PEGylated gene nanocarriers based on block catiomers bearing ethylenediamine repeating units directed to remarkable enhancement of photochemical transfection

Photochemical Internalization for Intracellular Drug Delivery. From Basic Mechanisms to Clinical Research

Photochemical internalisation (PCI) is a unique intervention which involves the release of endocytosed macromolecules into the cytoplasmic matrix. PCI is based on the use of photosensitizers placed in endocytic vesicles that, following light activation, lead to rupture of the endocytic vesicles and the release of the macromolecules into the cytoplasmic matrix. This technology has been shown to improve the biological activity of a number of macromolecules that do not readily penetrate the plasma membrane, including type I ribosome-inactivating proteins (RIPs), gene-encoding plasmids, adenovirus and oligonucleotides and certain chemotherapeutics, such as bleomycin. This new intervention has also been found appealing for intracellular delivery of drugs incorporated into nanocarriers and for cancer vaccination. PCI is currently being evaluated in clinical trials. Data from the first-in-human phase I clinical trial as well as an update on the development of the PCI technology towards clinical practice is presented here.

In vitro siRNA delivery via diethylenetriamine- and tetraethylenepentamine-modified carboxyl group-terminated Poly(amido)amine generation 4.5 dendrimers

The recent discovery of small interfering RNAs (siRNAs) has opened new avenues for designing personalized treatment options for various diseases. However, the therapeutic application of siRNAs has been confronted with many challenges because of short half-life in circulation, poor membrane penetration, difficulty in escaping from endosomes, and insufficient release into the cytosol. To overcome these challenges, we designed a diethylenetriamine (DETA)- and tetraethylenepentamine (TEPA)-modified polyamidoamine dendrimer generation 4.5 (PDG4.5), and characterized it using ¹H nuclear magnetic resonance (NMR), ¹³C NMR, correlation spectroscopy (COSY), heteronuclear single-quantum correlation spectroscopy (HSQC), and Fourier transform infrared (FTIR) spectroscopy followed by conjugation with siRNA. The PDG4.5-DETA and PDG4.5-TEPA polyplexes exhibited spherical nanosize, ideal zeta potential, and effective siRNA binding ability, protected the siRNA from nuclease attack, and revealed less cytotoxicity of PDG4.5-DETA and PDG4.5-TEPA in HeLa cells. More importantly, the polyplexes also revealed good cellular internalization and facilitated translocation of the siRNA into the cytosol. Thus, PDG4.5-DETA and PDG4.5-TEPA can act as potential siRNA carriers in future medical and pharmaceutical applications.

Development of polypeptide-based zwitterionic amphiphilic micelles for nanodrug delivery

Protein molecules, which typically have a hydrophobic core and a zwitterionic shell with a polypeptide backbone, could be ideal materials for nanodrug vehicles (NDVs) with low side effects. Here, we synthesized poly(l-aspartic acid(lysine))-b-poly(l-lysine(Z)) (PAsp(Lys)-b-PLys(Z)) (PALLZ), a novel amphiphilic block polypeptide with key structures of protein to investigate the possibility for use as a NDV. This polypeptide can spontaneously self-assemble into micelles in aqueous solution with a zwitterionic brush (the PAsp(Lys) part) to provide the nonfouling shell and a hydrophobic core (the PLys(Z) part) for loading hydrophobic drugs. The doxorubicin (DOX) loaded PALLZ micelles showed excellent resistance to nonspecific protein adsorption in FBS, which leads to very low internalization. Moreover, PALLZ micelles showed no cytotoxicity to MCF7, HeLa and HepG-2 cells up to 500 μg mL^-1. All these results indicated that zwitterionic amphiphilic block polypeptides could be promising materials for NDVs.

Synthesis, spectroscopic, and cellular properties of α-pegylated cis-A2B2- and A3B-types ZnPcs

A series of pegylated cis-A₂B₂- or A₃B-type ZnPcs, substituted on the α-positions with tri(ethylene glycol) and hydroxyl groups, were synthesized from a new bis-phthalonitrile. A clamshell-type bis-phthalocyanine was also obtained as a byproduct. The hydroxyl group of one ZnPc was alkylated with 3-dimethylaminopropyl chloride to afford a pegylated ZnPc functionalized with an amine group. All mononuclear ZnPcs were soluble in polar organic solvents, showed intense Q absorptions in DMF, and had fluorescence quantum yields in the range 0.10-0.23. The clamshell-type bis-phthalocyanine adopts mainly open shell conformations in DMF, and closed clamshell conformations in chloroform. All ZnPcs were highly phototoxic to human carcinoma HEp2 cells, particularly the amino-ZnPc mainly protonated under physiological conditions, which showed the highest phototoxicity (IC₅₀ = 0.5 μM at 1.5 J/cm²) and dark cytotoxicity (IC₅₀ = 22 μM), in part due to its high cellular uptake. The ZnPcs localized in multiple organelles, including mitochondria, lysosomes, Golgi and ER.

Enhancing nucleic acid delivery by photochemical internalization

Photochemical internalization (PCI) is a method for releasing macromolecules from endosomal and lysosomal compartments. The PCI approach uses a photosensitizer that localizes to endosomal and lysosomal compartments, and a light source with appropriate light spectra for excitation of the photosensitizer. Upon photosensitizer excitation, endosomal and lysosomal membranes are destroyed, due to the formation of reactive oxygen species, followed by release of the endocytosed material. PCI has been demonstrated to enhance and control (site- and time-specific) delivery of various macromolecules such as viruses, proteins, chemotherapeutics, nucleic acid, and so on. In this Review we present past and current studies of PCI-controlled delivery of natural and artificial nucleic acids, such as peptide nucleic acids, siRNA molecules, mRNA molecules and plasmids. We also discuss critical aspects to further the possibilities for successful gene targeting in space and time.

Polymeric micelles and alternative nanonized delivery vehicles for poorly soluble drugs

Poorly soluble drugs often encounter low bioavailability and erratic absorption patterns in the clinical setting. Due to the rising number of compounds having solubility issues, finding ways to enhance the solubility of drugs is one of the major challenges in the pharmaceutical industry today. Polymeric micelles, which form upon self-assembly of amphiphilic macromolecules, can act as solubilizing agents for delivery of poorly soluble drugs. This manuscript examines the fundamentals of polymeric micelles through reviews of representative literature and demonstrates possible applications through recent examples of clinical trial developments. In particular, the potential of polymeric micelles for delivery of poorly water-soluble drugs, especially in the areas of oral delivery and in cancer therapy, is discussed. Key considerations in utilizing polymeric micelles' advantages and overcoming potential disadvantages have been highlighted. Lastly, other possible strategies related to particle size reduction for enhancing solubilization of poorly water-soluble drugs are introduced.

Nanotechnology-based photodynamic therapy

According to recent advances in nanotechnology, various nano-sized formulations have been designed for the application in biomedical fields, including diagnosis, drug delivery, and therapeutics. The nanotechnology-based formulations have a great merit in the design of multifunctional platform for the biomedical applications. Therefore, recent trends in nanotechnology are moving onto the combination of nanotechnology and conventional therapeutic. Typically, photodynamic therapy (PDT) is one of promising techniques for the combination with nanotechnology owing to its less invasiveness. In this paper, we are going to briefly review recent advances in nanotechnology-based PDT, including selective delivery and excitation of photosensitizers, combination therapy, and multifunctional PDT.

Delivery, stabilization, and spatiotemporal activation of cargo molecules in cells with positively charged nanoparticles

Positively charged photodegradable nanoparticles that simultaneously encapsulated various compounds including small and large molecules were prepared. The nanoparticles were internalized to the cell by endocytosis and were stable within the cells for at least 4 days. The encapsulated molecules were released into the cytosol using light stimuli.

Syntheses and Photodynamic Activity of Pegylated Cationic Zn(II)-Phthalocyanines in HEp2 Cells

Di-cationic Zn(II)-phthalocyanines (ZnPcs) are promising photosensitizers for the photodynamic therapy (PDT) of cancers and for photoinactivation of viruses and bacteria. Pegylation of photosensitizers in general enhances their water-solubility and tumor cell accumulation. A series of pegylated di-cationic ZnPcs were synthesized from conjugation of a low molecular weight PEG group to a pre-formed Pc macrocycle, or by mixed condensation involving a pegylated phthalonitrile. All pegylated ZnPcs were highly soluble in polar organic solvents but were insoluble in water; they have intense Q absorptions centered at 680 nm and fluorescence quantum yields of ca. 0.2 in DMF. The non-pegylated di-cationic ZnPc 6a formed large aggregates, which were visualized by atomic force microscopy. The cytotoxicity, cellular uptake and subcellular distribution of all cationic ZnPcs were investigated in human carcinoma HEp2 cells. The most phototoxic compounds were found to be the α-substituted Pcs. Among these, Pcs 4a and 16a were the most effective (IC₅₀ ca. 10 μM at 1.5 J/cm²), in part due to the presence of a PEG group and the two positive charges in close proximity (separated by an ethylene group) in these macrocycles. The β-substituted ZcPcs 6b and 4b accumulated the most within HEp2 cells but had low photocytoxicity (IC₅₀ > 100 μM at 1.5 J/cm²), possibly as a result of their lower electron density of the ring and more extended conformations compared with the α-substituted Pcs. The results show that the charge distribution about the Pc macrocycle and the intracellular localization of the cationic ZnPcs mainly determine their photodynamic activity.

Core-shell structured nanoassemblies based on β-cyclodextrin containing block copolymer and poly(β-benzyl L-aspartate) via host-guest complexation

Double hydrophilic copolymers (PEG-b-PCDs) with one PEG block and another block containing β-cyclodextrin (β-CD) units were synthesized by macromolecular substitution reaction. Via a dialysis procedure, complex assemblies with a core-shell structure were prepared using PEG-b-PCDs in the presence of a hydrophobic homopolymer poly(β-benzyl L-aspartate) (PBLA). The hydrophobic PBLA resided preferably in the cores of assemblies, while the extending PEG chains acted as the outer shell. Host-guest interaction between β-CD and hydrophobic benzyl group was found to mediate the formation of the assemblies, where PEG-b-PCD and PBLA served as the host and guest macromolecules, respectively. The particle size of the assemblies could be modulated by the composition of the host PEG-b-PCD copolymer. The molecular weight of the guest polymer also had a significant effect on the size of the assemblies. The assemblies prepared from the host and guest polymer pair were stable during a long-term storage. These assemblies could also be successfully reconstituted after freeze-drying. The assemblies may therefore be used as novel nanocarriers for the delivery of hydrophobic drugs.

Design of biocompatible dendrimers for cancer diagnosis and therapy: current status and future perspectives

In the past decade, nanomedicine with its promise of improved therapy and diagnostics has revolutionized conventional health care and medical technology. Dendrimers and dendrimer-based therapeutics are outstanding candidates in this exciting field as more and more biological systems have benefited from these starburst molecules. Anticancer agents can be either encapsulated in or conjugated to dendrimer and be delivered to the tumour via enhanced permeability and retention (EPR) effect of the nanoparticle and/or with the help of a targeting moiety such as antibody, peptides, vitamins, and hormones. Imaging agents including MRI contrast agents, radionuclide probes, computed tomography contrast agents, and fluorescent dyes are combined with the multifunctional nanomedicine for targeted therapy with simultaneous cancer diagnosis. However, an important question reported with dendrimer-based therapeutics as well as other nanomedicines to date is the long-term viability and biocompatibility of the nanotherapeutics. This critical review focuses on the design of biocompatible dendrimers for cancer diagnosis and therapy. The biocompatibility aspects of dendrimers such as nanotoxicity, long-term circulation, and degradation are discussed. The construction of novel dendrimers with biocompatible components, and the surface modification of commercially available dendrimers by PEGylation, acetylation, glycosylation, and amino acid functionalization have been proposed as available strategies to solve the safety problem of dendrimer-based nanotherapeutics. Also, exciting opportunities and challenges on the development of dendrimer-based nanoplatforms for targeted cancer diagnosis and therapy are reviewed (404 references).

Photochemical internalization: a new tool for gene and oligonucleotide delivery

Photochemical internalization (PCI) is a novel technology for release of endocytosed macromolecules into the cytosol. The technology is based on the use of photosensitizers located in endocytic vesicles. Upon activation by light such photosensitizers induce a release of macromolecules from their compartmentalization in endocytic vesicles. PCI has been shown to increase the biological activity of a large variety of macromolecules and other molecules that do not readily penetrate the plasma membrane, including type I ribosome-inactivating proteins, immunotoxins, plasmids, adenovirus, various oligonucleotides, dendrimer-based delivery of chemotherapeutica and unconjugated chemotherapeutica such as bleomycin and doxorubicin. This review will present the basis for the PCI concept and the most recent significant developments.

Design and development of dendrimer photosensitizer-incorporated polymeric micelles for enhanced photodynamic therapy

Photodynamic therapy (PDT), which involves systemic administration of photosensitizers (PSs) followed by local photoillumination, is a promising method for the treatment of solid tumors and other diseases. Recently, considerable efforts have been devoted to the development of nanocarriers for the PS delivery with the aim of avoiding non-specific phototoxicity to normal tissues such as the skin. Here, we discuss the biological significance of the use of nanocarrier-encapsulated PSs in PDT. Also, we report our recent achievements on the development of dendrimer photosensitizer-loaded micelles as nanocarriers for PS delivery. We found that our nanocarriers greatly enhanced the PDT efficacy in vitro and in vivo, and also significantly reduced the skin phototoxicity. These results indicate the importance of a development strategy for nanocarriers and their great potential for clinical use. In addition, this review discusses the development of nanocarriers for emerging PDT-related technologies such as photodynamic diagnosis (PDD) and photochemical internalization (PCI).

Polymeric micelles from poly(ethylene glycol)-poly(amino acid) block copolymer for drug and gene delivery

Dramatic advances in biological research have revealed the mechanisms underlying many diseases at the molecular level. However, conventional techniques may be inadequate for direct application of this new knowledge to medical treatments. Nanobiotechnology, which integrates biology with the rapidly growing field of nanotechnology, has great potential to overcome many technical problems and lead to the development of effective therapies. The use of nanobiotechnology in drug delivery systems (DDS) is attractive for advanced treatment of conditions such as cancer and genetic diseases. In this review paper for a special issue on biomaterial research in Japan, we discuss the development of DDS based on polymeric micelles mainly in our group for anti-cancer drug and gene delivery, and also address our challenges associated with developing polymeric micelles as super-functionalized nanodevices with intelligent performance.

Polymeric core-shell assemblies mediated by host-guest interactions: versatile nanocarriers for drug delivery

Novel hydrophilic-hydrophilic block copolymer with one block containing β-cyclodextrin was synthesized. Core-shell structured nano-assemblies with chemical sensitivity could be constructed by this copolymer in the presence of hydrophobic compounds. By selecting appropriate guest components, polyion complex micelles could also be assembled. These results suggest the potential versatile applications of this type of copolymers in pharmaceutics, nanomedicine, and nano-biotechnology.

Cell-specific delivery of polymeric nanoparticles to carbohydrate-tagging cells

Carbohydrates on cell surfaces contribute a variety of communications between the cell and its environment, and they have been assumed to act as markers for cellular recognition. In this research, 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer nanoparticles, which can react with specific carbohydrates of target cells, were newly prepared to serve as novel drug carriers. A water-soluble MPC polymer bearing hydrazide groups (PMBH) was synthesized by conventional radical polymerization. The MPC polymer showed amphiphilic nature and worked as an emulsifier to form nanoparticles. The nanoparticles covered with PMBH were prepared by the solvent evaporation method and exhibited monodispersity. They were approximately 200 nm in diameter and -2.0 mV in surface potential. According to a surface analysis of the nanoparticles, phosphorylcholine and hydrazide groups were observed, and the surface was fully covered with PMBH. Unnatural carbohydrates having ketone groups on human cervical carcinoma cell (HeLa) surfaces were expressed by treatment with levulinoyl mannosamine (ManLev). When the PMBH nanoparticles were in contact with the ManLev-treated HeLa cells, they accumulated in the cells. In contrast, the nanoparticles were not observed in native HeLa cells (without unnatural carbohydrates). These results indicate that the hydrazide groups of the nanoparticles selectively reacted to the ketone groups of the carbohydrates on the cell surface. The PMBH nanoparticles immobilized with anticancer drugs such as doxorubicin or paclitaxel were in contact with either ManLev-treated or untreated HeLa cells. The viability of the ManLev-treated HeLa cells was effectively reduced, but that of the untreated cells was preserved. This indicated that the anticancer drugs were selectively delivered to the ManLev-treated cells. Nonspecific cellular uptake of the nanoparticles was effectively reduced by MPC polymer coating. Furthermore, the immobilization processes of the drugs differed because of the solubility of the drugs. In conclusion, cellular-specific drug delivery by means of the novel nanoparticles was demonstrated with the selective reaction between unnatural carbohydrates on the cell surface and the hydrazide groups bearing the phosphorylcholine polymer nanoparticles.

Ruthenium(II) Tris(bipyridine)-Centered Poly(ethylenimine) for Gene Delivery

Ruthenium(II) tris(bipyridine)-centered poly(ethylenimine) (Ru PEI) was synthesized via acid hydrolysis of Ru tris(bipyridine)-centered poly(2-ethyl-2-oxazoline) (Ru PEOX), and the luminescence, DNA entrapment, and transfection efficiencies were evaluated. Emission maxima for Ru PEI samples are red-shifted compared to Ru PEOX precursors, and the luminescence lifetimes are shorter in both methanol and aqueous solutions. Slower oxygen quenching of Ru PEOX and Ru PEI luminescence versus [Ru(bpy)3]Cl2 (bpy = bipyridine) is attributed to polymer shielding effects. Ru PEI luminescence is similar in the presence and absence of DNA. Ru PEI (7900 Da) and linear PEI (L-PEI; 22,000 Da) fully entrapped DNA (5.4 kb; pcDNA) at an N/P ratio of 2. LNCaP prostate cancer cells were transfected with a plasmid encoding for green fluorescent protein using Ru PEI and L-PEI vectors for comparison. For N/P = 48, the transfection efficiency for Ru PEI was approximately 50% relative to that of L-PEI.

Doxorubicin delivery by polyamidoamine dendrimer conjugation and photochemical internalization for cancer therapy

Coupling anticancer drugs to synthetic polymers is a promising approach to improve the efficacy and reduce the side effects of these drugs. The pH-activated polymer has been demonstrated to be a successful drug delivery vehicle system, whereas the photochemical internalization (PCI) was invented for site-specific delivery of membrane impermeable macromolecules from endocytic vesicles into the cytosol. In this study, doxorubicin (DOX) was conjugated to polyamidoamine (PAMAM) dendrimers via pH-sensitive and -insensitive linkers and was combined with different PCI strategies to evaluate the cytotoxic effects. Our results showed that both PCI strategies significantly improved the cytotoxicity of free DOX on Ca9-22 cells at higher concentrations. The 'light after' PCI treatment was efficient in releasing DOX from the PAMAM-hyd-DOX conjugates, resulted in more nuclear accumulation of DOX and more cell death through synergistic effects. On the other hand, antagonism was observed when 'light before' PCI combined with PAMAM-hyd-DOX conjugate. The distribution of PAMAM-amide-DOX was mainly cytosolic with or without PCI treatments. Both PCI strategies failed to improve the cytotoxicity of PAMAM-amide-DOX conjugates. Our results provide invaluable information in the future design of drug-polymer complexes for multi-modality cancer treatments.