A review of the developments of characteristics of PEI derivatives for gene delivery applications

Unravelling the essential elements for recombinant adeno-associated virus (rAAV) production in animal cell-based platforms

Recombinant adeno-associated viruses (rAAVs) stand at the forefront of gene therapy applications, holding immense significance for their safe and efficient gene delivery capabilities. The constantly increasing and unmet demand for rAAVs underscores the need for a more comprehensive understanding of AAV biology and its impact on rAAV production. In this literature review, we delved into AAV biology and rAAV manufacturing bioprocesses, unravelling the functions and essentiality of proteins involved in rAAV production. We discuss the interconnections between these proteins and how they affect the choice of rAAV production platform. By addressing existing inconsistencies, literature gaps and limitations, this review aims to define a minimal set of genes that are essential for rAAV production, providing the potential to advance rAAV biomanufacturing, with a focus on minimizing the genetic load within rAAV-producing cells.

Comparing chemical transfection, electroporation, and lentiviral vector transduction to achieve optimal transfection conditions in the Vero cell line

BACKGROUND

Transfection is an important analytical method for studying gene expression in the cellular environment. There are some barriers to efficient DNA transfection in host cells, including circumventing the plasma membrane, escaping endosomal compartmentalization, autophagy, immune sensing pathways, and translocating the nuclear envelope. Therefore, it would be very useful to introduce an optimum transfection approach to achieve a high transfection efficiency in the Vero cell line. The aim of this study was to compare various transfection techniques and introduce a highly efficient method for gene delivery in Vero cells.

METHODS

In the current study, three transfection methods were used, including chemical transfection, electroporation, and lentiviral vector transduction, to obtain the optimum transfection conditions in the Vero cell line. Vero cells were cultured and transfected with chemical transfection reagents, electroporation, or HIV-1-based lentivectors under different experimental conditions. Transfection efficiency was assessed using flow cytometry and fluorescence microscopy to detect GFP-positive cells.

RESULTS

Among the tested methods, TurboFect™ chemical transfection exhibited the highest efficiency. Optimal transfection conditions were achieved using 1 µg DNA and 4 µL TurboFect™ in 6 × 104 Vero cells.

CONCLUSION

TurboFect™, a cationic polymer transfection reagent, demonstrated superior transfection efficiency in Vero cells compared with electroporation and lentivirus particles, and is the optimal choice for chemical transfection in the Vero cell line.

PEI functionalized cell membrane for tumor targeted and glutathione responsive gene delivery

Polyethylenimine (PEI) is a broadly exploited cationic polymer due to its remarkable gene-loading capacity. However, the high cytotoxicity caused by its high surface charge density has been reported in many cell lines, limiting its application significantly. In this study, two different molecular weights of PEI (PEI10k and PEI25k) were crosslinked with red blood cell membranes (RBCm) via disulfide bonds to form PEI derivatives (RMPs) with lower charge density. Furthermore, the targeting molecule folic acid (FA) molecules were further grafted onto the polymers to obtain FA-modified PEI-RBCm copolymers (FA-RMP25k) with tumor cell targeting and glutathione response. In vitro experiments showed that the FA-RMP25k/DNA complex had satisfactory uptake efficiency in both HeLa and 293T cells, and did not cause significant cytotoxicity. Furthermore, the uptake and transfection efficiency of the FA-RMP25k/DNA complex was significantly higher than that of the PEI25k/DNA complex, indicating that FA grafting can increase transfection efficiency by 15 %. These results suggest that FA-RMP25k may be a promising non-viral gene vector with potential applications in gene therapy.

Optimization of Lung Surfactant Coating of siRNA Polyplexes for Pulmonary Delivery

PURPOSE

The aim of this study was to understand how coating with a pulmonary surfactant, namely Alveofact, affects the physicochemical parameters as well as in vitro behavior of polyethylenimine (PEI) polyplexes for pulmonary siRNA delivery.

METHODS

Alveofact-coated polyplexes were prepared at different Alveofact:PEI coating ratios and analyzed in terms of size, PDI and zeta potential as well as morphology by transmission electron microscopy. The biological behavior was evaluated in a lung epithelial cell line regarding cell viability, cellular uptake via flow cytometry and gene downregulation by qRT-PCR. Furthermore, a 3D ALI culture model was established to test the mucus diffusion and cellular uptake by confocal microscopy as well as gene silencing activity by qRT-PCR.

RESULTS

After optimizing the coating process by testing different Alveofact:PEI coating ratios, a formulation with suitable parameters for lung delivery was obtained. In lung epithelial cells, Alveofact-coated polyplexes were well tolerated and internalized. Furthermore, the coating improved the siRNA-mediated gene silencing efficiency. Alveofact-coated polyplexes were then tested on a 3D air-liquid interface (ALI) culture model that, by expressing tight junctions and secreting mucus, resembles important traits of the lung epithelium. Here, we identified the optimal Alveofact:PEI coating ratio to achieve diffusion through the mucus layer while retaining gene silencing activity. Interestingly, the latter underlined the importance of establishing appropriate in vitro models to achieve more consistent results that better predict the in vivo activity.

CONCLUSION

The addition of a coating with pulmonary surfactant to polymeric cationic polyplexes represents a valuable formulation strategy to improve local delivery of siRNA to the lungs.

Nanocarriers for gene delivery to the cardiovascular system

Cardiovascular diseases have posed a great threat to human health. Fortunately, gene therapy holds great promise in the fight against cardiovascular disease (CVD). In gene therapy, it is necessary to select the appropriate carriers to deliver the genes to the target cells of the target organs. There are usually two types of carriers, viral carriers and non-viral carriers. However, problems such as high immunogenicity, inflammatory response, and limited loading capacity have arisen with the use of viral carriers. Therefore, scholars turned their attention to non-viral carriers. Among them, nanocarriers are highly valued because of their easy modification, targeting, and low toxicity. Despite the many successes of gene therapy in the treatment of human diseases, it is worth noting that there are still many problems to be solved in the field of gene therapy for the treatment of cardiovascular diseases. In this review, we give a brief introduction to the common nanocarriers and several common cardiovascular diseases (arteriosclerosis, myocardial infarction, myocardial hypertrophy). On this basis, the application of gene delivery nanocarriers in the treatment of these diseases is introduced in detail.

Second-Generation Polyamidoamine Dendrimer Conjugated with Oligopeptides Can Enhance Plasmid DNA Delivery In Vitro

Poly(amidoamine) (PAMAM) dendrimers have attracted considerable attention in the field of gene therapy due to their flexibility in introducing different functional moieties and reduced toxicity at low generations. However, their transfection efficiency remains a limitation. Therefore, an essential approach for improving their transfection efficiency as gene carriers involves modifying the structure of PAMAM by conjugating functional groups around their surface. In this study, we successfully conjugated an RRHRH oligopeptide to the surface of PAMAM generation 2 (PAMAM G2) to create RRHRH-PAMAM G2. This construction aims to condense plasmid DNA (pDNA) and facilitate its penetration into cell membranes, leading to its promising potential for gene therapy. RRHRH-PAMAM G2/pDNA complexes were smaller than 100 nm and positively charged. Nano-polyplexes can enter the cell and show a high transfection efficiency after 24 h of transfection. The RRHRH-PAMAM G2 was non-toxic to HeLa, NIH3T3, A549, and MDA-MB-231 cell lines. These results strongly suggest that RRHRH-PAMAM G2 holds promise as a gene carrier for gene therapy owing to its biocompatibility and ability to deliver genes to the cell.

3D-bioprintable endothelial cell-laden sacrificial ink for fabrication of microvessel networks

Although various research efforts have been made to produce a vascular-like network structure as scaffolds for tissue engineering, there are still several limitations. Meanwhile, no articles have been published on the direct embedding of cells within a glucose sensitive sacrificial hydrogel followed by three-dimensional (3D) bioprinting to fabricate vascular structures. In this study, the hydrogel composed of reversibly crosslinked poly(ethylene glycol) diacrylate and dithiothreitol with borax and branched polyethylenimine was used as the sacrificial hydrogel to fabricate vascular-like network structure. The component proportion ratio of the sacrificial hydrogel was optimized to achieve proper self-healing, injectable, glucose-sensitive, and 3D printing properties through the balance of boronate ester bond, hydrogen bond, and steric hinderance effect. The endothelial cells (ECs) can be directly embedded into sacrificial hydrogel and then bioprinted through a 110μm nozzle into the neural stem cell (NSC)-laden non-sacrificial hydrogel, forming the customized EC-laden vascularized microchannel (one-step). The EC-laden sacrificial hydrogel was dissolved immediately in the medium while cells kept growing. The ECs proliferated well within the vascularized microchannel structure and were able to migrate to the non-sacrificial hydrogel in one day. ECs and NSCs interacted around the vascularized microchannel to form capillary-like structure and vascular-like structure expressing CD31 in 14 d. The sacrificial hydrogel conveniently prepared from commercially available chemicals through simple mixing can be used in 3D bioprinting to create customized and complex but easily removable vascularized structure for tissue engineering applications.

Highly Selective Fluorescent Sensors: Polyethylenimine Derivatives of Triphenylamine and Coumarin for GTP and ATP Interaction via Fluorescence Lifetime Imaging Microscopy

Chemical derivatives of polyethylenimine (PEI) receptors with either triphenylamine (TPA) or 7-hydroxy-4-methyl-coumarin (Cou) form stable complexes with adenine and guanine nucleotides in water. The host-guest complex modulation is found to be based on noncovalent molecular interactions such as π-π stacking and hydrogen bonding, which are dependent on the aromatic moieties attached to the polyaminic (PEI) backbone. PEI-TPA acts as a chemosensor with a recognition driving force based on aggregation-induced emission (AIE), involving π-π interaction between the nucleic base and TPA. It detects GTP by a chelation enhancement quenching effect of fluorescence (CHEQ) with a measured logarithm stability constant, log β = 7.7. By varying the chemical characteristics of the fluorophore, as in the PEI-Cou system, the driving force for recognition changes from a π-π interaction to an electrostatic interaction. The coumarin derivative detects ATP with a log β value one order of magnitude higher than that for GTP, allowing for the selective recognition of the two nucleotides in a 100% aqueous solution. Furthermore, fluorescence lifetime imaging microscopy (FLIM) allows for a correlation between the selectivity of PEI-TPA toward nucleotides and the morphology of the structures formed upon ATP and GTP recognition. This study offers valuable insights into the design of receptors for the selective recognition of nucleotides in water.

Synergistically enhanced cancer immunotherapy by combining protamine-based nanovaccine with PD-L1 gene silence nanoparticle

Tumor vaccine has brought a new dawn for cancer immunotherapy, but disillusionary therapeutic outcomes have been achieved due to the inefficient in vivo vaccine delivery. Moreover, tumor cells customarily resort to various wily tricks to circumvent the recognition and sweeping of the immune system, the immune escape effect has badly aggravated the difficulty of cancer management. With respect to the foregoing, in this study, a promising combinational strategy which cooperated nanovaccine with immune escape inhibition was developed for synergistically enhancing the oncotherapy efficiency. On the one hand, natural polycationic macromolecule protamine (PRT) was utilized as the carrier to construct an antigen and adjuvant co-packaged nanovaccine for facilitating the ingestion in antigen-presenting cells, amplifying antigen cross-presentation and optimizing in vivo delivery. On the other hand, PD-L1 silence gene was selected and hitchhiked in a pH-responsive nanoparticle developed in our previous study. The therapeutic gene could be successfully delivered into the tumors to down-regulate PD-L1 expression and cripple tumor immune escape. The combination of nanovaccine with PD-L1 gene silence nanoparticle could synchronously stimulate antitumor immune responses and reduce immune escape, synergistically enhance the therapeutic efficiency. This study will furnish the prospective tactics for the research of cancer immunotherapy.

Mesoporous Silica Nanoparticles as a Gene Delivery Platform for Cancer Therapy

Cancer remains a major global health challenge. Traditional chemotherapy often results in side effects and drug resistance, necessitating the development of alternative treatment strategies such as gene therapy. Mesoporous silica nanoparticles (MSNs) offer many advantages as a gene delivery carrier, including high loading capacity, controlled drug release, and easy surface functionalization. MSNs are biodegradable and biocompatible, making them promising candidates for drug delivery applications. Recent studies demonstrating the use of MSNs for the delivery of therapeutic nucleic acids to cancer cells have been reviewed, along with their potential as a tool for cancer therapy. The major challenges and future interventions of MSNs as gene delivery carriers for cancer therapy are discussed.

Preclinical developments in the delivery of protein antigens for vaccination

INTRODUCTION

Vaccine technology has constantly advanced since its origin. One of these advancements is where purified parts of a pathogen are used rather than the whole pathogen. Subunit vaccines have no chance of causing disease; however, alone these antigens are often poorly immunogenic. Therefore, they can be paired with immune stimulating adjuvants. Further, subunits can be combined with delivery strategies such as nano/microparticles to enrich their delivery to organs and cells of interest as well as protect them from in vivo degradation. Here, we seek to highlight some of the more promising delivery strategies for protein antigens.

AREAS COVERED

We present a brief description of the different types of vaccines, clinically relevant examples, and their disadvantages when compared to subunit vaccines. Also, specific preclinical examples of delivery strategies for protein antigens.

EXPERT OPINION

Subunit vaccines provide optimal safety given that they have no risk of causing disease; however, they are often not immunogenic enough on their own to provide protection. Advanced delivery systems are a promising avenue to increase the immunogenicity of subunit vaccines, but scalability and stability can be improved. Further, more research is warranted on systems that promote a mucosal immune response to provide better protection against infection.

Polymer-Based mRNA Delivery Strategies for Advanced Therapies

Messenger RNA (mRNA)-based therapies offer great promise for the treatment of a variety of diseases. In 2020, two FDA approvals of mRNA-based vaccines have elevated mRNA vaccines to global recognition. However, the therapeutic capabilities of mRNA extend far beyond vaccines against infectious diseases. They hold potential for cancer vaccines, protein replacement therapies, gene editing therapies, and immunotherapies. For realizing such advanced therapies, it is crucial to develop effective carrier systems. Recent advances in materials science have led to the development of promising nonviral mRNA delivery systems. In comparison to other carriers like lipid nanoparticles, polymer-based delivery systems often receive less attention, despite their unique ability to carefully tune their chemical features to promote mRNA protection, their favorable pharmacokinetics, and their potential for targeting delivery. In this review, the central features of polymer-based systems for mRNA delivery highlighting the molecular design criteria, stability, and biodistribution are discussed. Finally, the role of targeting ligands for the future of RNA therapies is analyzed.

Delivery of Therapeutic Biopolymers Employing Silica-Based Nanosystems

The use of nanoparticles is crucial for the development of a new generation of nanodevices for clinical applications. Silica-based nanoparticles can be tailored with a wide range of functional biopolymers with unique physicochemical properties thus providing several advantages: (1) limitation of interparticle interaction, (2) preservation of cargo and particle integrity, (3) reduction of immune response, (4) additional therapeutic effects and (5) cell targeting. Therefore, the engineering of advanced functional coatings is of utmost importance to enhance the biocompatibility of existing biomaterials. Herein we will focus on the most recent advances reported on the delivery and therapeutic use of silica-based nanoparticles containing biopolymers (proteins, nucleotides, and polysaccharides) with proven biological effects.

Synthesis and Evaluation of Poly(3-hydroxypropyl Ethylene-imine) and Its Blends with Chitosan Forming Novel Elastic Films for Delivery of Haloperidol

This study aimed to develop novel elastic films based on chitosan and poly(3-hydroxypropyl ethyleneimine) or P3HPEI for the rapid delivery of haloperidol. P3HPEI was synthesized using a nucleophilic substitution reaction of linear polyethyleneimine (L-PEI) with 3-bromo-1-propanol. ¹H-NMR and FTIR spectroscopies confirmed the successful conversion of L-PEI to P3HPEI, and the physicochemical properties and cytotoxicity of P3HPEI were investigated. P3HPEI had good solubility in water and was significantly less toxic than the parent L-PEI. It had a low glass transition temperature (T_g = -38.6 °C). Consequently, this new polymer was blended with chitosan to improve mechanical properties, and these materials were used for the rapid delivery of haloperidol. Films were prepared by casting from aqueous solutions and then evaporating the solvent. The miscibility of polymers, mechanical properties of blend films, and drug release profiles from these formulations were investigated. The blends of chitosan and P3HPEI were miscible in the solid state and the inclusion of P3HPEI improved the mechanical properties of the films, producing more elastic materials. A 35:65 (%w/w) blend of chitosan-P3HPEI provided the optimum glass transition temperature for transmucosal drug delivery and so was selected for further investigation with haloperidol, which was chosen as a model hydrophobic drug. Microscopic and X-ray diffractogram (XRD) data indicated that the solubility of the drug in the films was ~1.5%. The inclusion of the hydrophilic polymer P3HPEI allowed rapid drug release within ~30 min, after which films disintegrated, demonstrating that the formulations are suitable for application to mucosal surfaces, such as in buccal drug delivery. Higher release with increasing drug loading allows flexible dosing. Blending P3HPEI with chitosan thus allows the selection of desirable physicochemical and mechanical properties of the films for delivery of haloperidol as a poorly water-soluble drug.

Biocompatible Iron Oxide Nanoring-Labeled Mesenchymal Stem Cells: An Innovative Magnetothermal Approach for Cell Tracking and Targeted Stroke Therapy

Labeling stem cells with magnetic nanoparticles is a promising technique for in vivo tracking and magnetic targeting of transplanted stem cells, which is critical for improving the therapeutic efficacy of cell therapy. However, conventional endocytic labeling with relatively poor labeling efficiency and a short labeling lifetime has hindered the implementation of these innovative enhancements in stem-cell-mediated regenerative medicine. Herein, we describe an advanced magnetothermal approach to label mesenchymal stem cells (MSCs) efficiently by local induction of heat-enhanced membrane permeability for magnetic resonance imaging (MRI) tracking and targeted therapy of stroke, where biocompatible γ-phase, ferrimagnetic vortex-domain iron oxide nanorings (γ-FVIOs) with superior magnetoresponsive properties were used as a tracer. This approach facilitates a safe and efficient labeling of γ-FVIOs as high as 150 pg of Fe per cell without affecting the MSCs proliferation and differentiation, which is 3.44-fold higher than that by endocytosis labeling. Such a high labeling efficiency not only enables the ultrasensitive magnetic resonance imaging (MRI) detection of sub-10 cells and long-term tracking of transplanted MSCs over 10 weeks but also endows transplanted MSCs with a magnetic manipulation ability in vivo. A proof-of-concept study using a rat stroke model showed that the labeled MSCs facilitated MRI tracking and magnetic targeting for efficient replacement therapy with a significantly reduced dosage of 5 × 10⁴ transplanted cells. The findings in this study have demonstrated the great potential of the magnetothermal approach as an efficient labeling technique for future clinical usage.

Advances in CRISPR Delivery Methods: Perspectives and Challenges

With the advent of new genome editing technologies and the emphasis placed on their optimization, the genetic and phenotypic correction of a plethora of diseases sit on the horizon. Ideally, genome editing approaches would provide long-term solutions through permanent disease correction instead of simply treating patients symptomatically. Although various editing machinery options exist, the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas (CRISPR-associated protein) editing technique has emerged as the most popular due to its high editing efficiency, simplicity, and affordability. However, while CRISPR technology is gradually being perfected, optimization is futile without accessible, effective, and safe delivery to the desired cell or tissue. Therefore, it is important that scientists simultaneously focus on inventing and improving delivery modalities for editing machinery as well. In this review, we will discuss the critical details of viral and nonviral delivery systems, including payload, immunogenicity, efficacy in delivery, clinical application, and future directions.

In Situ Transformation of Electrospun Nanofibers into Nanofiber-Reinforced Hydrogels

Nanofiber-reinforced hydrogels have recently gained attention in biomedical engineering. Such three-dimensional scaffolds show the mechanical strength and toughness of fibers while benefiting from the cooling and absorbing properties of hydrogels as well as a large pore size, potentially aiding cell migration. While many of such systems are prepared by complicated processes where fibers are produced separately to later be embedded in a hydrogel, we here provide proof of concept for a one-step solution. In more detail, we produced core-shell nanofibers from the natural proteins zein and gelatin by coaxial electrospinning. Upon hydration, the nanofibers were capable of directly transforming into a nanofiber-reinforced hydrogel, where the nanofibrous structure was retained by the zein core, while the gelatin-based shell turned into a hydrogel matrix. Our nanofiber-hydrogel composite showed swelling to ~800% of its original volume and water uptake of up to ~2500% in weight. The physical integrity of the nanofiber-reinforced hydrogel was found to be significantly improved in comparison to a hydrogel system without nanofibers. Additionally, tetracycline hydrochloride was incorporated into the fibers as an antimicrobial agent, and antimicrobial activity against Staphylococcus aureus and Escherichia coli was confirmed.

Stimuli-Responsive Thiomorpholine Oxide-Derived Polymers with Tailored Hydrophilicity and Hemocompatible Properties

Thermo-responsive hydrophilic polymers, including those showing tuneable lower critical solution temperature (LCST), represent a continuous subject of exploration for a variety of applications, but particularly in nanomedicine. Since biological pH changes can inform the organism about the presence of disequilibrium or diseases, the development of dual LCST/pH-responsive hydrophilic polymers with biological potential is an attractive subject in polymer science. Here, we present a novel polymer featuring LCST/pH double responsiveness. The monomer ethylthiomorpholine oxide methacrylate (THOXMA) can be polymerised via the RAFT process to obtain well-defined polymers. Copolymers with hydroxyethyl methacrylate (HEMA) were prepared, which allowed the tuning of the LCST behaviour of the polymers. Both, the LCST behaviour and pH responsiveness of hydrophilic PTHOXMA were tested by following the evolution of particle size by dynamic light scattering (DLS). In weak and strong alkaline conditions, cloud points ranged between 40–60 °C, while in acidic medium no LCST was found due to the protonation of the amine of the THOX moieties. Additional cytotoxicity assays confirmed a high biocompatibility of PTHOXMA and haemolysis and aggregation assays proved that the thiomorpholine oxide-derived polymers did not cause aggregation or lysis of red blood cells. These preliminary results bode well for the use of PTHOXMA as smart material in biological applications.

Dually Active Polycation/miRNA Nanoparticles for the Treatment of Fibrosis in Alcohol-Associated Liver Disease

Alcohol-associated liver disease (AALD) is a major cause of liver disorders worldwide. Current treatment options are limited, especially for AALD-associated fibrosis. Promising approaches include RNA interference for miR-155 overexpression in Kupffer cells (KCs), as well as the use of CXCR4 antagonists that inhibit the activation of hepatic stellate cells (HSCs) through the CXCL12/CXCR4 axis. The development of dual-functioning nanoparticles for the effective delivery of antifibrotic RNA together with a CXCR4 inhibitor thus promises to improve the treatment of AALD fibrosis. In this study, cholesterol-modified polymeric CXCR4 inhibitor (Chol-PCX) was synthesized and used to encapsulate anti-miR-155 or non-coding (NC) miRNA in the form of Chol-PCX/miRNA nanoparticles. The results indicate that the nanoparticles induce a significant miR-155 silencing effect both in vitro and in vivo. Treatment with the Chol-PCX/anti-miR-155 particles in a model of moderate alcohol consumption with secondary liver insult resulted in a significant reduction in aminotransferase enzymes as well as collagen content in the liver parenchyma. Overall, our data support the use of Chol-PCX as a carrier for anti-miR-155 for the combined therapeutic inhibition of CXCR4 and miR-155 expression as a way to improve fibrotic damage in the liver.

Messenger RNA-Based Vaccines Against Infectious Diseases

In vitro-transcribed, messenger RNA-based infectious disease vaccines have the potential to successfully address many of the weaknesses of traditional vaccine platforms, such as the lack of potency and/or durability of vaccine protection, time-consuming, and expensive manufacturing, and, in some cases, safety issues. This optimism is fueled by a great deal of impressive recent data demonstrating that mRNA vaccines have many of the attributes that are necessary for a viable new vaccine class for human use. This review briefly describes mRNA vaccine types, discusses the most relevant and recent publications on infectious disease mRNA vaccines, and highlights the hurdles that need to be overcome to bring this promising novel vaccine modality to the clinic.

Stochasticity of poly(2-oxazoline) oligomer hydrolysis determined by tandem mass spectrometry

Understanding modification of synthetic polymer structures is necessary for their accurate synthesis and potential applications. In this contribution, a series of partially hydrolyzed poly(2-oxazoline) species were produced forming poly[(2-polyoxazoline)-co-(ethylenimine)] (P(EtOx-co-EI)) copolymers; EI being the hydrolyzed product of Ox. Bulk mass spectrometry (MS) measurements accurately measured the EI content. Tandem mass spectrometry analysis of the EI content in the copolymer samples determined the distribution of each monomer within the copolymer and corresponded to a theoretically modelled random distribution. The EI distribution across the polymers was shown to be effected by the choice of terminus, with a permanent hydrolysis event observed at an OH terminus. A neighbouring group effect wasn't observed at the polymer length analysed (approximately 25-mer species), suggesting that previously observed neighbouring group effects require a larger polymer chain. Although clearly useful for random polymer distribution this approach may be applied to many systems containing non-specific modifications to determine if they are directed or random locations across peptides, proteins, polymers, and nucleic acids.

Tandem mass spectrometry can be used to better understand modification sites of synthetic polymer structures providing more complete chemical knowledge which is necessary for their accurate synthesis and potential applications.

Calcium-based nanomaterials and their interrelation with chitosan: optimization for pCRISPR delivery

There have been numerous advancements in the early diagnosis, detection, and treatment of genetic diseases. In this regard, CRISPR technology is promising to treat some types of genetic issues. In this study, the relationship between calcium (due to its considerable physicochemical properties) and chitosan (as a natural linear polysaccharide) was investigated and optimized for pCRISPR delivery. To achieve this, different forms of calcium, such as calcium nanoparticles (CaNPs), calcium phosphate (CaP), a binary blend of calcium and chitosan including CaNPs/Chitosan and CaP/Chitosan, as well as their tertiary blend including CaNPs-CaP/Chitosan, were prepared via both routine and green procedures using Salvia hispanica to reduce toxicity and increase nanoparticle stability (with a yield of 85%). Such materials were also applied to the human embryonic kidney (HEK-293) cell line for pCRISPR delivery. The results were optimized using different characterization techniques demonstrating acceptable binding with DNA (for both CaNPs/Chitosan and CaNPs-CaP/Chitosan) significantly enhancing green fluorescent protein (EGFP) (about 25% for CaP/Chitosan and more than 14% for CaNPs-CaP/Chitosan).

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40097-021-00446-1.

Polyglutamine-Specific Gold Nanoparticle Complex Alleviates Mutant Huntingtin-Induced Toxicity

Huntington's disease (HD) belongs to protein misfolding disorders associated with polyglutamine (polyQ)-rich mutant huntingtin (mHtt) protein inclusions. Currently, it is indicated that the aggregation of polyQ-rich mHtt participates in neuronal toxicity and dysfunction. Here, we designed and synthesized a polyglutamine-specific gold nanoparticle (AuNP) complex, which specifically targeted mHtt and alleviated its toxicity. The polyglutamine-specific AuNPs were prepared by decorating the surface of AuNPs with an amphiphilic peptide (JLD1) consisting of both polyglutamine-binding sequences and negatively charged sequences. By applying the polyQ aggregation model system, we demonstrated that AuNPs-JLD1 dissociated the fibrillary aggregates from the polyQ peptide and reduced its β-sheet content in a concentration-dependent manner. By further integrating polyethyleneimine (PEI) onto AuNPs-JLD1, we generated a complex (AuNPs-JLD1-PEI). We showed that this complex could penetrate cells, bind to cytosolic mHtt proteins, dissociate mHtt inclusions, reduce mHtt oligomers, and ameliorate mHtt-induced toxicity. AuNPs-JLD1-PEI was also able to be transported to the brain and improved the functional deterioration in the HD Drosophila larva model. Our results revealed the feasibility of combining AuNPs, JLD1s, and cell-penetrating polymers against mHtt protein aggregation and oligomerization, which hinted on the early therapeutic strategies against HD.

Design of Polymeric Carriers for Intracellular Peptide Delivery in Oncology Applications

In recent decades, peptides, which can possess high potency, excellent selectivity, and low toxicity, have emerged as promising therapeutics for cancer applications. Combined with an improved understanding of tumor biology and immuno-oncology, peptides have demonstrated robust antitumor efficacy in preclinical tumor models. However, the translation of peptides with intracellular targets into clinical therapies has been severely hindered by limitations in their intrinsic structure, such as low systemic stability, rapid clearance, and poor membrane permeability, that impede intracellular delivery. In this Review, we summarize recent advances in polymer-mediated intracellular delivery of peptides for cancer therapy, including both therapeutic peptides and peptide antigens. We highlight strategies to engineer polymeric materials to increase peptide delivery efficiency, especially cytosolic delivery, which plays a crucial role in potentiating peptide-based therapies. Finally, we discuss future opportunities for peptides in cancer treatment, with an emphasis on the design of polymer nanocarriers for optimized peptide delivery.

Recent Advances in the Delivery Carriers and Chemical Conjugation Strategies for Nucleic Acid Drugs

With the development of new anticancer medicines, novel modalities are being explored for cancer treatment. For many years, conventional modalities, such as small chemical drugs and antibody drugs, have worked by "inhibiting the function" of target proteins. In recent years, however, nucleic acid drugs, such as ASOs and siRNAs, have attracted attention as a new modality for cancer treatment because nucleic acid drugs can directly promote the "loss of function" of target genes. Recently, nucleic acid drugs for use in cancer therapy have been extensively developed and some of them have currently been under investigation in clinical trials. To develop novel nucleic acid drugs for cancer treatment, it is imperative that cancer researchers, including ourselves, cover and understand those latest findings. In this review, we introduce and provide an overview of various DDSs and ligand modification technologies that are being employed to improve the success and development of nucleic acid drugs, then we also discuss the future of nucleic acid drug developments for cancer therapy. It is our belief this review will increase the awareness of nucleic acid drugs worldwide and build momentum for the future development of new cancer-targeted versions of these drugs.

Delivery of antisense oligonucleotides using multi-layer coated gold nanoparticles to methicillin-resistant S. aureus for combinatorial treatment

The spread of multidrug-resistant (MDR) bacterial infections has become a serious global threat. We introduce multi-layer coated gold nanoparticles (MLGNPs) delivering antisense oligonucleotides (ASOs) targeting the resistance gene of methicillin-resistant Staphylococcus aureus (MRSA), as a selective antimicrobial by restoring susceptibility. MLGNPs were prepared by multi-step surface immobilization of gold nanoparticles (GNPs) with polyethylenimine (PEI) and loaded with ASO targeting the mecA gene. The MLGNPs were shown to be efficiently internalized into various types of Gram-positive bacteria, including MRSA, Staphylococcus epidermidis, and Bacillus subtilis, which was superior to single-layer coated GNPs and free PEI polymer. The delivery of MLGNPs into MRSA resulted in up to 74% silencing of the mecA gene with high selectivity, in a dose-dependent manner. The treatment of MLGNPs to MRSA in the presence of oxacillin, a beta-lactam antibiotic, showed major suppression (~71%) of bacterial growth, due to the recovery of antibacterial sensitivity. Furthermore, the treatment of MLGNPs in a complex system showed preferential uptake into bacteria over mammalian cells, demonstrating the suitable characteristics of MLGNPs for selective delivery into bacteria. The current approach can be potentially applied for targeting various types of MDR bacterial infections by specific silencing of a resistance gene, as a combinatorial therapeutic used with conventional antibiotics.

Disaccharide-polyethylenimine organic nanoparticles as non-toxic in vitro gene transporters and their anticancer potential

Polyethylenimines (PEIs) have been shown as efficient gene delivery vectors due to their unique properties, however, toxicity as well as non-specific interactions with the tissues/cells because of high charge density have hampered their use in clinical applications. To counter these concerns, here, we have prepared disachharide-PEI organic nanoparticles by mixing PEIs with non-reducing disaccharides, i.e. trehalose (TPONs) and sucrose (SPONs), under mild conditions. The fabricated nanoparticles were complexed with pDNA and size of these complexes was found in the range of ~130-162 nm with zeta potential ~ +8-25 mV. Further evaluation of these nanoparticles revealed that substitution of disaccharides on PEIs successfully augmented cell viability. Transfection efficiency exhibited by these complexes was significantly higher than the unmodified polymer and the standard, Lipofectamine, complexes. Fabrication of organic nanoparticles did not alter the buffering capacity considerably which was found to be instrumental during endosomal escape of the complexes. Among both the series of nanoparticles, trehalose-PEI organic nanoparticles (TPONs) exhibited greater pDNA transportation potential than sucrose-PEI organic nanoparticles (SPONs) which was also established by flow cytometric data, wherein percent cells expressing GFP was higher in case of TP/pDNA complexes as compared to SP/pDNA complexes. Interestingly, TPONs also showed promising anticancer activity on cancer cell lines i.e. Mg63, MCF-7 and HepG2. Overall, the results advocate promising potential of disaccharide-PEI organic nanoparticles as efficient gene delivery agents which can be used effectively in future gene therapy applications along with anti-cancer competence of TPONs.

Chemical and physical Chitosan modification for designing enzymatic industrial biocatalysts: How to choose the best strategy?

Chitosan is one of the most abundant natural polymer worldwide, and due to its inherent characteristics, its use in industrial processes has been extensively explored. Because it is biodegradable, biocompatible, non-toxic, hydrophilic, cheap, and has good physical-chemical stability, it is seen as an excellent alternative for the replacement of synthetic materials in the search for more sustainable production methodologies. Thus being, a possible biotechnological application of Chitosan is as a direct support for enzyme immobilization. However, its applicability is quite specific, and to overcome this issue, alternative pretreatments are required, such as chemical and physical modifications to its structure, enabling its use in a wider array of applications. This review aims to present the topic in detail, by exploring and discussing methods of employment of Chitosan in enzymatic immobilization processes with various enzymes, presenting its advantages and disadvantages, as well as listing possible chemical modifications and combinations with other compounds for formulating an ideal support for this purpose. First, we will present Chitosan emphasizing its characteristics that allow its use as enzyme support. Furthermore, we will discuss possible physicochemical modifications that can be made to Chitosan, mentioning the improvements obtained in each process. These discussions will enable a comprehensive comparison between, and an informed choice of, the best technologies concerning enzyme immobilization and the application conditions of the biocatalyst.

Phenolic-enabled nanotechnology: versatile particle engineering for biomedicine

Phenolics are ubiquitous in nature and have gained immense research attention because of their unique physiochemical properties and widespread industrial use. In recent decades, their accessibility, versatile reactivity, and relative biocompatibility have catalysed research in phenolic-enabled nanotechnology (PEN) particularly for biomedical applications which have been a major benefactor of this emergence, as largely demonstrated by polydopamine and polyphenols. Therefore, it is imperative to overveiw the fundamental mechanisms and synthetic strategies of PEN for state-of-the-art biomedical applications and provide a timely and comprehensive summary. In this review, we will focus on the principles and strategies involved in PEN and summarize the use of the PEN synthetic toolkit for particle engineering and the bottom-up synthesis of nanohybrid materials. Specifically, we will discuss the attractive forces between phenolics and complementary structural motifs in confined particle systems to synthesize high-quality products with controllable size, shape, composition, as well as surface chemistry and function. Additionally, phenolic's numerous applications in biosensing, bioimaging, and disease treatment will be highlighted. This review aims to provide guidelines for new scientists in the field and serve as an up-to-date compilation of what has been achieved in this area, while offering expert perspectives on PEN's use in translational research.

A Cationic Metal-Organic Framework to Scavenge Cell-Free DNA for Severe Sepsis Management

Circulating cell-free DNA (cfDNA) released by damaged cells causes inflammation and has been associated with the progression of sepsis. One proposed strategy to treat sepsis is to scavenge this inflammatory circulating cfDNA. Here, we develop a cfDNA-scavenging nanoparticle (NP) that consists of cationic polyethylenimine (PEI) of different molecular weight grafted to zeolitic imidazolate framework-8 (PEI-g-ZIF) in a simple one-pot process. PEI-g-ZIF NPs fabricated using PEI 1800 and PEI 25k but not PEI 600 suppressed cfDNA-induced TLR activation and subsequent nuclear factor kappa B pathway activity. PEI 1800-g-ZIF NPs showed greater inhibition of cfDNA-associated inflammation and multiple organ injury than naked PEI 1800 (lacking ZIF), and had greater therapeutic efficacy in treating sepsis. These results indicate that PEI-g-ZIF NPs acts as a "nanotrap" that improves upon naked PEI in scavenging circulating cfDNA, reducing inflammation, and reversing the progression of sepsis, thus providing a novel strategy for sepsis treatment.

Hybrid Nanosystems for Biomedical Applications

Inorganic/organic hybrid nanosystems have been increasingly developed for their versatility and efficacy at overcoming obstacles not readily surmounted by nonhybridized counterparts. Currently, hybrid nanosystems are implemented for gene therapy, drug delivery, and phototherapy in addition to tissue regeneration, vaccines, antibacterials, biomolecule detection, imaging probes, and theranostics. Though diverse, these nanosystems can be classified according to foundational inorganic/organic components, accessory moieties, and architecture of hybridization. Within this Review, we begin by providing a historical context for the development of biomedical hybrid nanosystems before describing the properties, synthesis, and characterization of their component building blocks. Afterward, we introduce the architectures of hybridization and highlight recent biomedical nanosystem developments by area of application, emphasizing hybrids of distinctive utility and innovation. Finally, we draw attention to ongoing clinical trials before recapping our discussion of hybrid nanosystems and providing a perspective on the future of the field.

Peptide-Modified Biopolymers for Biomedical Applications

Polymeric biomaterials have been used in a variety of applications, like cargo delivery and tissue scaffolding, because they are easily synthesized and can be adapted to many systems. However, there is still a need to further enhance and improve their functions to progress their use in the biomedical field. A promising solution is to modify the polymer surfaces with peptides that can increase biocompatibility, cellular interactions, and receptor targeting. In recent years, peptide modifications have been used to overcome many challenges to polymer biomaterial development. This review discusses recent progress in developing peptide-modified polymers for therapeutic applications including cell-specific targeting and tissue engineering. Furthermore, we will explore some of the most frequently studied base components of these biomaterials.

Redox stimulus disulfide conjugated polyethyleneimine as a shuttle for gene transfer

Redox-responsive cationic polymers have gained considerable attention in gene delivery due to low cytotoxicity and spatio-temporal release of DNA into the cells. Here, we reported the synthesis of reducible disulfide conjugated polyethyleneimine (1.8 kDa) (denoted as SS-PEI) and its application to transfer pEGFP-ZNF580 plasmid (pZNF580) into EA.hy926 cell. This reducible SS-PEI polymer was prepared by one-step polycondensation reaction of low molecular weight PEI with bis-(p-nitrophenyl)-3,3'-dithiodipropionate. The SS-PEI successfully condensed pZNF580 into nano-sized complexes (170 ± 1.5 nm to 255 ± 1.6 nm) with zeta potentials of 3 ± 0.4 mV to 17 ± 0.9 mV. The complexes could be triggered to release pZNF580 when exposed to the reducing environment of 5 mM dithiothreitol. Besides, the SS-PEI exhibited low cytotoxicity. In vitro transfection results showed that SS-PEI exhibited good transfection efficiency comparable to PEI25kDa. Thus, the SS-PEI could act as an reducible gene carrier with good transfection efficiency and low cytotoxicity.

ZnAl nano layered double hydroxides for dual functional CRISPR/Cas9 delivery and enhanced green fluorescence protein biosensor

Evaluation of the effect of different parameters for designing a non-viral vector in gene delivery systems has great importance. In this manner, 2D crystals, precisely layered double hydroxides, have attracted the attention of scientists due to their significant adjustability and low-toxicity and low-cost preparation procedure. In this work, the relationship between different physicochemical properties of LDH, including pH, size, zeta potential, and synthesis procedure, was investigated and optimized for CRISPR/Cas9 delivery and reverse fluorescence response to the EGFP. In this manner, ZnAl LDH and ZnAl HMTA LDH were synthesized and characterized and applied in the HEK-293 cell line to deliver CRISPR/Cas9. The results were optimized by different characterizations as well as Gel Electrophoresis and showed acceptable binding ability with the DNA that could be considered as a promising and also new gold-standard for the delivery of CRISPR/Cas9. Also, the relationship of the presence of tertiary amines (in this case, hexamethylenetetramine (HMTA) as the templates) in the structure of the ZnAl LDH, as well as the gene delivery application, was evaluated. The results showed more than 79% of relative cell viability in most of the weight ratios of LDH to CRISPR/Cas9; fully quenching the fluorescence intensity of the EGFP/LDH in the presence of 15 µg mL-1 of the protoporphyrins along with the detection limit of below 2.1 µg mL-1, the transfection efficiency of around 33% of the GFP positive cell for ZnAl LDH and more than 38% for the ZnAl LDH in the presence of its tertiary amine template.

Off the beaten path: Novel mRNA-nanoformulations for therapeutic vaccination against HIV

Over the last few years, immunotherapy for HIV in general and therapeutic vaccination in particular, has received a tremendous boost, both in preclinical research and in clinical applications. This interest is based on the evidence that the immune system plays a crucial role in controlling HIV infection, as shown for long-term non-progressors and elite controllers, and that immune responses can be manipulated towards targeting conserved epitopes. So far, the most successful approach has been vaccination with autologous dendritic cells (DCs) loaded ex vivo with antigens and activation signals. Although this approach offers much promise, it also comes with significant drawbacks such as the requirement of a specialized infrastructure and expertise, as well as major challenges for logistics and storage, making it extremely time consuming and costly. Therefore, methods are being developed to avoid the use of ex vivo generated, autologous DCs. One of these methods is based on mRNA for therapeutic vaccination. mRNA has proven to be a very promising vaccine platform, as the coding information for any desired protein, including antigens and activation signals, can be generated in a very short period of time, showing promise both as an off-the-shelf therapy and as a personalized approach. However, an important drawback of this approach is the short half-life of native mRNA, due to the presence of ambient RNases. In addition, proper immunization requires that the antigens are expressed, processed and presented at the right immunological site (e.g. the lymphoid tissues). An ambivalent aspect of mRNA as a vaccine is its capacity to induce type I interferons, which can have beneficial adjuvant effects, but also deleterious effects on mRNA stability and translation. Thus, proper formulation of the mRNA is crucially important. Many approaches for RNA formulation have already been tested, with mixed success. In this review we discuss the state-of-the-art and future trends for mRNA-nanoparticle formulations for HIV vaccination, both in the prophylactic and in the therapeutic setting.

Supramolecular self-assemblies of engineered polyethylenimines as multifunctional nanostructures for DNA transportation with excellent antimicrobial activity

In this study, indole-3-butanoic acid (IBA), a biologically and environmentally safe entity, has been grafted onto low and high molecular weight (1.8 and 25 kDa) polyethylenimines (PEI) mainly through primary amines to obtain amphiphilic indole-3-butanoyl-polyethylenimines (IBPs). Two series of IBPs (IBP_1.8 and IBP₂₅) were prepared which, on self-assembly in aqueous medium, yielded multifunctional nanomicellar structures (IBP_1.8 and IBP₂₅) capable of transporting genetic material in vitro and exhibiting other biological activities. Physicochemical characterization showed the size of IBP_1.8 and IBP₂₅ nanostructures in the range of ~332-234 nm and ~283-166 nm, respectively, with zeta potential varying from ~+29-17 mV and ~+37-25 mV. DNA release assay demonstrated higher release of plasmid DNA from IBP nanostructures as compared to native PEIs. Cytotoxicity showed a decreasing pattern with increasing degree of grafting of IBA onto PEIs making these nanostructures non-toxic. pDNA complexes of these nanostructures (both IBPs_1.8 and IBPs₂₅) displayed considerably higher transfection efficiency, however, IBP_1.8/pDNA complexes performed much better (~7-9 folds) as compared to native PEI/pDNA and Lipofectamine/pDNA complexes on mammalian cells. CLSM analysis revealed that these complexes entered nucleus in sufficient amounts suggesting higher uptake and efficient internalization of the complexes. Besides, these supramolecular nanostructures not only exhibited excellent antimicrobial potential (MIC ~49-100 µg/ml) against clinical as well as resistant pathogenic strains but also found to possess antioxidant property. Overall, the projected low molecular weight PEI-based vectors could serve as more effective multifunctional nanomaterials having promising potential for future gene therapy applications with capability to provide protection against other bacterial infections.

Cyclopropenium Nanoparticles and Gene Transfection in Cells

Non-viral vectors for the transfection of genetic material are at the frontier of medical science. In this article, we introduce for the first time, cyclopropenium-containing nanoparticles as a cationic carrier for gene transfection, as an alternative to the common quaternary ammonium transfection agents. Cyclopropenium-based cationic nanoparticles were prepared by crosslinking poly(ethylene imine) (PEI) with tetrachlorocyclopropene. These nanoparticles were electrostatically complexed with plasmid DNA into nanoparticles (~50 nm). Their cellular uptake into F929 mouse fibroblast cells, and their eventual expression in vitro have been described. Transfection is enhanced relative to PEI with minimal toxicity. These cyclopropenium nanoparticles possess efficient gene transfection capabilities with minimal cytotoxicity, which makes them novel and promising candidates for gene therapy.

Antibiotic Resistance Profiles, Molecular Mechanisms and Innovative Treatment Strategies of Acinetobacter baumannii

Antibiotic resistance is one of the biggest challenges for the clinical sector and industry, environment and societal development. One of the most important pathogens responsible for severe nosocomial infections is Acinetobacter baumannii, a Gram-negative bacterium from the Moraxellaceae family, due to its various resistance mechanisms, such as the β-lactamases production, efflux pumps, decreased membrane permeability and altered target site of the antibiotic. The enormous adaptive capacity of A. baumannii and the acquisition and transfer of antibiotic resistance determinants contribute to the ineffectiveness of most current therapeutic strategies, including last-line or combined antibiotic therapy. In this review, we will present an update of the antibiotic resistance profiles and underlying mechanisms in A. baumannii and the current progress in developing innovative strategies for combating multidrug-resistant A. baumannii (MDRAB) infections.

Gold Nanoparticle-Assisted Virus Formation by Means of the Delivery of an Oncolytic Adenovirus Genome

Oncolytic adenoviruses are a therapeutic alternative to treat cancer based on their ability to replicate selectively in tumor cells. However, their use is limited mainly by the neutralizing antibody (Nab) immune response that prevents repeated dosing. An alternative to facilitate the DNA access to the tumor even in the presence of anti-viral Nabs could be gold nanoparticles able to transfer DNA molecules. However, the ability of these nanoparticles to carry large DNA molecules, such as an oncolytic adenovirus genome, has not been studied. In this work, gold nanoparticles were functionalized with different amounts of polyethylenimine to transfer in a safe and efficient manner a large oncolytic virus genome. Their transfer efficacy and final effect of the oncolytic virus in cancer cells are studied. For each synthesized nanoparticle, (a) DNA loading capacity, (b) complex size, (c) DNA protection ability, (d) transfection efficacy and (e) cytotoxic effect were studied. We observed that small gold nanoparticles (70–80 nm in diameter) protected DNA against nucleases and were able to transfect the ICOVIR-15 oncolytic virus genome encoded in pLR1 plasmid. In the present work, efficient transgene RNA expression, luciferase activity and viral cytopathic effect on cancer cells are reported. These results suggest gold nanoparticles to be an efficient and safe vector for oncolytic adenovirus genome transfer.

Dexamethasone loaded bilayered 3D tubular scaffold reduces restenosis at the anastomotic site of tracheal replacement: in vitro and in vivo assessments

Despite recent developments in the tracheal tissue engineering field, the creation of a patient specific substitute possessing both appropriate mechanical and biointerfacial properties remains challenging. Most tracheal replacement therapies fail due to restenosis at the anastomosis site. In this study, we designed a robust, biodegradable, 3D tubular scaffold by combining electrospinning (ELSP) and 3D (three-dimensional) printing techniques for use in transplantation therapy. After that, we loaded dexamethasone (DEX) onto the 3D tubular scaffold using mild surface modification reactions by using polydopamine (PDA), polyethyleneimine (PEI), and carboxymethyl-β-cyclodextrin (βCD). As a result, the fabricated 3D tubular scaffold had robust mechanical properties and the chemical modifications were confirmed to have proceeded successfully by physico-chemical analysis. The surface treatments allowed for a larger amount of DEX to be loaded onto the βCD modified scaffold as compared to the bare group. In vitro and in vivo studies demonstrated that the DEX loaded 3D tubular scaffold exhibited significantly enhanced anti-inflammation activity, enhanced tracheal mucosal regeneration, and formation of a patent airway. From our results, we believe that our system may represent an innovative paradigm in tracheal tissue engineering by providing proper mechanical properties and successful formation of tracheal tissue as a means of remodeling and healing tracheal defects for use in transplantation therapy.

Enhanced gene transfection efficiency by low-dose 25 kDa polyethylenimine by the assistance of 1.8 kDa polyethylenimine

Gene therapy is a promising strategy for treatments of various diseases. Efficient and safe introduction of therapeutic genes into targeted cells is essential to realize functions of the genes. High-molecular-weight polyethylenimines (HMW PEIs) including 25 kDa branched PEI and 22 kDa linear PEI are widely used for in vitro gene transfection. However, high-gene transfection efficiency is usually accompanied with high cytotoxicity, which hampers their further clinical study. On the contrary, low-molecular-weight polyethylenimines (LMW PEIs) such as 1.8 kDa PEI and 800 Da PEI show good biocompatibility but their applications are limited by the poor DNA condensation capability. In this study, we find that 1.8 kDa PEI, but not 800 Da PEI combined with low-dose 25 kDa PEI could significantly promote gene transfection with low cytotoxicity. Plasmids encoding enhanced green fluorescence protein (EGFP) were delivered by the combined PEI and gene transfection efficiency was evaluated by microscopic observation and flow cytometry. Parameters including concentrations of 25 kDa PEI and 1.8 kDa PEI and preparation ways were further optimized. This study presents an efficient and safe combined PEI-based non-viral gene delivery strategy with potential for in vivo applications.

Hydrogen-Bond Cyclization Programming of Ultrasensitive Esters and Its Application in Gene Delivery

The ester bond as a universal linker has recently been applied in gene delivery systems owing to its efficient gene release by electrostatic repulsion after its cleavage. However, the ester bond is nonlabile and is difficult to cleave in cells. This work reports a method in which a secondary amine was introduced to the β-position of the ester bond to generate a hydrogen-bond cyclization (HBC) structure that can make the ester bond hydrolysis ultrafast. A series of molecules comprising ultrasensitive esters that can be activated by H₂ O₂ were synthesized, and it was found that those able to form an HBC structure showed complete ester hydrolysis within 5 h in both water and phosphate-buffered saline solution, which was several times faster than other methods reported. Then, a series of amphiphilic poly(amidoamine) dendrimers were constructed, comprising the ultrasensitive ester groups for gene delivery; it was found that they could effectively release genes under quite a low concentration of H₂ O₂ (<200 μm) and transport them into the nucleus within 2 h in Hela cells with high safety. Their gene transfection efficiencies were higher than that of PEI_25k . The results demonstrated that the hydrogen-bond-induced ultrasensitive esters could be powerfully applied to construct gene delivery systems.

Synthetic Approaches for Nucleic Acid Delivery: Choosing the Right Carriers

The discovery of the genetic roots of various human diseases has motivated the exploration of different exogenous nucleic acids as therapeutic agents to treat these genetic disorders (inherited or acquired). However, the physicochemical properties of nucleic acids render them liable to degradation and also restrict their cellular entrance and gene translation/inhibition at the correct cellular location. Therefore, gene condensation/protection and guided intracellular trafficking are necessary for exogenous nucleic acids to function inside cells. Diversified cationic formulation materials, including natural and synthetic lipids, polymers, and proteins/peptides, have been developed to facilitate the intracellular transportation of exogenous nucleic acids. The chemical properties of different formulation materials determine their special features for nucleic acid delivery, so understanding the property-function correlation of the formulation materials will inspire the development of next-generation gene delivery carriers. Therefore, in this review, we focus on the chemical properties of different types of formulation materials and discuss how these formulation materials function as protectors and cellular pathfinders for nucleic acids, bringing them to their destination by overcoming different cellular barriers.

CRISPR-cas system: biological function in microbes and its use to treat antimicrobial resistant pathogens

The development of antibiotic resistance in bacteria is a major public health threat. Infection rates of resistant pathogens continue to rise against nearly all antimicrobials, which has led to development of different strategies to combat the antimicrobial resistance. In this review, we discuss how the newly popular CRISPR-cas system has been applied to combat antibiotic resistance in both extracellular and intracellular pathogens. We also review a recently developed method in which nano-size CRISPR complex was used without any phage to target the mecA gene. However, there is still challenge to practice these methods in field against emerging antimicrobial resistant pathogens.