An efficient and universal protoplast-based transient gene expression system for genome editing in Brassica crops

Protoplast-based transient gene expression system has been widely used in plant genome editing because of its simple operation and less time-consuming.In order to establish a universal protoplast-based transient transfection system for verifying activities of genome editing vectors containing targets in Brassica,we systematically optimized factors affecting protoplast isolation and transient gene expression.We established an efficient protoplast-based transient gene expression system(PTGE)in Chinese cabbage,achieving high protoplast yield of 4.9×10^(5)·g^(-1)FW,viability over 95%,and transfection efficiency of 76%.We showed for the first time that pretreatment of protoplasts with a hypotonic MMG could significantly enhance the transfection efficiency.Furthermore,protoplasts incubated at 37℃ for 6 min improved the transfection efficiency to 86%.We also demonstrated that PTGE worked well(more than 50%transfection efficiency)in multiple Brassica species including cabbage,Pak Choi,Chinese kale,and turnip.Finally,PTGE was used for validating the activities of CRISPR/Cas9 vectors containing targets in Chinese cabbage,cabbage,and pak choi,demonstrating the broad applicability of the established PTGE for genome editing in Brassica crops.

Poly(ethylenimine)-grafted-poly[(aspartic acid)-co-lysine]: A Non-viral Polymer with Potential for DNA Delivery

A biodegradable gene transfer vector, poly(ethylenimine)-grafted-poly[(aspartic acid)-co-lysine] has been developed by thermal polycondensation of aspartic acid and lysine, and branch poly(ethylenimine) (Mw less than 600) was grafted to the backbone. The polymer was characterized by 1H NMR. It appeared lower cytotoxity compared to poly(ethylenimine) (25KDa), which was quantified by MTT assay. Electrophoresis indicated that the polymer could retardate DNA at N/P ratio 1.2-1.8 (w/w). Transfection efficiency of the complexes was studied in NT2 cell lines. It was 1.5 fold higher than molecular weight PEI (Mw = 25KDa).

PEI-PEG as a siRNA Genetic Vector Demonstrating Interference in the Expression of CD44v6 Protein in Gastric Cancer Cells

OBJECTIVE To investigate the effect of polyethylene imine glycol （PEI-PEG）/siRNA nanocomposites in the in vitro transfection of human gastric cancer SGC7901 cell lines and the down-regulation of gene expression of the adherence factor CD44v6. METHODS PEI-PEG/siRNA nanoparticles, in different N/P ratios, were synthesized and transfected into gastric cancer cells. Lipo2000/siRNA was used in the control group. The transfection efficiencies were observed under fluorescence microscope. The cytotoxicity of the nanoparticles was measured using the MTT assay （mononuclear cell direct cytotoxicity assay）, and the down-regulation effect of siRNA on CD44v6 gene was evaluated by Western blot. Based on the different N/P ratios, PEI-PEG/siRNA composites were synthesized and transfected into gastric cancer cells. Lipo2000/siRNA was used in the controls. The transfection efficiency was observed under fluorescence microscope. The cytotoxicity of the nanoparticles was measured using the MTT assay and the down-regulation effect of siRNA on CD44v6 gene was evaluated by Western blot. RESULTS After transfection, the transfection efficiency of the PEI-PEG/siRNA nanocomposites increased incrementally in N/P ratio value. The transfection efficiency improved with an increase in N/P ratio. When the N/P value was 15, fluorescence became more intense in the PEI-PEG/siRNA group than in the Lipo2000/siRNA group. At the same time, cell viability was （80.4 ± 5.6）% in the MTT reduction assay, which was similar to that in the Lipo2000/siRNA group. The results of Western blot analysis showed that the expression level of CD44v6 protein decreased to （59.7 ± 3.0）% after siRNA-CD44v6 was inhibited. CONCLUSION PEI-PEG could effectively form the nanocomposite in combination with siRNA, be transfected into the SGC7901 gastric cancer cell lines and inhibit CD44v6 protein expression. Moreover, as a genetic carrier, PEI-PEG copolymer has greater advantages, including high transfection e. ciency, less cytotoxicity and an easily alterable vector structure.

Synthesis and Evaluation of Novel Chitosan Derivatives for Gene Delivery

A series of novel water soluble chitosan derivatives as gene vectors was synthesized. The delivery systems were tested for their ability to form complexes with plasmid DNA by utilizing agarose gel electrophoresis, particle size analysis, zeta potential measurement and scanning electron microscopy. Furthermore, cytotoxicity of chitosan derivatives and transfection efficiency of polyplexes were evaluated in vitro. The experimental results showed that the novel chitosan derivatives had lower cytotoxicity, good DNA condensation, and higher transfection efficiencies compared to chitosan in both 293T and HeLa cell lines. It was indicated that these chitosan derivatives were promising candidates for non-viral gene vectors.

Polyethylenimine (PEI)g-comb-poly(ethylene glycol)-transferrin(I): Tumor-targeted Vector for Gene Delivery In-vitro

The work described the synthesis and evaluation of PEI-g-comb-PEG-transferrin as a potential system for gene therapy in vitro. The MW of PEG was 10KDa, and PEI was 2KDa. Its structure was identified by NMR, FT-IR and TGA spectroscopy. MTT assay found that at concentration up to 4000 n mol/L of the polymer, cell viability was over 85%. The bio-character of polymer/DNA complex was characterized by agarose gel electrophoresis, ethidium bromide exclusion and zeta-potential assay. The polymer could retardate DNA at N/P ratio 3.0-3.5 （mol/mol）. The particle size of the polymer/DNA complex was less than 300 nm. Transfection efficiency of the complex was studied in COS7 and NT2 cell lines.

Optimization on cationic liposome-mediated cell transfection of plasmid DNA

Objective:The development of gene carriers for efficient gene delivery into cells has attracted growing attention in recent years.The aim of this study was to achieve a better outcome of AAV-293 cells transfection by plasmid DNA.Methods:We studied the optimal condition for higher efficiency of cationic lipid-mediated cell transfection.Four experimental groups were set.Plasmid DNA and liposome were mixed in each groups at different ratios(μg:μL),1:2.5,1:3.5,1:4.0 and 1:5.0,respectively.LacZ gene functioned as reporter gene,measuring the transfection efficiency of the four groups using the method of X-gal staining.Results:When the ratio was 1:3.5,the cell transfection rate was the highest.While the ratio of 1:2.5 recommended by product manual achieve the lowest transfection rate.Their difference had statistical significance.Conclusion:In order to obtain a higher transfection efficiency,optimization on conditions of the ratio of plasmid DNA to liposome is necessary in cell transfection.

Non-viral liposome-mediated transfer of brain-derived neurotrophic factor across the blood-brain barrier

Brain-derived neurotrophic factor（BDNF） plays an important role in the repair of central nervous system injury,but cannot directly traverse the blood-brain barrier.Liposomes are a new type of non-viral vector,able to carry macromolecules across the blood-brain barrier and into the brain.Here,we investigate whether BDNF could be transported across the blood-brain barrier by tail-vein injection of liposomes conjugated to transferrin（Tf） and polyethylene glycol（PEG）,and carrying BDNF modified with cytomegalovirus promoter（pC MV） or glial fibrillary acidic protein promoter（p GFAP）（Tf-p CMV-BDNF-PEG and Tf-p GFAP-BDNF-PEG,respectively）.Both liposomes were able to traverse the blood-brain barrier,and BDNF was mainly expressed in the cerebral cortex.BDNF expression in the cerebral cortex was higher in the Tf-p GFAP-BDNF-PEG group than in the Tf-p CMV-BDNF-PEG group.This study demonstrates the successful construction of a non-virus targeted liposome,Tf-p GFAP-BDNF-PEG,which crosses the blood-brain barrier and is distributed in the cerebral cortex.Our work provides an experimental basis for BDNF-related targeted drug delivery in the brain.

Effects of Headgroups and Serum on Gene Transfection of Alkaline Amino Acid Based Cationic Lipids

Three cationic lipids with lysylated（1）, histidylated（2）, and arginylated（3） headgroups and cholesterol hydrophobic moiety were synthesized. The average sizes of liposomes and lipoplexes were around 100 and 160 nm, respectively. The gene transfection efficiency of the three lipoplexes loaded with pGL3 or pORF-LacZ was compared on 293T cells in the presence or the absence of serum. The transfection efficiency of the three lipoplexes in a serum-free medium was 2 to 3-fold higher than that of dioleoyl-trimethylammonium propane（DOTAP）. In the presence of serum, however, most of the lipoplexes showed lower transfection activities; only lipoplex 3 retained its high transfection efficiency.

In Vivo Transfection Methods of DNA Vaccines

Advantages and disadvantages of four transfection methods of DNA vaccines into the body were introduced in this study, including direct transfection, transfection of bacterial vectors, cationic lipofection and cationic polymer transfection. Cationic polymer had the characteristics of high transfection efficiency, simple operation, wide application, good repeatability and low cell virulence, which could be expected as a new kind of effi- cient transfection reagents. In practical application, various transfection methods have their own advantages and disadvantages, so the best choice should be made in the design process of vaccines based on targets, test cost, using objects and its convenience.

Efficient gene transfection of suspension cells by highly branched poly(β-amino ester)

Suspension cells play a crucial role in many biological processes. However, compared to adherent cells, it is particularly challenging to introduce exogenous genes into suspension cells to regulate their biological functions with non-viral gene vectors, mainly due to the low cellular uptake and endosomal escape of polyplexes. Herein, to improve the interactions of polyplexes with cellular membranes, we design and synthesize highly branched poly(β-amino ester)(HPAE) via an “A2 + B4 + C2” Michael addition strategy.Results show that branching significantly increases DNA condensation of HPAE, cellular uptake and endosomal escape of HPAE/DNA polyplexes. In mast cells(MCs), HPAE exhibits up to 80-fold higher gene transfection efficiency compared to the corresponding linear poly(β-amino ester)(LPAE) and the leading commercial gene transfection reagents PEI25k, jetPEI, and Lipofectamine 3000, without causing obvious cytotoxicity. Our study establishes a reliable non-viral platform for efficient gene transfection of suspension cells.

Polymeric prodrug for bio-controllable gene and drug co-delivery

A polymeric polyethylenimine(PEI)-based prodrug of anticancer doxorubicin(DOX)(PEI-hyd-DOX) was designed by attaching DOX to PEI via an acid-labile hydrazone bond, for the achievement of biocontrollable gene and drug co-delivery in response to the intracellular acid microenvironments in the late endosome/lysosome compartments. The cytotoxicity of PEI-hyd-DOX was evaluated by the MTT assay and the cellular uptake was monitored using confocal laser scanning microscopy. The polymeric prodrug can respond with a high sensitivity to the specific acid condition inside cells, thus permitting the precise biocontrol over intracellular drug liberation with high drug efficacy. The chemical attachment of drug molecules also led to the relatively reduced toxicity and the enhanced transfection efficiency compared with parent PEI. The resulting data adumbrated the potential of PEI-hyd-DOX to co-deliver DOX and therapeutic gene for the combination of chemotherapy and gene therapy.

Multifunctional peptide conjugated amphiphilic cationic copolymer for enhancing ECs targeting, penetrating and nuclear accumulation

Gene therapy has drawn great attention in the treatments of many diseases,especially for cardiovascular diseases.However,the development of gene carriers with low cytotoxicity and multitargeting function is still a challenge.Herein,the multitargeting REDV-G-TATG-NLS peptide was conjugated to amphiphilic cationic copolymer poly(e-caprolactone-co-3(S)-methyl-morpho-line-2,5-dione)-g-polyethyleneimine(PCLMD-g-PEI)via a heterobifunctional orthopyridyl disulfde-poly(ethylene glycol)-N-hydroxysuccinimide(OPSS-PEG-NHS)linker to prepare PCLMD-g-PEI-PEG-REDV-G-TAT-G-NLS copolymers with the aim to develop the gene carriers with low cytotoxicity and high transfection efficiency.The multitargeting micelles were prepared from PCLMD-g-PEI-PEG-REDV-G-TAT-G-NLS copolymers by self-assembly method and used to load pEGFP-ZNF580 plasmids(pDNA)to form gene complexes for enhancing the proliferation and migration of endothelial cells(ECs).The loading pDNA capacity was proved by agarose gel electrophoresis assay.These multitargeting gene com-plexes exhibited low cytotoxicity by 3-(4,-dimethylthia-zol-2-yl)-2,5-diphenyltetrazolium bromide assay.The high internalization efficiency of these gene complexes was confirmed by flow cytometry.The results of in vitro transfection demonstrated that these multitargeting gene complexes possessed relatively high transfection effi-ciency.The rapid migration of ECs transfected by these gene complexes was verified by wound healing assay.Owing to ECs-targeting ability,cell-penetrating ability and nuclear targeting capacity of REDV-G-TAT-G-NLS pep-tide,the multitargeting polycationic gene carrier with low cytotoxicity and high transfection efficiency has great potential in gene therapy.

“Building-block crosslinking”micelles for enhancing cellular transfection of biocompatible polycations

Incorporating functional ligands and biodegradable bonds into biocompatible low-molecular-weight(LMW)polymers,such as 1.8 kDa poly(ethylenimine)(PEI1.8 k),is a common strategy to improve the properties of LMW polymers including biosafety and delivery efficacy.This study demonstrates the hypothesis that introducing different functional ligands and linked reductive disulfides in PEI 1.8k will achieve superior siRNA transfection efficiency.By incorporating PEI-X(X represents cholesterol(Ch),heptafluorobutyric anhydride(HFBA,F)and 4-carboxyphenylboronic acid(PBA))functional ligands into PEI 1.8k and subsequently crosslinking with each other via disulfide bond links,reductive-responsive PEI-X-SS-X-PEI copolymers were constructed to enhance the cellular transfection via the synergistic effect of the high affinity of Ch,F and PBA to cell membranes and the disulfide reduction triggered intracellular disassembly of micelles and subsequent siRNA release.Extraordinarily,ternary Ch-SS-F-SS-PBA micelles exhibited the strongest siRNA transfection efficiencies in in vitro cell experiments and in vivo animal experiments due to the coordination of enhanced serum stability,promoted cell uptake and endosomal escape,and cell targeting ability.This strategy of constructed multifunctional polymer here we called"building-block crosslinking"showed a simple and smart way to synthesize new materials.Also this strategy of constructing ligands-directed reduction-sensitive micelles improves the transfection efficiency of LMW PEI and provides a valuable insight to develop novel gene delivery systems.