PEGylated bioreducible poly(amido amine)s for non-viral gene delivery

Polymeric Nanoparticles Enable mRNA Transfection and Its Translation in Intervertebral Disc and Human Joint Cells, Except for M1 Macrophages

Chronic lower back pain caused by intervertebral disc degeneration and osteoarthritis (OA) are highly prevalent chronic diseases. Although pain management and surgery can alleviate symptoms, no disease-modifying treatments are available. mRNA delivery could halt inflammation and degeneration and induce regeneration by overexpressing anti-inflammatory cytokines or growth factors involved in cartilage regeneration. Here, we investigated poly(amidoamine)-based polymeric nanoparticles to deliver mRNA to human joint and intervertebral disc cells. Human OA chondrocytes, human nucleus pulposus (NP) cells, human annulus fibrosus (AF) cells, fibroblast-like synoviocytes (FLS) and M1-like macrophages were cultured and transfected with uncoated or PGA-PEG-coated nanoparticles loaded with EGFP-encoding mRNA. Cell viability and transfection efficiency were analyzed for all cell types. Nanoparticle internalization was investigated in FLS and M1-like macrophages. No significant decrease in cell viability was observed in most conditions. Only macrophages showed a dose-dependent reduction of viability. Transfection with either nanoparticle version resulted in EGFP expression in NP cells, AF cells, OA chondrocytes and FLS. Macrophages showed internalization of nanoparticles by particle-cell co-localization, but no detectable expression of EGFP. Taken together, our data show that poly (amidoamine)-based nanoparticles can be used for mRNA delivery into cells of the human joint and intervertebral disc, indicating its potential future use as an mRNA delivery system in OA and IVDD, except for macrophages.

A poly(amidoamine)-based polymeric nanoparticle platform for efficient in vivo delivery of mRNA

The successful use of mRNA vaccines enabled and accelerated the development of several new vaccine candidates and therapeutics based on the delivery of mRNA. In this study, we developed bioreducible poly(amidoamine)-based polymeric nanoparticles (PAA PNPs) for the delivery of mRNA with improved transfection efficiency. The polymers were functionalized with chloroquinoline (Q) moieties for improved endosomal escape and further stabilization of the mRNA-polymer construct. Moreover, these PAAQ polymers were covalently assembled around a core of multi-armed ethylenediamine (Mw 800, 2 % w/w) to form a pre-organized polymeric scaffolded PAAQ (ps-PAAQ) as a precursor for the formation of the mRNA-loaded nanoparticles. Transfection of mammalian cell lines with EGFP mRNA loaded into these PNPs showed a favorable effect of the Q incorporation on GFP protein expression. Additionally, these ps-PAAQ NPs were co-formulated with PEG-polymer coatings to shield the positive surface charge for increased stability and better in vivo applicability. The ps-PAAQ NPs coated with PEG-polymer displayed smaller particle size, electroneutral surface charge, and higher thermal stability. Importantly, these nanoparticles with both Q and PEG-polymer coating induced significantly higher luciferase activity in mice muscle than uncoated ps-PAAQ NPs, following intramuscular injection of PNPs loaded with luciferase mRNA. The developed technology is broadly applicable and holds promise for the development of new nucleotide-based vaccines and therapeutics in a range of infectious and chronic diseases.

Polymeric Nanoparticles for Drug Delivery in Osteoarthritis

Osteoarthritis (OA) is a degenerative musculoskeletal disorder affecting the whole synovial joint and globally impacts more than one in five individuals aged 40 and over, representing a huge socioeconomic burden. Drug penetration into and retention within the joints are major challenges in the development of regenerative therapies for OA. During the recent years, polymeric nanoparticles (PNPs) have emerged as promising drug carrier candidates due to their biodegradable properties, nanoscale structure, functional versatility, and reproducible manufacturing, which makes them particularly attractive for cartilage penetration and joint retention. In this review, we discuss the current development state of natural and synthetic PNPs for drug delivery and OA treatment. Evidence from in vitro and pre-clinical in vivo studies is used to show how disease pathology and key cellular pathways of joint inflammation are modulated by these nanoparticle-based therapies. Furthermore, we compare the biodegradability and surface modification of these nanocarriers in relation to the drug release profile and tissue targeting. Finally, the main challenges for nanoparticle delivery to the cartilage are discussed, as a function of disease state and physicochemical properties of PNPs such as size and surface charge.

Phosphonic acid-functionalized poly(amido amine) macromers for biomedical applications

Novel phosphonic acid-functionalized poly(amido amine) (PAA) macromers are synthesized through aza-Michael addition of 2-aminoethyl phosphonic acid or its mixture with 5-amino-1-pentanol at different ratios onto N,N'-methylene bis(acrylamide) to control the amount of phosphonic acid functionality. The macromers were homo- and copolymerized with 2-hydroxyethyl methacrylate at different ratios to obtain hydrogels with various hydrophilicities. The hydrogels' swelling, biodegradation and mineralization properties were evaluated. The swelling and degradation rates of the gels can be tuned by the chemical structure of PAA macromer precursors as well as pH and CaCl₂ pre-treatment. The hydrogels show composition-dependent mineralization in SBF and 5xSBF, as evidenced from Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) analyses. The degradation products of the hydrogels have no effect on U-2 OS, Saos-2 and NIH 3T3 cells, suggesting their cytocompatibility. Overall, these materials have potential to be used as nontoxic degradable biomaterials.

Hydroxyethyl substituted linear polyethylenimine for safe and efficient delivery of siRNA therapeutics

Linear polyethylenimine (LPEI) has been well reported as a carrier for siRNA delivery. However, its applications are limited due to its highly ionized state at physiologic pH and the resultant charge mediated toxicity. The presence of ionizable secondary amines in LPE are responsible for its unique characteristics such as pH dependent solubility and positive charge. Therefore, modification of LPEI was carried out to obtain hydroxyethyl substituted LPEI with the degree of substitution ranging from 15% to 45%. The impact of modification on the physicochemical parameters of the polymer, i.e. buffer capacity, solubility, biocompatibility and stability, was evaluated. Surprisingly, despite the loss of ionizable amines, the substitution improved solubility, and even overcame the pH dependent solubility of LPEI. In addition, the conversion of secondary amines to less basic tertiary amines after substitution improved the buffer capacity, in the endosomal pH range, required for efficient endosomal escape. It also reduced erythrocyte aggregation, hemolytic potential and in vitro cytotoxicity. The in vitro studies showed enhanced cell uptake and mRNA knockdown efficiency. Thus, the proposed modification shows a simple approach to overcome the limitation of LPEI for siRNA delivery.

Hydroxyethyl substitution of linear polyethylenimine (LPEI) and its effects on physico-chemical and biological properties of polymer.

Targeted delivery of Bcl-2 conversion gene by MPEG-PCL-PEI-FA cationic copolymer to combat therapeutic resistant cancer

Deregulation of anti-apoptosis Bcl-2 protein expression was a key feature in human cancers with therapeutic resistance. Nuclear receptor Nur77 could induce the conformation change of Bcl-2 protein and converted it into an apoptosis inducer by "enemy to friend" strategy. However, the safe and effective delivery of this gene to combat therapeutic resistant cancer remained largely unexplored. In this report, we designed an amphiphilic cationic MPEG-PCL-PEI-FA copolymer, comprising biocompatible and hydrophilic methoxy-poly(ethylene glycol) (MPEG), biodegradable and hydrophobic poly(ε-caprolactone) (PCL), cationic poly(ethylene imine) (PEI) segments, and folic acid (FA) as targeting group, as a high efficient Nur77 gene carrier to folate receptor (FR) highly expressed and therapeutic resistant HeLa/Bcl-2 cancer cells. Interestingly, due to the incorporation of PCL and PEG segments, this MPEG-PCL-PEI-FA copolymer showed less toxicity but better gene transfection efficiency than non-viral gene carrier gold standard PEI (25kDa). This might be due to the formation of micelles to stabilize polyplex for enhanced gene transfection ability. More importantly, MPEG-PCL-PEI-FA copolymer exhibited excellent growth inhibition ability on therapeutic resistant HeLa/Bcl-2 cancer cells, which was FR overexpressed HeLa cervical cancer cells with high expression of Bcl-2 protein, thanks to its FA induced targeting ability, high gene transfection efficiency, and low cytotoxicity. This work signifies the first time that cationic amphiphilic MPEG-PCL-PEI-FA copolymers could be utilized for the gene delivery to therapeutic resistant cancer cells with high expression of anti-apoptosis Bcl-2 protein and the positive results are encouraging for the further design of polymeric platforms for combating drug resistant tumors.

Disulfide-bridged cleavable PEGylation in polymeric nanomedicine for controlled therapeutic delivery

PEGylation in polymeric nanomedicine has gained substantial predominance in biomedical applications due to its resistance to protein absorption, which is critically important for a therapeutic delivery system in blood circulation. The shielding layer of PEGylation, however, creates significant steric hindrance that negatively impacts cellular uptake and intracellular distribution at the target site. This unexpected effect compromises the biological efficacy of the encapsulated payload. To address this issue, one of the key strategies is to tether the disulfide bond to PEG for constructing a disulfide-bridged cleavable PEGylation. The reversible disulfide bond can be cleaved to enable selective PEG detachment. This article provides an overview on the strategy, method and progress of PEGylation nanosystem with the cleavable disulfide bond.

Comblike Polyethylenimine-Based Polyplexes: Balancing Toxicity, Cell Internalization, and Transfection Efficiency via Polymer Chain Topology

Comblike polyethylenimines with varying degrees of polymerization of both the main and side chains as well as different grafting densities were evaluated as gene delivery vectors. They were able to condense linear and plasmid DNA into nanosized polyplex particles with dimensions and surface potentials in the 130-330 nm and -30 to +15 mV ranges, respectively, depending on the amine/phosphate (N/P) ratio. The polyplexes remained stable in aqueous and buffer solutions from several hours up to several days. The moderate colloidal stability was also manifested in a relatively broad size distribution (PDI typically above 0.2) and structural polymorphism observed by transmission electron microscopy. Both the neat polymers and polyplexes displayed low cytotoxicity in WISH cells as the relative cell viability was more than 60%. Experiments with lysosomal fluorescence staining revealed that the internalization pathways and, in turn, transfection efficiency of the polyplex nanoparticles depended on the polymer chain topology. The vector systems based on the polymers of denser structure can be considered to be promising systems for gene transfection in eukaryotic cells.

A family of cationic polyamides for in vitro and in vivo gene transfection

The purpose of this study is to develop biodegradable cationic polyamides for non-viral gene delivery and elucidate their structural effects on gene transfection activity. To this end, a group of novel cationic polyamides were synthesized by polycondensation reaction between different di-p-nitrophenyl esters and tertiary amine-containing primary diamines. These linear polyamides have flexible alkylene group (ethylene or propylene), protonable amino group and bioreducible disulfide linkage in the polyamide main chain. The alkylene group and disulfide linkage in these polyamides have a distinct effect on their gene delivery properties including buffering capacity, gene binding ability and intracellular gene release profile. Those cationic polyamides containing disulfide linkage and 1,4-bis(3-aminopropyl)piperazine (BAP) residue exhibited high buffering capacity (endosomal escape ability), high gene binding ability, and intracellular gene release ability, thus inducing fast gene nucleus translocation and robust gene transfection in vitro against different cell lines and rat bone marrow mesenchymal stem cells. Moreover, the transfection efficiencies in vitro were comparable or higher than those of 25 kDa branched polyethylenimine and Lipofectamine 2000 transfection agent as positive controls. These cationic polyamides and their polyplexes were of low cytotoxicity when an optimal transfection efficacy was achieved. In vivo transfection tests showed that bioreducible BAP-based polyamides were applicable for intravenous gene delivery in a mouse model, leading to higher level of transgene expression in the liver as compared to 22 kDa linear polyethylenimine as a positive control. These cationic polyamides provide a useful platform to elucidate the relationship between chemical functionalities and gene transfection activity.

A pH and redox dual responsive 4-arm poly(ethylene glycol)-block-poly(disulfide histamine) copolymer for non-viral gene transfection in vitro and in vivo

A novel 4-arm poly(ethylene glycol)-b-poly(disulfide histamine) copolymer was synthesized by Michael addition reaction of poly(ethylene glycol) (PEG) vinyl sulfone and amine-capped poly(disulfide histamine) oligomer, being denoted as 4-arm PEG-SSPHIS. This copolymer was able to condense DNA into nanoscale polyplexes (<200 nm in average diameter) with almost neutral surface charge (+(5–10) mV). Besides, these polyplexes were colloidal stable within 4 h in HEPES buffer saline at pH 7.4 (physiological environment), but rapidly dissociated to liberate DNA in the presence of 10 mM glutathione (intracellular reducing environment). The polyplexes also revealed pH-responsive surface charges which markedly increased with reducing pH values from 7.4–6.3 (tumor microenvironment). In vitro transfection experiments showed that polyplexes of 4-arm PEG-SSPHIS were capable of exerting enhanced transfection efficacy in MCF-7 and HepG2 cancer cells under acidic conditions (pH 6.3–7.0). Moreover, intravenous administration of the polyplexes to nude mice bearing HepG2-tumor yielded high transgene expression largely in tumor rather other normal organs. Importantly, this copolymer and its polyplexes had low cytotoxicity against the cells in vitro and caused no death of the mice. The results of this study indicate that 4-arm PEG-SSPHIS has high potential as a dual responsive gene delivery vector for cancer gene therapy.

Bioreducible polymer-delivered siRNA targeting human telomerase reverse transcriptase for human cancer gene therapy

The success of siRNA therapeutics for cancer therapy largely depends on the delivery carrier that can safely and efficiently escort siRNA from the extracellular environment into the targeted human cancer cells. Over the past few years, disulfide-containing (bioreducible) cationic polymers have been designed, prepared and successfully applied as nonviral carriers for powerful gene/siRNA transfer, meanwhile displaying lower cytotoxicity as compared with their counterparts lacking the disulfide linkage, in part due to the intracellular degradation of the disulfide linkage. We have recently developed bioreducible disulfide-based polyethylenimine (SSPEI) for potent in vitro and in vivo delivery of siRNA targeting human telomerase reverse transcriptase (hTERT). It was found that SSPEI-delivered hTERT siRNA induced significant growth inhibition of different human cancer cells in vitro and also tumor growth suppression in vivo. Importantly, the SSPEI, at an appropriate dose, revealed a negligible adverse effect on cellular metabolic activity in vitro and liver and kidney function in vivo.

Biodegradable Polymer-Coated, Gelatin Hydrogel/Bioceramics Ternary Composites for Antitubercular Drug Delivery and Tissue Regeneration

A simple and effective strategy for the treatment of osteoarticular tuberculosis is proposed through combining tissue engineering approach with anti-tuberculosis drug therapy. A series of tricalcium phosphate bioceramics (TPB) composites, coated by degradable polymer outside and loaded with rifampicin (RFP)-containing gelatin hydrogel inside, were thus fabricated and successfully applied to deliver antitubercular drug RFP into osseous lesion and concomitantly to induce tissue regeneration. RFP-loaded gelatin hydrogel/TPB composites could be readily prepared by filling RFP-containing gelatin solution into TPB and thenin situcrosslinking of gelatin with calcium ions. Depending on the concentrations of RFP, the loading efficiency of RFP in the composites varied in the range from approximately 2% to 5%. Moreover, the surface of these binary composites could be further coated by a biodegradable polymer, yielding biodegradable polymer-coated, RFP-containing gelatin hydrogel/TPB ternary composites. It was shown thatin vitrorelease of RFP from the ternary composites could be effectively sustained for a long period of time. Besides, these composites revealed good biocompatibility towards the survival of MC-3T3 cellsin vitroand could be used for tissue regenerationin vivoin a rabbit model. The results indicate that TPB ternary composites have great potential for the treatment of osteoarticular tuberculosis.