Molecular Weight Polyethylenimine Research Articles

Performance Evaluation of High-Strength Polyethyleneimine Gels and Syneresis Mechanism under High-Temperature and High-Salinity Conditions

Summary A high-strength gel was prepared by crosslinking a high-concentration but low molecular weight polyacrylamide-tert-butyl acrylate (PAtBA) copolymer with polyethyleneimine (PEI), and the various factors affecting the gelling were systematically evaluated. The results showed that, besides the concentration of polymer and crosslinker, the molecular weight of PEI, pH value and salinity of gelant, and temperature all affected the gelation time, gel strength, and stability. High-strength PAtBA-PEI gels could be stable for more than 240 days in synthetic brine with salinity less than 43 530 mg/L at a temperature not higher than 130°C. However, when the temperature is higher than 150°C, the gel would be broken within 60 days. When the salinity in the synthetic brine was too high, the gel also exhibited syneresis at 110°C within 15 days. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis showed that the syneresis of PAtBA-PEI gel under high-salinity conditions was caused by the reaction of carboxylate group generated by the hydrolysis of the amide group with divalent cations. In addition, Cryo-scanning electron microscope (Cryo-SEM) analysis showed that high-strength PAtBA-PEI gels had high crosslinking density and poor deformation ability. Nevertheless, the results of rheological tests and flooding experiments showed that the low deformation ability of the gel did not affect the sealing ability of the gel, and the high storage modulus and yield stress of the gel enabled it to exhibit high breakthrough pressure and residual resistance factor in the core. The results of this study are instructive for the field application of PEI gels.

Efficient drug delivery by polyethylenimine capped CdSe/ZnS quantum dots and their biological activity

Quantum dots (QDs) receive widespread attention for delivery of drugs, probing and bio-imaging exploiting their unique properties. Herein, we developed CdSe/ZnS QDs by modified low molecular weight polyethyleneimine (PEI) and conjugated them covalently with anticancer drug 10-hydroxycamptothecin (HCPT) to form a nano-drug delivery system (CdSe/ZnS@PEI-cHCPT). CdSe/ZnS@PEI-cHCPT could efficiently inhibit the proliferation of HeLa as well as other cancer cells. Moreover, CdSe/ZnS@PEI-cHCPT mediated formation of excessive reactive oxygen species (ROS), down regulation of the expression of Bcl-2 protein and up regulation of the expression of P53, Bak and PARP-1 proteins were found to be the molecular mechanisms underlying the effective anti-cancer potential of the nano-drug delivery system. Further, CdSe/ZnS@PEI-cHCPT displayed efficient therapeutic effect in inhibiting tumor growth in mice and had good biosafety and effectively enriched at the tumor site to improve the treatment effect, suggesting their great potential for future biomedical applications.

In Vitro Cytotoxicity and Cytokine Production by Lipid-Substituted Low Molecular Weight Branched PEIs Used for Gene Delivery

Lipid-modified low molecular weight branched polyethyleneimines (PEIs) are promising non-viral gene delivery systems that have been successfully explored for treatment of various diseases. The present study aims to determine in vitro safety of these delivery systems based on assessment of cytotoxicity with peripheral blood mononuclear cells (PBMCs), hemolysis with human red blood cells (RBC) and cytokine secretion from several sources of PBMCs. The viability of cells treated with lipopolymer/pDNA complexes was dependent on the polymer:pDNA ratio used but remained low at therapeutically relevant concentrations for most lipopolymers, except for the propionic acid substituted PEIs. The extent of hemolysis was minimal and below the accepted safety levels with most of the lipopolymers; however, some linoleic acid substituted PEIs yielded significant hemolysis activity. Unlike strong cytokine secretion from PMA/IO stimulated cells, most lipopolymer/pDNA complexes remained non-responsive, showing minimal changes in cytokine secretion (TNF-α, IL-6 and IFN-γ) irrespective of the lipopolymer/pDNA formulations. The 0.6 kDa PEI with lauric acid substituent displayed slight cytokine upregulation, however it remained low relative to the positive controls. This study demonstrated that the lipid modified LMW PEIs are expected to be safe in contact with blood components. However, close attention to lipopolymer concentration and ratio of polymer to pDNA in formulations might be required for individual lipopolymers for optimal safety response in nucleic acid therapies. Statement of significanceThis manuscript investigated the safety aspects of various lipid modified low molecular weight polyethylenimine (LMW-PEI) polymers employed for pDNA delivery through in vitro studies. Using peripheral blood mononuclear cells (PBMCs) from multiple sources, we show that the hemolysis ability was minimal for most polymers, although a particular lipid substituent (linoleic acid) at specific ratios exhibited hemolysis. The levels of pro-inflammatory cytokines (TNF-α, IL-6 and IFN-γ) were slightly upregulated only with a lauric acid substituted 0.6PEI, but remained low relative to positive control treatments. We further report the beneficial effect of polyacrylic acid additives on hemolysis and cytokine secretion to a reasonable extent. This study confirms the feasibility of using LMW-PEI as safe delivery agents for various therapeutic purposes.

Chitosan-Crosslinked Low Molecular Weight PEI-Conjugated Iron Oxide Nanoparticle for Safe and Effective DNA Delivery to Breast Cancer Cells.

Breast cancer has attracted tremendous research interest in treatment development as one of the major threats to public health. The use of non-viral carriers for therapeutic DNA delivery has shown promise in treating various cancer types, including breast cancer, due to their high DNA loading capacity, high cell transfection efficiency, and design versatility. However, cytotoxicity and large sizes of non-viral DNA carriers often raise safety concerns and hinder their applications in the clinic. Here we report the development of a novel nanoparticle formulation (termed NP-Chi-xPEI) that can safely and effectively deliver DNA into breast cancer cells for successful transfection. The nanoparticle is composed of an iron oxide core coated with low molecular weight (800 Da) polyethyleneimine crosslinked with chitosan via biodegradable disulfide bonds. The NP-Chi-xPEI can condense DNA into a small nanoparticle with the overall size of less than 100 nm and offer full DNA protection. Its biodegradable coating of small-molecular weight xPEI and mildly positive surface charge confer extra biocompatibility. NP-Chi-xPEI-mediated DNA delivery was shown to achieve high transfection efficiency across multiple breast cancer cell lines with significantly lower cytotoxicity as compared to the commercial transfection agent Lipofectamine 3000. With demonstrated favorable physicochemical properties and functionality, NP-Chi-xPEI may serve as a reliable vehicle to deliver DNA to breast cancer cells.

TRAIL Therapy for Breast Cancer Treatment by Employing Lipopolymer mRNA Delivery

Promising improvements in synthesis of stable and nonimmunogenic messenger RNA (mRNA) have enhanced the potential for mRNA in in situ production of therapeutic proteins. In this study, we explored the delivery of an mRNA expressing the tumor necrosis factor-related apoptosis-inducing ligand protein (mTRAIL) into breast cancer cells and human bone marrow stromal cells (hBMSCs) by using aliphatic lipid-modified small molecular weight polyethylenimine (PEI) carriers. The duration and extent of TRAIL secretion after mRNA delivery were dependent on the cell type, but mRNA delivery consistently showed earlier and higher protein expression compared with plasmid DNA delivery. Higher TRAIL-induced cytotoxicity and apoptosis induction were evident in breast cancer cells after mTRAIL transfection. In addition, hBMSCs transfected with mTRAIL were able to effectively kill breast cancer cells after coculture. mTRAIL delivery with the lipopolymers resulted in significant inhibition of breast cancer tumor growth in a xenograft model in mice. We conclude that an mRNA-based approach to TRAIL expression is a highly promising approach to retard the growth of breast cancer cells.

Tuning interlayer structure to construct steady dual-crosslinked graphene oxide membranes for desalination of hypersaline brine via pervaporation

Graphene oxide (GO) membranes have shown great potential in desalination. However, it is still a challenge to tune the interlayer structure of GO and suppress its swelling in water to realize superior separation performance and enhance the mechanical stability of membrane. Herein, polyethyleneimine (PEI) with different molecular weight was employed to crosslink GO nanosheets and tune interlayer spacing of lamellar GO membrane for desalination of hypersaline brine by pervaporation (PV). A dual crosslinking structure was performed via electrostatic interaction and covalent bonding between PEI and GO rendering effectively restricted swelling of GO. The interlayer spacing was adjusted by tuning PEI molecular weight and the surface charge of GO membrane was converted to positive to repel ions. The membrane crosslinked with larger PEI (c-GO-PEI 70k) exhibited the most robust structure and showed outstanding PV desalination performance with high water flux of 86.0 kg/m2 h and salt rejection of 99.99% in treating 10 wt% NaCl hypersaline solution at 90 °C. This work provides further understanding of regulating interlayer structure and constructing high-performance GO membranes for PV desalination.

Polyethyleneimine-Enabled Tunable Electrostatic Nanoparticle Assemblies on Ultrathin Protein Nanofibers for Plasmonics-Based Solar Energy Harvesting

Controlled assembly of nanoparticles (NPs) onto ultrathin, protein-based biotemplates was previously achieved mainly through the chemical or genetic engineering of the surface chemistry of the templates. However, not only is this approach tedious and complicated, but also such surface engineering is case-specific and lacks generality. Biotemplates with one type of surface chemistry are only suitable to assemble one or a few types of NPs, and different engineering methods are demanded for different types of nanomaterials. Here, instead of engineering the biotemplates, we developed a simple, universal plug-and-play approach through the engineering of the surface chemistry of NPs. We discovered that coating NPs with short-chain polyethyleneimine (PEI) can lead to the highly efficient and controllable electrostatic assembly of NPs onto unmodified protein-based bionanofibers. The PEI molecular weight played a key role in the NP–biotemplate interaction. Specifically, we found that only low-molecular-weight PEI-coated NPs could be loaded densely onto the bionanofibers, while the high-molecular-weight PEI, which individually carried more charges, only led to low-density NP assembly. Our method is facile and universal in several ways. It can assemble NPs of various compositions, sizes, and surface ligand structures onto different wild-type bionanofibers, including flagella, bacteriophages, and pili, without the hassle of the case-specific surface engineering of the biotemplates. Such 1D nanoparticle assembly has its unique advantage as starting materials in fabricating 3D structured linear plasmonic nanochains with broad optical bands for solar harvesting applications.

Non-viral siRNA transfection of primary mesenchymal stromal cells (MSCs): Assessment of tyrosine-modified PEI and PPI efficacy and biocompatibility

Mesenchymal stromal cells (MSCs) are multipotent cells derived from different sources and able to differentiate into distinct cell lineages. For their possible biomedical application, the “tuning” of MSCs also involves the specific knockdown of defined target genes. A major limitation, however, is the notoriously low transfection efficacy especially of primary MSCs.In this paper, we systemically analyze a large set of tyrosine-modified linear or branched low molecular weight polyethylenimines (PEIs) of different sizes, as well as the tyrosine-modified polypropylenimine dendrimer PPI-G4, for their capacity of non-viral siRNA transfection into umbilical cord-derived MSCs from two different donors. Knockdown efficacies are determined on the molecular level and confirmed in functional assays. Beyond the determination of cell viabilities, acute cytotoxicity, induction of apoptosis/necrosis and mitochondrial membrane alterations are also studied. On the molecular level, caspase activation, ROS induction and genotoxic effects are analyzed.Major differences are observed between the various tyrosine-modified PEIs, with some candidates showing high knockdown efficacy and biocompatibility. PPI-G4-Y dendrimers, however, are identified as most efficient for siRNA transfection into MSCs. PPI-G4-Y/siRNA nanoparticles lead to particularly high gene knockdown, without cytotoxic and genotoxic effects on the cellular and molecular level, and are thus particularly well-suited for the tuning of MSCs.

Zinc(II)-Cyclen Multifunctional Complex Module-Mediated Polycation-Based High-Performance pDNA Vectors.

A kind of novel multifunctional modules based on zinc(II)-coordinative cyclen has been developed, which is utilized to modify low molecular weight polyethylenimine (LMWPEI) obtaining high-performance DNA vectors. A series of in vitro experiments were carried out to explore the performance of the module in improving the key process of gene transfection, such as DNA condensation, serum resistance, cellular uptake, and endosomal escape. The results demonstrate that there is a significant synergistic effect between the functional module and PEI2.5k in the process of breaking through the key barriers of gene transfection. The optimal Zn-PCD mediates 160-fold higher gluciferase activity than commercial transfection reagents PEI25k in ADSC stem cells with more than 90% cell viability and achieves excellent transfection efficiency in diverse cell types, for instance, HepG2 cells, 293T cells, and 293F suspension cells.

Synthesis and Coordination Properties of a Water-Soluble Material by Cross-Linking Low Molecular Weight Polyethyleneimine with Armed Cyclotriveratrilene.

In this study, a full organic and water-soluble material was synthesized by coupling low molecular weight polyethylenimine (PEI-800) with cyclotriveratrilene (CTV). The water-soluble cross-linked polymer contains hydrophobic holes with a high coordination capability towards different organic drug molecules. The coordinating capability towards hydrophilic drugs (doxorubicin, gatifloxacin and sinomenine) and hydrophobic drugs (camptothecin and celastrol) was analyzed in an aqueous medium by using NMR, UV-Vis and emission spectroscopies. The coordination of drug molecules with the armed CTV unit through hydrophobic interactions was observed. In particular, celastrol exhibited more ionic interactions with the PEI moiety of the hosting system. In the case of doxorubicin, the host–guest detachment was induced by the addition of ammonium chloride, suggesting that the intracellular environment can facilitate the release of the drug molecules.

Polydopamine-assisted polyethylenimine grafting melamine foam and the application in wastewater purification

Melamine foam (MF) is a widely used commercial product and exhibits wide applications in many fields ranging from building, transportation to daily chemical product. Recent researches confirm that the special three-dimensional (3D) framework structure of MF can be an ideal substrate to prepare functional materials. In this work, the water-soluble polyethylenimine (PEI) was grafted onto the framework of MF to develop the water purification material toward heavy metal ions removal. The grafting of PEI on MF was achieved with the aids of polydopamine (PDA) coating and epoxy chloropropane (ECH) cross-linking successively. The 3D framework of MF could be well reserved and PEI was homogeneously grafted onto the framework surface. The adsorption capacity of the adsorbent was dependent upon the molecular wight of PEI. Lower PEI molecular weight endowed the adsorbent with better adsorption ability. The maximum adsorption capacity reached 328.95 mg/g, and the adsorbent exhibited extremely high adsorption stability with increasing cycling measurement numbers. Further results showed that the adsorbent also exhibited high reduction ability and induced about 62.5% toxic Cr(VI) to be reduced. This work confirms that the PEI-modified MF sample is a promising adsorbent in the removal of heavy metal ions and it can be used in wastewater treatment.

Dual DNA Transfection Using 1,6-Hexanedithiol-Conjugated Maleimide-Functionalized PU-PEI600 For Gene Correction in a Patient iPSC-Derived Fabry Cardiomyopathy Model.

Non-viral gene delivery holds promises for treating inherited diseases. However, the limited cloning capacity of plasmids may hinder the co-delivery of distinct genes to the transfected cells. Previously, the conjugation of maleimide-functionalized polyurethane grafted with small molecular weight polyethylenimine (PU-PEI600-Mal) using 1,6-hexanedithiol (HDT) could promote the co-delivery and extensive co-expression of two different plasmids in target cells. Herein, we designed HDT-conjugated PU-PEI600-Mal for the simultaneous delivery of CRISPR/Cas9 components to achieve efficient gene correction in the induced pluripotent stem cell (iPSC)-derived model of Fabry cardiomyopathy (FC) harboring GLA IVS4 + 919 G > A mutation. This FC in vitro model recapitulated several clinical FC features, including cardiomyocyte hypertrophy and lysosomal globotriaosylceramide (Gb3) deposition. As evidenced by the expression of two reporter genes, GFP and mCherry, the addition of HDT conjugated two distinct PU-PEI600-Mal/DNA complexes and promoted the co-delivery of sgRNA/Cas9 and homology-directed repair DNA template into target cells to achieve an effective gene correction of IVS4 + 919 G > A mutation. PU-PEI600-Mal/DNA with or without HDT-mediated conjugation consistently showed neither the cytotoxicity nor an adverse effect on cardiac induction of transfected FC-iPSCs. After the gene correction and cardiac induction, disease features, including cardiomyocyte hypertrophy, the mis-regulated gene expressions, and Gb3 deposition, were remarkably rescued in the FC-iPSC-differentiated cardiomyocytes. Collectively, HDT-conjugated PU-PEI600-Mal-mediated dual DNA transfection system can be an ideal approach to improve the concurrent transfection of non-viral-based gene editing system in inherited diseases with specific mutations.

In-Cell Crosslinked Enzymes: Improving Bacillus megaterium whole-cell biocatalyst stability for the decarboxylation of ferulic acid

In-Cell Crosslinked Enzymes (InCLEs) is a procedure to improve the thermal and operational stability of Bacillus megaterium intracellular decarboxylase activity, allowing to obtain enhanced whole-cell biocatalyst to produce 4-vinyl guaiacol (4VG). InCLEs were achieved using a fixed amount of biomass in a two-step procedure: 1) permeation of the membrane cell for reactants diffusion, and 2) intracellular proteins crosslinking. To optimize InCLEs preparation, 7.68 mg of biomass in the presence of different ethanol concentrations (10–50% v/v) were permeated, subsequently, the intracellular proteins were crosslinked with a glutaraldehyde/biomass ratios of 0, 1.63 and 3.26 μmol/mg. At the best conditions (10% v/v ethanol and 1.63 μmol/mg), thermostability increases 4.7-fold against the permeated uncrosslinked biocatalyst (PUCB). To further enhance the stability, the internalization of different molecular weight polyethyleneimine (PEI, 1.09 mg/mL) was evaluated. PEI-InCLEs using 25 kDa PEI, showed a half-life 68-fold higher than PUCB (1 min) at 50 °C. After 7 cycles (26.3 mM ferulic acid, pH 7), PEI-InCLEs retained 83 and 69% of the decarboxylase activity at 40 and 50 °C, producing 32.7 and 29.8 μmol of 4VG, respectively. Here we demonstrated that the InCLEs procedure is an effective strategy to obtain stable whole-cell biocatalysts for the production of high-valued biotechnological molecules.

Therapeutic delivery of siRNA with polymeric carriers to down-regulate STAT5A expression in high-risk B-cell acute lymphoblastic leukemia (B-ALL).

Overexpression and persistent activation of STAT5 play an important role in the development and progression of acute lymphoblastic leukemia (ALL), the most common pediatric cancer. Small interfering RNA (siRNA)-mediated downregulation of STAT5 represents a promising therapeutic approach for ALL to overcome the limitations of current treatment modalities such as high relapse rates and poor prognosis. However, to effectively transport siRNA molecules to target cells, development of potent carriers is of utmost importance to surpass hurdles of delivery. In this study, we investigated the use of lipopolymers as non-viral delivery systems derived from low molecular weight polyethylenimines (PEI) substituted with lauric acid (Lau), linoleic acid (LA) and stearic acid (StA) to deliver siRNA molecules to ALL cell lines and primary samples. Among the lipid-substituted polymers explored, Lau- and LA-substituted PEI displayed excellent siRNA delivery to SUP-B15 and RS4;11 cells. STAT5A gene expression was downregulated (36–92%) in SUP-B15 and (32%) in RS4;11 cells using the polymeric delivery systems, which consequently reduced cell growth and inhibited the formation of colonies in ALL cells. With regard to ALL primary cells, siRNA-mediated STAT5A gene silencing was observed in four of eight patient cells using our leading polymeric delivery system, 1.2PEI-Lau8, accompanied by the significant reduction in colony formation in three of eight patients. In both BCR-ABL positive and negative groups, three of five patients demonstrated marked cell growth inhibition in both MTT and trypan blue exclusion assays using 1.2PEI-Lau8/siRNA complexes in comparison with their control siRNA groups. Three patient samples did not show any positive results with our delivery systems. Differential therapeutic responses to siRNA therapy observed in different patients could result from variable genetic profiles and patient-to-patient variability in delivery. This study supports the potential of siRNA therapy and the designed lipopolymers as a delivery system in ALL therapy.

Photoactive Polyethylenimine-Coated Graphene Oxide Composites for Enhanced Cr(VI) Reduction and Recovery.

The application of positively charged polymers is a common treatment strategy for the sorption and separation of dissolved hexavalent chromium Cr(VI). In particular, polyethylenimine (PEI) has been demonstrated as an effective polymer for Cr treatment due to abundant amine groups and cost-effectiveness. However, PEI as a photoactive polymer has not been previously explored for Cr treatment. Toward this, we demonstrate the significant photoactive potential of PEI for Cr sorption and reduction [to Cr (III)], delineating amine structure-function relationships. Overall, Cr(VI) photoreduction is enhanced dramatically as a function of amine group density. Additionally, among the types of amine groups evaluated, tertiary amines are observed to be the most reactive followed by secondary and primary amines. When PEI is incorporated onto graphene oxide (GO) as a stabilizing scaffold, mass loading of PEI is a key variable for Cr(VI) treatment performance, which is observed to be a function of PEI molecular weight and oxidation extent of GO. Finally, when combined with magnetic nanomaterials, low energy, high efficiency separation, and reuse are demonstrated. For these, sorption-based separation processes maintained excellent performance over five cycles. Taken together, this work demonstrates that PEI can serve as highly effective, multifunctional material coating(s) not only for chromium treatment but potentially for other oxidized aqueous species as well.

Manipulating the solution environment to control the surface roughness of elastin-based polymer coatings

Elastin-like polypeptides (ELP) have been used as a genetically-engineered, biocompatible substitute for elastin. Cell culture coatings prepared using ELP conjugated to low molecular weight polyethyleneimine (PEI) entices cells to form three-dimensional cellular aggregates that mimic their in vivo counterparts. This study seeks to control the deposition of the ELP and ELP-PEI molecules to control the roughness of the final coatings. The two polymers were coated onto three different substrates (glass, polystyrene, tissue-culture polystyrene) and the solution environment was altered by changing the polymer concentration (0.5, 1.0, 1.5 mg/mL) and/or salt concentration (None, 0.2 M phosphate buffered saline) for a total of 36 conditions. Atomic force microscopy (AFM) was used to measure the average roughness (Ra) of the samples and found that ELP coated samples had a higher Ra than their ELP-PEI counterparts. The coatings were tested for stability by performing cell culture media changes every three days for 11 days. AFM showed that the average roughness of the tested samples increased with each media change. To address this, the surfaces were crosslinked using hexamethyl diisocyanate, which minimized the change in surface roughness even when subjected to an intense sonication process. This study provides parameters to achieve elastin-based coatings with controlled roughness that can be used to support stable, long-term in vitro cell culture.

Development of Covalent Chitosan-Polyethylenimine Derivatives as Gene Delivery Vehicle: Synthesis, Characterization, and Evaluation.

There is an increasing interest in cationic polymers as important constituents of non-viral gene delivery vectors. In the present study, we developed a versatile synthetic route for the production of covalent polymeric conjugates consisting of water-soluble depolymerized chitosan (dCS; MW 6–9 kDa) and low molecular weight polyethylenimine (PEI; 2.5 kDa linear, 1.8 kDa branched). dCS-PEI derivatives were evaluated based on their physicochemical properties, including purity, covalent bonding, solubility in aqueous media, ability for DNA condensation, and colloidal stability of the resulting polyplexes. They were complexed with non-integrating DNA vectors coding for reporter genes by simple admixing and assessed in vitro using liver-derived HuH-7 cells for their transfection efficiency and cytotoxicity. Using a rational screening cascade, a lead compound was selected (dCS-Suc-LPEI-14) displaying the best balance of biocompatibility, cytotoxicity, and transfection efficiency. Scale-up and in vivo evaluation in wild-type mice allowed for a direct comparison with a commercially available non-viral delivery vector (in vivo-jetPEI). Hepatic expression of the reporter gene luciferase resulted in liver-specific bioluminescence, upon intrabiliary infusion of the chitosan-based polyplexes, which exceeded the signal of the in vivo jetPEI reference formulation by a factor of 10. We conclude that the novel chitosan-derivative dCS-Suc-LPEI-14 shows promise and potential as an efficient polymeric conjugate for non-viral in vivo gene therapy.

Sustainable Aqueous Phase Separation membranes prepared through mild pH shift induced polyelectrolyte complexation of PSS and PEI

pH shift induced Aqueous phase separation (APS) is a novel and more sustainable water-based approach to create microfiltration, ultrafiltration, and nanofiltration membranes. APS allows for control over membrane pore size and structure in ways analogous to traditional non-solvent induced phase separation (NIPS). Unfortunately, existing APS approaches require extreme pH shifts (from pH 14 to pH 1) to obtain successful membranes, limiting their applicability for large scale production. Here we demonstrate that APS membranes, with tunable pore sizes ranging from ~80 nm to dense nanofiltration type, can be prepared using a mild pH shift (pH 12 to pH 4) based on the complexation of poly(styrene sulfonate) (PSS) and branched polyethyleneimine (PEI) in acetate buffer coagulation baths. The molecular weight of PEI, the concentration and the pH value of the buffer solution, and the concentration of glutaraldehyde cross-linking agent were systematically varied to control and optimize the membrane fabrication conditions. It was found that tight nanofiltration membranes having a molecular weight cut-off of ~200 g mol−1 and excellent salt (97% MgCl2) and micropollutant retentions (~96%) could be prepared alongside ultra/microfiltration type membranes with an average pore size of ~60 nm. These results indicate that APS membranes with tunable pore sizes can be prepared under mild pH conditions with excellent control over separation properties.

Polyethylenimine-modified graphitic carbon nitride nanosheets: a label-free Raman traceable siRNA delivery system.

Since the nanotoxicity of gene delivery carriers has raised world-wide concerns, it is important to trace their intracellular performance, for example via uptake visualization. Here, we develop a novel ultrathin graphitic carbon nitride (g-C3N4) composite nanosystem for label-free Raman-traceable small interfering RNA (siRNA) delivery. Through low molecular weight polyethylenimine (PEI) modifications, these nanosystems can obtain siRNA loading capabilities. The lateral size of the PEI-g-C3N4 composite is around 100-150 nm with a thickness of nearly 0.6 nm. The designed label-free delivery system could avoid possible obstacles associated with artificial labels and it shows cytotoxicity toward cancer cells and good biocompatibility in normal human cells. The label-free PEI-g-C3N4 gene nanocarrier can be directly traced via Raman microscopy, which makes it suitable for intracellular visualization. Intracellular uptake of the self-fluorescent g-C3N4 nanosheets can also be traced via fluorescence imaging. The PEI modified g-C3N4 ultrathin nanosheets possess gene delivery capacity together with unique dual-traceable Raman and fluorescence features. Raman traces not only have higher specificity than fluorescence ones but they can also avoid background noises. Thus, they may replace widely implemented fluorescence tracing. This work could provide a label-free traceable platform for investigating the intracellular performances of gene delivery nanosystems.

High molecular weight polyethylenimine encapsulated into a porous polymer monolithic by one-step polymerization for CO2 capture

A low-cost porous polymer monolithic with a well-interconnected 3D structure and high amino efficiency for CO2 capture.