Viruses have evolved to be outstandingly efficient at gene delivery, but their use as vectors is limited by safety risks. Inspired by the structure of viruses, we constructed a virus-mimicking vector (denoted as TR4@siRNA@Tf NCs) with virus-like architecture and infection properties. Composed of a hydrophilic peptide, an aggregation-induced emission (AIE) luminogen, and a lipophilic tail, TR4 imitates the viral capsid and endows the vector with AIE properties as well as efficient siRNA compaction. The outer glycoprotein transferrin (Tf) mimics the viral envelope protein and endows the vector with reduced cytotoxicity as well as enhanced targeting capability. Because of the strong interaction between Tf and transferrin receptors on the cell surface, the Tf coating can accelerate the intracellular release of siRNA into the cytosol. Tf and TR4 are eventually cycled back to the cell membrane. Our results confirmed that the constructed siRNA@TR4@Tf NCs show a high siRNA silencing efficiency of 85% with significantly reduced cytotoxicity. These NCs have comparable transfection ability to natural viruses while avoiding the toxicity issues associated with typical nonviral vectors. Therefore, this proposed virus-like siRNA vector, which integrates the advantages of both viral and nonviral vectors, should find many potential applications in gene therapy.Keywords: active targeting; aggregation-induced emission; gene delivery; transferrin; virus-like vectors;

High-efficiency gene transfer and suitably low cytotoxicity are the main goals of gene transfection systems based on nonviral vectors. In addition, it is desirable to track the gene transfer process in order to observe and explain the mechanism. Herein, inspired by viral structures that are optimized for gene delivery, we designed a small-molecule gene vector (TR4) with aggregation-induced emission properties by capping a peptide containing four arginine residues with tetraphenylethene (TPE) and a lipophilic tail. This novel vector can self-assemble with plasmid DNA to form nanofibers in solution with low cytotoxicity, high stability, and high transfection efficiency. pDNA@TR4 complexes were able to transfect a variety of different cell lines, including stem cells. The self-assembly process induces bright fluorescence from TPE, which makes the nanofibers visible by confocal laser scanning microscopy (CLSM). This allows us for the tracking of the gene delivery process.Keywords: gene delivery; nanofibers; peptide; self-indicating; transfection;

The microtechnology of controlling stimuli-responsive biomaterials at micrometer scale is crucial for biomedical applications. Here, we report bovine serum albumin (BSA)-based three-dimensional (3D) microstructures with tunable surface morphology and pH-responsive properties via two-photon polymerization microfabrication technology. The laser processing parameters, including laser power, scanning speed, and layer distance, are optimized for the fabrication of well-defined 3D BSA microstructures. The tunable morphology of BSA microstructures and a wide range of pH response corresponding to the swelling ratio of 1.08–2.71 have been achieved. The swelling behavior of the microstructures can be strongly influenced by the concentration of BSA precursor, which has been illustrated by a reasonable mechanism. A panda face-shaped BSA microrelief with reversible pH-responsive properties is fabricated and exhibits unique “facial expression” variations in pH cycle. We further design a mesh sieve-shaped microstructure as a functional device for promising microparticle separation. The pore sizes of microstructures can be tuned by changing the pH values. Therefore, such protein-based microstructures with controllable morphology and pH-responsive properties have potential applications especially in biomedicine and biosensors.Keywords: 3D microstructure; bovine serum albumin; morphology; pH response; two-photon polymerization;

•The relationship between the mechanical property of PEG 3D microstructures and fabrication parameters was illustrated by characterizing the Young’s modulus.•3D PEG microstructures simulating red blood cell morphology with high fidelity were fabricated.•The Young’s modulus of PEG hydrogels in water could be tuned to be close to that of cartilage tissue by changing layer space.Two-photon polymerization (TPP) microfabrication is an advanced technology to fabricate precise three-dimensional (3D) hydrogel micro/nanostructure. 3D hydrogel microstructures fabricated by TPP with sophisticated details and appropriate stiffness are able to effectively simulate the microenvironment used in tissue engineering and drug delivery. The mechanical property of the microstructures, for instance, the Young’s modulus is crucial to achieve the microstructures with high fidelity. In this study, the mechanical property of the poly(ethylene glycol) (PEG) 3D microstructures fabricated with various laser powers, writing speeds and layer distances in the air was investigated by characterizing the Young’s modulus. Meanwhile, the Young’s modulus of the microstructure with different layer distances in water was determined as 3.50–6.52 MPa. Furthermore, 3D PEG microstructures simulating red blood cell morphology of different postures and sizes were successfully fabricated.Download high-res image (206KB)Download full-size image

•The Ir/g was tuned to increase largely by precisely controlling Yb3+ concentration in core-shell.•The UCL intensity of Nd3+-doped UCNPs could increase with the shell thickness decreasing.•A high UCL intensity and the FRET efficiency between UCNPs and photosensitizers have been optimized simultaneously to efficiently produce 1O2.The introduction of a thick shell structure has been widely used to enhance the emission intensity of upconversion nanoparticles (UCNPs). However, a thick shell could increase the distance between UCNPs and photosensitizers, which is not favourable to the generation of singlet oxygen (1O2) in photodynamic therapy (PDT) due to the low fluorescence resonance energy transfer (FRET) efficiency. In this study, we used a facile method to prepare UCNPs that the emission intensity could increase with the shell thickness decreasing, which facilitated the efficient FRET between UCNPs and photosensitizers. In detail, the Nd3+-doped UCNPs with different dopant concentration of Yb3+ were prepared and characterized firstly. The Ir/g (intensity of red luminescence to green luminescence) was tuned to increase largely by precisely controlling Yb3+ concentration in core-shell, which could make UCNPs effectively activate methylene blue (MB). Then, a unique procedure was used to prepare NaYF4:Yb/Er/Nd@NaYF4:Nd (Yb3+:30%) core-shell nanoparticles with different shell thickness by tuning the amount of the core. The upconversion luminescence (UCL) intensity of those UCNPs enhanced dramatically with the shell thickness decreasing. Furthermore, UCNPs and MB were encapsulated into SiO2 nanoparticles. FRET efficiency between UCNPs and MB largely increased with the shell thickness of UCNPs decreasing. Correspondingly, the efficiency of 1O2 generation obviously increased. We provided a new method to optimize the UCL intensity and FRET efficiency at the same time to produce 1O2 efficiently.

In this study, poly(vinylidene fluoride) (PVDF)/polyhedral oligomeric silsesquioxanes (POSS) nanofibrous membranes are prepared through electrospun process. Field emission scanning electron microscope images clearly show that PVDF/POSS membranes have interconnected multi fibrous layers with ultrafine porous structures. The average fiber diameter and crystallinity of PVDF/POSS membranes are lesser than that of pure PVDF membrane. Thermal stability and electrolyte uptake of blend membranes increase with increasing POSS content. Finally, PVDF/POSS membranes are soaked in a liquid electrolyte to form the polymer electrolytes and are assembled in coin cells to test their electrochemical properties such as ionic conductivity, interfacial characteristics, and electrochemical stability windows. The ionic conductivity improves with increasing POSS content and the highest ionic conductivity reaches 2.91 × 10−3 S/cm at room temperature. It is also worth mention that the composite polymer electrolytes show low interfacial resistance and high electrochemical stability window of 5.6 V (vs. Li+ /Li) with storage time. POLYM. COMPOS., 38:629–636, 2017. © 2015 Society of Plastics Engineers

Open cage polyhedral oligomeric silsesquioxane (POSS) was firstly used to modify polyurethane (PU) to prepare a POSS–PU composite. Then a POSS–PU nanofiber membrane was prepared by electrospinning technology. The hydrophilic/hydrophobic properties, fiber morphology and biocompatibility of the POSS–PU nanofibers membrane were investigated. Contact angle increased by 24.3° for 2 wt% POSS–PU nanofibers membrane compared to PU. The ability of the nanofibers membrane surface to repel proteins and platelets was assessed by using platelet adhesion test and BSA static protein-adsorption experiment. Platelet adsorption amount obviously decreased compared with PU and very few platelet was adhered on the surfaces of nanofibers membranes when 1 wt% POSS was added. Protein adsorption was also decreased with addition of POSS. Hemolysis tests showed that hemolysis rate localized in the desired range of values (<5%) for all nanofibers membrane. Moreover, the antibacterial activity of nanofibers membranes was obviously improved after addition of POSS.

In this study, polyhedral oligomeric silsesquioxane (POSS) end-capped amphiphilic POSS-block-poly (N, N-dimethylaminoethyl methacrylate)-block-poly (methyl methacrylate) (POSS-b-PDMAEMA-b-PMMA) was synthesized by a two-step atom transfer radical polymerization (ATRP), and its assembly morphologies in different solvents were investigated. POSS-b-PDMAEMA-b-PMMA micelles were used to encapsulate tetraphenylethene (TPE) to study the effect of self-assembly shape on the fluorescent intensity and bioimaging of TPE. Spherical polymeric micelles enhanced the fluorescent intensity of TPE more than rod-like and necklace-like polymeric micelles while rod-like polymeric micelles had better intracellular uptake than spherical polymeric micelles.

3D printing technology has attracted much attention due to its high potential in scientific and industrial applications. As an outstanding 3D printing technology, two-photon polymerization (TPP) microfabrication has been applied in the fields of micro/nanophotonics, micro-electromechanical systems, microfluidics, biomedical implants and microdevices. In particular, TPP microfabrication is very useful in tissue engineering and drug delivery due to its powerful fabrication capability for precise microstructures with high spatial resolution on both the microscopic and the nanometric scale. The design and fabrication of 3D hydrogels widely used in tissue engineering and drug delivery has been an important research area of TPP microfabrication. The resolution is a key parameter for 3D hydrogels to simulate the native 3D environment in which the cells reside and the drug is controlled to release with optimal temporal and spatial distribution in vitro and in vivo. The resolution of 3D hydrogels largely depends on the efficiency of TPP initiators. In this paper, we will review the widely used photoresists, the development of TPP photoinitiators, the strategies for improving the resolution and the microfabrication of 3D hydrogels.

Cationic polymers (polycations) are promising gene vectors that are conveniently synthesized and easily modified. In order to study the relationship between structures and properties of the polycations in gene delivery, a graft copolymer called poly(N-vinylpyrrolidone)-g-poly(2-dimethylaminoethyl methacrylate) (PVP-g-PDMAEMA, i.e. PgP) and a block copolymer called PVP-b-PDMAEMA (PbP) with equal molecular weight of PDMAEMA and PVP were prepared by two advanced living radical polymerization reactions including atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) techniques. Compared with PbP, PgP could condense pDNA more effectively into polyplexes with smaller size, higher zeta potential and better stability. The transfection efficiency of PgP at a low N/P ratio of 4:1 was not only higher than that of PbP, but also much higher than that of the commercially available PEI as the gold standard of polycations and lipofectamine. In addition, both PgP and PbP had less BSA absorption compared with PEI, indicating that PVP could resist BSA absorption. In order to understand the mechanism behind the high transfection efficiency of PgP, cellular uptake and endosomal escape of PgP/pDNA and PbP/pDNA polyplexes were investigated. The results demonstrated that the improvement of the transfection efficiency of PgP originated from the promotion of the cellular uptake and endosome/lysosome escape. This study will provide useful information on designing effective non-viral vectors for gene delivery.

The charge-reversal strategy is usually employed in gene delivery to facilitate the endosomal escape of gene carriers and the release of the payload into cytoplasm. However, most of the charge-reversal materials are far from perfect biocompatible materials due to the cytotoxicity of themselves or their hydrolyzed products. In this study, an excellent charge-reversal material named modified bovine serum albumin (mBSA) was prepared. The charge reversal of biocompatible mBSA is a physical process and can instantly occur, which was confirmed by zeta potential, size detection and morphological studies. The introduction of mBSA can not only reduce the zeta potential of binary complexes (pDNA–PEI) but also increase the nuclease resistance ability of the pDNA–PEI binary complexes. In addition, cell viabilities tested by MTT assay and gene transfection assay demonstrated that mBSA can reduce the cytotoxicity of pDNA–PEI polyplexes and improve their gene transfection efficiency (serum free and 10% FBS medium) both in 293T and HepG2 cells at the same time. The experimental results of cell internalization and intracellular distribution of pDNA–PEI–mBSA ternary complexes confirmed that the improvement of transfection efficiency originated from the enhancement of endosomal escape of polyplexes. Therefore, mBSA has been proven to be a perfect charge-reversal platform to simultaneously improve the transfection efficiency and biocompatibility of polyplexes.

Hydrogels with precise 3D configuration (3D hydrogels) are crucial for biomedical applications such as tissue engineering and drug delivery, which require the improvement of the spatial resolution on both the microscopic and the nanometric scale. In this study, a water soluble two-photon polymerization (TPP) initiator (WI) with high initiating efficiency was prepared by using a poloxamer (PF127) to encapsulate 2,7-bis(2-(4-pentaneoxy-phenyl)-vinyl)anthraquinone via a hydrophilic–hydrophobic assembly. The threshold energy for WI was 6.29 mW at a linear scanning speed of 10 μm s−1, which was much lower than those reported previously. A lateral spatial resolution of 92 nm was achieved as the resolution breakthrough of 3D hydrogels. Finally, the microstructure with high accuracy simulating the morphology of adenovirus was fabricated at the laser power close to the threshold energy of TPP, further demonstrating the ultrahigh resolution of 3D hydrogels.

The low transfection efficiency of polycations is still a major problem for successful gene therapy. To address this issue, in this study, hydrophilic poly(vinyl pyrrolidone)-graft-poly[2-(N,N-dimethylamino)ethyl methacrylate] (PVP-g-PDMAEMA) and amphiphilic poly(vinyl pyrrolidone)-graft-poly[2-(N,N-dimethylamino)ethyl methacrylate]-block-poly(methylmethacrylate) (PVP-g-PDMAEMA-b-PMMA) were synthesized via the atom transfer radical polymerization (ATRP) method, and their properties as gene vectors were investigated subsequently. PVP-g-PDMAEMA formed random coils in water and PVP-g-PDMAEMA-b-PMMA self-assembled into spherical core–shell micelles with a very low critical micelle concentration of only 6.3 × 10−3 mg mL−1. PVP-g-PDMAEMA-b-PMMA/pDNA polyplexes demonstrated an excellent gene transfection efficiency, which showed not only much higher gene transfection efficiency than PVP-g-PDMAEMA/pDNA polyplexes, but obviously surpassed 25k PEI at low N/P ratio around 3 on 293T cell lines. Hence, the results suggested that PVP-g-PDMAEMA-b-PMMA could be a highly efficient gene vector.

Ytterbium and erbium co-doped sodium yttrium fluoride (NaYF4:Er3+, Yb3+) rare-earth upconversion nanoparticles (UCNPs) with different phases were prepared and characterized. The luminescence intensity of UCNPs can be enhanced by coating a uniform layer of the shell. The crystal structure, morphology and upconversion spectra of the sample were investigated using X-ray powder diffractometry, transmission electron microscopy, and laser upconversion spectrometry with a 980 nm diode laser. Finally, UCNPs with core–shell structure were modified to be hydrophilic by ligand-free hydrophilic modification. Moreover, the water dispersible UCNPs have much stronger luminescence compared with hydrophobic UCNPs.

Hydrogels with a precise 3D configuration (3D hydrogels) are required for a number of biomedical applications such as tissue engineering and drug delivery. Two-photon polymerization (TPP) is an advanced method to fabricate 3D hydrogels. However, TPP of 3D hydrogels has been challenged by the lack of TPP initiators with high efficiency in aqueous medium. In this study, a water soluble TPP initiator (WI) with high fabrication efficiency was prepared by combining hydrophobic 2,7-bis(2-(4-pentaneoxy-phenyl)-vinyl)anthraquinone (N) with a C2v symmetrical structure and 2-hydroxypropyl-β-cyclodextrins through host–guest chemical interaction. Both one and two-photon optical properties of WI have been investigated. In aqueous medium, WI showed a two-photon absorption cross-section of around 200 GM at the wavelength of 780 nm which was much higher compared with those of commercial initiators. The threshold energy of TPP for the resin with WI as a photoinitiator (the molar ratio of N in resin is 0.03%) was 8.6 mW. 3D hydrogels with a woodpile microstructure were further fabricated by using an average power of 9.7 mW and a scanning speed of 30 μm s−1.

Bovine serum albumin (BSA) was modified through a facile synthesis method to increase its isoelectric point (pI) from 4.8 to 6.0. When pH is higher than 6.0, the protein shows a negative surface charge, on the contrary, the protein is positively charged. In this study, the charge-reversal modified BSA (crBSA) was utilized to assemble with the binary complexes of pDNA/poly(vinylpyrrolidone)-graft-poly(2-dimethylaminoethyl methacrylate) (pDNA/PVP-g-PDMAEMA) to shield the excess positive charges of complexes at physiological pH (pH 7.4). When the complex coated with crBSA located in the environment at endosomal pH (pH 5.0), the charge-reversal of crBSA led to the deviation of crBSA from polyplex by electrostatic repulsion, which would benefit the transfection of the target gene. The crBSA shows great potential for improving the transfection efficiency of pDNA/PVP-g-PDMAEMA.Both of binary complex pDNA/PVP-g-PDMAEMA and ternary complex pDNA/PVP-g-PDMAEMA/crBSA were formed by electrostatic interactions at pH 7.4 (physiological pH). When pH changed to be 5.0 (endosomal pH), the crBSA particles became positive and broke away from the binary complex by the electrostatic repulsion.

In this study, well-defined amphiphilic cationic triblock copolymers with different lengths of polycationic chain, methoxy poly(ethylene glycol)-b-poly(D,L-lactide)-b-poly(2-dimethylaminoethyl methacrylate) (mPEG-b-PDLLA-b-PDMA), were synthesized and evaluated as carriers for gene delivery. The prepared copolymers can self-assemble into spherical core–shell nanoparticles (NPs). The NPs have a very low critical micelle concentration (CMC) value with only 0.025 mg mL−1. Both copolymers can completely condense the pDNA into spherical complexes when the N/P ratio is equal to or above 3. Bovine serum albumin challenging and DNase I protection assay results demonstrate the mPEG-b-PDLLA-b-PDMA NPs can effectively protect the DNA against protein and nucleases. MTT assay results indicate that mPEG-b-PDLLA-b-PDMA NP/pDNA complexes exhibit obviously lower cytotoxicity compared with commercial gene transfection reagent Lipofectamine 2000/pDNA complexes. Subsequently, in vitro gene transfection studies in HeLa cells without serum show that mPEG113-b-PDLLA10-b-PDMA120 NP/pDNA complexes exhibit higher transfection efficiency than Lipofectamine 2000. Although the transfection efficiency is lower than that in the absence of serum, mPEG113-b-PDLLA10-b-PDMA120 NPs still display equivalent gene transfection efficiency compared to Lipofectamine 2000 when N/P ratio is above 15 in DMEM with 10% serum.

Bovine serum albumin (BSA) was utilized to assemble with the binary complexes of poly(vinylpyrrolidone)-graft-poly(2-dimethylaminoethyl methacrylate) (PVP-g-PDMAEMA)/DNA formed by layer-by-layer electrostatic interactions to screen the residual surface positive charges of complexes. The coating of BSA was able to decrease the zeta potential of binary complexes nearly to electroneutrality without interfering with DNA condensation ability. The ternary complexes of BSA/PVP-g-PDMAEMA/DNA demonstrated lower cytotoxicity compared with the binary complexes and also maintained high gene transfection efficiency in HepG2 cells.

Protein adsorption is considered as an important factor for the low transfection efficiency of polycations in vivo. In this study, two typical polycations of equal molecular weight with different structures were chosen to investigate their adsorption on bovine serum albumin (BSA), including the block copolymer named poly (N-vinylpyrrolidone)-b-poly (2-dimethylaminoethyl methacrylate) (PVP-b-PDMAEMA, i.e. PbP) and graft copolymer named PVP-g-PDMAEMA (PgP), respectively. Fluorescence spectroscopy was used to confirm the binding constants and binding sites between polycations and BSA in static state. The binding constants were 4.1 × 104 M−1 vs 8.3 × 104 M−1 and binding sites were 0.3 vs 1.1 for PbP and PgP, respectively, indicating PgP had stronger binding affinity with BSA. Surface plasmon resonance (SPR) was used to study the dynamical non-specific interaction between BSA and polycations as well as the polyplexes. The numbers of both PbP and PgP adsorbed on BSA increased with concentration of polycations increasing, and the number of PgP adsorbed on BSA is higher compared with PbP when their concentration is low. When their concentration is high, the number of PbP adsorbed on BSA is more than that of PgP. However, PgP/DNA polyplexes showed higher adsorption amount compared with PbP/DNA polyplexes at different N/P ratios.

3D printing technology has attracted much attention due to its high potential in scientific and industrial applications. As an outstanding 3D printing technology, two-photon polymerization (TPP) microfabrication has been applied in the fields of micro/nanophotonics, micro-electromechanical systems, microfluidics, biomedical implants and microdevices. In particular, TPP microfabrication is very useful in tissue engineering and drug delivery due to its powerful fabrication capability for precise microstructures with high spatial resolution on both the microscopic and the nanometric scale. The design and fabrication of 3D hydrogels widely used in tissue engineering and drug delivery has been an important research area of TPP microfabrication. The resolution is a key parameter for 3D hydrogels to simulate the native 3D environment in which the cells reside and the drug is controlled to release with optimal temporal and spatial distribution in vitro and in vivo. The resolution of 3D hydrogels largely depends on the efficiency of TPP initiators. In this paper, we will review the widely used photoresists, the development of TPP photoinitiators, the strategies for improving the resolution and the microfabrication of 3D hydrogels.

Hydrogels with a precise 3D configuration (3D hydrogels) are required for a number of biomedical applications such as tissue engineering and drug delivery. Two-photon polymerization (TPP) is an advanced method to fabricate 3D hydrogels. However, TPP of 3D hydrogels has been challenged by the lack of TPP initiators with high efficiency in aqueous medium. In this study, a water soluble TPP initiator (WI) with high fabrication efficiency was prepared by combining hydrophobic 2,7-bis(2-(4-pentaneoxy-phenyl)-vinyl)anthraquinone (N) with a C2v symmetrical structure and 2-hydroxypropyl-β-cyclodextrins through host–guest chemical interaction. Both one and two-photon optical properties of WI have been investigated. In aqueous medium, WI showed a two-photon absorption cross-section of around 200 GM at the wavelength of 780 nm which was much higher compared with those of commercial initiators. The threshold energy of TPP for the resin with WI as a photoinitiator (the molar ratio of N in resin is 0.03%) was 8.6 mW. 3D hydrogels with a woodpile microstructure were further fabricated by using an average power of 9.7 mW and a scanning speed of 30 μm s−1.

Cationic polymers (polycations) are promising gene vectors that are conveniently synthesized and easily modified. In order to study the relationship between structures and properties of the polycations in gene delivery, a graft copolymer called poly(N-vinylpyrrolidone)-g-poly(2-dimethylaminoethyl methacrylate) (PVP-g-PDMAEMA, i.e. PgP) and a block copolymer called PVP-b-PDMAEMA (PbP) with equal molecular weight of PDMAEMA and PVP were prepared by two advanced living radical polymerization reactions including atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) techniques. Compared with PbP, PgP could condense pDNA more effectively into polyplexes with smaller size, higher zeta potential and better stability. The transfection efficiency of PgP at a low N/P ratio of 4:1 was not only higher than that of PbP, but also much higher than that of the commercially available PEI as the gold standard of polycations and lipofectamine. In addition, both PgP and PbP had less BSA absorption compared with PEI, indicating that PVP could resist BSA absorption. In order to understand the mechanism behind the high transfection efficiency of PgP, cellular uptake and endosomal escape of PgP/pDNA and PbP/pDNA polyplexes were investigated. The results demonstrated that the improvement of the transfection efficiency of PgP originated from the promotion of the cellular uptake and endosome/lysosome escape. This study will provide useful information on designing effective non-viral vectors for gene delivery.

Hydrogels with precise 3D configuration (3D hydrogels) are crucial for biomedical applications such as tissue engineering and drug delivery, which require the improvement of the spatial resolution on both the microscopic and the nanometric scale. In this study, a water soluble two-photon polymerization (TPP) initiator (WI) with high initiating efficiency was prepared by using a poloxamer (PF127) to encapsulate 2,7-bis(2-(4-pentaneoxy-phenyl)-vinyl)anthraquinone via a hydrophilic–hydrophobic assembly. The threshold energy for WI was 6.29 mW at a linear scanning speed of 10 μm s−1, which was much lower than those reported previously. A lateral spatial resolution of 92 nm was achieved as the resolution breakthrough of 3D hydrogels. Finally, the microstructure with high accuracy simulating the morphology of adenovirus was fabricated at the laser power close to the threshold energy of TPP, further demonstrating the ultrahigh resolution of 3D hydrogels.

The low transfection efficiency of polycations is still a major problem for successful gene therapy. To address this issue, in this study, hydrophilic poly(vinyl pyrrolidone)-graft-poly[2-(N,N-dimethylamino)ethyl methacrylate] (PVP-g-PDMAEMA) and amphiphilic poly(vinyl pyrrolidone)-graft-poly[2-(N,N-dimethylamino)ethyl methacrylate]-block-poly(methylmethacrylate) (PVP-g-PDMAEMA-b-PMMA) were synthesized via the atom transfer radical polymerization (ATRP) method, and their properties as gene vectors were investigated subsequently. PVP-g-PDMAEMA formed random coils in water and PVP-g-PDMAEMA-b-PMMA self-assembled into spherical core–shell micelles with a very low critical micelle concentration of only 6.3 × 10−3 mg mL−1. PVP-g-PDMAEMA-b-PMMA/pDNA polyplexes demonstrated an excellent gene transfection efficiency, which showed not only much higher gene transfection efficiency than PVP-g-PDMAEMA/pDNA polyplexes, but obviously surpassed 25k PEI at low N/P ratio around 3 on 293T cell lines. Hence, the results suggested that PVP-g-PDMAEMA-b-PMMA could be a highly efficient gene vector.

The charge-reversal strategy is usually employed in gene delivery to facilitate the endosomal escape of gene carriers and the release of the payload into cytoplasm. However, most of the charge-reversal materials are far from perfect biocompatible materials due to the cytotoxicity of themselves or their hydrolyzed products. In this study, an excellent charge-reversal material named modified bovine serum albumin (mBSA) was prepared. The charge reversal of biocompatible mBSA is a physical process and can instantly occur, which was confirmed by zeta potential, size detection and morphological studies. The introduction of mBSA can not only reduce the zeta potential of binary complexes (pDNA–PEI) but also increase the nuclease resistance ability of the pDNA–PEI binary complexes. In addition, cell viabilities tested by MTT assay and gene transfection assay demonstrated that mBSA can reduce the cytotoxicity of pDNA–PEI polyplexes and improve their gene transfection efficiency (serum free and 10% FBS medium) both in 293T and HepG2 cells at the same time. The experimental results of cell internalization and intracellular distribution of pDNA–PEI–mBSA ternary complexes confirmed that the improvement of transfection efficiency originated from the enhancement of endosomal escape of polyplexes. Therefore, mBSA has been proven to be a perfect charge-reversal platform to simultaneously improve the transfection efficiency and biocompatibility of polyplexes.