The role of assembly parameters on polyplex poly(beta-amino ester) nanoparticle transfections

Combinatorial Synthesis of Alkyl Chain-Capped Poly(β-Amino Ester)s for Effective siRNA Delivery

Poly (β-amino ester) (PBAE) is a class of biodegradable polymers containing ester bonds in their main chain, extensively investigated as cationic polymer carriers for siRNA. Most current PBAE carriers rely on termination with hydrophilic or charged amines. In this study, a polymer platform consisting of 168 PBAE polymers with hydrophobic alkyl chain terminals is constructed through sequential aza-Michael addition. A large number of effective carriers are identified through in vitro screening of the PBAE platform for siLuc delivery to HeLa-Luc cells. Specifically, PA8-C6 and PA8-C8 achieve remarkable gene knockdown efficacies of up to 80% with low cytotoxicity. Certain materials from the PA2 and PA5 series demonstrate potent siRNA delivery capabilities associated with elevated cytotoxicity. The pKa value of PBAE is predominantly determined by the hydrophilic amine side chains rather than the end-capping groups. A pKa range of ≈6.2-6.5 may contribute to the excellent delivery capability for PA8 series carriers. The co-formulation of PBAE carriers with helper lipids leads to the reduced size and surface charges of the polyplex NPs with siRNA, consequently decreasing the cytotoxicity and enhancing siRNA delivery efficacy. These findings hold significant implications for the development of novel degradable polymer carriers for siRNA delivery.

Engineering strategies for apoptotic bodies

Extracellular vesicles (EVs) are lipid bilayer vesicles containing proteins, lipids, nucleic acids, and metabolites secreted by cells under various physiological and pathological conditions that mediate intercellular communication. The main types of EVs include exosomes, microvesicles, and apoptotic bodies (ABs). ABs are vesicles released during the terminal stages of cellular apoptosis, enriched with diverse biological entities and characterized by distinct morphological features. As a result, ABs possess great potential in fields like disease diagnosis, immunotherapy, regenerative therapy, and drug delivery due to their specificity, targeting capacity, and biocompatibility. However, their therapeutic efficacy is notably heterogeneous, and an overdose can lead to side effects such as accumulation in the liver, spleen, lungs, and gastrointestinal system. Through bioengineering, the properties of ABs can be optimized to enhance drug-loading efficiency, targeting precision, and multifunctionality for clinical implementations. This review focuses on strategies such as transfection, sonication, electroporation, surface engineering, and integration with biomaterials to enable ABs to load cargoes and enhance targeting, providing insights into the engineering of ABs.

Biodegradable Polyester Nanoparticle Vaccines Deliver Self-Amplifying mRNA in Mice at Low Doses

Delivery of self-amplifying mRNA (SAM) has high potential for infectious disease vaccination due its self-adjuvating and dose-sparing properties. Yet a challenge is the susceptibility of SAM to degradation and the need for SAM to reach the cytosol fully intact to enable self-amplification. Lipid nanoparticles have been successfully deployed at incredible speed for mRNA vaccination, but aspects such as cold storage, manufacturing, efficiency of delivery, and the therapeutic window would benefit from further improvement. To investigate alternatives to lipid nanoparticles, we developed a class of >200 biodegradable end-capped lipophilic poly(beta-amino ester)s (PBAEs) that enable efficient delivery of SAM in vitro and in vivo as assessed by measuring expression of SAM encoding reporter proteins. We evaluated the ability of these polymers to deliver SAM intramuscularly in mice, and identified a polymer-based formulation that yielded up to 37-fold higher intramuscular (IM) expression of SAM compared to injected naked SAM. Using the same nanoparticle formulation to deliver a SAM encoding rabies virus glycoprotein, the vaccine elicited superior immunogenicity compared to naked SAM delivery, leading to seroconversion in mice at low RNA injection doses. These biodegradable nanomaterials may be useful in the development of next-generation RNA vaccines for infectious diseases.

Net anionic poly(β-amino ester)s: synthesis, pH-dependent behavior, and complexation with cationic cargo

As hydrolytically-labile, traditionally-cationic polymers, poly(β-amino ester)s (PBAEs) adeptly complex anionic compounds such as nucleic acids, and release their cargo as the polymer degrades. To engineer fully-degradable polyelectrolyte complexes and delivery vehicles for cationic therapeutics, we sought to invert PBAE net charge to generate net anionic PBAEs. Since PBAEs can carry up to a net charge of +1 per tertiary amine, we synthesized a series of alkyne-functionalized PBAEs that allowed installation of 2 anionic thiol-containing molecules per tertiary amine via a radical thiol-yne reaction. Finding dialysis in aqueous solution to lead to PBAE degradation, we developed a preparative size exclusion chromatography method to remove unreacted thiol from the net anionic PBAEs without triggering hydrolysis. The net anionic PBAEs display non-monotonic solution behavior as a function of pH, being more soluble at pH 4 and 10 than in intermediate pH ranges. Like cationic PBAEs, these net anionic PBAEs degrade in aqueous environments with hydrophobic content-dependent hydrolysis, as determined by 1H NMR spectroscopy. Further, these net anionic PBAEs form complexes with the cationic peptide (GR)10, which disintegrate over time as the polymer hydrolyzes. Together, these studies outline a synthesis and purification route to make previously inaccessible net anionic PBAEs with tunable solution and degradation behavior, allowing for user-determined complexation and release rates and providing opportunities for degradable polyelectrolyte complexes and cationic therapeutic delivery.

Poly (beta-amino ester) as an in vivo nanocarrier for therapeutic nucleic acids

Therapeutic nucleic acids are an emerging class of therapy for treating various diseases through immunomodulation, protein replacement, gene editing, and genetic engineering. However, they need a vector to effectively and safely reach the target cells. Most gene and cell therapies rely on ex vivo gene delivery, which is laborious, time-consuming, and costly; therefore, devising a systematic vector for effective and safe in vivo delivery of therapeutic nucleic acids is required to target the cells of interest in an efficient manner. Synthetic nanoparticle vector poly beta amino ester (PBAE), a class of degradable polymer, is a promising candidate for in vivo gene delivery. PBAE is considered the most potent in vivo vector due to its excellent transfection performance and biodegradability. PBAE nanoparticles showed tunable charge density, diverse structural characteristics, excellent encapsulation capacity, high stability, stimuli-responsive release, site-specific delivery, potent binding to nucleic acids, flexible binding ability to various conjugates, and effective endosomal escape. These unique properties of PBAE are an essential contribution to in vivo gene delivery. The current review discusses each of the components used for PBAE synthesis and the impact of various environmental and physicochemical factors of the body on PBAE nanocarrier.

Engineering poly- and micelleplexes for nucleic acid delivery - A reflection on their endosomal escape

For the longest time, the field of nucleic acid delivery has remained skeptical whether or not polycationic drug carrier systems would ever make it into clinical practice. Yet, with the disclosure of patents on polyethyleneimine-based RNA carriers through leading companies in the field of nucleic acid therapeutics such as BioNTech SE and the progress in clinical studies beyond phase I trials, this aloofness seems to regress. As one of the most striking characteristics of polymer-based vectors, the extraordinary tunability can be both a blessing and a curse. Yet, knowing about the adjustment screws and how they impact the performance of the drug carrier provides the formulation scientist committed to its development with a head start. Here, we equip the reader with a toolbox - a toolbox that should advise and support the developer to conceptualize a cutting-edge poly- or micelleplex system for the delivery of therapeutic nucleic acids; to be specific, to engineer the vector towards maximum endosomal escape performance at minimum toxicity. Therefore, after briefly sketching the boundary conditions of polymeric vector design, we will dive into the topic of endosomal trafficking. We will not only discuss the most recent knowledge of the endo-lysosomal compartment but further depict different hypotheses and mechanisms that facilitate the endosomal escape of polyplex systems. Finally, we will combine the different facets introduced in the previous chapters with the fundamental building blocks of polymer vector design and evaluate the advantages and drawbacks. Throughout the article, a particular focus will be placed on cellular peculiarities, not only as an additional barrier, but also to give inspiration to how such cell-specific traits might be capitalized on.

Length-Controlled Nanofiber Micelleplexes as Efficient Nucleic Acid Delivery Vehicles

Micelleplexes show great promise as effective polymeric delivery systems for nucleic acids. Although studies have shown that spherical micelleplexes can exhibit superior cellular transfection to polyplexes, to date there has been no report on the effects of micelleplex morphology on cellular transfection. In this work, we prepared precision, length-tunable poly(fluorenetrimethylenecarbonate)-b-poly(2-(dimethylamino)ethyl methacrylate) (PFTMC₁₆-b-PDMAEMA₁₃₁) nanofiber micelleplexes and compared their properties and transfection activity to those of the equivalent nanosphere micelleplexes and polyplexes. We studied the DNA complexation process in detail via a range of techniques including cryo-transmission electron microscopy, atomic force microscopy, dynamic light scattering, and ζ-potential measurements, thereby examining how nanofiber micelleplexes form, as well the key differences that exist compared to nanosphere micelleplexes and polyplexes in terms of DNA loading and colloidal stability. The effects of particle morphology and nanofiber length on the transfection and cell viability of U-87 MG glioblastoma cells with a luciferase plasmid were explored, revealing that short nanofiber micelleplexes (length < ca. 100 nm) were the most effective delivery vehicle examined, outperforming nanosphere micelleplexes, polyplexes, and longer nanofiber micelleplexes as well as the Lipofectamine 2000 control. This study highlights the potential importance of 1D micelleplex morphologies for achieving optimal transfection activity and provides a fundamental platform for the future development of more effective polymeric nucleic acid delivery vehicles.

Poly(Beta-Amino Ester)s as High-Yield Transfection Reagents for Recombinant Protein Production

Purpose

Transient transfection is an essential tool for recombinant protein production, as it allows rapid screening for expression without stable integration of genetic material into a target cell genome. Poly(ethylenimine) (PEI) is the current gold standard for transient gene transfer, but transfection efficiency and the resulting protein yield are limited by the polymer’s toxicity. This study investigated the use of a class of cationic polymers, poly(beta-amino ester)s (PBAEs), as reagents for transient transfection in comparison to linear 25 kDa PEI, a commonly used transfection reagent.

Methods

Transfection efficiency and protein production were assessed in human embryonic kidney 293F (HEK) and Chinese hamster ovary-S (CHO) cell suspensions using PBAE-based nanoparticles in comparison to linear 25 kDa PEI. Production of both a cytosolic reporter and secreted antibodies was investigated.

Results

In both HEK and CHO cells, several PBAEs demonstrated superior transfection efficiency and enhanced production of a cytosolic reporter compared to linear 25 kDa PEI. This result extended to secreted proteins, as a model PBAE increased the production of 3 different secreted antibodies compared to linear 25 kDa PEI at culture scales ranging from 20 to 2000 mL. In particular, non-viral gene transfer using the lead PBAE/plasmid DNA nanoparticle formulation led to robust transfection of mammalian cells across different constructs, doses, volumes, and cell types.

Conclusion

These results show that PBAEs enhance transfection efficiency and increase protein yield compared to a widespread commercially available reagent, making them attractive candidates as reagents for use in recombinant protein production.

Can pulmonary RNA delivery improve our pandemic preparedness?

The coronavirus pandemic has changed our perception of RNA medicines, and RNA vaccines have revolutionized our pandemic preparedness. But are we indeed prepared for the next variant or the next emerging virus? How can we prepare? And what does the role of inhaled antiviral RNA play in this regard? When the pandemic started, I rerouted much of the ongoing inhaled RNA delivery research in my group towards the inhibition and treatment of respiratory viral infections. Two years later, I have taken the literature, past and ongoing clinical trials into consideration and have gained new insights based on our collaborative research which I will discuss in this oration.

Synthesis and Characterization of Poly (β-amino Ester) and Applied PEGylated and Non-PEGylated Poly (β-amino ester)/Plasmid DNA Nanoparticles for Efficient Gene Delivery

Polymer-based nanocarriers require extensive knowledge of their chemistries to learn functionalization strategies and understand the nature of interactions that they establish with biological entities. In this research, the poly (β-amino ester) (PβAE-447) was synthesized and characterized, aimed to identify the influence of some key parameters in the formulation process. Initially; PβAE-447 was characterized for aqueous solubility, swelling capacity, proton buffering ability, and cytotoxicity study before nanoparticles formulation. Interestingly, the polymer-supported higher cell viability than the Polyethylenimine (PEI) at 100 μg/ml. PβAE-447 complexed with GFP encoded plasmid DNA (pGFP) generated nanocarriers of 184 nm hydrodynamic radius (+7.42 mV Zeta potential) for cell transfection. Transfection assays performed with PEGylated and lyophilized PβAE-447/pDNA complexes on HEK-293, BEAS-2B, and A549 cell lines showed better transfection than PEI. The outcomes toward A549 cells (above 66%) showed the highest transfection efficiency compared to the other cell lines. Altogether, these results suggested that characterizing physicochemical properties pave the way to design a new generation of PβAE-447 for gene delivery.

Design and development of Branched Poly(ß-aminoester) nanoparticles for Interleukin-10 gene delivery in a mouse model of atherosclerosis

Atherosclerosis progression is a result of chronic and non-resolving inflammation, effective treatments for which still remain to be developed. We designed and developed branched poly(ß-amino ester) nanoparticles (NPs) containing plasmid DNA encoding IL-10, a potent anti-inflammatory cytokine to atherosclerosis. The NPs (NP-VHPK) are functionalized with a targeting peptide (VHPK) specific for VCAM-1, which is overexpressed by endothelial cells at sites of atherosclerotic plaque. The anionic coating affords NP-VHPK with significantly lower toxicity than uncoated NPs in both endothelial cells and red blood cells (RBCs). Following injection of NP-VHPK in ApoE^-/- mice, Cy5-labelled IL-10 significantly accumulates in both whole aortas and aortic sinus sections containing plaque compared to injection with a non-targeted control. Furthermore, IL-10 gene delivery results in an attenuation of inflammation locally at the plaque site. NP-VHPK may thus have the potential to reduce the inflammatory component of atherosclerosis in a safe and effective manner. STATEMENT OF SIGNIFICANCE: Atherosclerosis is a chronic inflammatory disease that results in the formation of lipid-laden plaques within vascular walls. Although treatments using drugs and antibodies are now beginning to address the inflammation in atherosclerosis, neither is sufficient for long-term therapy. In this paper, we introduce a strategy to deliver genes encoding the anti-inflammatory protein interleukin-10 (IL-10) in vivo. We showed that Branched Poly(ß-aminoester) carrying the IL-10 gene are able to localize specifically at the plaque via surface-functionalized targeting moieties against inflamed VCAM-1 and/or ICAM-1 and to facilitate gene transcription by ECs to increase the local concentration of the IL-10 within the plaque. To date, there is no report involving non-viral nanotechnology to provide gene-based therapies for atherosclerosis.

Nanopesticides in Agriculture: Benefits and Challenge in Agricultural Productivity, Toxicological Risks to Human Health and Environment

Nanopesticides are nanostructures with two to three dimensions between 1 to 200 nm, used to carry agrochemical ingredients (AcI). Because of their unique properties, the loading of AcI into nanoparticles offers benefits when compared to free pesticides. However, with the fast development of new engineered nanoparticles for pests' control, a new type of environmental waste is being produced. This paper describes the nanopesticides sources, the harmful environmental and health effects arising from pesticide exposure. The potential ameliorative impact of nanoparticles on agricultural productivity and ecosystem challenges are extensively discussed. Strategies for controlled release and stimuli-responsive systems for slow, sustained, and targeted AcI and genetic material delivery are reported. Special attention to different nanoparticles source, the environmental behavior of nanopesticides in the crop setting, and the most recent advancements and nanopesticides representative research from experimental results are revised. This review also addresses some issues and concerns in developing, formulating and toxicity pesticide products for environmentally friendly and sustainable agriculture.

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.

The Role of Formamidine Groups in Dextran Based Nonviral Vectors for Gene Delivery on Their Physicochemical and Biological Characteristics

Dextran-formamidine esters (dextran-N-[(dimethylamino)methylene]-β-alanine ester) with different degrees of substitution (0.45-0.92) are synthesized in an one-pot reaction. Dextran (Mw 60 000 g mol^-1 ) is allowed to react with unprotected beta-alanine and iminium chloride and investigated regarding the potential as gene delivery system for the transfer of plasmid DNA. With degrees of substitution ≥ 0.63 improved DNA binding with formation of enzymatically stable complexes of about 130-160 nm with negative surface charges are obtained. These physicochemical characteristics correlated with increasing transfection rates in CHO-K1 cells determined by a luciferase reporter gene assay in dependency of the number of formamidine residues, N/P ratios and amount of DNA. The role of the number of formamidine groups is also highlighted by in vitro cyto- and hemotoxicity tests under the chosen conditions. These results indicate that dextran-formamidine esters are a very promising material for the safe and efficient gene delivery.

Efficiency of Cytosolic Delivery with Poly(β-amino ester) Nanoparticles is Dependent on the Effective pKa of the Polymer

The mechanism by which cationic polymers containing titratable amines mediate effective endosomal escape and cytosolic delivery of nucleic acids is not well understood despite the decades of research devoted to these materials. Here, we utilize multiple assays investigating the endosomal escape step associated with plasmid delivery by polyethylenimine (PEI) and poly(β-amino esters) (PBAEs) to improve the understanding of how these cationic polymers enable gene delivery. To probe the role of these materials in facilitating endosomal escape, we utilized vesicle membrane leakage and extracellular pH modulation assays to demonstrate the influence of polymer buffering capacity and effective pK_a on the delivery of the plasmid DNA. Our results demonstrate that transfection with PBAEs is highly sensitive to the effective pK_a of the overall polymer, which has broad implications for transfection. In more acidic environments, PBAE-mediated transfection was inhibited, while PEI was relatively unaffected. In neutral to basic environments, PBAEs have high buffering capacities that led to dramatically improved transfection efficacy. The cellular uptake of polymeric nanoparticles overall was unchanged as a function of pH, indicating that microenvironmental acidity was important for downstream intracellular delivery efficiency. Overall, this study motivates the use of polymer chemical characteristics, such as effective pK_a values, to more efficiently evaluate new polymeric materials for enhanced intracellular delivery characteristics.