Gene Transfection Efficacy Research Articles

Inhibitory effects of interferon-gamma plasmid DNA on DMBA-TPA induced mouse skin carcinogenesis

Interferon-gamma (IFN-γ) exhibits biological activities that are considered to have important roles in tumor suppression. Therefore, the IFN-γ gene is a potential candidate for in vivo cytokine gene therapy against skin cancer. The present study evaluated the efficacy of a hydrodynamics-based IFN-γ gene transfection for skin cancer treatment, in which the plasmid DNA encoding IFN-γ was administered into the tail vein of mice following 7,12-dimethylbenz[a]anthracene and 12-O-tetradecanoylphorbol-13-acetate-induced skin carcinogenesis. Serum levels of IFN-γ were substantially elevated without liver toxicity. The mice injected with IFN-γ plasmid DNA displayed a marked reduction in papilloma numbers, suppressed proliferation of epidermal cells and induction of caspase-3-mediated apoptosis. These results suggest that the hydrodynamics-based transfection of IFN-γ plasmid DNA is a convenient and efficient means of skin cancer gene therapy.

The intracellular plasmid DNA localization of cationic reducible cholesterol-disulfide lipids

Stimuli-responsive biomaterials derived from natural products toward efficient drug/gene delivery have been attracting increasing attention in the past decade. In this work, we first designed and prepared a new series of cholesterol-disulfide lipids, namely CHOSS-N, CHOSS-N+, CHOSS-Lys and CHOSS-4N bearing cholesterol and a variety of headgroups via disulfide and carbonate bond linkages, and their molecular structures were characterized by NMR and ESI-MS. Furthermore, plasmid DNA binding affinity for these new CHOSS lipids was separately examined by ethidium bromide displacement and agarose-gel retardant assay. Average diameter sizes and surface potentials of the CHOSS/pDNA lipoplex particles prepared under various N/P charge ratios were analyzed by dynamic laser light scattering (DLS). Under 10 m m dithiothreitol (DTT), stability and disassembly of the CHOSS/pDNA lipoplex nanoparticles were investigated by agarose-gel retardant assay and atomic force microscopy (AFM). Employing a COS-7 cell line, cell viability was examined for the prepared CHOSS lipids and their pDNA lipoplexes with branched PEI-25k as the reference. Finally, COS-7 cell gene transfection efficacies with these CHOSS lipids as potential delivery vectors were investigated by luciferase and EGFP transfection assay in the absence and presence of serum, and intracellular uptake capability, trafficking and cellular localization of Cy3-labeled pEGFP-N1 DNA were studied with a flow cytometer and fluorescent microscopy with Lipofectamine™ 2000 as the control. The results demonstrated low cytotoxicity, strong pDNA binding affinity and high transgenetic efficacy for new prepared CHOSS lipids, and particularly high intracellular uptake capability and specific cellular localization of pDNA at the periphery of cell nuclei were for the first time interestingly observed for the CHOSS lipid delivery carriers. In general, these may pave a new way to utilize cholesterol, amino acids and other functional natural products to prepare efficient gene/drug delivery carriers with simple structure and low cytotoxicity.

Amphiphilic Cationic [Dendritic poly(L‐lysine)]‐block‐poly(L‐lactide)‐block‐[dendritic poly(L‐lysine)]s in Aqueous Solution: Self‐Aggregation and Interaction with DNA as Gene Delivery Carriers

A new series of triblock [dendritic poly(L-lysine)]-block-PLLA-block-[dendritic poly(L-lysine)]s (DL(2) -PLLA-DL(2) ) with PLLA block lengths of 11.5-26.5 and double 2-generation PLL dendrons DL(2) as model cationic amphiphiles were synthesized and characterized. Their CAC, self-aggregation and plasmid DNA binding affinities in pure water and PBS were studied. The PLLA block length dependence of particle size, morphology and ξ potential for organized pDNA/amphiphile polyplex aggregates were examined. Finally, toxicities of these DL(2) -PLLA-DL(2) amphiphiles and their polyplexes were assayed by MTT with HeLa, SMMC-7721 and COS-7 cells, and COS-7 cell luciferase and eGFP gene transfection efficacies with these amphiphiles as the delivery carriers were investigated.

Non-viral eNOS gene delivery and transfection with stents for the treatment of restenosis

BackgroundIn this study, we have examined local non-viral gene delivery, transfection, and therapeutic efficacy of endothelial nitric oxide synthase (eNOS) encoding plasmid DNA administered using coated stents in a rabbit iliac artery restenosis model.MethodsLipopolyplexes (LPPs) with eNOS expressing plasmid DNA were immobilized on stainless steel stents using poly(D,L-lactide-co-glycolide) (PLGA) and type B gelatin coatings. The gene-eluting stents were implanted bilaterally in the denuded iliac arteries and eNOS transfection and therapeutic efficacy were examined 14 days after implantation.ResultsThe results show that non-viral lipopolyplex-coated stents can efficiently tranfect eNOS locally in the arterial lumen assessed by PCR and ELISA. Human eNOS ELISA levels were significantly raised 24 hours after transfection compared to controls (125 pg eNOS compared to <50 pg for all controls including naked DNA). Local eNOS production suppressed smooth muscle cell proliferation and promoted re-endothelialization of the artery showing a significant reduction in restenosis of 1.75 neointima/media ratio for stents with lipoplexes encoding eNOS compared with 2.3 neointima/media ratio for stents with lipoplexes encosing an empty vector.ConclusionsThese results support the hypothesis that a potent non-viral gene vector encoding for eNOS coated onto a stent can inhibit restenosis through inhibition of smooth muscle cell growth and promotion of a healthy endothelium.

The relationship between terminal functionalization and molecular weight of a gene delivery polymer and transfection efficacy in mammary epithelial 2-D cultures and 3-D organotypic cultures

Non-viral gene delivery vectors were developed for efficient gene transfer to hard-to-transfect mouse mammary epithelial cells. Ten modified versions of the same base poly(beta-amino ester), poly(1,4-butanediol diacrylate-co-5-amino-1-pentanol), were tested in both traditional 2-D monolayer and in 3-D organotypic cultures. The polymers self-assembled with plasmid DNA encoding enhanced green fluorescent protein to form nanoparticles (∼100 nm) used to transfect the cells. Nanoparticle transfection efficacy was tuned by changes in synthesis and fabrication conditions and the transfection efficacy was analyzed using confocal microscopy and flow cytometry. The best performing polymeric nanoparticles transfected 57 ± 6% of the cells in 2-D culture and 6 ± 1% of the cells in 3-D culture. Small modifications to the polymer end-capping molecules and tuning of polymer molecular weight could either significantly enhance the transfection efficacy up to 6-fold or instead abolish efficacy completely. The efficacy of leading polymers was higher than that of the commercial transfection agent FuGENE ® HD by a factor of 13 in 2-D and 2 in 3-D. These non-viral nanoparticles may be useful as delivery reagents or targeted therapeutics for breast cancer. This gene delivery strategy is also a promising approach for studying the normal development of the mammary gland.

Synergistic Effect of Low Cytotoxic Linear Polyethylenimine and Multiarm Polyethylene Glycol: Study of Physicochemical Properties and In Vitro Gene Transfection

Novel star-shaped copolymers consisting of multiarm polyethylene glycol and low molecular weight linear polyethylenimines (MAPEG-LPEIs) with a high transfection efficiency and low cytotoxicity were designed and synthesized as nonviral gene delivery carriers. The cationic polymers were prepared by conjugating low molecular weight linear PEI (2.5 kDa) to six-arm PEG-NHS (10 kDa) in two different compositions. Two copolymers, MAPEG-LPEI(3) and MAPEG-LPEI(6) with molecular weights of 17.5 kDa and 25 kDa respectively, were synthesized. The MAPEG-LPEI(3)/pDNA and MAPEG-LPEI(6)/pDNA polyplexes are stably dispersed in aqueous media with a narrowly distributed size range of <200 nm as determined by dynamic light scattering. Furthermore, these polyplexes showed different surface charges depending upon the relative proportion of MAPEG and LPEI. Moreover, these polyplexes can protect pDNA from enzymatic degradation in serum containing media up to 24 h. These polyplexes were able to efficiently transfect luciferase-coded reporter gene into HeLa cancer cells and showed considerable gene transfection efficacy even in 50% serum-conditioned media in vitro. MAPEG-LPEI(6) exhibited higher transfection activity than that of MAPEG-LPEI(3) at the same weight ratios. Furthermore, MAPEG-LPEI/pDNA polyplexes were less toxic than LPEI/pDNA complexes as determined by MTT assay. These favorable results could be attributed to the combined effect of low molecular weight LPEI and multiarm PEG. The special structural features of the multiarm star-shaped central PEG core play an important role in achieving higher transfection efficiency as it imparts higher charge density to polyplexes and prevents the unwanted aggregation of the smaller polyplex particles. These two important factors contributed toward enhanced gene transfection. On the other hand, LPEI provides low cytotoxicity and effective complexation with pDNA in the designed architecture. Therefore it is possible to achieve enhanced gene transfection by using these two components, namely, pivotal multiarm PEG core and LPEI, in optimal ratio as observed in the case of MAPEG-LPEI(6).

Combined delivery of heme oxygenase-1 gene and fibroblast growth factor-2 protein for therapeutic angiogenesis

Ectopic expression of heme oxygenase-1 (HO-1) in ischemic tissue protects the tissue from apoptosis and necrosis and promotes angiogenesis. However, apoptosis and necrosis will decrease HO-1 gene transfection efficacy. We hypothesized that fibroblast growth factor-2 (FGF2) would attenuate ischemic damage during the incipient period, improve HO-1 gene transfection and, in turn, enhance neovascularization. To test this hypothesis, we employed a mouse model of hindlimb ischemia and treated the mice with HO-1 gene therapy alone, FGF2 alone, or HO-1 gene therapy plus FGF2. As controls, a group of mice was left untreated. At 12 h, prior to the expression of exogenously delivered HO-1, apoptosis was significantly reduced in mice treated with FGF2, either alone or in combination with HO-1 gene therapy. At 3 days, HO-1 expression was greater in mice that also received FGF2 than in mice treated with HO-1 gene therapy alone. The expression of angiogenic growth factors and angiogenesis was greater in mice treated with HO-1 gene therapy plus FGF2 than in mice treated with HO-1 gene therapy alone. These data indicate that FGF2 rescued muscle necrosis prior to the exogenous expression of HO-1 and enhanced HO-1 gene transfection in ischemic murine limbs.

Advances in gene delivery through molecular design of cationic lipids

This feature article describes the recent developments in the design of cationic lipids and their applications in gene delivery. Various structure-activity investigations explaining the variations in gene transfection efficacies with respect to different molecular structures of the cationic lipids have been discussed. Gene transfer abilities are presented in relation to aggregation properties of different aqueous formulations such as cationic liposomes and surfactant aggregates from various amphiphiles and cationic lipids, as a function of their hydrophobic parts, linkers and head groups.

Development and Application of Glycosylated Particulate Carriers for Delivery of Nucleic Acid Medicine

Recently several systems including viral and non-viral carriers that can be used to transfer foreign genetic material into cells have been developed with the aim of enhancing gene transfer in vivo. Non-viral vectors are relatively easy to produce in clinically relevant quantities, and associated with fewer safety concerns. Furthermore, synthetic non-viral vectors provide flexibility in formulation design and can be tailored to interact efficiency with DNA cargo and the specific route of vector injection, and can enhance delivery to specific tissues or cells through incorporation of a targeting ligand. Applying cell-specific targeting technology to liposomes would improve in vivo gene transfection efficacy and reduce any unexpected side-effects. Among the various receptors, asialoglycoprotein receptors and mannose receptors are the most promising for gene targeting since they exhibit high affinity and are rapidly internalized. Receptor-mediated delivery systems are able to introduce foreign DNA into specific cell types in vivo. Our group succeeded in the development of glycosylated cationic liposomes for cell-selective targeting of plasmid DNA, siRNA, and NFkappaB decoy based on the optimization of physicochemical properties of glycosylated liposome complex.

Synthesis and Gene Transfection Efficacies of PEI−Cholesterol-Based Lipopolymers

Nine lipopolymers based on low molecular weight polyethyleneimines (PEI) and cholesterol via an ether linkage between the polymer amine and the cholesterol backbone have been synthesized. Different percentage of cholesterol moieties have been grafted on three types of PEI of molecular weights 800, 1200, and 2000. These lipopolymers were studied for gene transfection activities in HeLa cells. All the lipopolymers were first optimized for enhanced transfection efficacies as coliposomes with DOPE. All lipopolymers are better transfecting agents and highly serum compatible than commercially available PEI-25KDa. Transfection efficacies and serum compatibility of lipopolymers were found to be dependent upon the MW of PEI used for lipopolymer synthesis and percentage of cholesterol grafting on lipopolymers. Cell viability assay showed that PEI-25KDa is highly toxic as compared to all the lipopolymers. Lipopolyplexes were characterized by transmission electron microscopy, which showed the presence of spherical aggregates.

Effect of the Nature of the Spacer on Gene Transfer Efficacies of Novel Thiocholesterol Derived Gemini Lipids in Different Cell Lines: A Structure–Activity Investigation

A structure-activity investigation was undertaken to see the effect of the nature of the spacer on the gene transfection efficacies of thiocholesterol-derived cationic gemini lipids possessing disulfide linkage between the cationic headgroup and the thiocholesterol moiety. Three gemini cationic lipids possessing hydrophobic flexible (-(CH 2) 5-; 1), hydrophobic rigid (-C 6H 4-; 2), and hydrophilic flexible (-CH 2-CH 2-O-CH 2-CH 2-; 3) spacer segments were synthesized. In HeLa cells, lipid formulations 1 and 2 were found to be more effective as compared to lipid 3 formulation. In HT1080 cell line, the order of transfectability was 3 > 1 > 2. Transfection studies in HeLa and HT1080 cell line also showed 40-50% transfection efficacy in the presence of 10% serum conditions. These formulations were also able to transfect gene across difficult cells like HaCaT. Cytotoxic studies showed the nontoxic nature of these lipid-DNA complexes at different N/P ratios used for transfection studies.

Gene Transfection Efficacies of Novel Cationic Gemini Lipids Possessing Aromatic Backbone and Oxyethylene Spacers

Six novel gemini cationic lipids based on aromatic backbone, bearing n-C14H 29 or n-C16H33 hydrocarbon chains, differing in the length of oxyethylene type spacers -CH2-(CH2-O-CH2)m-CH2- between each ammonium headgroups have been synthesized, where m varies from 1 to 3. Each of these lipids formed stable suspensions in aqueous media. Cationic liposomes were prepared from each of these lipids individually and as mixtures of each cationic lipid and DOPE. These were used as nonviral gene delivery agents. Transfection studies showed that among lipids bearing n-C14H29 chains, the transfection efficacies decreased with the increase in the length of the spacer, whereas in case of lipids bearing n-C 16H33 chains, the transfection efficacies increased with the increase in the length of the spacer. Lipid bearing n-C16H33 hydrocarbon chains with a [-(CH2-CH2-O-CH2-CH2-O-CH2-CH2-O-CH2-CH2)-] spacer was found to be a potent gene transfer agent and its transfection was highly serum compatible even in the presence of 50% serum conditions.

Incorporation of all‐trans retinoic acid into lipoplexes inhibits nuclear factor κB activation mediated liver injury induced by lipoplexes in mice

All-trans retinoic acid (ATRA) is a natural derivative of vitamin A, which is well known to suppress inflammatory cytokine production. To date, there have been few reports about the systemic use of ATRA for inflammation because of acute resistance and the highly lipophilic nature of ATRA. ATRA-lipoplexes were prepared by mixing CMV-Luc plasmid DNA with ATRA-incorporated 1,2-dioleoyl-3-trimethylammoniopropane (DOTAP)/cholesterol liposome. After intravenous injection, tissue accumulation, transfection efficacy, NFkappaB activation, cytokine production, and hepatic toxicity of ATRA-lipoplexes were evaluated and compared with lipoplexes lacking ATRA. The particle size and zeta potential of ATRA-lipoplexes were similar to those of lipoplexes. After intravenous injection of ATRA-lipoplexes, tissue accumulation in liver and gene expression in liver and lung were similar to those of lipoplexes, supporting the hypothesis that ATRA incorporation did not affect the delivery and gene transfection efficacy. In addition, ATRA incorporated in ATRA-lipoplexes was delivered to liver in a manner similar to that for ATRA incorporated in liposomes. In addition, intravenous injection of ATRA-lipoplexes inhibited the activation of NFkappaB in liver, and subsequently suppressed the serum levels of tumor necrosis factor-alpha (TNF-alpha) and alanine aminotransferase (ALT) compared with lipoplexes. Liver histology data also demonstrated a low degree of liver injury produced by ATRA-lipoplexes compared with lipoplexes. ATRA-incorporated lipoplexes effectively suppress NFkappaB activation, cytokine response and liver injury induced by lipoplexes without affecting gene delivery and transfection efficacy in vivo.

Effect of the Hydrocarbon Chain and Polymethylene Spacer Lengths on Gene Transfection Efficacies of Gemini Lipids Based on Aromatic Backbone

Design, syntheses, and gene delivery efficacies of fifteen novel gemini (dimeric) and three monomeric cationic lipids anchored on an aromatic backbone have been described. Each new lipid has been used for liposome formation, and optimal formulations were used to determine the structure-activity correlation of the gene transfection efficacies of these lipids in HeLa and HT1080 cells. The results of the present investigation bring out the effect of hydrocarbon chain lengths and the length of the spacer between the headgroups on gene transfection efficiencies of the cationic gemini lipids based on aromatic backbone. The lipids bearing n-C 14H 29 hydrocarbon chain lengths have been found to be the best transfecting agents compared to their counterparts with n-C 16H 33 and n-C 12H 25 chains in HeLa cells. On the other hand, in HT1080 cells, the lipids based on n-C 12H 25 and n-C 14H 29 chains were found to be more potent transfecting agents than lipids possessing n-C 16H 33 chains. Transmission electron microscopy examination revealed the existence of spherical lipid-DNA complexes.

Dramatic Influence of the Orientation of Linker between Hydrophilic and Hydrophobic Lipid Moiety in Liposomal Gene Delivery

A number of prior studies have demonstrated that the DNA-binding and gene transfection efficacies of cationic amphiphiles crucially depend on their various structural parameters including hydrophobic chain lengths, headgroup functionalities, and the nature of the linker-functionality used in tethering the polar headgroup and hydrophobic tails. However, to date addressing the issue of linker orientation remains unexplored in liposomal gene delivery. Toward probing the influence of linker orientation in cationic lipid mediated gene delivery, we have designed and synthesized two structurally isomeric remarkably similar cationic amphiphiles 1 and 2 bearing the same hydrophobic tails and the same polar headgroups connected by the same ester linker group. The only structural difference between the cationic amphiphiles 1 and 2 is the orientation of their linker ester functionality. While lipid 1 showed high gene transfer efficacies in multiple cultured animal cells, lipid 2 was essentially transfection incompetent. Findings in both transmission electron microscopic and dynamic laser light scattering studies revealed no significant size difference between the lipoplexes of lipids 1 and 2. Findings in confocal microscopic and fluorescence resonance energy transfer (FRET) experiments, taken together, support the notion that the remarkably higher gene transfer efficacies of lipid 1 compared to those of lipid 2 presumably originate from higher biomembrane fusogenicity of lipid 1 liposomes. Differential scanning calorimetry (DSC) and fluorescence anisotropy studies revealed a significantly higher gel-to-liquid crystalline temperature for the lipid 2 liposomes than that for lipid 1 liposomes. Findings in the dye entrapment experiment were also consistent with the higher rigidity of lipid 2/cholesterol (1:1 mole ratio) liposomes. Thus, the higher biomembrane fusibility of lipid 1 liposomes than that of lipid 2 liposomes presumably originates from the more rigid nature of lipid 2 cationic liposomes. Taken together, the present findings demonstrate for the first time that even as minor a structural variation as linker orientation reversal in cationic amphiphiles can profoundly influence DNA-binding characteristics, membrane rigidity, membrane fusibility, cellular uptake, and consequently gene delivery efficacies of cationic liposomes.

803 がん遺伝子治療を目指した非侵襲撃組織標的性分子導入法の開発(1)(OS8-1 医療援用工学における流動ダイナミクス,OS8 医療援用工学における流動ダイナミクス,オーガナイズドセッション)

Gene transfer to cancer cells using nanobubbles (NBs) and ultrasound (US) is a non-invasive gene therapy. In order to improve efficacy of gene transfection, the impulsive pressures generated by cavitation bubbles created by the collapse of NBs have to be optimized. In addition, the mechanism of molecular transfer as d as subsequent therapeutic effect has to be investigated. In the present study, we delivered fluorescence molecules into cells with the NB-US method and quantified the intracellular fluorescence molecules. Next we verified the therapeutic effect of suicide gene therapy in vitro using harpes simplex virus thymidine kinase (HSV tk) gene and ganciclovir (GCV), Finally we analyzed the cavitation bubble behavior and the interaction of the shock wave with a lipid bilayer by using theoretical and numerical methods, We attributed the delivery exogenous molecules by the NS-US method to the structural change in the lipid bilayer caused by the interaction of the shock waves from the cavitation bubbles.

803 がん遺伝子治療を目指した非侵襲撃組織標的性分子導入法の開発(2)(OS8-1 医療援用工学における流動ダイナミクス,OS8 医療援用工学における流動ダイナミクス,オーガナイズドセッション)

Gene transfer to cancer cells using nanobubbles (NBs) and ultrasound (US) is a non-invasive gene therapy. In order to improve efficacy of gene transfection, the impulsive pressures generated by cavitation bubbles created by the collapse of NBs have to be optimized. In addition, the mechanism of molecular transfer as d as subsequent therapeutic effect has to be investigated. In the present study, we delivered fluorescence molecules into cells with the NB-US method and quantified the intracellular fluorescence molecules. Next we verified the therapeutic effect of suicide gene therapy in vitro using harpes simplex virus thymidine kinase (HSV tk) gene and ganciclovir (GCV), Finally we analyzed the cavitation bubble behavior and the interaction of the shock wave with a lipid bilayer by using theoretical and numerical methods, We attributed the delivery exogenous molecules by the NS-US method to the structural change in the lipid bilayer caused by the interaction of the shock waves from the cavitation bubbles.

Enhanced gene expression in lung by a stabilized lipoplex using sodium chloride for complex formation

In this study, we investigated the in vivo gene transfection efficacy of a 'surface charge regulated' (SCR) lipoplex, dispersed in the presence of an essential amount of NaCl during lipoplex formation. SCR lipoplexes were prepared and their physicochemical properties were analyzed. After intravenous (i.v.) administration, transfection efficacy, distribution characteristics, and liver toxicity were evaluated in mice. At NaCl concentrations of 10 mM, the particle sizes of the SCR lipoplexes were about 120 nm and were compatible with a conventional lipoplex. However, fluorescent resonance energy transfer analysis revealed that cationic liposomes in the SCR lipoplexes increased fusion. After i.v. administration, the transfection activity in the lung of the SCR lipoplex (10 mM NaCl solution in the lipoplex) was approximately 10-fold higher than that of the conventional lipoplex. Pharmacokinetic studies demonstrated a higher distribution in lung by the SCR lipoplex. When the gene expression levels of the SCR lipoplex and conventional lipoplex were compared, the SCR lipoplex at a dose of 30 microg was compatible with that of the conventional lipoplex at a dose of 50 microg. A significantly higher serum alanine aminotransferase (ALT) activity and TNFalpha concentration was observed by the conventional lipoplex (pDNA dose; 50 microg), but this was not the case for the SCR lipoplex (pDNA dose; 30 microg). We demonstrated that the SCR lipoplex could enhance the transfection efficacy in the lung without increasing the liver toxicity. Hence, the information will be valuable for the future use, design, and development of lipoplexes for in vivo applications.

Modulation of surface charge, particle size and morphological properties of chitosan–TPP nanoparticles intended for gene delivery

This work investigates the polyanion initiated gelation process in fabricating chitosan–TPP (tripolyphosphate) nanoparticles in the size range of 100–250 nm intended to be used as carriers for the delivery of gene or protein macromolecules. It demonstrates that ionic gelation of cationic chitosan molecules offers a flexible and easily controllable process for systematically and predictably manipulating particle size and surface charge which are important properties in determining gene transfection efficacy if the nanoparticles are used as non-viral vectors for gene delivery, or as delivery carriers for protein molecules. Variations in chitosan molecular weight, chitosan concentration, chitosan to TPP weight ratio and solution pH value were examined systematically for their effects on nanoparticle size, intensity of surface charge, and tendency of particle aggregation so as to enable speedy fabrication of chitosan nanoparticles with predetermined properties. The chitosan–TPP nanoparticles exhibited a high positive surface charge across a wide pH range, and the isoelectric point (IEP) of the nanoparticles was found to be at pH 9.0. Detailed imaging analysis of the particle morphology revealed that the nanoparticles possess typical shapes of polyhedrons (e.g., pentagon and hexagon), indicating a similar crystallisation mechanism during the particle formation and growth process. This study demonstrates that systematic design and modulation of the surface charge and particle size of chitosan–TPP nanoparticles can be readily achieved with the right control of critical processing parameters, especially the chitosan to TPP weight ratio.

A polyamidoamine dendrimer-capped mesoporous silica nanosphere-based gene transfection reagent.

We synthesized a MCM-41-type mesoporous silica nanosphere (MSN)-based gene transfection system, where second generation (G2) polyamidoamines (PAMAMs) were covalently attached to the surface of MSN. The G2-PAMAM-capped MSN material (G2-MSN) was used to complex with a plasmid DNA (pEGFP-C1) that encodes for an enhanced green fluorescence protein. The gene transfection efficacy, uptake mechanism, and biocompatibility of the G2-MSN system with various cell types, such as neural glia (astrocytes), human cervical cancer (HeLa), and Chinese hamster ovarian (CHO) cells, were investigated. The mesoporous structure of the MSN material allows membrane-impermeable molecules, such as pharmaceutical drugs and fluorescent dyes, to be encapsulated inside the MSN channels. The system renders the possibility to serve as a universal transmembrane carrier for intracellular drug delivery and imaging applications.