Aerosol-based fabrication of modified chitosans and their application for gene transfection

Reconstructed chitosan with alkylamine for enhanced gene delivery by promoting endosomal escape

Poor buffering capacity of chitosan (CS) results in insufficient intracellular gene release which poses the major barrier in gene delivery. Herein, we reconstructed pristine CS with propylamine (PA), (diethylamino) propylamine (DEAPA), and N, N-dimethyl- dipropylenetriamine (DMAMAPA) to obtain a series of alkylamine-chitosan (AA-CS). The introduction of multiple amino groups with rational ratios functionally enhance the buffering capacity of AA-CS, among which DMAPAPA-CS showed buffering capacity of 1.58 times that of chitosan. The reconstructed AA-CS functionally enhance the ability of gene binding and endosomal escape. It was observed that the DMAPAPA-CS/pDNA complexes exhibit a notable gene delivery efficiency, which promotes the functionalization of loaded pDNA. Importantly, the in vivo delivery assay reveals that the deep penetration issue can be resolved using DMAPAPA-CS gene delivery vector. Finally, the DMAPAPA-CS is applied to deliver the therapeutic p53 gene in A549 bearing mice, showing efficient therapeutic potential for cancer.

Easy on-demand single-pass self-assembly and modification to fabricate gold@graphene-based anti-inflammatory nanoplatforms

Zwitterionic chitosan (ZC) was modified by fully (both for lateral dimension and thickness) nanodimensional gold-graphene oxide (Au@GO) flakes under visible light and the potential of the resulting materials as biomedical nanoplatforms was investigated. Fully nanodimensional GO flakes floating in nitrogen gas were incorporated with Au nanoparticles to form Au@GO nanoflakes, and the Au@GO was then incorporated with ZC droplets to form the Au@GO-ZC hybrid nanoparticles. The collected particles were exposed to visible light to induce the photocatalytic activity of the Au@GO nanoflakes towards the ZC derivatives. The visible-light-exposed particles show different chemical and surface properties from the unexposed particles, while there were no significant differences in cytotoxicity and macrophage inflammatory protein production. This work suggests that incorporating fully nanodimensional Au@GO flakes with ZC is a suitable technique for ambient photo-modification of the chitosans' surface property without significant changes in size and shape and increases in cytotoxicity and inflammatory response.

Multifunctional metal-polymer nanoagglomerates from single-pass aerosol self-assembly

In this study, gold (Au)-iron (Fe) nanoagglomerates were capped by a polymer mixture (PM) consisting of poly(lactide-co-glycolic acid), protamine sulfate, and poly-l-lysine via floating self-assembly in a single-pass aerosol configuration as multibiofunctional nanoplatforms. The Au-Fe nanoagglomerates were directly injected into PM droplets (PM dissolved in dichloromethane) in a collison atomizer and subsequently heat-treated to liberate the solvent from the droplets, resulting in the formation of PM-capped Au-Fe nanoagglomerates. Measured in vitro, the cytotoxicities of the nanoagglomerates (>98.5% cell viability) showed no significant differences compared with PM particles alone (>98.8%), thus implying that the nanoagglomerates are suitable for further testing of biofunctionalities. Measurements of gene delivery performance revealed that the incorporation of the Au-Fe nanoagglomerates enhanced the gene delivery performance (3.2 × 10⁶ RLU mg⁻¹) of the PM particles alone (2.1 × 10⁶ RLU mg⁻¹), which may have been caused by the PM structural change from a spherical to a hairy structure (i.e., the change followed the agglomerated backbone). Combining the X-ray-absorbing ability of Au and the magnetic property of Fe led to magnetic resonance (MR)-computed tomography (CT) contrast ability in a phantom; and the signal intensities [which reached 64 s⁻¹T₂-relaxation in MR and 194 Hounsfield units (HUs) in CT at 6.0 mg mL⁻¹] depended on particle concentration (0.5–6.0 mg mL⁻¹).

Aerosol Nanoencapsulation: Single-Pass Floating Self-Assembly of Biofunctional Hybrid Nanoplatforms

Multifunctional nanoplatforms were prepared via floating self-assembly using a hard nanoparticle (NP) as the core and a modified-polymer (MP, cholesterol-chitosan linked with polyethylenimine) droplet as the shell in a single-pass aerosol nanoencapsulation process. The floating hard NPs (silica, calcium carbonate, gold-decorated graphene oxide, and thiol-capped gold) were directly injected into MP droplets at the opening of a spraying device. Subsequently, the solvent was thermally extracted from the droplets, resulting in the formation of biofunctional nanoplatforms. Measured in vitro, the genes complexed with the nanoplatforms were transfected into target cells, exhibiting higher efficiencies for the MP particles alone without a significant increase in in vitro cell cytotoxicity. The aerosol encapsulation could be further extended to prepare other combinations [gold-silica and gold-calcium carbonate including doxorubicin (Dox)] using the MP, and their hybrid natures demonstrated photothermal cancer cell killing and chemo-thermal Dox release capabilities through surface plasmon resonance heating.

Biocompatible polymer-Peptide hybrid-based DNA nanoparticles for gene delivery

Currently, research on polymers to be used as gene delivery systems is one of the most important directions in both polymer science and biomedicine. In this report, we describe a five-step procedure to synthesize a novel polymer-peptide hybrid system for gene transfection. The block copolymer based on the biocompatible polymer poly(2-methyl-2-oxazoline) (PMOXA) was combined with the biocleavable peptide block poly(aspartic acid) (PASP) and finally modified with diethylenetriamine (DET). PMOXA-b-PASP(DET) was produced in high yield and characterized by (1)H NMR and FT-IR. Our biopolymer complexed plasmid DNA (pDNA) efficiently, and highly uniform nanoparticles with a slightly negative zeta potential were produced. The polymer-peptide hybrid system was able to efficiently transfect HEK293 and HeLa cells with GFP pDNA in vitro. Unlike the commonly used polymer, 25 kDa branched poly(ethylenimine), our biopolymer had no adverse effects on cell growth and viability. In summary, the present work provides valuable information for the design of new polymer-peptide hybrid-based gene delivery systems with biocompatible and biodegradable properties.