of block copolymers was compared with the uptake of a random copolymer where monomers are statistically distributed along the chain. The results demonstrate that monomer distribution in itself has a negligible impact on copolymer uptake.

Design, synthesis and in vitro evaluation of d-glucose-based cationic glycolipids for gene delivery

A cationic lipid consists of a hydrophilic headgroup, backbone and hydrophobic tails which have an immense influence on the transfection efficiency of the lipid. In this paper, two novel series of cationic cyclic glycolipids with a quaternary ammonium headgroup and different-length hydrophobic tails (dodecyl, tetradecyl, hexadecyl) have been designed and synthesized for gene delivery. One contains lipids 1-3 with two hydrophobic alkyl chains linked to the glucose ring directly via an ether link. The other contains lipids 4-6 with two hydrophobic chains on the positively charged nitrogen atoms. All of the lipids were characterized for their ability to bind to DNA, size, ζ-potential, and toxicity. Atomic force microscopy showed that the lipids and DNA-lipid complexes were sphere-like forms. The lipids were used to transfer enhanced green fluorescent protein (EGFP-C3) to HEK293 cells without a helper lipid, the results indicated that lipids 4-6 have better transfection efficiency, in particular lipids 5-6 have similar or better efficiency, compared with the commercial transfection reagent lipofectamine 2000.

Smart pH/Redox Dual-Responsive Nanogels for On-Demand Intracellular Anticancer Drug Release

Efficient accumulation and intracellular drug release in cancer cells remain a crucial challenge in developing ideal anticancer drug delivery systems. Here, poly(N-isopropylacrylamide)-ss-acrylic acid (P(NIPAM-ss-AA)) nanogels based on NIPAM and AA cross-linked by N,N'-bis(acryloyl)cystamine (BAC) were constructed by precipitation polymerization. The nanogels exhibited pH/redox dual responsive doxorubicin (DOX) release behavior in vitro and in tumor cells, in which DOX release from nanogels was accelerated in lysosomal pH (pH 4.5) and cytosolic reduction (10 mM GSH) conditions. Moreover, intracellular tracking of DOX-loaded nanogels confirmed that after the nanogels and the loaded DOX entered the cells simultaneously mainly via lipid raft/caveolae-mediated endocytosis, DOX-loaded nanogels were transported to lysosomes and then the loaded DOX was released to nucleus triggered by lysosomal pH and cytoplasmic high GSH. MTT analysis showed that DOX-loaded nanogels could efficiently inhibit the proliferation of HepG2 cells. In vivo animal studies demonstrated that DOX-loaded nanogels were accumulated and penetrated in tumor tissues more efficiently than free DOX. Meanwhile, DOX-loaded nanogels exhibited stronger tumor inhibition activity and fewer side effects. This study indicated that pH/redox dual-responsive nanogels might present a prospective platform for intracellular drug controlled release in cancer therapy.

A Low Protein Binding Cationic Poly(2-oxazoline) as Non-Viral Vector

Developing safe and efficient non-viral gene delivery systems remains a major challenge. We present a new cationic poly(2-oxazoline) (CPOx) block copolymer for gene therapy that was synthesized by sequential polymerization of non-ionic 2-methyl-2-oxazoline and a new 2-oxazoline monomer, 2-(N-methyl, N-Boc-amino)-methyl-2-oxazoline, followed by deprotection of the pendant secondary amine groups. Upon mixing with plasmid DNA (pDNA), CPOx forms small (diameter ≈80 nm) and narrowly dispersed polyplexes (PDI <0.2), which are stable upon dilution in saline and against thermal challenge. These polyplexes exhibited low plasma protein binding and very low cytotoxicity in vitro compared to the polyplexes of pDNA and poly(ethylene glycol)-b-poly(L-lysine) (PEG-b-PLL). CPOx/pDNA polyplexes at N/P = 5 bound considerably less plasma protein compared to polyplexes of PEG-b-PLL at the same N/P ratio. This is a unique aspect of the developed polyplexes emphasizing their potential for systemic delivery in vivo. The transfection efficiency of the polyplexes in B16 murine melanoma cells was low after 4 h, but increased significantly for 10 h exposure time, indicative of slow internalization of polyplexes. Addition of Pluronic P85 boosted the transfection using CPOx/pDNA polyplexes considerably. The low protein binding of CPOx/pDNA polyplexes is particularly interesting for the future development of targeted gene delivery.

Cationic triblock copolymer micelles enhance antioxidant activity, intracellular uptake and cytotoxicity of curcumin

The aim of the present study was to develop curcumin loaded cationic polymeric micelles and to evaluate their loading, preservation of curcumin antioxidant activity and intracellular uptake ability. The micelles were prepared from a triblock copolymer consisting of poly(ϵ-caprolactone) and very short poly(2-(dimethylamino) ethyl methacrylate) segments (PDMAEMA9-PCL70-PDMAEMA9). The micelles showed monomodal size distribution, mean diameter of 145 nm, positive charge (+72 mV), critical micellar concentration around 0.05 g/l and encapsulation efficiency of 87%. The ability of the micellar curcumin to scavenge the ABTS radical and hypochlorite ions was higher than that of the free curcumin. Confocal microscopy revealed that the uptake of curcumin by chronic myeloid leukemia derived K-562 cells and human multiple myeloma cells U-266 was more intensive when curcumin was loaded into the micelles. These results correlated with the higher cytotoxicity of the micellar curcumin compared to free curcumin. Intraperitoneal treatment of Wistar rats indicated that PDMAEMA-PCL-PDMAEMA copolymer, comprising very short cationic chains, did not change the levels of malondialdehyde and glutathione in livers indicating an absence of oxidative stress. Thus, PDMAEMA-PCL-PDMAEMA triblock micelles could be considered efficient and safe platform for curcumin delivery.

Effects of hydrophobic core components in amphiphilic PDMAEMA nanoparticles on siRNA delivery

Due to their biodegradable character, polyesters such as polycaprolactone (PCL), poly(D,L-lactide) (PDLLA), and polylactic-co-glycolic acid (PLGA) were widely used as the hydrophobic cores of amphiphilic cationic nanoparticles (NPs) for siRNA delivery. However, fewer researches focused on facilitating siRNA delivery by adjusting the polyester composition of these nanoparticles. Herein, we investigated the contribution of polyester segments in siRNA delivery in vitro by introducing different ratio of DLLA moieties in PCL segments of mPEG-block-PCL-graft-poly(dimethylamino ethyl methacrylate)(PEG-b-PCL-g-PDMAEMA). It was noticed that compared with the other ratios of DLLA moieties, a certain molar ratio (about 70%) of the NPs, named mPEG45-P(CL21-co-DLLA48)-g-(PDMAEMA29)2 (PECLD-70), showed the highest gene knockdown efficiency but poorest cellular uptake ability in vitro. Further research revealed that NPs with various compositions of the polyester cores showed different physicochemical properties including particle size, zeta potential and stiffness, leading to different endocytosis mechanisms thus influencing the cellular uptake efficiency. Subsequently, we observed that the cells treated by PECLD-70 NPs/Cy5 siRNA complexes exhibited more diffuse Cy5 signal distribution than other NPs by confocal laser scanning microscope, which suggested that siRNA delivered by PECLD-70 NPs/Cy5 siRNA complexes possessed of stronger capabilities in escaping from endosome/lysosome, entering the RNA-induced silencing complex (RISC) and cutting the target mRNA efficiently. The different siRNA release profile was dominated by the degradation rate of polyester segments. Therefore, it could be concluded that the adjustment of hydrophobic core of cationic nanoparticles could significantly affect their transfection behavior and appropriate polyester composition should be concerned in designing of analogous siRNA vectors.

The influence of polymer architecture on in vitro pDNA transfection

In the field of polymer-based gene delivery, the tuning potential of polymers by using different architectures like graft- and star-shaped polymers as well as self-assembled block copolymers is immense. In the last years numerous new polymer designs showed enhanced transfections properties in combination with a good biocompatibility.

Structural impact of graft and block copolymers based on poly(N-vinylpyrrolidone) and poly(2-dimethylaminoethyl methacrylate) in gene delivery

The characteristics of graft and block copolymers based on PVP and PDMAEMA in pDNA compaction, cytotoxicity, transfection efficiency, internalization and intracellular distribution were systematically investigated.

Establishing α-bromo-γ-butyrolactone as a platform for synthesis of functional aliphatic polyesters – bridging the gap between ROP and SET-LRP

Utilizing α-bromo-γ-butyrolactone (αBrγBL) as a comonomer with ε-caprolactone (εCL) or l-lactide (LLA) produces copolymers with active and available grafting sites, e.g., for SET-LRP, where the choice of the grafting monomers is limited only by one's imagination.