No abstract

Abstract. One-step functionalization of alginate with boronic acid groups allowed spontaneous formation of biocompatible hydrogels under basic conditions without additional complementary molecules or crosslinking agents. The dynamic nature of boronate ester bonds formed with vicinal diols present on alginate pyranose rings provided remarkable self-healing, injectable and multi-stimuli responsive properties to the material.Stimuli-responsive hydrogels are characterized by the ability to respond to external triggers (e.g. pH, temperature, light, specific molecules, etc.), a major property typically associated with their potential use for biomedical applications.1,2 In addition, the development of biomimetic gelbased materials with self-healing properties has extended their prospect for new applications. Nature relies on the use of reversible sacrificial bonds that allow for a better adaptation of a biomaterial to specific environments as well as for self-reparation upon damage. [3][4][5][6] This has inspired an emerging research area devoted to the fabrication of self-healable hydrogel networks based on dynamic covalent chemistry. [7][8][9] In sharp contrast to covalently crosslinked hydrogels, whose stable bonds do not undergo exchange reactions, gels based on dynamic bonds are able to reform bonds around a damaged zone, allowing the restitution of their functional properties. 9Within this context, boronic acids have been extensively studied due to their excellent ability to interact reversibly with diols, forming boronate

Cancer is one of the most complex diseases that has resulted in multiple genetic disorders and cellular abnormalities. Globally, cancer is the most common health concern disease that is affecting human beings. Great efforts have been made over the past decades in biology with the aim of searching novel and more efficient tools in therapy. Thus, small interfering RNAs (siRNAs) have been considered one of the most noteworthy developments which are able to regulate gene expression following a process known as RNA interference (RNAi). RNAi is a post-transcriptional mechanism that involves the inhibition of gene expression through promoting cleavage on a specific area of a target messenger RNA (mRNA). This technology has shown promising therapeutic results for a good number of diseases, especially in cancer. However, siRNA therapeutics have to face important drawbacks in therapy including stability and successful siRNA delivery in vivo. In this regard, the development of effective siRNA delivery systems has helped addressing these issues by opening novel therapeutic windows which have allowed to build up important advances in Nanomedicine. In this review, we discuss the progress of siRNA therapy as well as its medical application via nanoparticle-mediated delivery for cancer treatment.

Hydrogels are hydrophilic three-dimensional networks with demonstrated potential for medical and pharmaceutical applications. Specifically, biopolymer-based hydrogels offer certain advantages over synthetic polymers in terms of biocompatibility and biodegradability. Because of their inherent properties, hydrogels are able to efficiently encapsulate and liberate in a controlled release manner, different hydrophobic and hydrophilic therapeutic molecules, including nucleic acids, proteins and antibodies. Several strategies have been reported in the literature to minimize the potential burst release of encapsulated drugs, thus preventing their local accumulation and consequent toxic responses. Within this context, liposomes embedded in hydrogels have emerged as an attractive strategy to reduce this undesirable effect. This tutorial review covers a selection of the most promising cationic, neutral and anionic biopolymer-based hydrogels containing liposomes, niosomes or vesicles for drug delivery or tissue engineering applications.

The development of novel non-viral delivery vehicles is essential in the search of more efficient strategies for retina and brain diseases. Herein, optimized niosome formulations prepared by oil-in water (o/w) and film-hydration techniques were characterized in terms of size, PDI, zeta potential, morphology and stability. Three ionizable glycerol-based cationic lipids containing a primary amine group (lipid 1), a triglycine group (lipid 2) and a dimethylamino ethyl pendent group (lipid 3) as polar head-groups were part of such niosomes. Upon the addition of pCMS-EGFP plasmid, nioplexes were obtained at different cationic lipid/DNA ratios (w/w). The resultant nioplexes were further physicochemically characterized and evaluated to condense, release and protect the DNA against enzymatic digestion. In vitro experiments were performed to evaluate transfection efficiency and cell viability in HEK-293, ARPE-19 and PECC cells. Interestingly, niosome formulations based on lipid 3 showed better transfection efficiencies in ARPE-19 and PECC cells than the rest of cationic lipids showed in this study. In vivo experiments in rat retina after intravitreal and subretinal injections together with in rat brain after cerebral cortex administration showed promising transfection efficiencies when niosome formulations based on lipid 3 were used. These results provide new insights for the development of non-viral vectors based on cationic lipids and their applications for efficient delivery of genetic material to the retina and brain.

We designed niosomes based on three lipids that differed only in the polar-head group to analyze their influence on the transfection efficiency. These lipids were characterized by small-angle X-ray scattering before being incorporated into the niosomes which were characterized in terms of pKa, size, zeta potential, morphology and physical stability. Nioplexes were obtained upon the addition of a plasmid. Different ratios (w/w) were selected to analyze the influence of this parameter on size, charge and the ability to condense, release and protect the DNA. In vitro transfection experiments were performed in HEK-293, ARPE-19 and MSC-D1 cells. Our results show that the chemical composition of the cationic head-group clearly affects the physicochemical parameters of the niosomes and especially the transfection efficiency. Only niosomes based on cationic lipids with a dimethyl amino head group (lipid 3) showed a transfection capacity when compared with their counterparts amino (lipid 1) and tripeptide head-groups (lipid 2). Regarding cell viability, we clearly observed that nioplexes based on the cationic lipid 3 had a more deleterious effect than their counterparts, especially in ARPE-19 cells at 20/1 and 30/1 ratios. Similar studies could be extended to other series of cationic lipids in order to progress in the research on safe and efficient non-viral vectors for gene delivery purposes.

Cationic niosomes have become important non-viral vehicles for transporting a good number of small drug molecules and macromolecules. Growing interest shown by these colloidal nanoparticles in therapy is determined by their structural similarities to liposomes. Cationic niosomes are usually obtained from the self-assembly of non-ionic surfactant molecules. This process can be governed not only by the nature of such surfactants but also by others factors like the presence of additives, formulation preparation and properties of the encapsulated hydrophobic or hydrophilic molecules. This review is aimed at providing recent information for using cationic niosomes for gene delivery purposes with particular emphasis on improving the transportation of antisense oligonucleotides (ASOs), small interference RNAs (siRNAs), aptamers and plasmids (pDNA).

The development of novel and efficient delivery systems is often the limiting step in fields such as antisense therapies. In this context, poly(d,l-lactide-co-glycolide) acid (PLGA) nanoparticles have been obtained by a versatile and simple technology based on nano-emulsion templating and low-energy emulsification methods, performed in mild conditions, providing good size control. O/W polymeric nano-emulsions were prepared by the phase inversion composition method at 25°C using the aqueous solution/polysorbate80/[4 wt% PLGA in ethyl acetate] system. Nano-emulsions formed at oil-to-surfactant (O/S) ratios between 10/90-90/10 and aqueous contents above 70 wt%. Nano-emulsion with 90 wt% of aqueous solution and O/S ratio of 70/30 was chosen for further studies, since they showed the appropriate characteristics to be used as nanoparticle template: hydrodynamic radii lower than 50 nm and enough kinetic stability. Nanoparticles, prepared from nano-emulsions by solvent evaporation, showed spherical shape, sizes about 40 nm, negative surface charges and high stability. The as-prepared nanoparticles were functionalized with carbosilane cationic dendrons through a carbodiimide-mediated reaction achieving positively charged surfaces. Antisense oligonucleotides were electrostatically attached to nanoparticles surface to perform gene-silencing studies. These complexes were non-haemolytic and non-cytotoxic at the concentrations required. The ability of the complexes to impart cellular uptake was also promising. Therefore, these novel nanoparticulate complexes might be considered as potential non-viral carriers in antisense therapy.