Charge-reversal lipids, peptide-based lipids, and nucleoside-based lipids for gene delivery

Development and applications of lipid hydrophilic headgroups for nucleic acid therapy

Nucleic acid therapy is currently the most promising method for treating tumors and genetic diseases and for preventing infectious diseases. However, the biggest obstacle to this therapy is delivery of the nucleic acids to the target site, which requires overcoming problems such as capture by the immune system, the need to penetrate biofilms, and degradation of nucleic acid performance. Designing suitable delivery vectors is key to solving these problems. Lipids-which consist of a hydrophilic headgroup, a linker, and a hydrophobic tail-are crucial components for the construction of vectors. The headgroup is particularly important because it affects the drug encapsulation rate, the vector cytotoxicity, and the transfection efficiency. Herein, we focus on various headgroup structures (tertiary amines, quaternary ammonium salts, peptides, piperazines, dendrimers, and several others), and we summarize and classify important lipid-based carriers that have been developed in recent years. We also discuss applications of cationic lipids with various headgroups for delivery of nucleic acid drugs, and we analyze how headgroup structure affects transport efficiency and carrier toxicity. Finally, we briefly describe the challenges of developing novel lipid carriers, as well as their prospects.

Endolysosomal trapping of therapeutics and endosomal escape strategies

Internalizing therapeutic molecules or genes into cells and safely delivering them to the target tissue where they can perform the intended tasks is one of the key characteristics of the smart gene/drug delivery vector. Despite much research in this field, endosomal escape continues to be a significant obstacle to the development of effective gene/drug delivery systems. In this review, we discuss in depth the several types of endocytic pathways involved in the endolysosomal trapping of therapeutic agents. In addition, we describe numerous mechanisms involved in nanoparticle endosomal escape. Furthermore, many other techniques are employed to increase endosomal escape to minimize entrapment of therapeutic compounds within endolysosomes, which have been reviewed at length in this study.

Esterase-Labile Quaternium Lipidoid Enabling Improved mRNA-LNP Stability and Spleen-Selective mRNA Transfection

Ionizable cationic lipids are recognized as an essential component of lipid nanoparticles (LNPs) for messenger RNA (mRNA) delivery but can be confounded by low lipoplex stability with mRNA during storage and in vivo delivery. Herein, the rational design and combinatorial synthesis of esterase-triggered decationizable quaternium lipid-like molecules (lipidoids) are reported to develop new LNPs with high delivery efficiency and improved storage stability. This top lipidoid carries positive charges at the physiological condition but promptly acquires negative charges in the presence of esterase, thus permitting stable mRNA encapsulation during storage and in vivo delivery while balancing efficient mRNA release in the cytosol. An optimal LNP formulation is then identified through orthogonal optimization, which enables efficacious mRNA transfection selectively in the spleen following intravenous administration. LNP-mediated delivery of ovalbumin (OVA)-encoding mRNA induces efficient antigen expression in antigen-presenting cells and elicits robust antigen-specific immune responses against OVA-transduced tumors. The work demonstrates the potential of decationizable quaternium lipidoids for spleen-selective RNA transfection and cancer immunotherapy.

Elevating nucleic acid delivery via a stable anionic peptide-dextran ternary system

Nucleic acid-based therapies hold promise for treating previously intractable diseases but require effective delivery vectors to protect the therapeutic agents and ensure efficient transfection. Cationic polymeric vectors are particularly notable for their adaptability, high transfection efficiency, and low cost, but their positive charge often attracts blood proteins, causing aggregation and reduced transfection efficiency. Addressing this, we designed an anionic peptide-grafted dextran (Dex-LipE5H) to serve as a cross-linkable coating to bolster the stability of cationic polymer/nucleic acid complexes. The Dex-LipE5H was synthesized through a Michael addition reaction, combining an anionic peptide (LipE5H) with dextran modified by divinyl sulfone. We demonstrated Dex-lipE5H utility in a novel ternary nucleic acid delivery system, CDex-LipE5H/PEI/nucleic acid. CDex-LipE5H/PEI/nucleic acid demonstrated lower cytotoxicity and superior anti-protein absorption ability compared to PEI/pDNA and Dex-LipE5H/PEI/pDNA. Most notably, the crosslinked CDex-LipE5H/PEI/pDNA demonstrated remarkable transfection performance in HepG2 cells, which poses significant transfection challenges, even in a medium with 20% serum. This system's effective siRNA interference performance was further validated through a PCSK9 gene knockdown assay. This investigation provides novel insights and contributes to the design of cost-effective, next-generation nucleic acid delivery systems with enhanced blood stability and transfection efficiency.

Biodegradable Cationic and Ionizable Cationic Lipids: A Roadmap for Safer Pharmaceutical Excipients

Cationic and ionizable cationic lipids are broadly applied as auxiliary agents, but their use is associated with adverse effects. If these excipients are rapidly degraded to endogenously occurring metabolites such as amino acids and fatty acids, their toxic potential can be minimized. So far, synthesized and evaluated biodegradable cationic and ionizable cationic lipids already showed promising results in terms of functionality and safety. Within this review, an overview about the different types of such biodegradable lipids, the available building blocks, their synthesis and cleavage by endogenous enzymes is provided. Moreover, the relationship between the structure of the lipids and their toxicity is described. Their application in drug delivery systems is critically discussed and placed in context with the lead compounds used in mRNA vaccines. Moreover, their use as preservatives is reviewed, guidance for their design is provided, and an outlook on future developments is given.

Nucleic acid-based artificial nanocarriers for gene therapy

Nucleic acid nanotechnology is a powerful tool in the fields of biosensing and nanomedicine owing to their high editability and easy synthesis and modification. Artificial nucleic acid nanostructures have become an emerging research hotspot as gene carriers with low cytotoxicity and immunogenicity for therapeutic approaches. In this review, recent progress in the design and functional mechanisms of nucleic acid-based artificial nano-vectors especially for exogenous siRNA and antisense oligonucleotide delivery is summarized. Different types of DNA nanocarriers, including DNA junctions, tetrahedrons, origami, hydrogels and scaffolds, are introduced. The enhanced targeting strategies to improve the delivery efficacy are demonstrated. Furthermore, RNA based gene nanocarrier systems by self-assembly of short strands, rolling circle transcription, chemical crosslinking and using RNA motifs and DNA-RNA hybrids are demonstrated. Finally, the outlook and potential challenges are highlighted. The nucleic acid-based artificial nanocarriers offer a promising and precise tool for gene delivery and therapy.

Boron clusters as broadband membrane carriers

The membrane translocation of hydrophilic substances constitutes a challenge for their application as therapeutic compounds and labelling probes^1–4. To remedy this, charged amphiphilic molecules have been classically used as carriers^3,5. However, such amphiphilic carriers may cause aggregation and non-specific membrane lysis^6,7. Here we show that globular dodecaborate clusters, and prominently B₁₂Br₁₂²⁻, can function as anionic inorganic membrane carriers for a broad range of hydrophilic cargo molecules (with molecular mass of 146–4,500 Da). We show that cationic and neutral peptides, amino acids, neurotransmitters, vitamins, antibiotics and drugs can be carried across liposomal membranes. Mechanistic transport studies reveal that the carrier activity is related to the superchaotropic nature of these cluster anions^8–12. We demonstrate that B₁₂Br₁₂²⁻ affects cytosolic uptake of different small bioactive molecules, including the antineoplastic monomethyl auristatin F, the proteolysis targeting chimera dBET1 and the phalloidin toxin, which has been successfully delivered in living cells for cytoskeleton labelling. We anticipate the broad and distinct delivery spectrum of our superchaotropic carriers to be the starting point of conceptually distinct cell-biological, neurobiological, physiological and pharmaceutical studies.

The superchaotropic nature of globular boron cluster anions enables direct passage of a wide range of molecules across lipid membranes.

Carbodiimide-Driven Dimerization and Self-Assembly of Artificial, Ribose-Based Amphiphiles

The aqueous self‐assembly of amphiphiles into aggregates such as micelles and vesicles has been widely investigated over the past decades with applications ranging from materials science to drug delivery. The combination of characteristic properties of nucleic acids and amphiphiles is of substantial interest to mimic biological self‐organization and compartmentalization. Herein, we present ribose‐ and ribonucleotide‐based amphiphiles and investigate their self‐assembly as well as their fundamental reactivity. We found that various types of aggregates are formed, ranging in size from nanometers to micrometers and all amphiphiles exhibit aggregation‐induced emission (AIE) in solution as well as in the solid state. We also observed that the addition of 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide (EDC) leads to rapid and selective dimerization of the amphiphiles into pyrophosphates, which decreases the critical aggregation concentration (CAC) by a factor of 25 when compared to the monomers. Since the propensity for amphiphile dimerization is correlated with their tendency to self‐assemble, our results may be relevant for the formation of rudimentary compartments under prebiotic conditions.

Serum Compatible Spermine-based Cationic Lipids with Non-identical Hydrocarbon Tails Mediate High Transfection Efficiency

Cationic lipids are widely used as non-viral synthetic vectors for gene delivery as a safer alternative to viral vectors. In this work, a library of L-shaped spermine-based cationic lipids with identical and non-identical hydrophobic chains having variable carbon length (from C10 to C18) was designed and synthesized. These lipids were characterized and the structure-activity relationships of these compounds were determined for DNA binding and transfection ability when formulated as cationic liposomes. The liposomes were then used successfully for the transfection of HEK293T, HeLa, PC3, H460, HepG2, SH-SY5Y and Calu'3 cell lines. The transfection efficiency of lipids with non-identical hydrocarbon chains was greater than the identical analog. These reagents exhibited superior efficiency to the commercial reagent, Lipofectamine3000, under both serum-free and 10-40% serum conditions in HEK293T, HeLa and H460 cell lines. The lipids were also not toxic to the tested cells. The results suggested that L-shaped spermine-based cationic lipids with non-identical hydrocarbon tails could serve as an efficient and safe non-viral vector gene carrier for further in vivo studies.

Rational preparation and application of a mRNA delivery system with cytidinyl/cationic lipid

The messenger RNA (mRNA)-based therapy, especially mRNA vaccines, has shown its superiorities in versatile design, rapid development and scale production, since the outbreak of coronavirus disease 2019 (COVID-19). Although the Pfizer-BioNTech and Moderna COVID-19 mRNA vaccines had been approved for application, unexpected adverse events were reported to be most likely associated with the mRNA delivery systems. Thus, the development of mRNA delivery system with good efficacy and safety remains a challenge. Here, for the first time, we report that the neutral cytidinyl lipid, 2-(4-amino-2-oxopyrimidin-1-yl)-N-(2,3-dioleoyl-oxypropyl) acetamide (DNCA), and the cationic lipid, dioleoyl-3,3'-disulfanediylbis-[2-(2,6-diaminohexanamido)] propanoate (CLD), could encapsulate and deliver the COVID-19 mRNA-1096 into the cytoplasm to induce robust adaptive immune response. In the formulation, the molar ratio of DNCA/CLD to a single nucleotide of COVID-19 mRNA-1096 was about 0.9: 0.5: 1 (the N/P ratio was about 7: 1). The DNCA/CLD-mRNA-1096 lipoplexes were rationally prepared by the combination of the lipids DNCA/CLD with the aqueous mRNA solution under mild sonication to stimulate multiple interactions, including H-bonding, π-stacking and electrostatic force between the lipids and the mRNA. After intramuscular applications of the DNCA/CLD-mRNA-1096 lipoplexes, robust neutralizing antibodies and long-lived Th1-biased SARS-CoV-2-specific cell immunity were detected in the immunized mice, thus suggesting the DNCA/CLD a promising mRNA delivery system. Moreover, our study might also inspire better ideas for developing mRNA delivery systems.

Charge-Conversion Strategies for Nucleic Acid Delivery

Nucleic acids are now considered as one of the most potent therapeutic modalities, as their roles go beyond storing genetic information and chemical energy or as signal transducer. Attenuation or expression of desired genes through nucleic acids have profound implications in gene therapy, gene editing and even in vaccine development for immunomodulation. Although nucleic acid therapeutics bring in overwhelming possibilities towards the development of molecular medicines, there are significant loopholes in designing and effective translation of these drugs into the clinic. One of the major pitfalls lies in the traditional design concepts for nucleic acid drug carriers, viz. cationic charge induced cytotoxicity in delivery pathway. Targeting this bottleneck, several pioneering research efforts have been devoted to design innovative carriers through charge-conversion approaches, whereby built-in functionalities convert from cationic to neutral or anionic, or even from anionic to cationic enabling the carrier to overcome several critical barriers for therapeutics delivery, such as serum deactivation, instability in circulation, low transfection and poor endosomal escape. This review will critically analyze various molecular designs of charge-converting nanocarriers in a classified approach for the successful delivery of nucleic acids. Accompanied by the narrative on recent clinical nucleic acid candidates, the review concludes with a discussion on the pitfalls and scope of these interesting approaches.

From Interaction to Function in DNA-Templated Supramolecular Self-Assemblies

DNA-templated self-assembly represents a rich and growing subset of supramolecular chemistry where functional self-assemblies are programmed in a versatile manner using nucleic acids as readily-available and readily-tunable templates. In this review, we summarize the different DNA recognition modes and the basic supramolecular interactions at play in this context. We discuss the recent results that report the DNA-templated self-assembly of small molecules into complex yet precise nanoarrays, going from 1D to 3D architectures. Finally, we show their emerging functions as photonic/electronic nanowires, sensors, gene delivery vectors, and supramolecular catalysts, and their growing applications in a wide range of area from materials to biological sciences.

Overcoming the delivery barrier of oligonucleotide drugs and enhancing nucleoside drug efficiency: The use of nucleolipids

With the rapid development of synthetic technology and biological technology, many nucleic acid-based drugs have entered the clinical trials. However, their inherent disabilities in actively and efficiently penetrating cell membranes still severely restrict their further application. The main drawback of cationic lipids, which have been widely used as nonviral vectors of nucleic acids, is their high cytotoxicity. A series of nucleoside-based or nucleotide-based nucleolipids have been reported in recent years, due to their oligonucleotide delivery capacity and low toxicity in comparison with cationic lipids. Lipophilic prodrugs of nucleoside analogs have extremely similar structures with nucleolipid vectors and are thus helpful for improving the transmembrane ability. This review introduces the progress of nucleolipids and provides new strategies for improving the delivery efficiency of nucleic acid-based drugs, as well as lipophilic prodrugs of nucleosides or nucleotides for antiviral or anticancer therapies.

Cytidine and ribothymidine nucleolipids synthesis, organogelation, and selective anion and metal ion responsiveness

Nucleolipids of 2′,3′-O-diacylatedribothymidine supports the organogelation by utilizing inherent self-base pairing and solvent mediated bifurcated H-bonding and hydrophobic effect. These organogels exhibits unusual Hg²⁺ mediated base pairing.

Self-Assembled Nanomedicines for Anticancer and Antibacterial Applications

Self-assembly strategies have been widely applied in the nanomedicine field, which provide a convenient approach for building various structures for delivery carriers. When cooperating with biomolecules, self-assembly systems have significant influence on the cell activity and life process and could be used for regulating nanodrug activity. In this review, self-assembled nanomedicines are introduced, including materials, encapsulation, and releasing strategies, where self-assembly strategies are involved. Furthermore, as a promising and emerging area for nanomedicine, in situ self-assembly of anticancer drugs and supramolecular antibiotic switches is also discussed about how to regulate drug activity. Selective pericellular assembly can block mass transformation of cancer cells inducing cell apoptosis, and the intracellular assembly can either cause cell death or effectively avoid drug elimination from cytosol of cancer cells because of the assembly-induced retention (AIR) effect. Host-guest interactions of drug and competitive molecules offer reversible regulations of antibiotic activity, which can reduce drug-resistance and inhibit the generation of drug-resistant bacteria. Finally, the challenges and development trend in the field are discussed.

Biodegradable Gene Carriers Containing Rigid Aromatic Linkage with Enhanced DNA Binding and Cell Uptake

The linking and modification of low molecular weight cationic polymers (oligomers) has become an attracted strategy to construct non-viral gene carriers with good transfection efficiency and much reduced cytotoxicity. In this study, PEI 600 Da was linked by biodegradable bridges containing rigid aromatic rings. The introduction of aromatic rings enhanced the DNA-binding ability of the target polymers and also improved the stability of the formed polymer/DNA complexes. The biodegradable property and resulted DNA release were verified by enzyme stimulated gel electrophoresis experiment. These materials have lower molecular weights compared to PEI 25 kDa, but exhibited higher transfection efficiency, especially in the presence of serum. Flow cytometry and confocal laser scanning microscopy results indicate that the polymers with aromatic rings could induce higher cellular uptake. This strategy for the construction of non-viral gene vectors may be applied as an efficient and promising method for gene delivery.

Transfection by cationic gemini lipids and surfactants

Diseases that are linked to defective genes or mutations can in principle be cured by gene therapy, in which damaged or absent genes are either repaired or replaced by new DNA in the nucleus of the cell. Related to this, disorders associated with elevated protein expression levels can be treated by RNA interference via the delivery of siRNA to the cytoplasm of cells. Polynucleotides can be brought into cells by viruses, but this is not without risk for the patient. Alternatively, DNA and RNA can be delivered by transfection, i.e. by non-viral vector systems such as cationic surfactants, which are also referred to as cationic lipids. In this review, recent progress on cationic lipids as transfection vectors will be discussed, with special emphasis on geminis, surfactants with 2 head groups and 2 tails connected by a spacer.

Annealing novel nucleobase-lipids with oligonucleotides or plasmid DNA based on H-bonding or π-π interaction: Assemblies and transfections

Lipid derivatives of nucleoside analogs have been highlighted for their potential for effective gene delivery. A novel class of nucleobase-lipids are rationally designed and readily synthesized, comprising thymine/cytosine, an ester/amide linker and an oleyl lipid. The diversity of four nucleobase-lipids termed DXBAs (DOTA, DNTA, DOCA and DNCA) is investigated. Besides, DNCA is demonstrated to be an effective neutral transfection material for nucleic acid delivery, which enbles to bind to oligonucleotides via H-bonding and π-π stacking with reduced toxicity in vitro and in vivo. Several kinds of nucleic acid drugs including aptamer, ssRNA, antisense oligonucleotide, and plasmid DNAs can be delivered by DXBAs, especially DNCA. In particular, G4-aptamer AS1411 encapsulated by DNCA exhibits cellular uptake enhancement, lysosome degradation reduction, cell apoptosis promotion, cell cycle phase alteration in vitro and duration prolongation in vivo, resulting in significant anti-proliferative activity. Our results demonstrate that DNCA is a promising transfection agent for G4-aptamers and exhibites bright application prospects in the permeation improvement of single-stranded oligonucleotides or plasmid DNAs.

Skeleton-Controlled pDNA Delivery of Renewable Steroid-Based Cationic Lipids, the Endocytosis Pathway Analysis and Intracellular Localization

Using renewable and biocompatible natural-based resources to construct functional biomaterials has attracted great attention in recent years. In this work, we successfully prepared a series of steroid-based cationic lipids by integrating various steroid skeletons/hydrophobes with (l-)-arginine headgroups via facile and efficient synthetic approach. The plasmid DNA (pDNA) binding affinity of the steroid-based cationic lipids, average particle sizes, surface potentials, morphologies and stability of the steroid-based cationic lipids/pDNA lipoplexes were disclosed to depend largely on the steroid skeletons. Cellular evaluation results revealed that cytotoxicity and gene transfection efficiency of the steroid-based cationic lipids in H1299 and HeLa cells strongly relied on the steroid hydrophobes. Interestingly, the steroid lipids/pDNA lipoplexes inclined to enter H1299 cells mainly through caveolae and lipid-raft mediated endocytosis pathways, and an intracellular trafficking route of “lipid-raft-mediated endocytosis→lysosome→cell nucleic localization” was accordingly proposed. The study provided possible approach for developing high-performance steroid-based lipid gene carriers, in which the cytotoxicity, gene transfection capability, endocytosis pathways, and intracellular trafficking/localization manners could be tuned/controlled by introducing proper steroid skeletons/hydrophobes. Noteworthy, among the lipids, Cho-Arg showed remarkably high gene transfection efficacy, even under high serum concentration (50% fetal bovine serum), making it an efficient gene transfection agent for practical application.

siRNA Delivery Using a Cationic-Lipid-Based Highly Selective Human DNA Ligase I Inhibitor

The present article illustrates the serendipitous discovery of a cationic-lipid-based human DNA ligase (hLig) I inhibitor and the development of siRNA delivering, a hLigI-targeted cationic-lipid-based nonviral vector. We have tested a small in-house library of structurally similar cationic lipo-anisamides for antiligase activity, and amongst tested, N-dodecyl-N-(2-(4-methoxybenzamido)ethyl)-N-methyldodecan-1-ammonium iodide (C12M) selectively and efficiently inhibited the enzyme activity of hLigI, compared to other human ligases (hLigIIIβ and hLigIV/XRCC4) and bacterial T4 DNA ligase. Furthermore, upon hydration with equimolar cholesterol, C12M produced antiligase cationic liposomes, which transfected survivin siRNA and showed significant inhibition of tumor growth.

Engineering liposomal nanoparticles for targeted gene therapy

Recent mechanistic studies have attempted to deepen our understanding of the process by which liposome-mediated delivery of genetic material occurs. Understanding the interactions between lipid nanoparticles and cells is still largely elusive. Liposome-mediated delivery of genetic material faces systemic obstacles alongside entry into the cell, endosomal escape, lysosomal degradation and nuclear uptake. Rational design approaches for targeted delivery have been developed to reduce off-target effects and enhance transfection. These strategies, which have included the modification of lipid nanoparticles with target-specific ligands to enhance intracellular uptake, have shown significant promise at the proof-of-concept stage. Control of physical and chemical specifications of liposome composition, which includes lipid-to-DNA charge, size, presence of ester bonds, chain length and nature of ligand complexation, is integral to the performance of targeted liposomes as genetic delivery agents. Clinical advances are expected to rely on such systems in the therapeutic application of liposome nanoparticle-based gene therapy. Here, we discuss the latest breakthroughs in the development of targeted liposome-based agents for the delivery of genetic material, paying particular attention to new ligand and cationic lipid design as well as recent in vivo advances.

Plant-derived phosphocholine facilitates cellular uptake of anti-pulmonary fibrotic HJT-sRNA-m7

Pulmonary fibrosis, a progressive chronic disease with a high mortality rate, has limited treatment options. Currently, lung transplantation remains the only effective treatment. Here we report that a small RNA, HJT-sRNA-m7, from a Chinese herbal medicine Hong Jing Tian (HJT, RHODIOHAE CRENULATAE RADIX ET RHIZOMA, Rhodiola crenulata) can effectively reduce the expressions of fibrotic hallmark genes and proteins both in alveolar in vitro and in mouse lung tissues in vivo. We also discovered over one hundred oil-soluble chemicals from HJT decoctions, most of which are found in lipid extracts from other Chinese herbals decoctions, including Pu Gong Ying (PGY, TARAXACI HERBA, Taraxacum mongolicum), Chuan Xin Lian (CXL, changed to "ANDROGRAPHIS HERBA, Andrographis paniculata"), and Jin Yin Hua (JYH, lonicera japonica or Honeysuckle). We identified the active component in these decoctions as two forms of phosphocholines, PC (18:0/18:2) and PC (16:0/18:2). These PCs potentially could form liposomes with small RNAs to enter human alveolar and gastric cells. Our experimental results suggest an unprecendent lipid complex route through which botanic small RNA can enter human bodies. Our results provide an innovative treatment strategy for oral delivery of siRNAs as therapeutic medication.

pH and reduction dual-responsive dipeptide cationic lipids with α-tocopherol hydrophobic tail for efficient gene delivery

A series of tocopherol-based cationic lipid 3a-3f bearing a pH-sensitive imidazole moiety in the dipeptide headgroup and a reduction-responsive disulfide linkage were designed and synthesized. Acid-base titration of these lipids showed good buffering capacities. The liposomes formed from 3 and co-lipid 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) could efficiently bind and condense DNA into nanoparticles. Gel binding and HPLC assays confirmed the encapsulated DNA could release from lipoplexes 3 upon addition of 10 mM glutathione (GSH). MTT assays in HEK 293 cells demonstrated that lipoplexes 3 had low cytotoxicity. The in vitro gene transfection studies showed cationic dipeptide headgroups clearly affected the transfection efficiency (TE), and arginine-histidine based dipeptide lipid 3f give the best TE, which was 30.4 times higher than Lipofectamine 3000 in the presence of 10% serum. Cell-uptake assays indicated that basic amino acid containing dipeptide cationic lipids exhibited more efficient cell uptake than serine and aromatic amino acids based dipeptide lipids. Confocal laser scanning microscopy (CLSM) studies corroborated that 3 could efficiently deliver and release DNA into the nuclei of HeLa cells. These results suggest that tocopherol-based dipeptide cationic lipids with pH and reduction dual-sensitive characteristics might be promising non-viral gene delivery vectors.

Bifunctional cationic solid lipid nanoparticles of β-NaYF4:Yb,Er upconversion nanoparticles coated with a lipid for bioimaging and gene delivery

We demonstrate the possibility of novel bifunctional cationic solid lipid nanoparticles (CSLNs) for bioimaging and gene delivery through peptide lipid coated UCNPs.

Physicochemical properties of lipopeptide-based liposomes and their complexes with siRNA

siRNA/cationic liposome complexes are efficient systems for transmembrane delivery. The aim of this study was to prepare a novel complex consisted of lipotripeptide OrnOrnGlu(C16H33)2 and siRNA molecule and examined their physicochemical properties. Electron microscopy study has shown that the siRNA/liposome complex (m/m 1/10) tends to form sandwich-like structures that may protect nucleic acid from nuclease degradation. Photon correlation spectroscopy data indicate that the particle size increased after siRNA adding, but did not exceed 300 nm in diameter, while z-potential of lipoplexes decreased from 22 mV to 14 mV, compared to the empty liposomes thus indicating positive charge neutralization by negatively charged siRNA. These data allow to hypothesize that such size and total positive charge could provide efficient cellular uptake by endocytosis. That may have good prospects for gene silencing therapy.

Synthesis and evaluation of novel lipopeptide as a vehicle for efficient gene delivery and gene silencing

Nucleic acid-based therapeutics have recently emerged as a new class of next generation agents for treatment and prevention of viral infection, cancer, and genetic disorders, but their wide use is limited by their relatively weak delivery into target cells. Usage of synthetic cationic amphiphiles with peptide hydrophilic domain as agents for non-viral gene delivery is an attractive approach. We developed the schemes for the synthesis of aliphatic peptides with different length of the hydrocarbon chains in hydrophobic domains and different amino acids in polar head. For the obtained derivatives we determined transfection efficiency, critical vesicle concentration, particle size, ζ-potential and aggregates stability. We have found that the transfection efficiency is increased if the ornithine is a part of polar head in an amphiphile. The most promising amphiphile for liposomal formation OrnOrnGlu(C16H33)2 was examined more carefully. It has been shown that the lipopeptide possesses low toxicity (in vitro and in vivo) and high transfection efficiency with pDNA and siRNA in different cell lines. In addition, the production of liposomes based on this lipopeptide is simple, quick and cheap. Thus OrnOrnGlu(C16H33)2 is a promising vehicle for gene delivery and gene silencing.

Spermine-modified Antheraea pernyi silk fibroin as a gene delivery carrier

The development of a novel cationized polymer used as a gene delivery carrier that can conveniently and effectively transfect cells resulting in a stably expressed target gene remains a challenge. Antheraea pernyi silk fibroin (ASF) is a cytocompatible and biodegradable natural polymer, and it possesses Arg-Gly-Asp sequences but a negative charge. In order to render ASF amenable to packaging plasmid DNA (pDNA), spermine was used to modify ASF to synthesize cationized ASF (CASF), which was used as a gene delivery carrier. CASF was characterized using trinitrobenzene sulfonic acid assay, the zeta potential determination, and a Fourier transform infrared analysis, and the results of these characterizations indicated that the -NH2 in spermine effectively reacts with the -COOH in the side chains of ASF. Spermine grafted to the side chains of ASF resulted in the conversion of the negative charge of ASF to a positive charge. CASF packaged pDNA and formed CASF/pDNA complexes, which exhibited spherical morphology with average particle sizes of 215-281 nm and zeta potential of approximately +3.0 mV to +3.2 mV. The results of the MTT assay, confocal laser scanning microscopy, and flow cytometry analysis in a human endothelial cell line revealed that CASF/pDNA complexes exhibited lower cytotoxicity and higher transfection efficiency compared to the pDNA complexes of polyethyleneimine. These results indicate that our synthesized CASF, a cationized polymer, is a potential gene delivery carrier with the advantages of biodegradability and low cytotoxicity.

Bioactive clusters promoting cell penetration and nucleic acid complexation for drug and gene delivery applications: from designed to self-assembled and responsive systems

Recent developments in the (self-)assembly of cationic clusters promoting nucleic acids complexation and cell penetration open the door to applications in drug and gene delivery.

Complex self-assembly of pyrimido[4,5-d]pyrimidine nucleoside supramolecular structures

Supramolecular self-assembly is not only one of the chemical roots of biological structure but is also drawing attention in different industrial fields. Here we study the mechanism of the formation of a complex flower-shaped supramolecular structure of pyrimido[4,5-d]pyrimidine nucleosides by dynamic light scattering, scanning electron microscopy, differential scanning calorimetry, nuclear magnetic resonance and X-ray analysis. Upon removing the hydroxyl group of sugars, different flower-shaped superstructures can be produced. These works demonstrate that complex self-assembly can indeed be attained through hierarchical non-covalent interactions of single molecules. Furthermore, chimerical structures built from molecular recognition by these monomers indicate their potential in other fields if combined with other chemical entities.

Supramolecular self-assembly is a fundamentally important process in fields ranging from structural biology to materials chemistry. Here, the authors report the supramolecular assembly of complex nanostructures from simple nucleosides, and probe the formation process using various in situ techniques.

Tri-peptide cationic lipids for gene delivery

Several novel tri-peptide cationic lipids were designed and synthesized for delivering DNA and siRNA. They have tri-lysine and tri-ornithine as head groups, carbamate group as linker and 12 and 14 carbon atom alkyl groups as tails. These tri-peptide cationic lipids were prepared into cationic liposomes for the study of the physicochemical properties and gene delivery. Their particle size, Zeta potential and DNA-binding were characterized to show that they were suitable for gene transfection. The further results indicate that these lipids can transfer DNA and siRNA very efficiently into NCI-H460 and Hep-2 tumor cells. The selected lipid, CDO14, was able to deliver combined siRNAs against c-Myc and VEGF for silencing distinct oncogenic pathways in lung tumors of mice, with little in vitro and in vivo toxicity.

PGMA-based starlike polycations with flanking phenylboronic acid groups for highly efficient multifunctional gene delivery systems

A simple strategy to prepare starlike PGMA-based vectors with phenylboronic acid groups was proposed for multifunctional gene delivery systems.

Small cyclen-imidazolium-containing molecules and their interactions with DNA

Three small organic molecules containing different numbers of cyclen and imidazolium units were synthesized. Their interactions with plasmid DNA and their potential for gene delivery vectors were investigated. Agarose gel retardation and ethidium bromide exclusion assays revealed that these molecules can effectively condense DNA, and compounds with higher molecular weights are needed to lower w/w ratio for full condensation. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) indicated that these compounds may form nanosized spherical particles with DNA. Furthermore, the complex formed from 10, i.e., 10/DNA, can partially release DNA from compact state at a relatively higher concentration of NaCl (200 mM). In the presence of the lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), 10 could transfer plasmid DNA into BEL-7402 cells. In addition, these compounds exhibited much lower cytotoxicity than PEI 25 kDa.

Molecular recognition of nucleic acids by nucleolipid/dendrimer surface complexes

We show for the first time that 1,2-dilauroyl-sn-glycero-3-phosphatidyladenosine nucleolipid surface complexes with cationic poly(amidoamine) dendrimers can be used to selectively bind DNA including oligonucleotides. This molecular recognition has high potential for applications involving biomedical and bioanalytic devices as well as drug delivery systems based on nucleic acids.

Nanostructural systems developed with positive charge generation to drug delivery

The surface charge of a nanostructure plays a critical role in modulating blood circulation time, nanostructure-cell interaction, and intracellular events. It is unfavorable to have positive charges on the nanostructure surface before arriving at the disease site because positively charged nanostructures interact strongly with blood components, resulting in rapid clearance from the blood, and suboptimal targeted accumulation at the tumor site. Once at the tumor site, however, the positive charge on the nanostructure surface accelerates uptake by tumor cells and promotes the release of payloads from the lysosomes to the cytosol or nucleus inside cells. Thus, the ideal nanocarrier systems for drug delivery would maintain a neutral or negatively charged surface during blood circulation but would then generate a positive surface charge after accumulation at the tumor site or inside the cancer cells. This Progress Report focuses on the design and application of various neutral or negatively charged nanostructures that can generate a positive charge in response to the tumor microenvironment or an external stimulus.

Designer lipids for drug delivery: from heads to tails

For four decades, liposomes composed of both naturally occurring and synthetic lipids have been investigated as delivery vehicles for low molecular weight and macromolecular drugs. These studies paved the way for the clinical and commercial success of a number of liposomal drugs, each of which required a tailored formulation; one liposome size does not fit all drugs! Instead, the physicochemical properties of the liposome must be matched to the pharmacology of the drug. An extensive biophysical literature demonstrates that varying lipid composition can influence the size, membrane stability, in vivo interactions, and drug release properties of a liposome. In this review we focus on recently described synthetic lipid headgroups, linkers and hydrophobic domains that can provide control over the intermolecular forces, phase preference, and macroscopic behavior of liposomes. These synthetic lipids further our understanding of lipid biophysics, promote targeted drug delivery and improve liposome stability. We further highlight the immune reactivity of novel synthetic headgroups as a key design consideration. For instance it was originally thought that synthetic PEGylated lipids were immunologically inert; however, it's been observed that under certain conditions PEGylated lipids induce humoral immunity. Such immune activation may be a limitation to the use of other engineered lipid headgroups for drug delivery. In addition to the potential immunogenicity of engineered lipids, future investigations on liposome drugs in vivo should pay particular attention to the location and dynamics of payload release.

Glucose- and pH-responsive charge-reversal surfaces

We have shown a pH- and glucose-responsive charge reversal on silica surface through heterogeneous functionalization utilizing amines and boronic acid moieties. The dual responsiveness of the charge reversal has been unambiguously demonstrated through the desorption of charged chromophores. Interestingly, we observed a concentration-dependent desorption response to glucose at physiologically relevant levels.

Monitoring the interaction of nucleolipoplexes with model membranes

We report on the interaction of nucleolipid/DNA assemblies with model membranes, studied with small angle X-ray scattering, fluorescence microscopy and correlation spectroscopy. The fusion with the membrane can be monitored by following the diffusion properties of a lipid probe, shedding light on the parameters that regulate the internalization of the complexes.

Enhanced cellular uptake of amphiphilic gold nanoparticles with ester functionality

Gold nanoparticles (AuNPs) coated with ester-headed or ether-headed PEG ligands were synthesized.