A novel biodegradable gene carrier based on polyphosphoester

Solid implantable devices for sustained drug delivery

Implantable drug delivery systems (IDDS) are an attractive alternative to conventional drug administration routes. Oral and injectable drug administration are the most common routes for drug delivery providing peaks of drug concentrations in blood after administration followed by concentration decay after a few hours. Therefore, constant drug administration is required to keep drug levels within the therapeutic window of the drug. Moreover, oral drug delivery presents alternative challenges due to drug degradation within the gastrointestinal tract or first pass metabolism. IDDS can be used to provide sustained drug delivery for prolonged periods of time. The use of this type of systems is especially interesting for the treatment of chronic conditions where patient adherence to conventional treatments can be challenging. These systems are normally used for systemic drug delivery. However, IDDS can be used for localised administration to maximise the amount of drug delivered within the active site while reducing systemic exposure. This review will cover current applications of IDDS focusing on the materials used to prepare this type of systems and the main therapeutic areas of application.

Synthesis and Characterization of Amphiphilic Diblock Polyphosphoesters Containing Lactic Acid Units for Potential Drug Delivery Applications

Multistep one-pot polycondensation reactions synthesized amphiphilic diblock polyphosphoesters containing lactic acid units in the polymer backbone. At the first step was synthesized poly[poly(ethylene glycol) H-phosphonate-b-poly(ethylene glycol)lactate H-phosphonate] was converted through one pot oxidation into poly[alkylpoly(ethylene glycol) phosphate-b-alkylpoly(ethylene glycol)lactate phosphate]s. They were characterized by ¹H, ¹³C {H},³¹P NMR, and size exclusion chromatography (SEC). The effects of the polymer composition on micelle formation and stability, and micelle size were studied via dynamic light scattering (DLS). The hydrophilic/hydrophobic balance of these polymers can be controlled by changing the chain lengths of hydrophobic alcohols. Drug loading and encapsulation efficiency tests using Sudan III and doxorubicin revealed that hydrophobic substances can be incorporated inside the hydrophobic core of polymer micelles. The micelle size was 72-108 nm when encapsulating Sudan III and 89-116 nm when encapsulating doxorubicin. Loading capacity and encapsulation efficiency depend on the length of alkyl side chains. Changing the alkyl side chain from 8 to 16 carbon atoms increased micelle-encapsulated Sudan III and doxorubicin by 1.6- and 1.1-fold, respectively. The results obtained indicate that these diblock copolymers have the potential as drug carriers.

RNA-inspired intramolecular transesterification accelerates the hydrolysis of polyethylene-like polyphosphoesters

To synthesize new (bio)degradable alternatives to commodity polymers, adapting natural motives can be a promising approach. We present the synthesis and characterization of degradable polyethylene (PE)-like polyphosphoesters, which exhibit increased degradation rates due to an intra-molecular transesterification similar to RNA. An α,ω-diene monomer was synthesized in three steps starting from readily available compounds. By acyclic diene metathesis (ADMET) polymerization, PE-like polymers with molecular weights up to 38 400 g mol-1 were obtained. Post-polymerization functionalization gave fully saturated and semicrystalline polymers with a precise spacing of 20 CH2 groups between each phosphate group carrying an ethoxy hydroxyl side chain. This side chain was capable of intramolecular transesterification with the main-chain similar to RNA-hydrolysis, mimicking the 2'-OH group of ribose. Thermal properties were characterized by differential scanning calorimetry (DSC (T m ca. 85 °C)) and the crystal structure was investigated by wide-angle X-ray scattering (WAXS). Polymer films immersed in aqueous solutions at different pH values proved an accelerated degradation compared to structurally similar polyphosphoesters without pendant ethoxy hydroxyl groups. Polymer degradation proceeded also in artificial seawater (pH = 8), while the polymer was stable at physiological pH of 7.4. The degradation mechanism followed the intra-molecular "RNA-inspired" transesterification which was detected by NMR spectroscopy as well as by monitoring the hydrolysis of a polymer blend of a polyphosphoester without pendant OH-group and the RNA-inspired polymer, proving selective hydrolysis of the latter. This mechanism has been further supported by the DFT calculations. The "RNA-inspired" degradation of polymers could play an important part in accelerating the hydrolysis of polymers and plastics in natural environments, e.g. seawater.

Glucose-Sensitive Core-Cross-Linked Nanoparticles Constructed with Polyphosphoester Diblock Copolymer for Controlling Insulin Delivery

This work aims to construct biocompatible, biodegradable core-cross-linked and insulin-loaded nanoparticles which are sensitive to glucose and release insulin via cleavage of the nanoparticles in a high-concentration blood glucose environment. First, a polyphosphoester-based diblock copolymer (PBYP-g-Gluc)-b-PEEP was prepared via ring-opening copolymerization (ROP) and the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) in which PBYP and PEEP represent the polymer segments from 2-(but-3-yn-1-yloxy)-2-oxo-1,3,2-dioxaphospholane and 2-ethoxy-2-oxo-1,3,2-dioxaphospholane, respectively, and Gluc comes from 2-azidoethyl-β-d-glucopyranoside (Gluc-N3) that grafted with PBYP. The structure and molecular weight of the copolymer were characterized by 1H NMR, 31P NMR, GPC, FT-IR, and UV-vis measurements. The amphiphilic copolymer could self-assemble into core-shell uncore-cross-linked nanoparticles (UCCL NPs) in aqueous solutions and form core-cross-linked nanoparticles (CCL NPs) after adding cross-linking agent adipoylamidophenylboronic acid (AAPBA). Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to study the self-assembly behavior of the two kinds of NPs and the effect of different Gluc group contents on the size of NPs further to verify the stability and glucose sensitivity of CCL NPs. The ability of NPs to load fluorescein isothiocyanate-labeled insulin (FITC-insulin) and their glucose-triggered release behavior were detected by a fluorescence spectrophotometer. The results of methyl thiazolyl tetrazolium (MTT) assay and hemolysis activity experiments showed that the CCL NPs had good biocompatibility. An in vivo hypoglycemic study has shown that FITC-insulin-loaded CCL NPs could reduce blood glucose and have a protective effect on hypoglycemia. This research provides a new method for constructing biodegradable and glucose-sensitive core-cross-linked nanomedicine carriers for controlled insulin release.

Nanomedicine for Gene Delivery and Drug Repurposing in the Treatment of Muscular Dystrophies

Muscular Dystrophies (MDs) are a group of rare inherited genetic muscular pathologies encompassing a variety of clinical phenotypes, gene mutations and mechanisms of disease. MDs undergo progressive skeletal muscle degeneration causing severe health problems that lead to poor life quality, disability and premature death. There are no available therapies to counteract the causes of these diseases and conventional treatments are administered only to mitigate symptoms. Recent understanding on the pathogenetic mechanisms allowed the development of novel therapeutic strategies based on gene therapy, genome editing CRISPR/Cas9 and drug repurposing approaches. Despite the therapeutic potential of these treatments, once the actives are administered, their instability, susceptibility to degradation and toxicity limit their applications. In this frame, the design of delivery strategies based on nanomedicines holds great promise for MD treatments. This review focuses on nanomedicine approaches able to encapsulate therapeutic agents such as small chemical molecules and oligonucleotides to target the most common MDs such as Duchenne Muscular Dystrophy and the Myotonic Dystrophies. The challenge related to in vitro and in vivo testing of nanosystems in appropriate animal models is also addressed. Finally, the most promising nanomedicine-based strategies are highlighted and a critical view in future developments of nanomedicine for neuromuscular diseases is provided.

Efficacy of topotecan nanoparticles for intravitreal chemotherapy of retinoblastoma

Retinoblastoma (Rb) is the most common intraocular malignancy in children that accounts for approximately 4% of all pediatric malignancies. Since chemotherapy is a widely practiced treatment for Rb, there is a growing interest in developing new and effective drugs to overcome systemic and local side effects of chemotherapy to improve the quality of life and increase the chances of survival. This study sought to fabricate thiolated chitosan nanoparticles containing topotecan (TPH-TCs-NPs) with a view of enhancing drug loading and release control. This research was also designed to assess the ability of TPH-TCs-NPs to improve cell association, increase treatment efficacy in retinoblastoma cells and xenograft-rat-model of retinoblastoma, and overcome current topotecan hydrochloride (TPH) intravitreal administration challenges, including stability loss and poor cellular uptake. Modified ionic gelation method was optimized to fabricate TPH-TCs-NPs and TPH-TMC-NPs (N-trimethyl chitosan nanoparticles containing TPH). We characterized the NPs and quantified topotecan loading and release against a free TPH standard. The efficacy of TPH-NPs was quantified in human retinoblastoma cells (Y79) by XTT and flow cytometry measurement. In addition, Y79 cells were injected intravitreally in both eyes of immunodeficient wistar albino rats to create a xenograft-rat-model to compare the antitumor effectiveness of TPH-NPs and TPH by intravitreal administration. TPH-NPs complexation was confirmed by EDX, FTIR, and DSC techniques. TPH-TCs-NPs and TPH-TMC-NPs had high encapsulation efficiency (85.23 ± 2 and 73.34 ± 2% respectively). TPH-TCs-NPs showed a mean diameter, polidispersity index, and zeta potential of 25±2 nm, 0.21 ± 0.03 and +12 ± 2 mV, respectively. As a function of dose, TCs and TMC NPs were more efficacious than free topotecan (IC50s 53.17 and 85.88 nM, relative to 138.30 nM respectively, P = 0.012). Kruskal-Wallis test showed a statistically significant difference between the groups. Additionally, a significant difference between the tumor control and TPH-TCs-NPs treated group in xenograft-rat-model ( Range of P-value: 0.026 to 0.035) was shown by Bonferroni post hoc test. The current investigation demonstrated enhanced efficacy and association of TPH-TCs-NPs relative to free TPH in retinoblastoma cells and tumor in vitro and in vivo.

Insight into Protein-Polymer Conjugate Relaxation Dynamics: The Importance of Polymer Grafting

The bio and chemical physics of protein-polymer conjugates are related to parameters that characterize each component. With this work, it is intended to feature the dynamical properties of the protein-polymer conjugate myoglobin (Mb)-poly(ethyl ethylene phosphate), in the ps and ns time scales, in order to understand the respective roles of the protein and of the polymer size in the dynamics of the conjugate. Elastic and quasi-elastic neutron scattering is performed on completely hydrogenated samples with variable number of polymer chains covalently attached to the protein. The role of the polymer length in the protein solvation and internal dynamics is investigated using two conjugates formed by polymers of different molecular weight. It is confirmed that the flexibility of the complex increases with the number of grafted polymer chains and that a sharp dynamical transition appears when either grafting density or polymer molecular weight are high. It is shown that protein size is crucial for the polymer structural organization and interaction on the protein surface and it is established that the glass properties of the polymer change upon conjugation. The results give a better insight of the equivalence of the polymer coating and the role of water on the surface of proteins.

Cationic cross-linked polymers containing labile disulfide and boronic ester linkages for effective triple responsive DNA release

Disruption of DNA carriers triggered by intracellular bio-stimulants has been broadly considered as most convenient strategy for efficient DNA delivery. In this direction, we have designed and synthesized pH, redox and ATP responsive cationic cross-linked polymers (CLPs) having disulfide and reversible boronic ester linkages. These CLPs also contain folate groups that are known for their targeting capability towards cancer cells. Biophysical studies showed that these cationic CLPs exhibited more effective DNA condensation in comparison to cationic linear polymers resulting in the formation of nano-sized polyplexes with sufficient positive zeta potentials and good colloidal stability at neutral pH (∼7.4). More interestingly, the polyplexes prepared from these CLPs have the ability to selectively release complexed DNA under conditions similar to those prevalent in cancer cells such as acidic pH, ATP rich surroundings or presence of glutathione, as revealed by ethidium bromide exclusion assay, agarose gel electrophoresis, AFM measurements, etc. Therefore, these cross-linked polymers have high potential of being effective non-viral gene delivery vehicles.

Immobilization of polyphosphoesters on poly(ether ether ketone) (PEEK) for facilitating mineral coating

Poly(ether ether ketone) (PEEK) is an alternative material to metals for orthopedic applications. However, the compatibility of PEEK with hard tissues needs to be improved. To address this issue, this study proposes a novel technique for PEEK surface modifications. A polyphosphodiester macromonomer (PEPMA·Na) was synthesized via the demethylation of polyphosphotriester macromonomer obtained via the ring-opening polymerization of cyclic phosphoesters using 2-hydroxypropyl methacrylamide as the initiator. The surface modification of PEEK was performed via photoinduced and self-initiated graft polymerization of PEPMA·Na without using any photoinitiators. The amount of phosphorus due to poly(PEPMA·Na) immobilized on PEEK increased with an increase in the photoirradiation time. The PEEK surface turned hydrophilic due to poly(PEPMA·Na) grafting, with almost similar advancing and receding contact angles, implying that the modified PEEK surface (PEEK-g-poly(PEPMA·Na)) was homogeneous. Specimens were mineral coated by simple static soaking in ×1.5 simulated body fluid (1.5SBF) and by an alternative process that included additional soaking steps in 200 mM CaCl₂ aq. and 200 mM K₂HPO₄ aq. before static soaking in 1.5SBF. Specimens were immersed in 1.5SBF for 28 days in simple static soaking, after which the PEEK-g-poly(PEPMA·Na) surface was completely covered with spherical cauliflower-like mineral deposits that resembled octacalcium phosphate (OCP). Their structural similarities were confirmed via X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDS), and X-ray fluorescence (XRF) analyses. However, these mineral deposits were not observed on the bare PEEK surface. Due to the additional soaking steps (alternative soaking) undertaken before the static soaking of the specimens in 1.5SBF, the mineral coating on the PEEK-g-poly(PEPMA·Na) was dramatically accelerated and the surface was fully covered with mineral deposits in only one day of soaking. The mineral deposits resulting from both the soaking processes had similar structures. Compared with bare PEEK, osteoblastic MC3T3-E1 cells proliferated more actively on mineral-coated PEEK-g-poly(PEPMA·Na). Thus, the surface immobilization of poly(PEPMA·Na) on a PEEK surface is effective for mineral coating and may be useful to provide hard-tissue compatibility on PEEK.

Multifunctional Polymeric Prodrug with Simultaneous Conjugating Camptothecin and Doxorubicin for pH/Reduction Dual-Responsive Drug Delivery

Amphiphilic polymeric prodrugs show improved therapeutic indices with respect to traditional hydrophobic anticancer drugs because these prodrugs can self-assemble into nanoparticles, prolong the circulation of drugs in the blood, improve the accumulation of drugs in the disease site, reduce the side effects of drugs, and achieve therapeutic effect. Here, we describe a novel pH/reduction dual-responsive polymeric prodrug, abbreviated as CPT- ss-poly(BYP_{- hyd-DOX}- co-EEP), with simultaneous conjugating camptothecin (CPT) and doxorubicin (DOX), wherein BYP and EEP represent two cyclic phosphate monomers, respectively, that is, 2-(but-3-yn-1-yloxy)-2-oxo-1,3,2-dioxaphospholane and 2-ethoxy-2-oxo-1,3,2-dioxaphospholane. This prodrug was prepared through a polyphosphoester-DOX conjugate using a CPT derivative (CPT- ss-OH) as the initiator. CPT is linked to the terminal of polyphosphoester via disulfide carbonate, which is easy to break up under intracellular reductive environment and release the parent CPT, whereas DOX was efficiently incorporated onto the pendants of polyphosphoester through a hydrazone bond (- hyd-), which would be cleaved in the intracellular acidic medium. We show that the stable prodrug nanoparticles formed by self-assembly could release CPT and DOX simultaneously in the tumor microenvironment. The results of MTT assay demonstrate that the prodrug, which binds two antitumor drugs simultaneouly, has the properties of dual pH/reduction sensitiveness, biocompatibility, biodegradability, and effective tumor therapy.

Functional biodegradable polymers via ring-opening polymerization of monomers without protective groups

Biodegradable polymers are of current interest and chemical functionality in such materials is often demanded in advanced biomedical applications. Functional groups often are not tolerated in the polymerization process of ring-opening polymerization (ROP) and therefore protective groups need to be applied. Advantageously, several orthogonally reactive functions are available, which do not demand protection during ROP. We give an insight into available, orthogonally reactive cyclic monomers and the corresponding functional synthetic and biodegradable polymers, obtained from ROP. Functionalities in the monomer are reviewed, which are tolerated by ROP without further protection and allow further post-modification of the corresponding chemically functional polymers after polymerization. Synthetic concepts to these monomers are summarized in detail, preferably using precursor molecules. Post-modification strategies for the reported functionalities are presented and selected applications highlighted.

Synthesis and Aqueous Solution Properties of an Amino Bisphosphonate Methacrylate Homopolymer via RAFT Polymerization

The present contribution reports on the synthesis via reversible addition-fragmentation chain transfer (RAFT) polymerization of a methacrylate derivative bearing an aminobisphosponate moiety as a pendant group, namely, ethyl N,N-tetramethylbis(phosphonate)-bis(methylene) amine methacrylate (MAC₂NP₂). The polymerization was performed by the use of cyanoisopropyl dithiobenzoate as chain transfer agent at 70 °C in various solvents with different polarities including N,N-dimethylformamide, acetonitrile, tetrahydrofuran, and in bulk. Best results were obtained in N,N-dimethylformamide where higher conversions and polymerization rates were noticed. The successful hydrolysis of the phosphonate ester groups was performed using bromotrimethylsilane with excellent yields leading to the formation of highly water soluble and pH-responsive polymers. Finally, a preliminary solution behavior study was carried out by investigating the aqueous solution properties of synthesized amino bisphosphonate methacrylate homopolymers and their phosphonic acid analogs via potentiometric titration and zeta potential measurements.

Responsive Nanocarriers as an Emerging Platform for Cascaded Delivery of Nucleic Acids to Cancer

Cascades of systemic and intracellular obstacles, including low stability in blood, little tumor accumulation, weak tumor penetration, poor cellular uptake, inefficient endosomal escape and deficient disassembly in the cytoplasm, must be overcome in order to deliver nucleic acid drugs for cancer therapy. Nanocarriers that are sensitive to a variety of physiological stimuli, such as pH, redox status, and cell enzymes, are substantially changing the landscape of nucleic acid drug delivery by helping to overcome cascaded systemic and intracellular barriers. This review discusses nucleic acid-based therapeutics, systemic and intracellular barriers to efficient nucleic acid delivery, and nanocarriers responsive to extracellular and intracellular biological stimuli to overcome individual barriers. In particular, responsive nanocarriers for the cascaded delivery of nucleic acids in vivo are highlighted. Developing novel cascaded nanocarriers that transform their physicochemical properties in response to various stimuli in a timely and spatially controlled manner for nucleic acid drug delivery holds great potential for translating the promise of nucleic acid drugs and achieving clinically successful cancer therapy.

pH Triggered Size Increasing Gene Carrier for Efficient Tumor Accumulation and Excellent Antitumor Effect

High efficiency and serum resistant capacity are important for gene carrier in vivo usage. In this study, transfection efficiency and cell toxicity of polyethylenimine (PEI) (branched, Mw = 25K) was remarkably improved, when mixed with polyanion (polyethylene glycol-polyglutamic acid (PEG-PLG) or polyglutamic acid (PLG)). Different composite orders of PEI, polyanion, and gene, for example, PEI is first complexed with DNA, and then with polyanion, or PEI is first complexed with polyanion, and then with DNA, were studied. Results showed that only the polyanion/PEI complexes exhibited additional properties, such as decreased pH, resulting in increased particle size, as well as enhanced serum resistance capability and improved tumor accumulation. The prepared gene carrier showed excellent antitumor effect, with no damage on major organs, which is suitable for in vivo gene antitumor therapy.

Self-assembly of a novel Cu(ii) coordination complex forms metallo-vesicles that are able to transfect mammalian cells

Coordination-directed self-assembly of a Cu(ii) amphiphilic complex forms homogeneous nanometer-sized metallo-vesicles in water with low toxicity and gene transfection properties.

Polyphosphoesters: New Trends in Synthesis and Drug Delivery Applications

Polymers with repeating phosphoester linkages in the backbone are biodegradable materials that emerge as a promising class of novel biomaterials, especially in the field of drug delivery systems. In contrast to aliphatic polyesters, the pentavalency of the phosphorus atom offers a large diversity of structures and as a consequence a wide range of properties for these materials. In this paper, it is focused on the synthesis of well-defined polyphosphoesters (PPEs) by organocatalyzed ring-opening polymerization, improving the functionalities by combination with click reactions, degradation of functional PPEs and their cytotoxicity, and inputs for applications in drug delivery.

PGMA-Based Star-Like Polycations with Plentiful Hydroxyl Groups Act as Highly Efficient miRNA Delivery Nanovectors for Effective Applications in Heart Diseases

Poly(glycidyl methacrylate)-based star-like polycations with rich hydrophilic hydroxyl groups can efficiently transfer miRNA into primary cardiac fibroblasts for effective applications in cardiac diseases, such as inhibition of cardiac fibrosis and hypertrophy.

Cell-Penetrating, Guanidinium-Rich Oligophosphoesters: Effective and Versatile Molecular Transporters for Drug and Probe Delivery

The design, synthesis, and biological evaluation of a new family of highly effective cell-penetrating molecular transporters, guanidinium-rich oligophosphoesters, are described. These unique transporters are synthesized in two steps, irrespective of oligomer length, by the organocatalytic ring-opening polymerization (OROP) of 5-membered cyclic phospholane monomers followed by oligomer deprotection. Varying the initiating alcohol results in a wide variety of cargo attachment strategies for releasable or nonreleasable transporter applications. Initiation of oligomerization with a fluorescent probe produces, upon deprotection, a transporter-probe conjugate that is shown to readily enter multiple cell lines in a dose-dependent manner. These new transporters are superior in cell uptake to previously studied guanidinium-rich oligocarbonates and oligoarginines, showing over 2-fold higher uptake than the former and 6-fold higher uptake than the latter. Initiation with a protected thiol gives, upon deprotection, thiol-terminated transporters which can be thiol-click conjugated to a variety of probes, drugs and other cargos as exemplified by the conjugation and delivery of the model probe fluorescein-maleimide and the medicinal agent paclitaxel (PTX) into cells. Of particular significance given that drug resistance is a major cause of chemotherapy failure, the PTX-transporter conjugate, designed to evade Pgp export and release free PTX after cell entry, shows efficacy against PTX-resistant ovarian cancer cells. Collectively this study introduces a new and highly effective class of guanidinium-rich cell-penetrating transporters and methodology for their single-step conjugation to drugs and probes, and demonstrates that the resulting drug/probe-conjugates readily enter cells, outperforming previously reported guanidinium-rich oligocarbonates and peptide transporters.

Novel Disulfide-Containing Poly(β-amino ester)-Functionalised Magnetic Nanoparticles for Efficient Gene Delivery

Poly(β-amino ester)s (PBAEs) have been proved to effectively transfer DNA to various cell types. However, PBAEs with high molecular weights also show considerable toxicities, partly resulting from inadequate degradation of their polyester backbone. In this study, we created novel poly(β-amino ester)s (SF-1, 2, 3, and 4; notation SFs refers to all the four polymers) which were characterised by the cleavable disulfide bonds. Moreover, a new technique, termed magnetofection that uses magnetic nanoparticles to enhance gene expression, has recently been well developed. The negatively charged magnetic nanoparticles (MNPs) with good biocompatibility in vitro were prepared here to subsequently combine with SFs and DNA via electrostatic interaction, leading to the formation of the magnetic gene complexes MNP/SFs/DNA. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays and transfection experiments were performed in A549 cells to investigate all the resulting complexes. Studies indicated that the synthesised PBAEs exhibited good biodegradation and regulated release of DNA as a result of the reductive cleavage of the disulfide bonds, giving higher transfection efficiency along with much lower cytotoxicity compared with commercially available transfection agent polyethylenimine (Mw 25 kDa). Furthermore, when MNP was involved at a MNP/DNA weight ratio of 0.5, the magnetic gene complexes MNP/SFs/DNA showed enhanced levels of gene expression while maintaining low cytotoxicity.

Side-chain poly(phosphoramidate)s via acyclic diene metathesis polycondensation

Side-chain poly(phosphoramidate)s (PPAs) have been prepared by ADMET polycondensation and compared to structural analogues of poly(phosphoester)s. Thermal properties, stability, and crystallization behavior were analyzed. This is the first example for PPAs prepared by ADMET.

A block copolymer of zwitterionic polyphosphoester and polylactic acid for drug delivery

Zwitterionic polyphosphoester containing polymers are synthesized and evaluated as an alternative to poly(ethylene glycol) block copolymers for anticancer drug delivery.

Polyspermine imine, a pH responsive polycationic siRNA carrier degradable to endogenous metabolites

Cationic polymers readily degradable in response to cellular environment are especially favored as easy-formulating materials to pack siRNA into a nanoparticle and to release the cargo in the cytoplasm in time. In addition to the efficiency of cytosomal release, the degradation products should best be free of safety concerns, a typical challenge for cationic polymers. To satisfy the two criteria, we report a new cationic polymer, polyspermine imine, named as PSP-Imine, which is formed by condensing two endogenous molecules, spermine and glyoxal, through conjugated π linkage, -N═C-C═N- (Schiff base reaction), a poly linkage structure sufficiently stable under neutral condition but dissociative under the endosomal pH. Cellular assays under a confocal microscope indicated that the polyplex formed of PSP-Imine readily released the loaded siRNA to the cytoplasm after being engulfed in the target cells and efficiently silenced the target genes in different cell lines and xenograft mouse model of human cervical carcinoma, as compared with nondegradable PEI 25 kDa. Cell viability assays confirmed that PSP-Imine showed no visible cytotoxicity within the concentration being tested. The present study suggests that PSP-Imine is an excellent siRNA condensing material for forming the core of a therapeutically feasible synthetic carrier system.

Current progress in gene delivery technology based on chemical methods and nano-carriers

Gene transfer methods are promising in the field of gene therapy. Current methods for gene transfer include three major groups: viral, physical and chemical methods. This review mainly summarizes development of several types of chemical methods for gene transfer in vitro and in vivo by means of nano-carriers like; calcium phosphates, lipids, and cationic polymers including chitosan, polyethylenimine, polyamidoamine dendrimers, and poly(lactide-co-glycolide). This review also briefly introduces applications of these chemical methods for gene delivery.

Surface charges and shell crosslinks each play significant roles in mediating degradation, biofouling, cytotoxicity and immunotoxicity for polyphosphoester-based nanoparticles

The construction of nanostructures from biodegradable precursors and shell/core crosslinking have been pursued as strategies to solve the problems of toxicity and limited stability, respectively. Polyphosphoester (PPE)-based micelles and crosslinked nanoparticles with non-ionic, anionic, cationic, and zwitterionic surface characteristics for potential packaging and delivery of therapeutic and diagnostic agents, were constructed using a quick and efficient synthetic strategy, and importantly, demonstrated remarkable differences in terms of cytotoxicity, immunotoxicity, and biofouling properties, as a function of their surface characteristics and also with dependence on crosslinking throughout the shell layers. For instance, crosslinking of zwitterionic micelles significantly reduced the immunotoxicity, as evidenced from the absence of secretions of any of the 23 measured cytokines from RAW 264.7 mouse macrophages treated with the nanoparticles. The micelles and their crosslinked analogs demonstrated lower cytotoxicity than several commercially-available vehicles, and their degradation products were not cytotoxic to cells at the range of the tested concentrations. PPE-nanoparticles are expected to have broad implications in clinical nanomedicine as alternative vehicles to those involved in several of the currently available medications.

Polyphosphoester-based cationic nanoparticles serendipitously release integral biologically-active components to serve as novel degradable inducible nitric oxide synthase inhibitors

A degradable polyphosphoester (PPE)-based cationic nanoparticle (cSCK), which is integrated constructed as a novel degradable drug device, demonstrates surprisingly efficient inhibition of inducible nitric oxide synthase (iNOS) transcription, and eventually inhibits nitric oxide (NO) over-production, without loading of any specific therapeutic drugs. This system may serve as a promising anti-inflammatory agent toward the treatment of acute lung injury.