Synthesis and Properties of New Multilayer Chitosan@layered Double Hydroxide/Drug Loaded Phospholipid Bilayer Nanocomposite Bio-Hybrids

A novel bio-hybrid drug delivery system was obtained involving a Mg/Al-NO₃ layered double hydroxide (LDH) intercalated either with ibuprofenate anions (IBU) or a phospholipid bilayer (BL) containing a neutral drug, i.e., 17β-estradiol, and then embedded in chitosan beads. The combination of these components in a hierarchical structure led to synergistic effects investigated through characterization of the intermediates and the final bio-composites by XRD, TG, SEM, and TEM. That allowed determining the presence and yield of IBU and of BL in the interlayer space of LDH, and of the encapsulated LDH in the beads, as well as the morphology of the latter. Peculiar attention has been paid to the intercalation process of the BL for which all available data substantiate the hypothesis of a first interaction at the defect of the LDH, as well as on the interaction mode of these components. ¹H, ³¹P and ²⁷Al MAS-NMR studies allowed establishing that the intercalated BL is not homogeneous and likely formed patches. Release kinetics were performed for sodium ibuprofenate as well as for the association of 17β-estradiol within the negatively charged BL, each encapsulated in the LDH/chitosan hybrid materials. Such new bio-hybrids offer an interesting outlook into the pharmaceutical domain with the ability to be used as sustained release systems for a wide variety of anionic and, importantly, neutral drugs.

Supramolecular Reassembly of Self-Exfoliated Ionic Covalent Organic Nanosheets for Label-Free Detection of Double-Stranded DNA

Ionic covalent organic nanosheets (iCONs), a member of the two-dimensional (2D) nanomaterials family, offer a unique functional platform for a wide range of applications. Herein, we explore the potential of an ethidium bromide (EB)-based covalent organic framework (EB-TFP) that self-exfoliates in water resulting in 2D ionic covalent organic nanosheets (EB-TFP-iCONs) for the selective detection of double-stranded DNA (dsDNA). In an aqueous medium, the self-exfoliated EB-TFP-iCONs reassemble in the presence of dsDNA resulting in hybrid EB-TFP-iCONs-DNA crystalline nanosheets with enhanced fluorescence at 600 nm. Detailed steady-state and time-resolved emission studies revealed that the reassembly phenomenon was highly selective for dsDNA when compared to single-stranded DNA (ssDNA), which allowed us to use the EB-TFP-iCONs as a 2D fluorescent platform for the label-free detection of complementary DNA strands.

2D Inorganic-Antimalarial Drug-Polymer Hybrid with pH-Responsive Solubility

Artesunic acid (ASH), an antimalarial drug, has low oral bioavailability due to its low aqueous solubility. To overcome this problem, artesunate (AS) was intercalated into zinc basic salt (ZBS) via co-precipitation. AS was immobilized with a tilted double layer arrangement, which was also confirmed by XRD and 1-D electron density mapping. In order to decrease the release rate of AS under gastrointestinal conditions and to simultaneously increase the release rate of AS under intestinal conditions, ZBS-AS was coated with EUDRAGIT L100 (ZBS-AS-L100). Finally, we performed an in-vivo pharmacokinetic study to compare the oral bioavailability of AS of ZBS-AS-L100 with that of ASH. Surprisingly, it was found that the former is 5.5 times greater than the latter due to an enhanced solubility of AS thanks to the ternary hybridization with ZBS and EUDRAGIT L100. Therefore, the present ZBS-AS-L100 system has a great potential as a novel antimalarial drug formulation with pH selectivity and enhanced bioavailability.

Synthesis and characterization of layered double hydroxides and their potential as nonviral gene delivery vehicles

Layered double hydroxides (LDHs) exhibit characteristic anion-exchange chemistry making them ideal carriers of negatively charged molecules like deoxyribonucleic acid (DNA). In this study, hydrotalcite (Mg-Al) and hydrotalcite-like compounds (Mg-Fe, Zn-Al, and Zn-Fe), also known as LDHs, were evaluated for their potential application as a carrier of DNA. LDHs were prepared by coprecipitation at low supersaturation and characterized by Powder X-ray diffraction (XRD), infrared (IR), Raman, and inductively coupled plasma-optical emission spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD patterns showed strong and sharp diffraction peaks for the (003) and (006) planes indicating well-ordered crystalline materials. TEM images yielded irregular circular to hexagonal-shaped particles of 50-250 nm in size. Varying degrees of DNA binding was observed for all the compounds, and nuclease digestion studies revealed that the LDHs afford some degree of protection to the bound DNA. Minimal toxicity was observed in human embryonic kidney (HEK293), cervical cancer (HeLa) and hepatocellular carcinoma (HepG2) cell lines with most showing a cell viability in excess of 80 %. All LDH complexes promoted significant levels of luciferase gene expression, with the DNA:Mg-Al LDHs proving to be the most efficient in all cell lines.

Inorganic nanoparticles as carriers of nucleic acids into cells

The transfer of nucleic acids (DNA or RNA) into living cells, that is, transfection, is a major technique in current biochemistry and molecular biology. This process permits the selective introduction of genetic material for protein synthesis as well as the selective inhibition of protein synthesis (antisense or gene silencing). As nucleic acids alone are not able to penetrate the cell wall, efficient carriers are needed. Besides viral, polymeric, and liposomal agents, inorganic nanoparticles are especially suitable for this purpose because they can be prepared and surface-functionalized in many different ways. Herein, the current state of the art is discussed from a chemical viewpoint. Advantages and disadvantages of the available methods are compared.

Flow cytometry: Interesting tool for studying binding behavior of DNA on inorganic layered double hydroxide (LDH)

BACKGROUND

A new method was established to characterize the binding kinetics of DNA toward layered double hydroxides (LDHs). The setup consisted of a newly developed sampling tube that allows the injection of analyte during the flow cytometric measurement.

METHODS

Layered double hydroxides consist of cationic metal hydroxide layers and exchangeable interlayer anions. This negatively charged structure permits biomolecules such as DNA to adsorb, and a so-called DNA-LDH hybrid is formed. The hydroxide layers can be removed in acidic media and the DNA will be released. CERATOFIX (a registered trademark of Sud-Chemie AG NA that belongs to the family of LDHs, produced by Sud-Chemie AG). The chemical structure can be summarized as [Mg(2)Al(OH)(6)](CO(3))(0.5). The binding capacity and kinetic characteristics of different types of CERATOFIX NA for a model DNA was determined by flow cytometry.

RESULTS

The static binding capacities of the different LDHs were determined after 1- and 16-h incubation with DNA solution, showing different binding patterns between the LDH materials. The binding kinetics were revealed by flow cytometric measurements in short-term and long-term kinetic experiments, showing that the majority of DNA adsorbs within the first 60 s.

CONCLUSIONS

DNA removal from cell culture supernatants is one of the major concerns in downstream processing. Due to the anion exchange capabilities of LDHs it seemed a very interesting approach to use these materials for binding of DNA for elimination purposes.