Construction of Polycation-Based Non-Viral DNA Nanoparticles and Polyanion Multilayers via Layer-by-Layer Self-Assembly

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Layer-By-Layer Nanocoating of Antiviral Polysaccharides on Surfaces to Prevent Coronavirus Infections

In 2020, the world is being ravaged by the coronavirus, SARS-CoV-2, which causes a severe respiratory disease, Covid-19. Hundreds of thousands of people have succumbed to the disease. Efforts at curing the disease are aimed at finding a vaccine and/or developing antiviral drugs. Despite these efforts, the WHO warned that the virus might never be eradicated. Countries around the world have instated non-pharmaceutical interventions such as social distancing and wearing of masks in public to curb the spreading of the disease. Antiviral polysaccharides provide the ideal opportunity to combat the pathogen via pharmacotherapeutic applications. However, a layer-by-layer nanocoating approach is also envisioned to coat surfaces to which humans are exposed that could harbor pathogenic coronaviruses. By coating masks, clothing, and work surfaces in wet markets among others, these antiviral polysaccharides can ensure passive prevention of the spreading of the virus. It poses a so-called "eradicate-in-place" measure against the virus. Antiviral polysaccharides also provide a green chemistry pathway to virus eradication since these molecules are primarily of biological origin and can be modified by minimal synthetic approaches. They are biocompatible as well as biodegradable. This surface passivation approach could provide a powerful measure against the spreading of coronaviruses.

Construction of redox-active multilayer film for electrochemically controlled release

An electrochemically controlled drug release from a redox-active multilayer film is reported. The multilayer film is fabricated by alternate assembly of the electrochemical redox-active micelles and DNA. The buildup of multilayer films is monitored by spectroscopic ellipsometry, UV-vis spectroscopy, and fluorescence spectroscopy. A ferrocene-modified poly (ethyleneimine) (PEI-Fc) is used to form a hydrophobic ferrocene core and hydrophilic PEI shell micelle, showing the electrochemical redox-active properties. Hydrophobic pyrene (Py) molecules are then incorporated into the micelles. The PEI-Fc@Py micelles are assembled into the (PEI-Fc@Py/DNA) multilayer film by layer-by-layer assembly. Thanks to ferrocene groups with the properties of the hydrophilic-to-hydrophobic switch based on the electrical potential trigger, pyrene molecules can be control released from the multilayer film. The electrochemically controlled release of pyrene is investigated and confirmed by electrochemical quartz crystal microbalance and electrochemistry workstation. The (PEI-Fc@drug/DNA) multilayer film may have potential applications in the field of biomedical and nanoscale devices.

Effective gene transfer into central nervous system following ultrasound-microbubbles-induced opening of the blood-brain barrier

To investigate whether ultrasound-targeted microbubble destruction (UTMD) could transfer gene into central nervous system (CNS) following blood-brain barrier disruption (BBBD), DNA-loaded microbubbles were infused into the mice intravenously following ultrasonic exposure. Opening of the BBB, changes of mRNA and expression of enhanced green fluorescent protein (EGFP), and safety evaluation were measured. By UTMD, EGFP were substantially expressed in the cytoplasm of the neurons at the sonicated area with minor erythrocytes extravasation and the mRNA and expression of EGFP were markedly enhanced by about 15-fold and 10-fold, respectively, than that with US alone (p < 0.01). No EGFP was detected in the mice treated with DNA-loaded microbubbles or plasmid alone. The gene expression reached a climax at 48 h, gradually reduced to a much lower level thereafter. These results demonstrated UTMD could effectively enhance exogenous gene delivery and expression in CNS following BBBD, and this technique may provide a new method for CNS gene therapy.

A facile approach to construct hybrid multi-shell calcium phosphate gene particles

The calcium phosphate (CaP) particles have attracted much attention in gene therapy. How to construct stable gene particles was the determining factor. In this study, hybrid multi-shell CaP gene particles were successfully constructed. First, CaP nanoparticles served as a core and were coated with DNA for colloidal stabilization. The xi-potential of DNA-coated CaP nanoparticles was -15 mV. Then polyethylenimine (PEI) was added and adsorbed outside of the DNA layer due to the electrostatic attraction. The xi-potential of hybrid multi-shell CaP particles was slightly positive. With addition of PEI, the hybrid multi-shell particles could condense DNA effectively, which was determined by ethidium bromide (EtBr) exclusion assay. The hybrid particles were spherical and uniform with diameters of about 150 nm at proper conditions. By simple modification of PEI, the hybrid multi-shell CaP gene particles were successfully constructed. They may have great potential in gene therapy.

Construction of multifunctional coatings via layer-by-layer assembly of sulfonated hyperbranched polyether and chitosan

Layer-by-layer assembly has shown a great deal of promise in biomedical coatings, as well as local drug delivery systems. The poor loading capacity of hydrophobic drugs within the multilayers is a drawback in their potential applications. Herein, sulfonated hyperbranched polyether (HBPO-SO(3)) with a hydrophobic core was incorporated into LBL films to provide nanoreservoirs for hydrophobic guest molecules. HBPO-SO(3) was proven to form stable micelles in the sodium acetate and acetic acid buffer solution (HAc buffer) for LbL assembly. The QCM and ellipsometry experiments demonstrated that the LBL films can be fabricated via alternating deposition of HBPO-SO(3) micelles and chitosan. The fluorescence emission spectra verified that the hydrophobic pyrene can be incorporated both by pre-encapsulation in HBPO-SO(3) micelles and post-diffusion in preassembled multilayer films. Compared with the pre-encapsulation approach, the post-diffusion process was more efficient in incorporating hydrophobic guest molecules into the LbL films and carried out a much more controllable release of the guest molecules. A multifunctional coating with potential anticoagulation, antibacterial, and local release of hydrophobic drug Probucal, which has powerful antioxidant properties and can prevent restenosis after coronary angioplasty, was then developed via post-diffusion of the anti-restenosis agents into the multilayer films of HBPO-SO(3) and chitosan.

Modulating the release kinetics through the control of the permeability of the layer-by-layer assembly: a review

The layer-by-layer (LbL) self-assembly technique has emerged as a simple and versatile method for coating biological and non-biological templates for various biomedical applications. A promising avenue of this technique lies in the encapsulation of drugs and other biological substances for controlled release. Fundamental studies of LbL assembly on flat surfaces have provided a sound understanding of film deposition theory and its pertinence to ionic and molecular transport and diffusion through polyelectrolyte multilayer (PEM) films. However, there is a lack of information on the permeability of three-dimensional PEM shell systems. In either PEM films or shells, it has been shown that drug release is a function of the ionic strength, pH and/or multilayer thickness. This report aims to provide an overview of the physicochemical parameters affecting the permeability of two- and three-dimensional multilayer shells, including ionic strength, layer number and pH. Furthermore, their synergic effect on loading and release of biologically active molecules from LbL multilayers are discussed.

Microbial Biosynthesis of Polyglutamic Acid Biopolymer and Applications in the Biopharmaceutical, Biomedical and Food Industries

This review article provides an updated critical literature review on the production and applications of Polyglutamic Acid (PGA). alpha-PGA is synthesized chemically, whereas gamma-PGA can be produced by a number of microbial species, most prominently various Bacilli. Great insight into the microbial formation of gamma-PGA has been gained thanks to the development of molecular biological techniques. Moreover, there is a great variety of applications for both isoforms of PGA, many of which have not been discovered until recently. These applications include: wastewater treatment, food products, drug delivery, medical adhesives, vaccines, PGA nanoparticles for on-site drug release in cancer chemotherapy, and tissue engineering.

Construction of caged polyplexes with a reversible intracellular unpacking property to improve stability and transfection

Cross-linking of protein macromonomers accompanies the assembly of viral particles, which provides the virus with high stability in the host. Following inspiration, caged polyplexes were fabricated via a biomimetic cross-linker. Thiolated polyethylenimine was synthesized and showed sufficient DNA condensation ability. Spherical particles with a diameter of about 150nm were formed at an N/P ratio of 10. Shell-cross-linked polyplexes were then constructed by the oxidation of thiol groups in air. All the results indicate that the cross-linking shell via disulfide bonds could improve the stability of polyplexes in the physiological condition and showed a reversible unpacking property at the intracellular GSH concentration. By selecting the proper preparation conditions, polyplexes caged via a biomimetic cross-linker could efficiently release DNA for transfection.

A facile entrapment approach to construct PEGylated polyplexes for improving stability in physiological condition

PEGylated polyplexes had been proved to improve the stability of DNA complexes. However, the conjugation reaction might reduce the capacity of efficient DNA complexation. Herein we described an easy and favorable approach to construct PEGylated polyplexes via entrapping poly(ethylene glycol) cholesterol ether (CPEG) into polyplexes. It was of interest to find the addition sequence of CPEG had great effect on the stability of polyplexes in physiological salt concentration. The addition of CPEG into the formed PEI(25k)/DNA polyplexes had no effect to improve the stability. Whereas by the "CPEG first" method of adding CPEG and PEI(25k) mixture into the DNA solution, the PEI(25k)/CPEG/DNA polyplexes showed excellent anti-aggregation effect and enhanced transfection efficiency in physiological condition. The difference performance might be explained by the possibility of CPEG entrapment. By the "CPEG first" method, PEGylated polyplexes was constructed due to the hydrophobic interaction between the cholesterol group of CPEG and hydrophobic charged-compensated core. The PEG coating significantly improved the stability of polyplexes in physiological condition. This facile entrapment approach to prepare PEGylated polyplexes might have great potential in non-viral gene delivery research and application.

The development and characterization of a glutathione-sensitive cross-linked polyethylenimine gene vector

A glutathione-sensitive cross-linked polyethylenimine gene vector CLPEI(50%) was specially designed via the cross-linking reaction between the low molecular weight polyethylenimine (PEI(1800)) and dimethyl 3.3'-dithiopropionimidate dihydrochloride (DTBP). The acid-base titration test indicated that CLPEI(50%) still possessed efficient proton sponge effect. The property of CLPEI(50%)-DNA complexes were investigated by atomic force microscopy (AFM) and dynamic light scattering (DLS). CLPEI(50%) induced DNA condensation and formed spherical nanoparticles. The diameter of polyplexes prepared at pH value of 6.0 and 7.4 was about 150 and 260 nm, respectively. It was interesting to find the polyplexes were sensitive to the reductive glutathione (GSH). The CLPEI(50%)-DNA polyplexes prepared at N/P ratio of 10 were unpacked at GSH concentration of 3mm, which was comparable to the intracellular environment. The in vitro cytotoxicity of CLPEI(50%) was also significantly reduced comparing with PEI(25k). The biomimetic CLPEI(50%)-DNA polyplexes with the low cytotoxicity and GSH-sensitive property could be a good candidate for gene delivery.