The Design of Cationic Lipids for Gene Delivery

Study of the correlation between the structure of selected triester of phosphatidylcholine and their impact on physicochemical properties of model mammalian membranes

Cationic lipids are synthetic compounds of amphiphilic character used in Drug Delivery Systems (DDS), especially in gene therapy, as the carriers of genetic material. As it is known, the main limitation of the application of cationic lipids in DDS is their high cytotoxicity after in vivo administration and low bioactivity. This is probably related to not fully known the relationship between the lipid structure and its activity as well as the mechanism of lipofection or drug delivery. Therefore, in this work we determined the impact of a selected group of cationic lipids - triesters of phosphatidylcholine (Et-PCs) - differing in their hydrophobic structure on model mammalian membranes. In the research, as model systems, Langmuir monolayers and liposomes were applied. It was shown that the incorporation of Et-PCs into model mammalian membranes weakens interactions between lipids, causing the increase of fluidity, disordering degree and permeability of membrane. The destabilization of the membrane in this way can facilitate the entry of drugs, carried inside cationic liposomes, into the pathological cell. Moreover, the studies prove that the structure of the hydrophobic part of cationic lipids also affects the properties of lipid membranes.

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.

Dual-Targeted Therapy in HER2-Overexpressing Breast Cancer with Trastuzumab and Novel Cholesterol-Based Nioplexes Silencing Mcl-1

The challenge in HER2-overexpressing breast cancer therapy lies in creating an effective target therapy to overcome treatment resistance. Monoclonal antibodies and target gene silencing by siRNA are two potential strategies that have been widely developed for treating HER2-positive breast cancer. The siRNA delivery system is a crucial factor that influences siRNA therapy's success. In this study, lipid-based nanoparticles (cationic niosomes) composed of different cholesterol-based cationic lipids were formulated and characterized for delivering siRNA into HER2-overexpressing breast cancer cells. Niosomes containing a trimethylammonium headgroup showed the highest siRNA delivery efficiency with low toxicity. The myeloid cell leukemia-1 (Mcl-1) siRNA nioplex treatment significantly decreased mRNA expression and breast cancer cell growth. Dual-targeted therapy, consisting of treatment with an Mcl-1 siRNA nioplex and trastuzumab (TZ) solution, noticeably promoted cell-growth inhibition and apoptosis. The synergistic effect of dual therapy was also demonstrated by computer modeling software (CompuSyn version 1.0). These findings suggest that the developed cationic niosomes were effective nanocarriers for siRNA delivery in breast cancer cells. Furthermore, the Mcl-1 nioplex/TZ dual treatment establishes a synergistic outcome that may have the potential to treat HER2-overexpressing breast cancer.

Tunable pH Sensitive Lipoplexes

To provide long circulating nanoparticles able to carry a gene to tumor cells, we have designed anionic pegylated lipoplexes which are pH sensitive. The reduction of positive charges in nucleic acid carriers allows reducing the elimination rate, increasing circulation time in the blood, leading to improved tumor accumulation of lipid nanoparticles. Anionic pegylated lipoplexes have been prepared from the combined formulation of cationic lipoplexes and pegylated anionic liposomes. The neutralization of the particle surface charge as a function of the pH was monitored by dynamic light scattering in order to determine the ratio between anionic and cationic lipids that would give pH-sensitive complexes. This ratio has been optimized to form particles sensitive to pH change in the range 5.5-6.5. Compaction of DNA into these newly formed anionic complexes was checked by DNA accessibility to Picogreen. The transfection efficiency and pH-sensitive property of these formulations were shown in vitro using bafilomycin, a vacuolar H⁺-ATPase inhibitor.

Development of a spermine lipid for transient antibody expression

Transient expression is the only way to quickly obtain a small scale of antibodies for biomedical research and therapeutic evaluation. The agents for transfecting the suspension cells, e.g. PEI or commercial agents, either lack efficiency or excessively expensive. Herein, a novel spermine-based lipid was developed and fabricated into a cationic liposome for antibody expression. This new transfection agent, designated as sperminoliposome, is feasible, cheap, and highly effective to produce antibodies. Compared to PEI, a 3 times higher yield of antibody was obtained by sperminoliposome during the transient expression of cetuximab in suspension 293F cells. Characterizations confirmed that the expressed antibody is fully functional and eligible for further research. Our study provides an effective tool for the rapid production of antibodies economically and feasibly.

Preparation and Physical Characterization of DNA Binding Cationic Liposomes

Cationic liposomes are routinely employed as one of the major nonviral transfecting agents for intracellular delivery of hydrophilic molecules such as nucleic acids, peptides, and proteins. Cationic liposomes when complexed with DNA form a strong positively charged cationic liposome-DNA complex or lipoplex. The chapter discusses, primarily, the major preparation technique for cationic liposomes and its physical characterization, with a focus on SYBR Green I dye exclusion assay and DNA encapsulation enhancement by freeze-thaw technique. SYBR Green I dye exclusion assay is a technique to determine the total amount of liposomal lipids required to bind a unit weight of DNA, which is critical for transfection experiments. Freeze-thaw technique on the other hand is one of the major techniques to improve DNA encapsulation efficiency in liposomes.

State-of-art high-performance Nano-systems for mutated coronavirus infection management: From Lab to Clinic

The emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants made emerging novel coronavirus diseases (COVID-19) pandemic/endemic/or both more severe and difficult to manage due to increased worry about the efficacy and efficiency of present preventative, therapeutic, and sensing measures. To deal with these unexpected circumstances, the development of novel nano-systems with tuneable optical, electrical, magnetic, and morphological properties can lead to novel research needed for (1) COVID-19 infection (anti-microbial systems against SARS-CoV-2), (2) early detection of mutated SARS-CoV-2, and (3) targeted delivery of therapeutics using nano-systems, i.e., nanomedicine. However, there is a knowledge gap in understanding all these nano-biotechnology potentials for managing mutated SARS-CoV-2 on a single platform. To bring up the aspects of nanotechnology to tackle SARS-CoV-2 variants related COVID-19 pandemic, this article emphasizes improvements in the high-performance of nano-systems to combat SARS-CoV-2 strains/variants with a goal of managing COVID-19 infection via trapping, eradication, detection/sensing, and treatment of virus. The potential of state-of-the-art nano-assisted approaches has been demonstrated as an efficient drug delivery systems, viral disinfectants, vaccine productive cargos, anti-viral activity, and biosensors suitable for point-of-care (POC) diagnostics. Furthermore, the process linked with the efficacy of nanosystems to neutralize and eliminate SARS-CoV-2 is extensively highligthed in this report. The challenges and opportunities associated with managing COVID-19 using nanotechnology as part of regulations are also well-covered. The outcomes of this review will help researchers to design, investigate, and develop an appropriate nano system to manage COVID-19 infection, with a focus on the detection and eradication of SARS-CoV-2 and its variants. This article is unique in that it discusses every aspect of high-performance nanotechnology for ideal COVID pandemic management.

Lipid nanomaterials-based RNA therapy and cancer treatment

We summarize the most important advances in RNA delivery and nanomedicine. We describe lipid nanoparticle-based RNA therapeutics and the impacts on the development of novel drugs. The fundamental properties of the key RNA members are described. We introduced recent advances in the nanoparticles to deliver RNA to defined targets, with a focus on lipid nanoparticles (LNPs). We review recent advances in biomedical therapy based on RNA drug delivery and state-of-the-art RNA application platforms, including the treatment of different types of cancer. This review presents an overview of current LNPs based RNA therapies in cancer treatment and provides deep insight into the development of future nanomedicines sophisticatedly combining the unparalleled functions of RNA therapeutics and nanotechnology.

Cimetidine-Based Cationic Amphiphiles for In Vitro Gene Delivery Targetable to Colon Cancer

Cimetidine, a histamine-2 (H2) receptor antagonist, has been found to have anticancer properties against a number of cancer-type cells. In this report, we have demonstrated that cimetidine can acts as a hydrophilic domain in cationic lipids and targetable to the gastric system by carrying reporter genes and therapeutic genes through in vitro transfection. Two lipids, namely, Toc-Cim and Chol-Cim consisting cimetidine as the main head group and hydrophobic moieties as alpha-tocopherol or cholesterol, respectively, were designed and synthesized. 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) is a well-known co-lipid employed to produce liposomes as uniform vesicles. The liposomes and lipoplexes were structurally and functionally evaluated for global surface charges and hydrodynamic diameters, and results found that both liposome and lipoplex size and surface charges are optimal to screen the transfection potentials. DNA-binding studies were analyzed as complete binding at all formulated N/P ratios. The liposomes and lipoplexes of both the lipids Toc-Cim and Chol-Cim show minimal cytotoxicity even though at higher concentrations. The results of the transfection experiments revealed that tocopherol-based cationic lipids (Toc-Cim) show finer transfection efficacy with optimized N/P ratios (2:1 and 4:1) in the colon cancer cell line. Toc-Cim lipoplexes show higher cellular uptake compare to Chol-Cim in the colon cancer cell line at 2:1 and 4:1 N/P ratios. Toc-Cim and Chol-Cim lipids showed highly compatible serum, examined up to 50% of the serum concentration. To evaluate the apoptotic cell death in CT-26 cells, exposed to Toc-Cim:p53 and Chol-Cim:p53 lipoplexes at 2:1 N/P ratios, superior results showed with Toc-Cim:p53. An effect of TP53 protein expression in CT-26 cell lines assayed by western blot, transfected with Toc-Cim:p53 and Chol-Cim:p53 lipoplexes, demonstrated the superior efficacy of Toc-Cim. All of the findings suggest that Toc-Cim lipid is relatively secure and is an effective transfection agent to colon cancer gene delivery.

Novel branched amphiphilic peptides for nucleic acids delivery

Highly efficient and safe non-viral vectors for nucleic acids delivery have attracted much attention due to their potential applications in gene therapy, gene editing and vaccination against infectious diseases, and various materials have been investigated and designed as delivery vectors. Herein, we designed a series of branched amphiphilic peptides (BAPs) and tested their applications as pDNA/mRNA delivery vectors. The BAP structure was inspired by the phospholipids, in which lysine oligomers were used as the "polar head", segments containing phenylalanine, histidine and leucine were used as the "hydrophobic tails", and a lysine residue was used as the branching point. By comparing the gel retardation, particle sizes and zeta potentials of the BAP/pDNA complexes of the short-branch BAPs (BAP-V1 ∼ BAP-V4), we determined the optimal lysine oligomer was K₆. However, their cell transfection efficiencies were not satisfactory, and thus three long-branch BAPs (BAP-V5 ∼ BAP-V7) were further designed. In these long-branch BAPs, more hydrophobic residues were added and the overall amphiphilicity increased accordingly. The results showed that these three BAPs could effectively compact the nucleic acids, including both pDNA and mRNA, and all could transfect nucleic acids into HEK 293 cells, with low cytotoxicity. Among the three long-branch BAPs, BAP-V7 (bis(FFLFFHHH)-K-K₆) showed the best transfection efficiency at N/P = 10, which was better than the commercial transfection reagent PEI-25 K. These results indicate that increased amphiphilicity would also benefit for BAP mediated nucleic acid delivery. The designed BAPs provide more documents of such novel type of nucleic acids delivery vectors, which is worth of further investigation as a new gene theranostic platforms.

Design and synthesis of hybrid compounds as novel drugs and medicines

The development of highly effective conjugate chemistry approaches is a way to improve the quality of drugs and of medicines. The aim of this paper is to highlight and review such hybrid compounds and the strategies underpinning their design. A variety of unique hybrid compounds provide an excellent toolkit for novel biological activity, e.g. anticancer and non-viral gene therapy (NVGT), and as templates for killing bacteria and preventing antibiotic drug resistance. First we discuss the anticancer potential of hybrid compounds, containing daunorubicin, benzyl- or tetrahydroisoquinoline-coumarin, and cytotoxic NSAID-pyrrolizidine/indolizine hybrids, then NVGT cationic lipid-based delivery agents, where steroids or long chain fatty acids as the lipid moiety are bound to polyamines as the cationic moiety. These polyamines can be linear as in spermidine or spermine, or on a polycyclic sugar template, aminoglycosides kanamycin and neomycin B, the latter substituted with six amino groups. They are highly efficient for the delivery of both fluorescent DNA and siRNA. Molecular precedents can be found for the design of hybrid compounds in the natural world, e.g., squalamine, the first representative of a previously unknown class of natural antibiotics of animal origin. These polyamine-bile acid (e.g. cholic acid type) conjugates display many exciting biological activities with the bile acids acting as a lipidic region and spermidine as the polycationic region. Analogues of squalamine can act as vectors in NVGT. Their natural role is as antibiotics. Novel antibacterial materials are urgently needed as recalcitrant bacterial infection is a worldwide problem for human health. Ribosome inhibitors founded upon dimers of tobramycin or neomycin, bound as ethers by a 1,6-hexyl linker or a more complex diether-disulfide linker, improved upon the antibiotic activity of aminoglycoside monomers by 20- to 1200-fold. Other hybrids, linked by click chemistry, conjugated ciprofloxacin to neomycin, trimethoprim, or tedizolid, which is now in clinical trials.

Liposomes: An emerging carrier for targeting Alzheimer's and Parkinson's diseases

The function of the brain can be affected by various factors that include infection, tumor, and stroke. The major disorders reported with altered brain function are Alzheimer's disease (AD), Parkinson's disease (PD), dementia, brain cancer, seizures, mental disorders, and other movement disorders. The major barrier in treating CNS disease is the blood-brain barrier (BBB), which protects the brain from toxic molecules, and the cerebrospinal fluid (CSF) barrier, which separates blood from CSF. Brain endothelial cells and perivascular elements provide an integrated cellular barrier, the BBB, which hamper the invasion of molecules from the blood to the brain. Even though many drugs are available to treat neurological disorders, it fails to reach the desired site with the required concentration. In this purview, liposomes can carry required concentrations of molecules intracellular by diverse routes such as carrier-mediated transport and receptor-mediated transcytosis. Surface modification of liposomes enables them to deliver drugs to various brain cells, including neurons, astrocytes, oligodendrocytes, and microglia. The research studies supported the role of liposomes in delivering drugs across BBB and in reducing the pathogenesis of AD and PD. The liposomes were surface-functionalized with various molecules to reach the cells intricated with the AD or PD pathogenesis. The targeted and sustained delivery of drugs by liposomes is disturbed due to the antibody formation, renal clearance, accelerated blood clearance, and complement activation-related pseudoallergy (CARPA). Hence, this review will focus on the characteristics, surface functionalization, drug loading, and biodistribution of liposomes respective to AD and PD. In addition, the alternative strategies to overcome immunogenicity are discussed briefly.

Evaluation of pentaerythritol-based and trimethylolpropane-based cationic lipidic materials for gene delivery

The chemical and physical structure of cationic liposomes pays an important effect on their gene transfection efficiency. Investigation on the structure-function relationship of cationic liposomes will guide the design of novel cationic liposomes with high transfection efficiency and biosafety. In this paper, two novel series of lipids based on the backbone of pentaerythritol and trimethylolpropane were discovered, and their gene transfection efficiencies were assayed in vitro. The four lipids 8c, 9c, 14b, and 15b, exhibited much better transfection efficiency in the HEK293 cell lines compared with Lipo2000, lipid 9c also showed good transfection efficiency in the SW480 cell lines. And the structure-efficiency relationship revealed that a hydroxyethyl polar head group boosted transfer potency in trimethylolpropane-type lipids, but reduced in pentaerythritol-type lipids.

Influence of Hydrophobicity in the Hydrophilic Region of Cationic Lipids on Enhancing Nucleic Acid Delivery and Gene Editing

Intracellular delivery of biomolecules using non-viral vectors critically depends on the vectors' ability to allow the escape and release of the contents from the endosomes. Prior findings demonstrated that aromatic/hydrophobic group-containing amino acids such as phenylalanine (F) and tryptophan (W) destabilize cellular membranes by forming pores in the lipid bilayer. Taking cues from these findings, we have developed four α-tocopherol-based cationic amphiphiles by varying the aromatic/hydrophobic amino acids such as glycine (G), proline (P), phenylalanine (F), and tryptophan (W) as head groups and triazole in the linker region to study their impact on endosomal escape for the enhanced transfection efficacy. The lipids tocopherol-triazole-phenylalanine (TTF) and tocopherol-triazole-tryptophan (TTW) exhibited similar potential to commercial transfecting reagents, Lipofectamine (LF) 3000 and Lipofectamine Messenger Max (LFMM), respectively, in transfecting plasmid DNA and messenger RNA in multiple cultured cell lines. The TTW liposome was also found to be effective in delivering Cas9 mRNA and demonstrated equal efficiency of gene editing AAVS1 locus compared to LFMM in CHO, Neuro-2a, and EA.HY926 cell lines. In this current investigation, it is shown that the synthesized cationic lipids with aromatic hydrophobic R group-containing amino acids are safe, economic, and actually more efficient in nucleic acid delivery and genome-editing applications. These findings can be further explored in the genome-editing approach for treating genetic disorders.

Targeted Delivery of mRNA with One-Component Ionizable Amphiphilic Janus Dendrimers

Targeted and efficient delivery of nucleic acids with viral and synthetic vectors is the key step of genetic nanomedicine. The four-component lipid nanoparticle synthetic delivery systems consisting of ionizable lipids, phospholipids, cholesterol, and a PEG-conjugated lipid, assembled by microfluidic or T-tube technology, have been extraordinarily successful for delivery of mRNA to provide Covid-19 vaccines. Recently, we reported a one-component multifunctional sequence-defined ionizable amphiphilic Janus dendrimer (IAJD) synthetic delivery system for mRNA relying on amphiphilic Janus dendrimers and glycodendrimers developed in our laboratory. Amphiphilic Janus dendrimers consist of functional hydrophilic dendrons conjugated to hydrophobic dendrons. Co-assembly of IAJDs with mRNA into dendrimersome nanoparticles (DNPs) occurs by simple injection in acetate buffer, rather than by microfluidic devices, and provides a very efficient system for delivery of mRNA to lung. Here we report the replacement of most of the hydrophilic fragment of the dendron from IAJDs, maintaining only its ionizable amine, while changing its interconnecting group to the hydrophobic dendron from amide to ester. The resulting IAJDs demonstrated that protonated ionizable amines play dual roles of hydrophilic fragment and binding ligand for mRNA, changing delivery from lung to spleen and/or liver. Replacing the interconnecting ester with the amide switched the delivery back to lung. Delivery predominantly to liver is favored by pairs of odd and even alkyl groups in the hydrophobic dendron. This simple structural change transformed the targeted delivery of mRNA mediated with IAJDs, from lung to liver and spleen, and expands the utility of DNPs from therapeutics to vaccines.

Liposomal nanoparticles based on steroids and isoprenoids for nonviral gene delivery

Natural lipid molecules are an essential part of life as they constitute the membrane of cells and organelle. In most of these cases, the hydrophobicity of natural lipids is contributed by alkyl chains. Although natural lipids with a nonfatty acid hydrophobic backbone are quite rare, steroids and isoprenoids have been strong candidates as part of a lipid. Over the years, these natural molecules (steroid and isoprenoids) have been used to make either lipid-based nanoparticle or functionalize in such a way that it could form nano assembly alone for therapeutic delivery. Here we mainly focus on the synthetic functionalized version of these natural molecules which forms cationic liposomal nanoparticles (LipoNPs). These cationic LipoNPs were further used to deliver various negatively charged genetic materials in the form of pDNA, siRNA, mRNA (nucleic acids), and so on. This article is categorized under: Biology-Inspired Nanomaterials > Lipid-Based Structures.

Nanotechnology-Assisted RNA Delivery: From Nucleic Acid Therapeutics to COVID-19 Vaccines

In recent years, the main quest of science has been the pioneering of the groundbreaking biomedical strategies needed for achieving a personalized medicine. Ribonucleic acids (RNAs) are outstanding bioactive macromolecules identified as pivotal actors in regulating a wide range of biochemical pathways. The ability to intimately control the cell fate and tissue activities makes RNA-based drugs the most fascinating family of bioactive agents. However, achieving a widespread application of RNA therapeutics in humans is still a challenging feat, due to both the instability of naked RNA and the presence of biological barriers aimed at hindering the entrance of RNA into cells. Recently, material scientists' enormous efforts have led to the development of various classes of nanostructured carriers customized to overcome these limitations. This work systematically reviews the current advances in developing the next generation of drugs based on nanotechnology-assisted RNA delivery. The features of the most used RNA molecules are presented, together with the development strategies and properties of nanostructured vehicles. Also provided is an in-depth overview of various therapeutic applications of the presented systems, including coronavirus disease vaccines and the newest trends in the field. Lastly, emerging challenges and future perspectives for nanotechnology-mediated RNA therapies are discussed.

One-Component Multifunctional Sequence-Defined Ionizable Amphiphilic Janus Dendrimer Delivery Systems for mRNA

Efficient viral or nonviral delivery of nucleic acids is the key step of genetic nanomedicine. Both viral and synthetic vectors have been successfully employed for genetic delivery with recent examples being DNA, adenoviral, and mRNA-based Covid-19 vaccines. Viral vectors can be target specific and very efficient but can also mediate severe immune response, cell toxicity, and mutations. Four-component lipid nanoparticles (LNPs) containing ionizable lipids, phospholipids, cholesterol for mechanical properties, and PEG-conjugated lipid for stability represent the current leading nonviral vectors for mRNA. However, the segregation of the neutral ionizable lipid as droplets in the core of the LNP, the "PEG dilemma", and the stability at only very low temperatures limit their efficiency. Here, we report the development of a one-component multifunctional ionizable amphiphilic Janus dendrimer (IAJD) delivery system for mRNA that exhibits high activity at a low concentration of ionizable amines organized in a sequence-defined arrangement. Six libraries containing 54 sequence-defined IAJDs were synthesized by an accelerated modular-orthogonal methodology and coassembled with mRNA into dendrimersome nanoparticles (DNPs) by a simple injection method rather than by the complex microfluidic technology often used for LNPs. Forty four (81%) showed activity in vitro and 31 (57%) in vivo. Some, exhibiting organ specificity, are stable at 5 °C and demonstrated higher transfection efficiency than positive control experiments in vitro and in vivo. Aside from practical applications, this proof of concept will help elucidate the mechanisms of packaging and release of mRNA from DNPs as a function of ionizable amine concentration, their sequence, and constitutional isomerism of IAJDs.

Cationic lipids for gene delivery: many players, one goal

Lipid-based carriers represent the most widely used alternative to viral vectors for gene expression and gene silencing purposes. This class of non-viral vectors is particularly attractive for their ease of synthesis and chemical modifications to endow them with desirable properties. Despite combinatorial approaches have led to the generation of a large number of cationic lipids displaying different supramolecular structures and improved behavior, additional effort is needed towards the development of more and more effective cationic lipids for transfection purposes. With this review, we seek to highlight the great progress made in the design of each and every constituent domain of cationic lipids, that is, the chemical structure of the headgroup, linker and hydrophobic moieties, and on the specific effect on the assembly with nucleic acids. Since the complexity of such systems is known to affect their performances, the role of formulation, stability and phase behavior on the transfection efficiency of such assemblies will be thoroughly discussed. Our objective is to provide a conceptual framework for the development of ever more performing lipid gene delivery vectors.

Comprehensive Survey on Nanobiomaterials for Bone Tissue Engineering Applications

One of the most important ideas ever produced by the application of materials science to the medical field is the notion of biomaterials. The nanostructured biomaterials play a crucial role in the development of new treatment strategies including not only the replacement of tissues and organs, but also repair and regeneration. They are designed to interact with damaged or injured tissues to induce regeneration, or as a forest for the production of laboratory tissues, so they must be micro-environmentally sensitive. The existing materials have many limitations, including impaired cell attachment, proliferation, and toxicity. Nanotechnology may open new avenues to bone tissue engineering by forming new assemblies similar in size and shape to the existing hierarchical bone structure. Organic and inorganic nanobiomaterials are increasingly used for bone tissue engineering applications because they may allow to overcome some of the current restrictions entailed by bone regeneration methods. This review covers the applications of different organic and inorganic nanobiomaterials in the field of hard tissue engineering.

Linear Polyethylenimine-DNA Nanoconstruct for Corneal Gene Delivery

PURPOSE

This study investigated the efficiency and potential toxicity of a linear 22-kDa polyethylenimine (PEI)-DNA nanoconstruct for delivering genes to corneal cells and the effects of PEI nitrogen-to-DNA phosphate (N:P) ratio on gene transfer efficiency in vitro and in vivo.

METHODS

A gel retardation assay, zeta potential measurement, bright-field microscopy, transfection with green fluorescent protein (GFP), immunofluorescence, and enzyme-linked immunosorbent assay (ELISA) were used to characterize the physicochemical and biological properties and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH), and reactive oxygen species (ROS) assay for cytotoxicity of the linear PEI-DNA nanoconstruct using in vitro cultured primary human corneal fibroblast and in vivo mouse models.

RESULTS

Of the several evaluated N:P ratios, the highest gene transfection efficiency achieved without any notable cytotoxicity was observed at an N:P ratio of 30:1 (N:P 30). In vivo gene transfer studies revealed substantial GFP gene delivery into the corneas of mice 3 days after a single 5-min topical application without any significant adverse ocular effects. Slit-lamp biomicroscope ophthalmic examination of the mouse exposed to the linear PEI-DNA nanoconstruct showed no evidence of hyperemia (redness), corneal edema, ocular inflammation, or epiphora (excessive tearing).

CONCLUSIONS

The 22-kDa linear PEI-DNA nanoconstruct is an efficient and well-tolerated vector for corneal gene therapy in vitro and in vivo and could be used as a platform for developing novel gene-based nanomedicine approaches for corneal diseases.

Mesenchymal Stem Cells: A New Generation of Therapeutic Agents as Vehicles in Gene Therapy

In recent years, mesenchymal stem cells (MSCs) as a new tool for therapeutic gene delivery in clinics have attracted much attention. Their advantages cover longer lifespan, better isolation, and higher transfection efficiency and proliferation rate. MSCs are the preferred approach for cell-based therapies because of their in vitro self-renewal capacity, migrating especially to tumor tissues, as well as anti-inflammatory and immunomodulatory properties. Therefore, they have considerable efficiency in genetic engineering for future clinical applications in cancer gene therapy and other diseases. For improving therapeutic efficiency, targeted therapy of cancers can be achieved through the sustained release of therapeutic agents and functional gene expression induction to the intended tissues. The development of a new vector in gene therapy can improve the durability of a transgene expression. Also, the safety of the vector, if administered systemically, may resolve several problems, such as durability of expression and the host immune response. Currently, MSCs are prominent candidates as cell vehicles for both preclinical and clinical trials due to the secretion of therapeutic agents in several cancers. In the present study, we discuss the status of gene therapy in both viral and non-viral vectors along with their limitations. Throughout this study, the use of several nano-carriers for gene therapy is also investigated. Finally, we critically discuss the promising advantages of MSCs in targeted gene delivery, tumor inhibition and their utilization as the gene carriers in clinical situations.

Development of new self-assembled cationic amino liposomes for efficient gene delivery

A library of 83 structurally diverse cationic amino liposomes is rationally designed and parallelly synthesized for the transfection of plasmid DNA and siRNA. Our designed self-assembled liposomes not only exhibit excellent transfection efficiency in HEK 293T cells and mouse embryonic stem cells, but also show low cytotoxicity.

Phosphorylated PEG-emulsifier: Powerful tool for development of zeta potential changing self-emulsifying drug delivery systems (SEDDS)

AIM

It was the aim of this study to synthesize a phosphorylated emulsifier possessing a PEG-linker for establishment of a potent zeta potential changing system in self-emulsifying drug delivery systems (SEDDS).

METHODS

N,N'-Bis(polyoxyethylene)oleylamine (POA) was phosphorylated utilizing pyrophosphoric acid. Successful synthesis of POA bisphosphate (POAP) was confirmed by NMR and HR CS MAS. After incorporation of 1% POAP into SEDDS (Kolliphor RH 40, Capmul PG-8, Labrafac Lipophile WL 1349, Labrafac PG; 30/20/20/30, v/v), according emulsions were incubated with intestinal alkaline phosphatase (IAP) and the zeta potential was measured. Additionally, the amount of released phosphate upon incubation with IAP or on Caco-2 cells was quantified by malachite green assay. Finally, cell viability studies on Caco-2 cells were performed and mucus permeation properties with and without IAP preincubation were assessed.

RESULTS

POAP was synthesized as brown viscous liquid with a yield of 36% and could be incorporated into SEDDS. By incubation with IAP a zeta potential shift from -15.1 to 6.5 mV was observed. A corresponding phosphate release in presence of isolated IAP as well as on Caco-2 cells was found. Assessment of the cytotoxic potential revealed no significant alteration in the safety profile of SEDDS by incorporation of POAP. Mucus permeation studies exposed a 2-fold higher permeation of fluorescein diacetate (FDA) having been embedded in SEDDS loaded with POAP in comparison to blank formulation and 3-fold higher permeability than for emulsions having been preincubated with phosphatase.

CONCLUSION

The novel phosphorylated surfactant exhibiting a PEG-linker facilitated a potent zeta potential change of SEDDS.

Effect of hydrophobic tails of plier-like cationic lipids on nucleic acid delivery and intracellular trafficking

In the optimization of transfection efficacy, one of the crucial barriers to effective gene delivery is in fact the intracellular trafficking of nucleic acids, besides the first and the last steps of gene transfer, i.e., delivery to the cell and transcription. Modifications of cationic lipid structure have been reported to have a significant effect on gene delivery. Therefore, the plier-like cationic lipids (PCLs) have been synthesized and the effect of the different types of hydrophobic tails (chain length and unsaturated hydrocarbon) on physicochemical properties, cellular uptake, trafficking process, transfection, and silencing efficiency has been investigated. In this study, the plier-like cationic niosomes (PCNs) containing PCL (A, B, and C) were evaluated their performance to deliver pDNA and siRNA to HeLa cells. Among the PCNs, PCN-B with saturated asymmetric hydrocarbon tails (C18 and C12) provided the highest efficiency for pDNA and siRNA delivery. Furthermore, the results revealed that the structure of the cationic lipids affected the internalization pathway and the intracellular trafficking. PCL-B and PCL-C with asymmetric tails preferred clathrin- and caveolae-mediated endocytosis as the predominant internalization pathways and were also involved in the polymerization process for transfection. However, PCL-A with symmetry hydrocarbon tails (C12) was predominantly taken up via macropinocytosis. All PCNs were able to escape from endosomal-lysosomal systems through facilitation of acidification. Results obtained from the cytotoxicity test revealed that the PCNs were safe in vitro. Therefore, PCNs provide a great prospect as an alternative effective gene delivery system.

Gene delivery into hepatic cells with ternary complexes of plasmid DNA, cationic liposomes and apolipoprotein E-derived peptide

Cationic liposomes containing a cationic lipid, such as 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), have often been used for the transduction of plasmid DNA (pDNA) in vivo. However, such liposomes induce gene expression primarily in the lungs after intravenous injection. To improve the delivery of cationic liposomes/pDNA complexes (pDNA lipoplexes) to the liver by intravenous administration, the current study synthesized two apolipoprotein E (ApoE)-derived peptides, dApoE-R9 and ApoE-F-R9, for liver targeting via certain ApoE receptors, including the low-density lipoprotein receptor. Ternary complexes of pDNA, cationic liposomes and ApoE-R9 peptide were also prepared. After in vitro transfection, ternary complexes with DOTAP/1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) liposomes exhibited high transfection activity in HepG2 cells compared with DOTAP/cholesterol (Chol) liposomes. In particular, ternary complexes with dApoE-R9 exhibited high transfection activity in cells compared with ApoE-F-R9. However, in vivo transfection studies revealed that ternary complexes with DOTAP/DOPE liposomes and dApoE-R9 did not increase gene expression in the liver compared with DOTAP/DOPE lipoplexes. In contrast, ternary complexes with DOTAP/Chol liposomes and dApoE-R9 increased gene expression in the liver compared with DOTAP/Chol lipoplexes. The results demonstrated that the in vivo optimal liposomal formulation in ternary complexes with ApoE-R9 peptide for liver delivery were different from those that were in vitro.

Lipidic Aminoglycoside Derivatives: A New Class of Immunomodulators Inducing a Potent Innate Immune Stimulation

Development of simple and fully characterized immunomodulatory molecules is an active area of research to enhance current immunotherapies. Monophosphoryl lipid A (MPL), a nontoxic lipidic derivative from bacteria, is the first and currently only adjuvant approved in humans. However, its capacity to induce a potent response against weak immunogenic tumoral-associated antigens remains limited. Herein, a new generation of lipidic immunomodulators to conduct a structure-activity relationship study to determine the minimal structural elements conferring immunomodulatory properties is introduced. Two lead molecules characterized by a short succinyl linker between two oleyl chains and a polar headgroup consisting of either naturally occurring tobramycin (DOST) or kanamycin (DOSK) are identified. These two lipoaminoglycosides self-assemble in very small vesicles. In a wide variety of cells including 3D human cell culture, DOST and DOSK induce the upregulation of proinflammatory cytokines and interferon-inducible proteins in a dose and time-dependent manner via a caveolae-dependent proinflammatory mechanism and phosphatidylinositol phospholipase C activation. Furthermore, after intratumoral administration, these lipoaminoglycosides induce an efficient immune response leading to significant antitumor activity in a mouse breast cancer model. Altogether, these findings indicate that DOST and DOSK are two groundbreaking synthetic lipid immunostimulators that can be used as adjuvants to enhance current immunotherapeutic treatments.

Lipid Nanoparticles for Delivery of Therapeutic RNA Oligonucleotides

Gene therapy is an exciting field that has the potential to address emerging scientific and therapeutic tasks. RNA-based gene therapy has made remarkable progress in recent decades. Nevertheless, efficient targeted delivery of RNA therapeutics is still a prerequisite for entering the clinics. In this review, we introduce current delivery methods for RNA gene therapeutics based on lipid nanoparticles (LNPs). We focus on the clinical appeal of recent RNA NPs and discuss existing challenges of fabrication and screening LNP candidates for effective translation into drugs of human metabolic diseases and cancer.

siRNA nanotherapeutics: a promising strategy for anti‐HBV therapy

Chronic hepatitis B (CHB) is the most common cause of hepatocellular carcinoma (HCC) and liver cirrhosis worldwide. In spite of the numerous advances in the treatment of CHB, drugs and vaccines have failed because of many factors like complexity, resistance, toxicity, and heavy cost. New RNA interference (RNAi)‐based technologies have developed innovative strategies to target Achilles' heel of the several hazardous diseases involving cancer, some genetic disease, autoimmune illnesses, and viral disorders particularly hepatitis B virus (HBV) infections. Naked siRNA delivery has serious challenges including failure to cross the cell membrane, susceptibility to the enzymatic digestion, and excretion by renal filtration, which ideally can be addressed by nanoparticle‐mediated delivery systems. cccDNA formation is a significant problem in obtaining HBV infections complete cure because of strength, durability, and lack of proper immune response. Nano‐siRNA drugs have a great potential to address this problem by silencing specific genes which are involved in cccDNA formation. In this article, the authors describe siRNA nanocarrier‐mediated delivery systems as a promising new strategy for HBV infections therapy. Simultaneously, the authors completely represent the clinical trials which use these strategies for treatment of the HBV infections.

Effect of Cationic Lipid Type in Folate-PEG-Modified Cationic Liposomes on Folate Receptor-Mediated siRNA Transfection in Tumor Cells

In this study, we examined the effect of cationic lipid type in folate (FA)-polyethylene glycol (PEG)-modified cationic liposomes on gene-silencing effects in tumor cells using cationic liposomes/siRNA complexes (siRNA lipoplexes). We used three types of cationic cholesterol derivatives, cholesteryl (3-((2-hydroxyethyl)amino)propyl)carbamate hydroiodide (HAPC-Chol), N-(2-(2-hydroxyethylamino)ethyl)cholesteryl-3-carboxamide (OH-Chol), and cholesteryl (2-((2-hydroxyethyl)amino)ethyl)carbamate (OH-C-Chol), and we prepared three types of FA-PEG-modified siRNA lipoplexes. The modification of cationic liposomes with 1–2 mol % PEG-lipid abolished the gene-silencing effect in human nasopharyngeal tumor KB cells, which overexpress the FA receptor (FR). In contrast, FA-PEG-modification of cationic liposomes restored gene-silencing activity regardless of the cationic lipid type in cationic liposomes. However, the optimal amount of PEG-lipid and FA-PEG-lipid in cationic liposomes for selective gene silencing and cellular uptake were different among the three types of cationic liposomes. Furthermore, in vitro transfection of polo-like kinase 1 (PLK1) siRNA by FA-PEG-modified liposomes exhibited strong cytotoxicity in KB cells, compared with PEG-modified liposomes; however, in in vivo therapy, intratumoral injection of PEG-modified PLK1 siRNA lipoplexes inhibited tumor growth of KB xenografts, as well as that of FA-PEG-modified PLK1 siRNA lipoplexes. From these results, the optimal formulation of PEG- and FA-PEG-modified liposomes for FR-selective gene silencing might be different between in vitro and in vivo transfection.

Interaction of Anionic Bulk Nanobubbles with Cationic Liposomes: Evidence for Reentrant Condensation

We investigated the interaction of bulk nanobubbles with cationic liposomes composed of 1,2-dioleoyl- sn-glycero-3-ethylphosphocholine and anionic liposomes assembled from 1-palmitoyl-2-oleoyl- sn-glycero-3-phospho-(1'- rac-glycerol). We employed dynamic light scattering and fluorescence microscopy to investigate both the hydrodynamic and electrophoretic properties of the nanobubble/liposome complexes. These optical techniques permit direct visualization of structural changes as a function of the bubble/liposome ratio. We observed reentrant condensation with cationic liposomes and gas nucleation with anionic liposomes. This is the first report of charge inversion and reentrant condensation of cationic liposomes induced by bulk nanobubbles.

Click-Shielded and Targeted Lipopolyplexes

Lipopolyplexes present well-established nucleic acid carriers assembled from sequence-defined cationic lipo-oligomers and DNA or RNA. They can be equipped with additional surface functionality, like shielding and targeting, in a stepwise assembly method using click chemistry. Here, we describe the synthesis of the required compounds, an azide-bearing lipo-oligomer structure and dibenzocyclooctyne (DBCO) click agents as well as the assembly of the compounds with siRNA into a surface-functionalized formulation. Both the lipo-oligomer and the DBCO-equipped shielding and targeting agents are produced by solid-phase synthesis (SPS). This enables for precise variation of all functional units, like variation in the amount of DBCO attachment sites or polyethylene glycol (PEG) length. Special cleavage conditions with only 5% trifluoroacetic acid (TFA) must be applied for the synthesis of the shielding and targeting agents due to acid lability of the DBCO unit. The two-step lipopolyplex assembly technique allows for separate optimization of the core and the shell of the formulation.

Strategies to overcome the polycation dilemma in drug delivery

Because of polycationic auxiliary agents such as chitosan, polyethyleneimine and cell penetrating peptides as well as cationic lipids assembling to polycationic systems, drug carriers can tightly interact with cell membranes exhibiting a high-density anionic charge. Because of these interactions the cell membrane is depolarized and becomes vulnerable to various uptake mechanisms. On their way to the target site, however, the polycationic character of all these drug carriers is eliminated by polyanionic macromolecules such as mucus glycoproteins, serum proteins, proteoglycans of the extracellular matrix (ECM) and polyanionic surface substructures of non-target cells such as red blood cells. Strategies to overcome this polycation dilemma are focusing on a pH-, redox- or enzyme-triggered charge conversion at the target site. The pH-triggered systems are making use of a slight acidic environment at the target site such as in case of solid tumors, inflammatory tissue and ischemic tissue. Due to a pH shift from 7.2 to slightly acidic mainly amino substructures of polymeric excipients are protonated or shielding groups such as 2,3 dimethylmaleic acid are cleaved off unleashing the underlying cationic character. Redox-triggered systems are utilizing disulfide linkages to bulky side chains such as PEGs masking the polycationic character. Under mild reducing conditions such as in the tumor microenvironment these disulfide bonds are cleaved. Enzyme-triggered systems are targeting enzymes such as alkaline phosphatase, matrix metalloproteinases or hyaluronidase in order to eliminate anionic moieties via enzymatic cleavage resulting in a charge conversion from negative to positive. Within this review an overview about the pros and cons of these systems is provided.

Dynamic constitutional chemistry towards efficient nonviral vectors

Dynamic constitutional chemistry has been used to design nonviral vectors for gene transfection. Their design has been thought in order to fulfill ab initio the main requirements for gene therapy. As building blocks were used hyperbranched PEI as hydrophilic part and benzentrialdehyde and a diamine linear siloxane as hydrophobic part, connected through reversible imine linkages. The obtaining of the envisaged structures has been confirmed by NMR and FTIR spectroscopy. The dynamic synthesized amphiphiles proved to be able to self-assemble in nano-sized spherical entities as was demonstrated by TEM and DLS, characterized by a narrow dimensional polydispersity. Agarose gel electrophoresis proved the ability of the synthesized compounds to bind DNA, while TEM revealed the spherical morphology of the formed polyplexes. As a proof of the concept, the nonviral vectors promoted an efficient transfection on HeLa cells, demonstrating that dynamic constitutional chemistry can be an important tool in the development of this domain.

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.

Fluorescence Correlation Spectroscopy to find the critical balance between extracellular association and intracellular dissociation of mRNA complexes

Fluorescence Correlation Spectroscopy (FCS) is a promising tool to study interactions on a single molecule level. The diffusion of fluorescent molecules in and out of the excitation volume of a confocal microscope leads to the fluorescence fluctuations that give information on the average number of fluorescent molecules present in the excitation volume and their diffusion coefficients. In this context, we complexed mRNA into lipoplexes and polyplexes and explored the association/dissociation degree of complexes by using gel electrophoresis and FCS. FCS enabled us to measure the association and dissociation degree of mRNA-based complexes both in buffer and protein-rich biological fluids such as human serum and ascitic fluid, which is a clear advantage over gel electrophoresis that was only applicable in protein-free buffer solutions. Furthermore, following the complex stability in buffer and biological fluids by FCS assisted to understand how complex characteristics, such as charge ratio and strength of mRNA binding, correlated to the transfection efficiency. We found that linear polyethyleneimine prevented efficient translation of mRNA, most likely due to a too strong mRNA binding, whereas the lipid based carrier Lipofectamine® messengerMAX did succeed in efficient release and subsequent translation of mRNA in the cytoplasm of the cells. Overall, FCS is a reliable tool for the in depth characterization of mRNA complexes and can help us to find the critical balance keeping mRNA bound in complexes in the extracellular environment and efficient intracellular mRNA release leading to protein production.

STATEMENT OF SIGNIFICANCE

The delivery of messenger RNA (mRNA) to cells is promising to treat a variety of diseases. Therefore, the mRNA is typically packed in small lipid particles or polymer particles that help the mRNA to reach the cytoplasm of the cells. These particles should bind and carry the mRNA in the extracellular environment (e.g. blood, peritoneal fluid, …), but should release the mRNA again in the intracellular environment. In this paper, we evaluated a method (Fluorescence Correlation Spectroscopy) that allows for the in depth characterization of mRNA complexes and can help us to find the critical balance keeping mRNA bound in complexes in the extracellular environment and efficient intracellular mRNA release leading to protein production.

Different-Length Hydrazone Activated Polymers for Plasmid DNA Condensation and Cellular Transfection

The recent advances in genetic engineering demand the development of conceptually new methods to prepare and identify efficient vectors for the intracellular delivery of different nucleotide payloads ranging from short single-stranded oligonucleotides to larger plasmid double-stranded circular DNAs. Although many challenges still have to be overcome, polymers hold great potential for intracellular nucleotide delivery and gene therapy. We here develop and apply the postpolymerization modification of polyhydrazide scaffolds, with different degree of polymerization, for the preparation of amphiphilic polymeric vehicles for the intracellular delivery of a circular plasmid DNA. The hydrazone formation reactions with a mixture of cationic and hydrophobic aldehydes proceed in physiologically compatible aqueous conditions, and the resulting amphiphilic polyhydrazones are directly combined with the biological cargo without any purification step. This methodology allowed the preparation of stable polyplexes with a suitable size and zeta potential to achieve an efficient encapsulation and intracellular delivery of the DNA cargo. Simple formulations that performed with efficiencies and cell viabilities comparable to the current gold standard were identified. Furthermore, the internalization mechanism was studied via internalization experiments in the presence of endocytic inhibitors and fluorescence microscopy. The results reported here confirmed that the polyhydrazone functionalization is a suitable strategy for the screening and identification of customized polymeric vehicles for the delivery of different nucleotide cargos.

Exploring membrane permeability of Tomatidine to enhance lipid mediated nucleic acid transfections

Intracellular delivery of nucleic acids is one of the critical steps in the transfections. Prior findings demonstrated various strategies including membrane fusion, endosomal escape for the efficient cytoplasmic delivery. In our continuing efforts to improve the nucleic acids transfections, we harnessed cell permeable properties of Tomatidine (T), a steroidal alkaloid abundantly found in green tomatoes for maximizing intracellular delivery of lipoplexes. We doped Tomatidine into liposomes of cationic lipid with amide linker (A) from our lipid library. Six liposomal formulations (AT) of Lipid A (1 mM) with varying concentrations of Tomatidine (0-1 mM) were prepared and evaluated for their transfection efficacies. Owing to its signature characteristic of cell membrane permeability, Tomatidine modulated endocytosis process, enhanced the intracellular delivery of the lipoplexes, and in turn increased the transfection efficacy of cationic liposomes. Our findings provide 'proof of concept' for enhancing transfections in gene delivery applications with Tomatidine in cationic liposomal formulations. These findings can be further applied in lipid mediated gene therapy and drug delivery applications.

Novel carbamate-linked quaternary ammonium lipids containing unsaturated hydrophobic chains for gene delivery

In this paper, two novel carbamate-linked quaternary ammonium lipids (MU18: a lipid with a mono-ammonium head; GU18: a lipid with a Gemini-ammonium head) containing unsaturated hydrophobic chains were designed and synthesized. The chemical structures of the synthetic lipids were characterized by infrared spectrum, ESI-MS, ¹H NMR, ¹³C NMR, and HPLC. For investigating the effect of unsaturation on gene delivery, the previous reported saturated cationic liposomes (MS18 and GS18) were used as comparison. Cationic liposomes were prepared by using these cationic lipids and neutral lipid DOPE at the molar ratio of 1:1. Particle sizes and zeta potentials of the cationic liposomes were studied to show that they were suitable for gene transfection. The binding abilities of the cationic liposomes were investigated by gel electrophoresis at various N/P ratios from 0.5/1 to 8/1. The results indicated that the binding ability of GU18 was much better than MU18 and the saturated cationic liposomes (MS18 and GS18). DNA transfection of these liposomes comparable to commercially available reagent (DOTAP) was achieved in vitro against Hela, HepG-2 and NCI-H460 cell lines. GU18 showed higher transfection at the N/P ratio of 3/1 than other cationic liposomes and the positive control, DOTAP. All of the liposomes presented a relatively low cytotoxicity, which was measured by MTT. Therefore, the synthetic lipids bearing unsaturated hydrophobic chains and Gemini-head could be promising candidates for gene delivery.

Therapeutic approaches for the delivery of TNF-α siRNA

Immune-mediated diseases are emerging as a major healthcare concern in the present era. TNF-α, a proinflammatory cytokine, plays a major role in the manifestation of these diseases by mediating different pathways and inducing the expression of other cytokines. In last decades, monoclonal antibodies and extracellular portion of human TNF-α receptors are explored in this area; however, the risk of immunological response and undesired effects urge a need to develop more effective therapies to control TNF-α levels. siRNA therapeutic strategies are emerging for the treatment of myriad of diseases, but the delivery challenges associated with siRNA require the development of suitable delivery vectors. For delivery of TNF-α siRNA, both viral and nonviral vectors are explored. This review attempts to describe different delivery approaches for TNF-α siRNA with special focus on nonviral delivery vectors.

Nanotechnology based approaches for detection and delivery of microRNA in healthcare and crop protection

Nanobiotechnology has the potential to revolutionize diverse sectors including medicine, agriculture, food, textile and pharmaceuticals. Disease diagnostics, therapeutics and crop protection strategies are fast emerging using nanomaterials preferably nanobiomaterials. It has potential for development of novel nanobiomolecules which offer several advantages over conventional treatment methods. RNA nanoparticles with many unique features are promising candidates in disease treatment. The miRNAs are involved in many biochemical and developmental pathways and their regulation in plants and animals. These appear to be a powerful tool for controlling various pathological diseases in human, plants and animals, however there are challenges associated with miRNA based nanotechnology. Several advancements made in the field of miRNA therapeutics make it an attractive approach, but a lot more has to be explored in nanotechnology assisted miRNA therapy. The miRNA based technologies can be employed for detection and combating crop diseases as well. Despite these potential advantages, nanobiotechnology applications in the agricultural sector are still in its infancy and have not yet made its mark in comparison with healthcare sector. The review provides a platform to discuss nature, role and use of miRNAs in nanobiotechnology applications.

Recent progress in nanomaterials for gene delivery applications

Nanotechnology-based gene delivery is the division of nanomedicine concerned with the synthesis, characterization, and functionalization of nanomaterials to be used in targeted-gene delivery applications. Nanomaterial-based gene delivery systems hold great promise for curing fatal inherited and acquired diseases, including neurological disorders, cancer, cardiovascular diseases, and acquired immunodeficiency syndrome (AIDS). However, their use in clinical applications is still controversial. To date, the Food and Drug Administration (FDA) has not approved any gene delivery system because of the unknown long-term toxicity and the low gene transfection efficiency of nanomaterials in vivo. Compared to viral vectors, nonviral gene delivery vectors are characterized by a low preexisting immunogenicity, which is important for preventing a severe immune response. In addition, nonviral vectors provide higher loading capacity and ease of fabrication. For these reasons, this review article focuses on applications of nonviral gene delivery systems, including those based on lipids, polymers, graphene, and other inorganic nanoparticles, and discusses recent advances in nanomaterials for gene therapy. Methods of synthesizing these nanomaterials are briefly described from a materials science perspective. Also, challenges, critical issues, and concerns about the in vivo applications of nanomaterial-based gene delivery systems are discussed. It should be noted that this article is not a comprehensive review of the literature.