A universal discoidal nanoplatform for the intracellular delivery of PNAs

Morphological control and modern applications of bicelles

Bicellar systems have become popularized as their rich morphology can be applied in biochemistry, physical chemistry, and drug delivery technology. To the biochemical field, bicelles are powerful model membranes for the study of transmembrane protein behavior, membrane transport, and environmental interactions with the cell. Their morphological responses to environmental changes reveal a profound fundamental understanding of physical chemistry related to the principle of self-assembly. Recently, they have also drawn significant attention as theranostic nanocarriers in biopharmaceutical and diagnostic research due to their superior cellular uptake compared to liposomes. It is evident that applications are becoming broader, demanding to understand how the bicelle will form and behave in various environments. To consolidate current works on the bicelle's modern applications, this review will discuss various effects of composition and environmental conditions on the morphology, phase behavior, and stability. Furthermore, various applications such as payload entrapment and polymerization templating are presented to demonstrate their versatility and chemical nature.

Next-generation poly-L-histidine formulations for miRNA mimic delivery

Many diseases, especially cancer, are caused by the abnormal expression of non-coding microRNAs (miRNAs), which regulate gene expression, leading to the development of miRNA-based therapeutics. Synthetic miRNA inhibitors have shown promising efficacy in blocking the activity of aberrant miRNAs that are upregulated in disease-specific pathologies. On the other hand, miRNAs that aid in preventing certain diseases and are reduced in expression in the disease state need different strategies. To tackle this, miRNA mimics, which mimic the activity of endogenous miRNAs, can be delivered for those miRNAs downregulated in different disease states. However, the delivery of miRNA mimics remains a challenge. Here, we report a cationic polylactic-co-glycolic acid (PLGA)-poly-L-histidine delivery system to deliver miRNA mimics. We chose miR-34a mimics as a proof of concept for miRNA delivery. miR-34a-loaded PLGA-poly-L-histidine nanoparticles (NPs) were formulated and biophysically characterized to analyze the structural properties of miRNA mimic-loaded NPs. In vitro efficacy was determined by investigating miR-34a and downstream target levels and performing cell viability and apoptosis assays. We confirmed in vivo efficacy through prolonged survival of miR-34a NP-treated A549-derived xenograft mice treated intratumorally. The results of these studies establish PLGA-poly-L-histidine NPs as an effective delivery system for miRNA mimics for treating diseases characterized by downregulated miRNAs.

Multivalent Lactobionic Acid and N-Acetylgalactosamine-Conjugated Peptide Nucleic Acids for Efficient In Vivo Targeting of Hepatocytes

Peptide nucleic acids (PNAs) are used/applied in various studies to target genomic DNA and RNA to modulate gene expression. Non-specific targeting and rapid elimination always remain a challenge for PNA-based applications. Here, the synthesis, characterization, in vitro and in vivo study of di lactobionic acid (diLBA) and tris N-acetyl galactosamine (tGalNAc) conjugated PNAs for liver-targeted delivery are reported. For proof of concept, diLBA, and tGalNAc conjugated PNAs (anti-miR-122 PNAs) were synthesized to target microRNA-122 (miR-122) which is over-expressed in the hepatic tissue. Different lengths of anti-miR-122 PNAs conjugated with diLBA and tGalNAc are tested. Cell culture and in vivo analyses to determine biodistribution, efficacy, and toxicity profile are performed. This work indicates that diLBA conjugates show significant retention in hepatocytes in addition to tGalNAc conjugates after in vivo delivery. Full-length PNA conjugates show significant downregulation of miR-122 levels and subsequent de-repression of its downstream targets with no evidence of toxicity. The results provide a robust framework for ligand-conjugated delivery systems for PNAs that can be explored for broader biomedical applications.

Stable Discoidal Bicelles: Formulation, Characterization, and Functions

Bicellar mixtures have been used as alignable membrane substrates under a magnetic field applicable for the structural characterization of membrane-associated proteins. Recently, it has shown that bicelles can serve as nanocarriers to effectively deliver hydrophobic therapeutic molecules to cancer cells with a three- to ten-fold enhancement compared to that of liposomes of a chemically identical composition. In this chapter, detailed preparation protocol, common structural characterization methods, the structural stability, the cellular uptake and a few unique functions of bicellar nanodiscs are discussed.

Development of Surface Chemical Strategies for Synthesizing Redox-Responsive Diatomite Nanoparticles as a Green Platform for On-Demand Intracellular Release of an Antisense Peptide Nucleic Acid Anticancer Agent

Redox-responsive silica drug delivery systems are synthesized by aeco-friendly diatomite source to achieve on-demand release of peptide nucleic acid (PNA) in tumor reducing microenvironment, aiming to inhibit the immune checkpoint programmed cell death 1 receptor/programmed cell death receptor ligand 1 (PD-1/PD-L1) in cancer cells. The nanoparticles (NPs) are coated with polyethylene glycol chains as gatekeepers to improve their physicochemical properties and control drug release through the cleavable disulfide bonds (S-S) in a reductive environment. This study describes different chemical conditions to achieve the highest NPs' surface functionalization yield, exploring both multistep and one-pot chemical functionalization strategies. The best formulation is used for covalent PNA conjugation via the S-S bond reaching a loading degree of 306 ± 25 µg _PNA mg^-1 _DNPs . These systems are used for in vitro studies to evaluate the kinetic release, biocompatibility, cellular uptake, and activity on different cancer cells expressing high levels of PD-L1. The obtained results prove the safety of the NPs up to 200 µg mL^-1 and their advantage for controlling and enhancing the PNA intracellular release as well as antitumor activity. Moreover, the downregulation of PD-L1 observed only with MDA-MB-231 cancer cells paves the way for targeted immunotherapy.

Effect of drug-to-lipid ratio on nanodisc-based tenofovir drug delivery to the brain for HIV-1 infection

Background

Combination antiretroviral therapy has significantly advanced HIV-1 infection treatment. However, HIV-1 remains persistent in the brain; the inaccessibility of the blood–brain barrier allows for persistent HIV-1 infections and neuroinflammation. Nanotechnology-based drug carriers such as nanodiscoidal bicelles can provide a solution to combat this challenge.

Methods

This study investigated the safety and extended release of a combination antiretroviral therapy drug (tenofovir)-loaded nanodiscs for HIV-1 treatment in the brain both in vitro and in vivo.

Result

The nanodiscs entrapped the drug in their interior hydrophobic core and released the payload at the desired location and in a controlled release pattern. The study also included a comparative pharmacokinetic analysis of nanodisc formulations in in vitro and in vivo models.

Conclusion

The study provides potential applications of nanodiscs for HIV-1 therapy development.

Changes Experienced by Low-Concentration Lipid Bicelles as a Function of Temperature

Differential scanning calorimetry (DSC) of dipalmitoyl phosphatidylcholine (DPPC), dihexanoyl phosphatidylcholine, and dipalmitoyl phosphatidylglycerol bicelles reveals two endothermic peaks. Based on analysis of small angle neutron scattering and small angle X-ray scattering data, the two DSC peaks are associated with the melting of DPPC and a change in bicellar morphology─namely, either bicelle-to-spherical vesicle or oblate-to-spherical vesicle. The reversibility of the two structural transformations was examined by DSC and found to be consistent with the corresponding small angle scattering data. However, the peak that is not associated with the melting of DPPC does not correspond to any structural transformation for bicelles containing distearoyl phosphatidylethanolamine conjugated with polyethylene glycol. Based on complementary experimental data, we conclude that membrane flexibility, lipid miscibility, and differential solubility between the long- and short-chain lipids in water are important parameters controlling the reversibility of morphologies experienced by the bicelles.

Gene Regulation Using Nanodiscs Modified with HIF-1-α Antisense Oligonucleotides

Delivery of nucleic acids can be hindered by multiple factors including nuclease susceptibility, endosome trapping, and clearance. Multiple nanotechnology scaffolds have offered promising solutions, and among these, lipid-based systems are advantageous because of their high biocompatibility and low toxicity. However, many lipid nanoparticle systems still have issues regarding stability, rapid clearance, and cargo leakage. Herein, we demonstrate the use of a synthetic nanodisc (ND) scaffold functionalized with an anti-HIF-1-α antisense oligonucleotide (ASO) to reduce HIF-1-α mRNA transcript levels. We prepared ND conjugates by using a mixture of phosphoglycerolipids with phosphocholine and phosphothioethanol headgroups that self-assemble into a ∼13 × 5 nm discoidal structure upon addition of a 22-amino-acid ApoA1 mimetic peptide. Optimized reaction conditions yield 15 copies of the anti-HIF-1-α ASO DNA covalently conjugated to the thiolated phospholipids using maleimide-thiol chemistry. We show that DNA-ND conjugates are active, nuclease resistant, and rapidly internalized into cells to regulate HIF-1-α mRNA levels without the use of transfection agents. DNA-ND uptake is partially mediated through Scavenger Receptor B1 and the ND conjugates show enhanced knockdown of HIF-1-α compared to that of the soluble ASOs in multiple cell lines. Our results demonstrate that covalently functionalized NDs may offer an improved platform for ASO therapeutics.

Head on Comparison of Self- and Nano-assemblies of Gamma Peptide Nucleic Acid Amphiphiles

Peptide nucleic acids (PNAs) are nucleic acid analogs with superior hybridization properties and enzymatic stability than deoxyribonucleic acid (DNA). In addition to gene targeting applications, PNAs have garnered significant attention as bio-polymer due to the Watson-Crick -based molecular recognition and flexibility of synthesis. Here, we engineered PNA amphiphiles using chemically modified gamma PNA (8 mer in length) containing hydrophilic diethylene glycol units at the gamma position and covalently conjugated lauric acid (C12) as a hydrophobic moiety. Gamma PNA (γPNA) amphiphiles self-assemble into spherical vesicles. Further, we formulate nano-assemblies using the amphiphilic γPNA as a polymer via ethanol injection-based protocols. We perform comprehensive head-on comparison of the physicochemical and cellular uptake properties of PNA derived self- and nano-assemblies. Small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) analysis reveal ellipsoidal morphology of γPNA nano-assemblies that results in superior cellular delivery compate to the spherical self-assembly. Next, we compare the functional activities of γPNA self-and nano-assemblies in lymphoma cells via multiple endpoints, including gene expression, cell viability, and apoptosis-based assays. Overall, we establish that γPNA amphiphile is a functionally active bio-polymer to formulate nano-assemblies for a wide range of biomedical applications.

Nanocomplex made up of antimicrobial metallo-supramolecules and model biomembranes - characterization and enhanced fluorescence

Antimicrobial pentatopic 2,2':6',2''-terpyridines that form 3-D supramolecular hexagonal prisms with Cd2+ through coordination driven self-assembly can be entrapped by lipid discoidal bicelles, composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dihexanoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) lipid, forming a well-defined nanocomplex. Structural characterization performed by very small angle neutron scattering, small angle X-ray scattering and transmission electron microscopy suggests that the hexagonal prisms are preferably located at the rim of bicellar discs with the hexagonal face in parallel with the bilayers, instead of face-to-face stacking. Such a configuration reduces the π-π interaction and consequently enhances the fluorescence emission. Since novel supramolecules were reported to have antibiotic functions, this study provides insight into the interactions of antimicrobial supermolecules with lipid membranes, leading to potential theranostic applications.

Peptide nucleic acids and their role in gene regulation and editing

The unique properties of peptide nucleic acid (PNA) makes it a desirable candidate to be used in therapeutic and biotechnological interventions. It has been broadly utilized for numerous applications, with a major focus in regulation of gene expression, and more recently in gene editing. While the classic PNA design has mainly been employed to date, chemical modifications of the PNA backbone and nucleobases provide an avenue to advance the technology further. This review aims to discuss the recent developments in PNA based gene manipulation techniques and the use of novel chemical modifications to improve the current state of PNA mediated gene targeting.

Aggregation-Enhanced Photoluminescence and Photoacoustics of Atomically Precise Gold Nanoclusters in Lipid Nanodiscs (NANO2)

The authors designed a structurally stable nano-in-nano (NANO2) system highly capable of bioimaging via an aggregation-enhanced NIR excited emission and photoacoustic response achieved based on atomically precise gold nanoclusters protected by linear thiolated ligands [Au25(SC n H2n+1)18, n = 4-16] encapsulated in discoidal phospholipid bicelles through a one-pot synthesis. The detailed morphological characterization of NANO2 is conducted using cryogenic transmission electron microscopy, small/wide angle X-ray scattering with the support of molecular dynamics simulations, providing information on the location of Au nanoclusters in NANO2. The photoluminescence observed for NANO2 is 20-60 times more intense than that of the free Au nanoclusters, with both excitation and emission wavelengths in the near-infrared range, and the photoacoustic signal is more than tripled. The authors attribute this newly discovered aggregation-enhanced photoluminescence and photoacoustic signals to the restriction of intramolecular motion of the clusters' ligands. With the advantages of biocompatibility and high cellular uptake, NANO2 is potentially applicable for both in vitro and in vivo imaging, as the authors demonstrate with NIR excited emission from in vitro A549 human lung and the KB human cervical cancer cells.

Multifunctional Delivery Systems for Peptide Nucleic Acids

The number of applications of peptide nucleic acids (PNAs)-oligonucleotide analogs with a polyamide backbone-is continuously increasing in both in vitro and cellular systems and, parallel to this, delivery systems able to bring PNAs to their targets have been developed. This review is intended to give to the readers an overview on the available carriers for these oligonucleotide mimics, with a particular emphasis on newly developed multi-component- and multifunctional vehicles which boosted PNA research in recent years. The following approaches will be discussed: (a) conjugation with carrier molecules and peptides; (b) liposome formulations; (c) polymer nanoparticles; (d) inorganic porous nanoparticles; (e) carbon based nanocarriers; and (f) self-assembled and supramolecular systems. New therapeutic strategies enabled by the combination of PNA and proper delivery systems are discussed.

Formulation of PLGA nanoparticles containing short cationic peptide nucleic acids

Peptide nucleic acids (PNAs) have emerged as one of the most versatile tools with a wide range of biomedical applications including antisense, antimiR, antigene, as well as site-specific gene editing. The application and potential of PNAs has been limited due to low solubility and poor cellular uptake. Several strategies have been employed to overcome the aforementioned challenges like conjugation to cationic peptides or nanotechnology to achieve superior transfection efficiency ex vivo and in vivo. Here, we report a detailed procedure optimized in our lab for synthesis of short cationic PNA probes, which exhibit high purity and yield in comparison to full-length PNA oligomers. We also provide step-by-step details of encapsulating short cationic PNA probes in poly (lactic-co-glycolic acid) nanoparticles by double emulsion solvent evaporation technique. 1.Detailed procedure for synthesis of short cationic PNAs with or without fluorophore (dye) conjugation while ensuring high yield and purity.2.Step-by-step details for encapsulation of short cationic PNAs in PLGA nanoparticles via double emulsion solvent evaporation technique.

Effects of fluidity and charge density on the morphology of a bicellar mixture - A SANS study

The spontaneously formed structures of physiologically relevant lipid model membranes made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) and 1,2-hexanoyl-sn-glycero-3-phosphocholine have been evaluated in depth using small angle neutron scattering. Although a common molar ratio of long- to short- chain phospholipids (~4) as reported in many bicellar mixtures was used, discoidal bicelles were not found as the major phase throughout the range of lipid concentration and temperature studied, indicating that the required condition for the formation of bicelle is the immiscibility between the long- and short- chain lipids, which were in the gel and L_α phases, respectively, in previous reports. In this study, all lipids are in the L_α phase. The characterization outcome suggests that the spontaneous structures tie strongly with the physical parameters of the system such as melting transition temperature of the long-chain lipid, total lipid concentration and charge density of the system. Multilamellar vesicles, unilamellar vesicles, ribbons and perforated lamellae can be obtained based on the analysis of the small angle neutron scattering results, leading to the construction of structural diagrams. This report provides the important map to choose suitable lipid systems for the structural study of membrane-associated proteins, design of theranostic nanocarriers or other related research fields.

Next generation miRNA inhibition using short anti-seed PNAs encapsulated in PLGA nanoparticles

Selective inhibition of microRNAs (miRNAs) offers a new avenue for cancer therapeutics. While most of the current anti-miRNA (antimiR) reagents target full length miRNAs, here we investigate novel nanoparticle-delivered short PNA probes containing cationic domains targeting the seed region of the miRNA for effective antimiR therapy. For proof of concept, we tested PNAs targeting miRNA-155 and employed poly(lactic-co-glycolic acid) (PLGA)-based nanoparticle formulation for delivery. A comprehensive evaluation of PLGA nanoparticles (NPs) containing short PNA probes showed significantly superior loading, release profile, and uniform size distribution, compared to conventional non-cationic PNA probes. Confocal microscopy and flow cytometry analyses showed efficient transfection efficiency and uniform distribution of PLGA NPs containing short PNA probes in the cytoplasm. Functional analysis also confirmed efficient miRNA-155 inhibition including an effect on its downstream target proteins. Further, reduced tumor growth was observed after systemic delivery of PLGA nanoparticles containing short PNA probes in vivo in a xenograft mouse model following inhibition of miR-155. There was no evidence of acute or chronic toxicity associated with systemic delivery of PLGA NPs containing short PNA probes in the mice. Overall, in this paper we present a novel antimiR strategy based on PLGA nanoparticle delivered short PNA probes for potential cancer therapy.

Microbiota-governed microRNA-204 impairs endothelial function and blood pressure decline during inactivity in db/db mice

An impaired decline in blood pressure at rest is typical in people with diabetes, reflects endothelial dysfunction, and increases the risk of end-organ damage. Here we report that microRNA-204 (miR-204) promotes endothelial dysfunction and impairment in blood pressure decline during inactivity. We show that db/db mice overexpress miR-204 in the aorta, and its absence rescues endothelial dysfunction and impaired blood pressure decline during inactivity despite obesity. The vascular miR-204 is sensitive to microbiota, and microbial suppression reversibly decreases aortic miR-204 and improves endothelial function, while the endothelial function of mice lacking miR-204 remained indifferent to the microbial alterations. We also show that the circulating miR-122 regulates vascular miR-204 as miR-122 inhibition decreases miR-204 in endothelial cells and aorta. This study establishes that miR-204 impairs endothelial function, promotes impairment in blood pressure decline during rest, and opens avenues for miR-204 inhibition strategies against vascular dysfunction.

Modulation of DNA and RNA by PNA

Peptide nucleic acid (PNA), a synthetic DNA mimic that is devoid of the (deoxy)ribose-phosphate backbone yet still perfectly retains the ability to recognize natural nucleic acids in a sequence-specific fashion, can be employed as a tool to modulate gene expressions via several different mechanisms. The unique strength of PNA compared to other oligonucleotide analogs is its ability to bind to nucleic acid targets with secondary structures such as double-stranded and quadruplex DNA as well as RNA. This digest aims to introduce general readers to the advancement in the area of modulation of DNA/RNA functions by PNA, its current status and future research opportunities, with emphasis on recent progress in new targeting modes of structured DNA/RNA by PNA and PNA-mediated gene editing.