Fabrication, characterization and in vitro evaluation of poly(D,L-lactide-co-glycolide) microparticles loaded with polyamidoamine-plasmid DNA dendriplexes for applications in nonviral gene delivery

Cationic nanoparticles enhance T cell tumor infiltration and antitumor immune responses to a melanoma vaccine

In clinical settings, cancer vaccines as monotherapies have displayed limited success compared to other cancer immunotherapeutic treatments. Nanoscale formulations have the ability to increase the efficacy of cancer vaccines by combatting the immunosuppressive nature of the tumor microenvironment. Here, we have synthesized a previously unexplored cationic polymeric nanoparticle formulation using polyamidoamine dendrimers and poly(d,l-lactic-co-glycolic acid) that demonstrate adjuvant properties in vivo. Tumor-challenged mice vaccinated with an adenovirus-based cancer vaccine [encoding tumor-associated antigen (TAA)] and subsequently treated with this nanoparticulate formulation showed significant increases in TAA-specific T cells in the peripheral blood, reduced tumor burden, protection against tumor rechallenge, and a significant increase in median survival. An investigation into cell-based pathways suggests that administration of the nanoformulation at the site of the developing tumor may have created an inflammatory environment that attracted activated TAA-specific CD8+ T cells to the vicinity of the tumor, thus enhancing the efficacy of the vaccine.

Amine-terminated dendritic polymers as promising nanoplatform for diagnostic and therapeutic agents' modification: A review

It is often challenging to design diagnostic and therapeutic agents that fulfill all functional requirements. So, bulk and surface modifications as a common approach for biomedical applications have been suggested. There have been considerable research interests in using nanomaterials to the prementioned methods. Among all nanomaterials, dendritic materials with three-dimensional structures, host-guest properties, and nano-polymeric dimensions have received considerable attention. Amine-terminated dendritic structures including, polyamidoamine (PAMAM), polypropyleneimine (PPI), and polyethyleneimine (PEI), have been enormously utilized in bio-modification. This review briefly described the structure of these three common dendritic polymers and their use to modify diagnostic and therapeutic agents in six major applications, including drug delivery, gene delivery, biosensor, bioimaging, tissue engineering, and antimicrobial activity. The current review covers amine-terminated dendritic polymers toxicity challenging and improvement strategies as well.

Polydopamine functionalized VEGF gene-activated 3D printed scaffolds for bone regeneration

Bone is a highly vascularized organ and the formation of new blood vessels is essential to regenerate large critical bone defects. In this study, polylactic acid (PLA) scaffolds of 20-80% infill were three-dimensionally (3D) printed using a fused deposition modeling based 3D printer. The PLA scaffolds were coated with polydopamine (PDA) and then were surface-functionalized with polyethyleneimine (PEI) and VEGF-encoding plasmid DNA (pVEGF) nanoplexes (PLA-PDA-PEI-pVEGF). The PLA-PDA-PEI-pVEGF scaffolds with 40% infill demonstrated higher encapsulation efficiency and sustained release of pVEGF than scaffolds with 20, 60 and 80% infill and were therefore used for in vitro and in vivo studies. The PLA-PDA-PEI-pVEGF increased the translation and secretion of VEGF and BMP-2. The PLA-PDA-PEI-pVEGF also yielded a 2- and 4.5-fold change in VEGF and osteocalcin gene expression in vitro, respectively. A tube formation assay using human umbilical vascular endothelial cells (HUVECs) showed a significant increase in tube length when exposed to the PLA-PDA-PEI-pVEGF scaffold, in comparison to PLA and PLA-PDA scaffolds. The PLA-PDA-PEI-pVEGF scaffold in an in vivo rat calvarial critical bone defect model demonstrated 1.6-fold higher new bone formation compared to the PLA-PDA scaffold. H&E and Masson's trichrome staining of bone sections also revealed that the PLA-PDA-PEI-pVEGF scaffold facilitated the formation of more blood vessels in the newly formed bone compared to the PLA and PLA-PDA scaffold groups. Thus, PLA-PDA-PEI-pVEGF might be a potential 3D printed gene activated scaffold for bone regeneration in clinical situations.

Encapsulating Polyethyleneimine-DNA Nanoplexes into PEGylated Biodegradable Microparticles Increases Transgene Expression In Vitro and Reduces Inflammatory Responses In Vivo

Encapsulating genetic material into biocompatible polymeric microparticles is a means to improving gene transfection while simultaneously decreasing the tendency for inflammatory responses; and can be advantageous in terms of delivering material directly to the lungs via aerosolization for applications such as vaccinations. In this study, we investigated the advantages of using polymeric microparticles carrying the luciferase reporter gene in increasing transfection efficiency in the readily transfectable HEK293 cell line and the difficult to transfect RAW264.7 cell line. The results indicated that there was a limit to the ratio of nitrogen in polyethylenimine (PEI) to phosphate in DNA (N/P ratio) beyond which further increases in transgene expression no longer, or only marginally, occurred. Microparticles encapsulating PEI:DNA nanoplexes induced cellular toxicity in a dose-dependent manner. PEGylation increased transgene expression, likely related to enhanced degradation of particles. Furthermore, intra-tracheal instillation in rats allowed us to investigate the inflammatory response in the lung as a function of PEGylation, porosity, and size. Porosity did not influence cell counts in bronchoalveolar lavage fluid in the absence of PEG, but in particles containing PEG, non-porous particles recruited fewer inflammatory cells than their porous counterparts. Finally, both 1 μm and 10 μm porous PLA-PEG particles recruited more neutrophils than 4 μm particles. Thus, we have shown that PEGylation and lack of porosity are advantageous for faster release of genetic cargo from microparticles and a reduced inflammatory response, respectively.

An injectable microparticle formulation for the sustained release of the specific MEK inhibitor PD98059: in vitro evaluation and pharmacokinetics

PD98059 is a reversible MEK inhibitor that we are investigating as a potential treatment for neurochemical changes in the brain that drive neurohumoral excitation in heart failure. In a rat model that closely resembles human heart failure, we found that central administration of PD98059 inhibits phosphorylation of ERK1/2 in the paraventricular nucleus of the hypothalamus, ultimately reducing sympathetic excitation which is a major contributor to clinical deterioration. Studies revealed that the pharmacokinetics and biodistribution of PD98059 match a two-compartment model, with drug found in brain as well as other body tissues, but with a short elimination half-life in plasma (approximately 73 min) that would severely limit its potential clinical usefulness in heart failure. To increase its availability to tissues, we prepared a sustained release PD98059-loaded PLGA microparticle formulation, using an emulsion solvent evaporation technique. The average particle size, yield percent, and encapsulation percent were found to be 16.73 μm, 76.6%, and 43%, respectively. In vitro drug release occurred over 4 weeks, with no noticeable burst release. Following subcutaneous injection of the microparticles in rats, steady plasma levels of PD98059 were detected by HPLC for up to 2 weeks. Furthermore, plasma and brain levels of PD98059 in rats with heart failure were detectable by LC/MS, despite expected erratic absorption. These findings suggest that PD98059-loaded microparticles hold promise as a novel therapeutic intervention countering sympathetic excitation in heart failure, and perhaps in other disease processes, including cancers, in which activated MAPK signaling is a significant contributing factor. Graphical abstract.

Tunable Properties of Poly-DL-Lactide-Monomethoxypolyethylene Glycol Porous Microparticles for Sustained Release of Polyethylenimine-DNA Polyplexes

Direct pulmonary delivery is a promising step in developing effective gene therapies for respiratory disease. Gene therapies can be used to treat the root cause of diseases, rather than just the symptoms. However, developing effective therapies that do not cause toxicity and that successfully reach the target site at therapeutic levels is challenging. We have developed a polymer-DNA complex utilizing polyethylene imine (PEI) and DNA, which was then encapsulated into poly(lactic acid)-co-monomethoxy poly(ethylene glycol) (PLA-mPEG) microparticles via double emulsion, solvent evaporation. Then, the resultant particle size, porosity, and encapsulation efficiency were measured as a function of altering preparation parameters. Microsphere formation was confirmed from scanning electron micrographs and the aerodynamic particle diameter was measured using an aerodynamic particle sizer. Several formulations produced particles with aerodynamic diameters in the 0-5 μm range despite having larger particle diameters which is indicative of porous particles. Furthermore, these aerodynamic diameters correspond to high deposition within the airways when inhaled and the measured DNA content indicated high encapsulation efficiency. Thus, this formulation provides promise for developing inhalable gene therapies.

Nanoparticle-Based Delivery of CRISPR/Cas9 Genome-Editing Therapeutics

The recent progress in harnessing the efficient and precise method of DNA editing provided by CRISPR/Cas9 is one of the most promising major advances in the field of gene therapy. However, the development of safe and optimally efficient delivery systems for CRISPR/Cas9 elements capable of achieving specific targeting of gene therapy to the location of interest without off-target effects is a primary challenge for clinical therapeutics. Nanoparticles (NPs) provide a promising means to meet such challenges. In this review, we present the most recent advances in developing innovative NP-based delivery systems that efficiently deliver CRISPR/Cas9 constructs and maximize their effectiveness.

Biomimetic Mineralization of Biomaterials Using Simulated Body Fluids for Bone Tissue Engineering and Regenerative Medicine<sup/>

Development of synthetic biomaterials imbued with inorganic and organic characteristics of natural bone that are capable of promoting effective bone tissue regeneration is an ongoing goal of regenerative medicine. Calcium phosphate (CaP) has been predominantly utilized to mimic the inorganic components of bone, such as calcium hydroxyapatite, due to its intrinsic bioactivity and osteoconductivity. CaP-based materials can be further engineered to promote osteoinductivity through the incorporation of osteogenic biomolecules. In this study, we briefly describe the microstructure and the process of natural bone mineralization and introduce various methods for coating CaP onto biomaterial surfaces. In particular, we summarize the advantages and current progress of biomimetic surface-mineralizing processes using simulated body fluids for coating bone-like carbonated apatite onto various material surfaces such as metals, ceramics, and polymers. The osteoinductive effects of integrating biomolecules such as proteins, growth factors, and genes into the mineral coatings are also discussed.

The effect of polyanhydride chemistry in particle-based cancer vaccines on the magnitude of the anti-tumor immune response

The goal of this research was to study the effect of polyanhydride chemistry on the immune response induced by a prophylactic cancer vaccine based on biodegradable polyanhydride particles. To achieve this goal, different compositions of polyanhydride copolymers based on 1,8-bis-(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG), 1,6-bis-(p-carboxyphenoxy)-hexane (CPH), and sebacic anhydride (SA) were synthesized by melt polycondensation, and polyanhydride copolymer particles encapsulating a model antigen, ovalbumin (OVA), were then synthesized using a double emulsion solvent evaporation technique. The ability of three different compositions of polyanhydride copolymers (50:50 CPTEG:CPH, 20:80 CPTEG:CPH, and 20:80 CPH:SA) encapsulating OVA to elicit immune responses was investigated. In addition, the impact of unmethylated oligodeoxynucleotides containing deoxycytidyl-deoxyguanosine dinucleotides (CpG ODN), an immunological adjuvant, on the immune response was also studied. The immune response to cancer vaccines was measured after treatment of C57BL/6J mice with two subcutaneous injections, seven days apart, of 50μg OVA encapsulated in particles composed of different polyanhydride copolymers with or without 25μg CpG ODN. In vivo studies showed that 20:80 CPTEG:CPH particles encapsulating OVA significantly stimulated the highest level of CD8⁺ T lymphocytes, generated the highest serum titers of OVA-specific IgG antibodies, and provided longer protection against tumor challenge with an OVA-expressing thymoma cell line in comparison to formulations made from other polyanhydride copolymers. The results also revealed that vaccination with CpG ODN along with polyanhydride particles encapsulating OVA did not enhance the immunogenicity of OVA. These results accentuate the crucial role of the copolymer composition of polyanhydrides in stimulating the immune response and provide important insights on rationally designing efficacious cancer vaccines.

STATEMENT OF SIGNIFICANCE

Compared to soluble cancer vaccine formulations, tumor antigens encapsulated in biodegradable polymeric particles have been shown to sustain antigen release and provide long-term protection against tumor challenge by improving the immune response towards the antigen. Treatment of mice with cancer vaccines based on different polyanhydride copolymers encapsulating OVA resulted in stimulation of tumor-specific immune responses with different magnitudes. This clearly indicates that polyanhydride chemistry plays a substantial role in stimulating the immune response. Vaccination with 20:80 CPTEG:CPH/OVA, the most hydrophobic formulation, stimulated the strongest cellular and humoral immune responses and provided the longest survival outcome without adding any other adjuvant. The most important finding in this study is that the copolymer composition of polyanhydride particle-based vaccines can have a direct effect on the magnitude of the antitumor immune response and should be selected carefully in order to achieve optimal cancer vaccine efficacy.

Aeromonas hydrophila OmpW PLGA Nanoparticle Oral Vaccine Shows a Dose-Dependent Protective Immunity in Rohu (Labeo rohita)

Aeromonas hydrophila is a Gram-negative bacterium that causes high mortality in different fish species and at different growth stages. Although vaccination has significantly contributed to the decline of disease outbreaks in aquaculture, the use of oral vaccines has lagged behind the injectable vaccines due to lack of proven efficacy, that being from primary immunization or by use of boost protocols. In this study, the outer membrane protein W (OmpW) of A. hydrophila was cloned, purified, and encapsulated in poly d,l-lactide-co-glycolic acid (PLGA) nanoparticles (NPs) for oral vaccination of rohu (Labeo rohita Hamilton). The physical properties of PLGA NPs encapsulating the recombinant OmpW (rOmpW) was characterized as having a diameter of 370–375 nm, encapsulation efficiency of 53% and −19.3 mV zeta potential. In vitro release of rOmpW was estimated at 34% within 48 h of incubation in phosphate-buffered saline. To evaluate the efficacy of the NP-rOmpW oral vaccine, two antigen doses were orally administered in rohu with a high antigen (HiAg) dose that had twice the amount of antigens compared to the low antigen (LoAg) dose. Antibody levels obtained after vaccination showed an antigen dose dependency in which fish from the HiAg group had higher antibody levels than those from the LoAg group. The antibody levels corresponded with post challenge survival proportions (PCSPs) and relative percent survival (RPS) in which the HiAg group had a higher PCSP and RPS than the LoAg group. Likewise, the ability to inhibit A. hydrophila growth on trypticase soy agar (TSA) by sera obtained from the HiAg group was higher than that from the LoAg group. Overall, data presented here shows that OmpW orally administered using PLGA NPs is protective against A. hydrophila infection with the level of protective immunity induced by oral vaccination being antigen dose-dependent. Future studies should seek to optimize the antigen dose and duration of oral immunization in rohu in order to induce the highest protection in vaccinated fish.

Synthesis of Polyamidoamine Dendrimer for Encapsulating Tetramethylscutellarein for Potential Bioactivity Enhancement

The biomedical potential of flavonoids is normally restricted by their low water solubility. However, little has been reported on their encapsulation into polyamidoamine (PAMAM) dendrimers to improve their biomedical applications. Generation four (G4) PAMAM dendrimer containing ethylenediaminetetraacetic acid core with acrylic acid and ethylenediamine as repeating units was synthesized by divergent approach and used to encapsulate a flavonoid tetramethylscutellarein (TMScu, 1) to study its solubility and in vitro release for potential bioactivity enhancement. The as-synthesized dendrimer and the dendrimer-TMScu complex were characterized by spectroscopic and spectrometric techniques. The encapsulation of 1 into dendrimer was achieved by a co-precipitation method with the encapsulation efficiency of 77.8% ± 0.69% and a loading capacity of 6.2% ± 0.06%. A phase solubility diagram indicated an increased water solubility of 1 as a function of dendrimer concentration at pH 4.0 and 7.2. In vitro release of 1 from its dendrimer complex indicated high percentage release at pH 4.0. The stability study of the TMScu-dendrimer at 0, 27 and 40 °C showed the formulations to be stable when stored in cool and dark conditions compared to those stored in light and warmer temperatures. Overall, PAMAM dendrimer-G4 is capable of encapsulating 1, increasing its solubility and thus could enhance its bioactivity.

Diaminosulfide based polymer microparticles as cancer vaccine delivery systems

The aim of the research presented here was to determine the characteristics and immunostimulatory capacity, in vivo, of antigen and adjuvant co-loaded into microparticles made from a novel diaminosulfide polymer, poly(4,4'-trimethylenedipiperdyl sulfide) (PNSN), and to assess their potential as cancer vaccine vectors. PNSN microparticles co-loaded with the antigen, ovalbumin (OVA), and adjuvant, CpG 1826, (PNSN(OVA + CpG)) were fabricated and characterized for size (1.64 μm diameter; PDI=0.62), charge (-23.1 ± 0.3), and loading efficiencies of antigen (7.32 μg/mg particles) and adjuvant (0.95 μg/mg particles). The ability of PNSN(OVA + CpG) to stimulate cellular and humoral immune responses in vivo was compared with other PNSN microparticle formulations as well as with poly(lactic-co-glycolic acid)(PLGA)-based microparticles, co-loaded with OVA and CpG (PLGA(OVA + CpG)), an adenovirus encoding OVA (Ad5-OVA), and OVA delivered with incomplete Freund's adjuvant (IFA(OVA)). In vivo OVA-specific IgG1 responses, after subcutaneous prime/boosts in mice, were similar when PNSN(OVA + CpG) and PLGA(OVA + CpG) were compared and the presence of CpG 1826 within the PNSN microparticles demonstrated significantly improved responses when compared to PNSN microparticles loaded with OVA alone (PNSN(OVA)), plus or minus soluble CpG 1826. Cellular immune responses to all particle-based vaccine formulations ranged from being negligible to modest with PNSN(OVA + CpG) generating the greatest responses, displaying significantly increased levels of OVA-specific CD8+ T lymphocytes compared to controls and IFA(OVA) treated mice. Finally, it was shown that of all vaccination formulations tested PNSN(OVA + CpG) was the most protective against subsequent challenge with an OVA-expressing tumor cell line, E.G7. Thus, microparticles made from poly(diaminosulfide)-based macromolecules possess promising potential as vaccine vectors and, as demonstrated here, may have impact as cancer vaccines in particular.

Synthesis, characterization, and immune efficacy of layered double hydroxide@SiO2 nanoparticles with shell-core structure as a delivery carrier for Newcastle disease virus DNA vaccine

Layered double hydroxide (LDH)@SiO2 nanoparticles were developed as a delivery carrier for the plasmid DNA expressing the Newcastle disease virus F gene. The LDH was hydrotalcite-like materials. The plasmid DNA encapsulated in the LDH@SiO2 nanoparticles (pFDNA-LDH@SiO2-NPs) was prepared by the coprecipitation method, and the properties of pFDNA-LDH@SiO2-NPs were characterized by transmission electron microscopy, zeta potential analyzer, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The results demonstrated that the pFDNA-LDH@SiO2-NPs had a regular morphology and high stability with a mean diameter of 371.93 nm, loading capacity of 39.66%±0.45%, and a zeta potential of +31.63 mV. A release assay in vitro showed that up to 91.36% of the total plasmid DNA could be sustainably released from the pFDNA-LDH@SiO2-NPs within 288 hours. The LDH@SiO2 nanoparticles had very low toxicity. Additionally, their high transfection efficiency in vitro was detected by fluorescent microscopy. Intranasal immunization of specific pathogen-free chickens with pFDNA-LDH@SiO2-NPs induced stronger cellular, humoral, and mucosal immune responses and achieved a greater sustained release effect than intramuscular naked plasmid DNA, and the protective efficacy after challenge with the strain F48E9 with highly virulent (mean death time of chicken embryos ≤60 hours, intracerebral pathogenicity index in 1 -day-old chickens >1.6) was 100%. Based on the results, LDH@SiO2 nanoparticles can be used as a delivery carrier for mucosal immunity of Newcastle disease DNA vaccine, and have great application potential in the future.

Dendrimer-PLGA based multifunctional immuno-nanocomposite mediated synchronous and tumor selective delivery of siRNA and cisplatin: potential in treatment of hepatocellular carcinoma

The in-house synthesized PLK-1 siRNA and cisplatin loaded innovative dendrimer-PLGA immuno-nanocomposite bears the capacity of delivering both the cargos simultaneously to the same liver cancer cell in a targeted manner.

Current Uses of Poly(lactic-co-glycolic acid) in the Dental Field: A Comprehensive Review

Poly(lactic-co-glycolic acid) or PLGA is a biodegradable polymer used in a wide range of medical applications. Specifically PLGA materials are also developed for the dental field in the form of scaffolds, films, membranes, microparticles, or nanoparticles. PLGA membranes have been studied with promising results, either alone or combined with other materials in bone healing procedures. PLGA scaffolds have been used to regenerate damaged tissues together with stem cell-based therapy. There is solid evidence that the development of PLGA microparticles and nanoparticles may be beneficial to a wide range of dental fields such as endodontic therapy, dental caries, dental surgery, dental implants, or periodontology. The aim of the current paper was to review the recent advances in PLGA materials and their potential uses in the dental field.

Polymer-peptide delivery platforms: effect of oligopeptide orientation on polymer-based DNA delivery

The success of nonviral transfection using polymers hinges on efficient nuclear uptake of nucleic acid cargo and overcoming intra- and extracellular barriers. By incorporating PKKKRKV heptapeptide pendent groups as nuclear localization signals (NLS) on a polymer backbone, we demonstrate protein expression levels higher than those obtained from JetPEI and Lipofectamine 2000, the latter being notorious for coupling high transfection efficiency with cytotoxicity. The orientation of the NLS peptide grafts markedly affected transfection performance. Polymers with the sequence attached to the backbone from the valine residue achieved a level of nuclear translocation higher than the levels of those having the NLS groups attached in the opposite orientation. The differences in nuclear localization and DNA complexation strength between the two orientations correlated with a striking difference in protein expression, both in cell culture and in vivo. Polyplexes formed from these comb polymer structures exhibited transfection efficiencies superior to those of Lipofectamine 2000 but with greatly reduced toxicity. Moreover, these novel polymers, when administered by intramuscular ultrasound-mediated delivery, allowed a high level of reporter gene expression in mice, demonstrating their therapeutic promise in vivo.

Preparation and efficacy of Newcastle disease virus DNA vaccine encapsulated in PLGA nanoparticles

Background

Although the Newcastle disease virus (NDV) inactivated vaccines and attenuated live vaccines have been used to prevent and control Newcastle disease (ND) for years, there are some disadvantages. Recently, newly developed DNA vaccines have the potential to overcome these disadvantages. The low delivery efficiency, however, hindered the application of DNA vaccines for ND in practice.

Methodology/Principal Findings

The eukaryotic expression plasmid pVAX1-F (o) DNA that expressed the F gene of NDV encapsulated in PLGA nanoparticles (pFNDV-PLGA-NPs) were prepared by a double emulsion-solvent evaporation method and optimal preparation conditions of the pFNDV-PLGA-NPs were determined. Under the optimal conditions, the pFNDV-PLGA-NPs were produced in good morphology and had high stability with a mean diameter of 433.5±7.5 nm, with encapsulation efficiency of 91.8±0.3% and a Zeta potential of +2.7 mV. Release assay in vitro showed that the fusion gene plasmid DNA could be sustainably released from the pFNDV-PLGA-NPs up to 93.14% of the total amount. Cell transfection test indicated that the vaccine expressed and maintained its bioactivity. Immunization results showed that better immune responses of SPF chickens immunized with the pFNDV-PLGA-NPs were induced compared to the chickens immunized with the DNA vaccine alone. In addition, the safety of mucosal immunity delivery system of the pFNDV-PLGA-NPs was also tested in an in vitro cytotoxicity assay.

Conclusions/Significance

The pFNDV-PLGA-NPs could induce stronger cellular, humoral, and mucosal immune responses and reached the sustained release effect. These results laid a foundation for further development of vaccines and drugs in PLGA nanoparticles.

Biodegradable particles as vaccine antigen delivery systems for stimulating cellular immune responses

There is a need for both new and improved vaccination formulations for a range of diseases for which current vaccines are either inadequate or non-existent. Biodegradable polymer-based vaccines fulfill many of the desired properties in achieving effective long-term protection in a manner that is safe, economical, and potentially more practicable on a global scale. Here we discuss some of the work performed with micro/nanoparticles made from either synthetic (poly[lactic-co-glycolic acid] [PLGA] and polyanhydrides) or natural (chitosan) biodegradable polymers. Our attention is focused on, but not limited to, the generation of antitumor immunity where we stress the importance of particle size and co-delivery of antigen and adjuvant.

Transplantation of novel vascular endothelial growth factor gene delivery system manipulated skeletal myoblasts promote myocardial repair

BACKGROUND

Skeletal myoblast (SkM) transplantation combined with vascular endothelial growth factor (VEGF) gene delivery has been proposed as a promising therapy for cardiac repair. Nevertheless, the defective gene vectors and unregulable VEGF expression in vivo hinder its application. Therefore, the search for an economical, effective, controllable gene delivery system is quite necessary.

METHODS

In our study, hyperbranched polyamidoamine (h-PAMAM) dendrimer was synthesized as a novel gene delivery vector using a modified method. And hypoxia-regulated human VEGF-165 plasmids (pHRE-hVEGF165) were constructed for controllable VEGF gene expression. The efficiency and feasibility of h-PAMAM-HRE-hVEGF165 gene delivery system manipulated SkM transplantation for cardiac repair were investigated in myocardial infarction models.

RESULTS

The h-PAMAM encapsulated pHRE-hVEGF165 could resist nuclease digestion for over 120 min. In primary SkMs, h-PAMAM-pHRE-hVEGF165 gene delivery system showed high transfection efficiency (43.47 ± 2.22%) and minor cytotoxicity (cell viability = 91.38 ± 0.48%). And the transfected SkMs could express hVEGF165 for 18 days under hypoxia in vitro. For myocardial infarction models, intramyocardial transplantation of the transfected SkMs could result in reduction of apoptotic myocardiocytes, improvement of grafted cell survival, decrease of infarct size and interstitial fibrosis, and increase of blood vessel density, which inhibited left ventricle remodeling and improved heart function at the late phase following infarction.

CONCLUSIONS

These results indicate that h-PAMAM based pHRE-hVEGF165 gene delivery into SkMs is feasible and effective, and may serve as a novel and promising gene therapy strategy in ischemic heart disease.

Characterizing the antitumor response in mice treated with antigen-loaded polyanhydride microparticles

Delivery of vaccine antigens with an appropriate adjuvant can trigger potential immune responses against cancer leading to reduced tumor growth and improved survival. In this study, various formulations of a bioerodible amphiphilic polyanhydride copolymer based on 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) and 1,6-bis(p-carboxyphenoxy) hexane (CPH) with inherent adjuvant properties were evaluated for antigen-loading properties, immunogenicity and antitumor activity. Mice were vaccinated with 50:50 CPTEG:CPH microparticles encapsulating a model tumor antigen, ovalbumin (OVA), in combination with the Toll-like receptor-9 agonist, CpG oligonucleotide 1826 (CpG ODN). Mice treated with OVA-encapsulated CPTEG:CPH particles elicited the highest CD8(+) T cell responses on days 14 and 20 when compared to other treatment groups. This treatment group also displayed the most delayed tumor progression and the most extended survival times. Particles encapsulating OVA and CpG ODN generated the highest anti-OVA IgG(1) antibody responses in mice but these mice did not show significant tumor protection. These results suggest that antigen-loaded CPTEG:CPH microparticles can stimulate antigen-specific cellular responses and could therefore potentially be used to promote antitumor responses in cancer patients.

Polymeric nucleic acid vehicles exploit active interorganelle trafficking mechanisms

Materials that self-assemble with nucleic acids into nanocomplexes (e.g. polyplexes) are widely used in many fundamental biological and biomedical experiments. However, understanding the intracellular transport mechanisms of these vehicles remains a major hurdle in their effective usage. Here, we investigate two polycation models, Glycofect (which slowly degrades via hydrolysis) and linear polyethyleneimine (PEI) (which does not rapidly hydrolyze), to determine the impact of polymeric structure on intracellular trafficking. Cells transfected using Glycofect underwent increasing transgene expression over the course of 40 h and remained benign over the course of 7 days. Transgene expression in cells transfected with PEI peaked at 16 h post-transfection and resulted in less than 10% survival after 7 days. While saccharide-containing Glycofect has a higher buffering capacity than PEI, polyplexes created with Glycofect demonstrate more sustained endosomal release, possibly suggesting an additional or alternative delivery mechanism to the classical "proton sponge mechanism". PEI appeared to promote release of DNA from acidic organelles more than Glycofect. Immunofluorescence images indicate that both Glycofect and linear PEI traffic oligodeoxynucleotides to the Golgi and endoplasmic reticulum, which may be a route towards nuclear delivery. However, Glycofect polyplexes demonstrated higher co-localization with the ER than PEI polyplexes, and co-localization experiments indicate the retrograde transport of polyplexes via COP I vesicles from the Golgi to the ER. We conclude that slow release and unique trafficking behaviors of Glycofect polyplexes may be due to the presence of saccharide units and the degradable nature of the polymer, allowing more efficacious and benign delivery.

Diaminopropionic acid lipopeptides: characterization studies of polyplexes aimed at pDNA delivery

Here we report a novel class of peptides-d-diaminopropionic acids (Dap)-for gene delivery. These peptides have attractive properties for gene delivery, and the advantage that they can be easily manipulated in relation to their composition, abiding with tailored-design. We characterized the toxicological and biophysical properties of DNA particles resulting from the interaction of the nucleic acid with a series of Dap(8) peptides conjugated to different alkyl groups. These peptides formed small and homogenous DNA particle populations that protected against DNase I degradation at non-toxic concentrations. However, despite the similarity between these peptides and others that are arginine-rich, and efficient vectors, functional studies suggest the need for additional modifications in the carriers to improve their DNA delivery efficiency. Taken together, these studies underscore the relevance of the overall structure of the carrier and the complexity of designing from scratch a carrier.

Recent advances in polymeric microspheres for parenteral drug delivery--part 2

INTRODUCTION

Currently marketed microsphere products are manufactured with the use of organic solvents which have a negative impact on the environment and stability of biological molecules. With recent advances in fabrication technologies, solvent free methods have demonstrated potential for the preparation of microspheres.

AREAS COVERED

New technical advances recently achieved in solvent based microsphere manufacturing processes have allowed for major improvement in product quality and properties. Novel solvent free fabrication methods combined with newly functionalized biodegradable polymers have been explored for their application in the preparation of microspheres containing biological molecules.

EXPERT OPINION

Novel fabrication methods for microspheres have been recently reported but technical challenges and development risks remain high for scale up from bench to industrial commercialization. While the applications of microspheres for delivery of proteins, genes and vaccines have shown promise for clinical use, the approval of newly functionalized polymers as carriers may still face scrutiny on safety and biocompatibility, which can be key factors in securing the regulatory approval of the product.

Effect of combined locally delivered growth factors and systemic sildenafil citrate on microrecanalization in biodegradable conduit for vas deferens reconstruction

OBJECTIVE

To investigate the effect of the combination of locally delivered growth factors and oral sildenafil citrate on cross-conduit microrecanalization.

METHODS

A total of 42 rats were divided into 7 groups. Of the 42 rats, 6 underwent bilateral vasectomy and bilateral end-to-end vasovasostomy and 12 underwent bilateral vasectomy. Of the latter 12, 6 received sildenafil citrate orally (10 mg/kg/d) for 24 weeks and 6 received placebo. A total of 24 rats underwent bilateral vasectomy and bilateral reconstruction with implantation of a 5-mm biodegradable conduit that bridged the 2 vasal ends. Of the 24 rats with conduits, 12 also had 250 pg of transforming growth factor-β and 12.5 pg of platelet-derived growth factor-β sustained release nanoparticles placed in immediate proximity to the conduit. The remaining 12 rats with conduits (6 without growth factors and 6 with growth factors) also received sildenafil citrate orally (10 mg/kg/d) for 24 weeks; the others received placebo. The reconstructed segments were harvested for histologic examination at 24 weeks.

RESULTS

Five of 6 primary vasovasostomy and no vasectomy-only rats sired litters. Significantly more microcanals per conduit were observed in rats receiving sildenafil citrate: without growth factors, 3.9 vs. 0 canals/conduit (P < 0.001); with growth factors, 5.5 vs. 0.25 canals/conduit (P < 0.001). The rats receiving sildenafil citrate with growth factors showed a trend toward more microcanals per conduit than the rats receiving sildenafil citrate without growth factors (5.5 vs 3.9; P = .10). Rats receiving growth factors but no sildenafil citrate did not produce more canals than the rats receiving neither growth factor nor sildenafil citrate (0.25 vs 0; P = NS).

CONCLUSION

Orally administered sildenafil citrate enhances formation of microcanalization after postvasectomy reconstruction using a biodegradable conduit in a rat model. Locally delivered growth factors appear to increase the number of microcanals.

Novel hyperbranched polyamidoamine nanoparticles for transfecting skeletal myoblasts with vascular endothelial growth factor gene for cardiac repair

We investigated the feasibility and efficacy of hyperbranched polyamidoamine (hPAMAM) mediated human vascular endothelial growth factor-165 (hVEGF(165)) gene transfer into skeletal myoblasts for cardiac repair. The hPAMAM was synthesized using a modified one-pot method. Encapsulated DNA was protected by hPAMAM from degradation for over 120 min. The transfection efficiency of hPAMAM in myoblasts was 82.6 ± 7.0% with cell viability of 94.6 ± 1.4% under optimal conditions. The hPAMAM showed much higher transfection efficiency (P < 0.05) than polyetherimide and Lipofectamine 2000 with low cytotoxicity. The transfected skeletal myoblasts gave stable hVEGF(165) expression for 18 days. After transplantation of hPAMAM-hVEGF(165) transfected cells, apoptotic myocardial cells decreased at day 1 and heart function improved at day 28, with increased neovascularization (P < 0.05). These results indicate that hPAMAM-based gene delivery into myoblasts is feasible and effective and may serve as a novel and promising non-viral DNA vehicle for gene therapy in myocardial infarction.

Efficacy of polymeric encapsulated C5a peptidase-based group B streptococcus vaccines in a murine model

OBJECTIVE

The purpose was to examine in mice the efficacy of various polymeric-encapsulated C5a peptidase vaccine formulations in eliciting a long-term immune response and preventing group B streptococcus (GBS) infection.

STUDY DESIGN

C5a peptidase was encapsulated in semipermeable microspheres of poly(lactide-coglycolide) (PLGA). Female ICR mice were immunized with 0, 10, or 30 μg of encapsulated C5a peptidase within 2 different formulations of PLGA polymers. Booster doses were given at weeks 4 and 8. Antibody responses were measured by enzyme-linked immunosorbent assay at weeks 4, 8, 11, and 40. Vaginal challenges with GBS types 1a, III, and V were performed at week 12.

RESULTS

Thirty microgram doses of the 75:25 and 50:50 PLGA formulations generate the highest and most sustained C5a peptidase-specific immune responses. Mice that received encapsulated C5a peptidase were significantly protected from vaginal colonization compared with mice that received empty microspheres.

CONCLUSION

Encapsulated C5a peptidase elicited significant immune responses and protection against a GBS challenge. C5a peptidase microsphere encapsulation has potential as a GBS vaccine.

Rational design, fabrication, characterization and in vitro testing of biodegradable microparticles that generate targeted and sustained transgene expression in HepG2 liver cells

Poly(lactide-co-glycolide) (PLGA) microparticles have significant potential for sustained delivery of plasmid DNA (pDNA). However, unmodified PLGA microparticles have poor transfection efficiencies. In this study, we use several approaches to enhance the transfection efficiencies of PLGA microparticles in a HepG2 liver cell line. Polyethylenimine (PEI) is used to condense the pDNA prior to loading into the PLGA microparticles. This provides enhanced loading efficiencies and greater protection to the pDNA during the entrapment process. In addition, the pDNA used (ApoE) incorporates a hybrid liver-specific murine albumin enhancer/α1 antitrypsin promoter (AlbE/hAAT) to enhance transgene expression in human liver (HepG2) cells. The percentage of surfactant used in the preparation of the microparticles, the polymer composition of the PLGA, the ratio of the PEI to pDNA (N/P), the structure of the PEI and the potential utility of a galactose targeting ligand were then investigated to further optimize the efficacy of the cationic microparticle non-viral delivery system in transfecting HepG2 cells. For each PLGA PEI-pDNA microparticle formulation prepared, we evaluated particle size, ζ-potential, loading of pDNA, cytotoxicity, and transgene expression in HepG2 cells and control human embryonic kidney (HEK293) and monkey African green kidney fibroblast-like (COS7) cells. Loading PLGA particles with PEI-ApoE pDNA complexes resulted in a significant reduction in particle size when compared to PLGA microparticles loaded with ApoE pDNA alone. Scanning electron microscopy images showed that all the particle formulations were smooth and spherical in appearance. Incorporation of the cationic PEI in the PLGA particles changed the ζ-potential from negative to positive. Complexing PEI with ApoE pDNA increased the loading efficiency of the ApoE pDNA into the PLGA microparticles. The cytotoxicity of PLGA particles loaded with PEI-ApoE pDNA complexes was similar to PLGA particles loaded with ApoE pDNA alone. The transfection efficiency of all particle formulations prepared with ApoE pDNA was significantly higher in HepG2 cells when compared to HEK293 and COS7 cell lines. The release of PEI-pDNA complexes from particles prepared with different PLGA polymer compositions including PLGA 50-50, PLGA 75-25, and PLGA 85-15 was sustained in all cases but the release profile was dependent on the polymer composition. Transmission electron microscopy images showed that PEI-pDNA complexes remained structurally intact after release. The optimum formulation for PLGA particles loaded with PEI-ApoE pDNA complexes was prepared using 2% polyvinyl alcohol, 50-50 PLGA compositions and N/P ratios of 5-10. Strong sustained transgene expression in HepG2 cells was generated by PLGA PEI-ApoE pDNA particles up to the full 13 days tested.

Intracellular release of 17-β estradiol from cationic polyamidoamine dendrimer surface-modified poly (lactic-co-glycolic acid) microparticles improves osteogenic differentiation of human mesenchymal stromal cells

Human bone marrow mesenchymal stromal cells (MSCs) are considered a potential cell source for MSC-based bone regeneration, but improvements in the proliferation and differentiation capacity of MSCs are necessary for practical applications. Estrogen effectively improves MSC capabilities and has strong potential as a regulator of MSCs. The aim of this study was to develop a delivery system that provides intracellular release of estrogen and test its ability to improve osteogenic differentiation of MSCs. Biodegradable poly (lactic-co-glycolic acid) (PLGA) microparticles were developed that entrap 17-β estradiol (E2) and provide intracellular release of E2. The results show that we can prepare PLGA particles with efficient loading of E2 and maintain release of E2 up to 7 days. Surface modifying E2-loaded PLGA particles with cationic polyamidoamine dendrimers enabled increased uptake by human MSCs. Human MSC uptake of the E2-loaded PLGA particles significantly upregulates osteogenic differentiation markers of alkaline phosphatase and osteocalcin. In conclusion, cationic-modified PLGA particles can serve as a tool for intracellular delivery of estrogen to effectively execute estrogen regulation of MSCs. This approach has the potential to improve the osteogenic capabilities of MSCs and to develop appropriate environments of implantation for MSC-based bone tissue engineering.

Nanoparticle delivery systems in cancer vaccines

Therapeutic strategies that involve the manipulation of the host's immune system are gaining momentum in cancer research. Antigen-loaded nanocarriers are capable of being actively taken up by antigen-presenting cells (APCs) and have shown promising potential in cancer immunotherapy by initiating a strong immunostimulatory cascade that results in potent antigen-specific immune responses against the cancer. Such carrier systems offer versatility in that they can simultaneously co-deliver adjuvants with the antigens to enhance APC activation and maturation. Furthermore, modifying the surface properties of these nanocarriers affords active targeting properties to APCs and/or enhanced accumulation in solid tumors. Here, we review some recent advances in these colloidal and particulate nanoscale systems designed for cancer immunotherapy and the potential for these systems to translate into clinical cancer vaccines.