Preparation, characterization and photostability assessment of curcumin microencapsulated within methacrylic copolymers

Electrospun nanofibers with antibacterial properties for wound dressings

The antibacterial nanofibers have been proposed as an interesting material for wound healing management, since the majority of traditional wound dressings exhibit issues and complications such as infection, pain, discomfort, and poor adhesive proprieties. It allows the organism's passage through the dressing and delay the wound healing progression. Electrospun nanofibers have been intensively investigated for wound dressings in tissue engineering applications due to their distinctive features and structural similarities to the extracellular matrix including the various available methods to load the antibacterial compounds onto the nanofiber webs. To construct an effective electrospun wound dressing, various efforts have been made to design different strategies to develop advanced polymers, such as employing synthetic and/or natural materials, modifying fiber orientation, and incorporating chemicals and metallic nanoparticles (NPs) as intriguing materials for antibacterial bandages. Thus, this review summarizes the relevant recent studies on the production of electrospun antibacterial nanofibers from a wide variety of polymers used in biomedical applications for wound dressings.

Drug Delivery Strategies for Curcumin and Other Natural Nrf2 Modulators of Oxidative Stress-Related Diseases

Oxidative stress is associated with a wide range of diseases characterised by oxidant-mediated disturbances of various signalling pathways and cellular damage. The only effective strategy for the prevention of cellular damage is to limit the production of oxidants and support their efficient removal. The implication of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in the cellular redox status has spurred new interest in the use of its natural modulators (e.g., curcumin, resveratrol). Unfortunately, most natural Nrf2 modulators are poorly soluble and show extensive pre-systemic metabolism, low oral bioavailability, and rapid elimination, which necessitates formulation strategies to circumvent these limitations. This paper provides a brief introduction on the cellular and molecular mechanisms involved in Nrf2 modulation and an overview of commonly studied formulations for the improvement of oral bioavailability and in vivo pharmacokinetics of Nrf2 modulators. Some formulations that have also been studied in vivo are discussed, including solid dispersions, self-microemulsifying drug delivery systems, and nanotechnology approaches, such as polymeric and solid lipid nanoparticles, nanocrystals, and micelles. Lastly, brief considerations of nano drug delivery systems for the delivery of Nrf2 modulators to the brain, are provided. The literature reviewed shows that the formulations discussed can provide various improvements to the bioavailability and pharmacokinetics of natural Nrf2 modulators. This has been demonstrated in animal models and clinical studies, thereby increasing the potential for the translation of natural Nrf2 modulators into clinical practice.

Curcumin Loaded Polymeric vs. Lipid Nanoparticles: Antioxidant Effect on Normal and Hypoxic Olfactory Ensheathing Cells

Background: Curcumin (Cur) shows anti-inflammatory and antioxidant effects on central nervous system diseases. The aim of this study was to develop Cur-loaded polymeric and lipid nanoparticles for intranasal delivery to enhance its stability and increase antioxidant effect on olfactory ensheathing cells (OECs). Methods: The nanosuspensions were subjected to physico-chemical and technological evaluation through photon correlation spectroscopy (PCS), differential scanning calorimetry (DSC) and UV-spectrophotometry. The cytotoxicity studies of nanosuspensions were carried out on OECs. A viability test was performed after 24 h of exposure of OECs to unloaded and curcumin-loaded nanosuspensions. The potential protective effect of Cur was assessed on hypoxic OECs cells. Uptake studies were performed on the same cell cultures. Thermal analysis was performed to evaluate potential interaction of Cur with a 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) biomembrane model. Results: PCS analysis indicated that lipid and polymeric nanosuspensions showed a mean size of 127.10 and 338.20 nm, respectively, high homogeneity and negative zeta potential. Incorporation of Cur into both nanocarriers increased drug stability up to 135 days in cryoprotected freeze-dried nanosuspensions. Cell viability was improved when hypoxic OECs were treated with Cur-loaded polymeric and lipid nanosuspensions compared with the control. Conclusions: Both nanocarriers could improve the stability of Cur as demonstrated by technological studies. Biological studies revealed that both nanocarriers could be used to deliver Cur by intranasal administration for brain targeting.

Polymer-Based Materials Loaded with Curcumin for Wound Healing Applications

Some of the currently used wound dressings have interesting features such as excellent porosity, good water-absorbing capacity, moderate water vapor transmission rate, high drug loading efficiency, and good capability to provide a moist environment, but they are limited in terms of antimicrobial properties. Their inability to protect the wound from microbial invasion results in wound exposure to microbial infections, resulting in a delayed wound healing process. Furthermore, some wound dressings are loaded with synthetic antibiotics that can cause adverse side effects on the patients. Natural-based compounds exhibit unique features such as good biocompatibility, reduced toxicity, etc. Curcumin, one such natural-based compound, has demonstrated several biological activities such as anticancer, antibacterial and antioxidant properties. Its good antibacterial and antioxidant activity make it beneficial for the treatment of wounds. Several researchers have developed different types of polymer-based wound dressings which were loaded with curcumin. These wound dressings displayed excellent features such as good biocompatibility, induction of skin regeneration, accelerated wound healing processes and excellent antioxidant and antibacterial activity. This review will be focused on the in vitro and in vivo therapeutic outcomes of wound dressings loaded with curcumin.

Development, Optimization and Characterization of Eudraguard®-based Microparticles for Colon Delivery

Development of pH-dependent systems for colon delivery of natural active ingredients is an attractive area of research in the field of nutraceutical products. This study was focused on Eudraguard^® resins, that are methacrylate copolymers approved as “food grade” by European Commission and useful for the production of food supplements. In particular, Eudraguard^® Biotic (EUG-B), characterized by a pH-dependent solubility and Eudraguard^® Control (EUG-C), whose chemical properties support a prolonged release of the encapsulated compounds, were tested. To obtain EUG microparticles, different preparation techniques were tested, in order to optimize the preparation method and observe the effect upon drug encapsulation and specific colonic release. Unloaded microparticles were initially produced to evaluate the influence of polymer characteristics on the formulation process; subsequently microparticles loaded with quercetin (QUE) as a low solubility model drug were prepared. The characterization of microparticles in the solid-state (FT-IR spectroscopy, differential scanning calorimetry and X-ray diffractometry) indicated that QUE was uniformly dispersed in a non-crystalline state in the polymeric network, without strong signs of chemical interactions. Finally, to assess the ability of EUG-C and EUG-B to control the drug release in the gastric environment, and to allow an increased release at a colonic level, suitable in vitro release tests were carried out by simulating the pH variations along the gastro-intestinal tract. Among the evaluated preparation methods, those in which an aqueous phase was not present, and in particular the emulsion-solvent evaporation method produced the best microparticle systems. The in vitro tests showed a limited drug release at a gastric level and a good specific colon release.

Detection and Quantification of eDNA-Associated Bacterial Membrane Vesicles by Flow Cytometry

Bacteria generate membrane vesicles, which are structures known as extracellular vesicles (EVs), reported to be involved in different pathogenic mechanisms, as it has been demonstrated that EVs participate in biofilm formation, cell-to-cell communication, bacteria–host interactions, and nutrients supply. EVs deliver nucleic acids, proteins, and polysaccharides. It has been reported that Helicobacter pylori (H. pylori) and Lactobacillus reuteri (L. reuteri), of both planktonic and biofilm phenotypes, produce EVs carrying extracellular DNA (eDNA). Here, we used polychromatic flow cytometry (PFC) to identify, enumerate, and characterize EVs as well as the eDNA-delivering EV compartment in the biofilm and planktonic phenotypes of H.pylori ATCC 43629 and L. reuteri DSM 17938. Biofilm formation was demonstrated and analyzed by fluorescence microscopy, using a classical live/dead staining protocol. The enumeration of EVs and the detection of eDNA-associated EVs were performed by PFC, analyzing both whole samples (cells plus vesicles) and EVs isolated by ultracentrifugation confirm EVs isolated by ultracentrifugation. PFC analysis was performed relying on a known-size beaded system and a mix of three different fluorescent tracers. In detail, the whole EV compartment was stained by a lipophilic cationic dye (LCD), which was combined to PKH26 and PicoGreen that selectively stain lipids and DNA, respectively. Fluorescence microscopy results displayed that both H. pylori and L. reuteri produced well-structured biofilms. PFC data highlighted that, in both detected bacterial species, biofilms produced higher EVs counts when paralleled to the related planktonic phenotypes. Furthermore, the staining with PicoGreen showed that most of the generated vesicles were associated with eDNA. These data suggest that the use of PFC, set according to the parameters here described, allows for the study of the production of eDNA-associated EVs in different microbial species in the same or several phases of growth, thus opening new perspectives in the study of microbial derived EVs in clinical samples.

Antioxidant activity and photostability assessment of trans-resveratrol acrylate microspheres

Trans-resveratrol (RSV) was microencapsulated in Eudragit^® RS100 and RL100 resin blends. Lyophilized microspheres were characterized in the solid state for their micromeritic properties and drug loading. FT-IR, PXRD, and DSC analyzes suggested that RSV formed an intimate microcrystalline dispersion within the polymer network, also confirmed by SEM analysis. This produced a reduced degradation of RSV after storage at 40 °C, compared to the neat drug, and a protection of the drug from UV light-induced trans-cis isomerization (60% intact drug was found after 60 s irradiation at 350 nm, compared to 37% for the pure drug). Solubility and in vitro dissolution studies indicated that microencapsulation did not improve the dissolution pattern of RSV in simulated gastric and intestinal aqueous fluids. Evaluation of the in vitro antioxidant activity showed that, compared to the neat drug in aqueous solution, RSV loaded in the microspheres retained for a longer time, up to 22 days of incubation, the initial ORAC capacity. The present study thus demonstrated that Eudragit^® Retard resins can be used to easily produce micro-sized solid dispersions with RSV, for potential oral administration, contributing to ameliorate the physico-chemical stability and antioxidant activity of this compound.

Polyelectrolyte Complex Nanoparticles from Chitosan and Acylated Rapeseed Cruciferin Protein for Curcumin Delivery

Curcumin is a polyphenol that exhibits several biological activities, but its low aqueous solubility results in low bioavailability. To improve curcumin bioavailability, this study has focused on developing a polyelectrolyte complexation method to form layer-by-layer assembled nanoparticles, for curcumin delivery, with positively charged chitosan (CS) and negatively charged acylated cruciferin (ACRU), a rapeseed globulin. Nanoparticles (NPs) were prepared from ACRU and CS (2:1) at pH 5.7. Three samples with weight of 5%, 10%, and 15% of curcumin, respectively, in ACRU/CS carrier were prepared. To verify the stability of the NPs, encapsulation efficiency and size of the 5% Cur-ACRU/CS NPs were determined at intervals of 5 days in a one month period. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, and differential scanning calorimetry confirmed the electrostatic interaction and hydrogen bond formation between the carrier and core. The result showed that hollow ACRU/CS nanocapsules (ACRU/CS NPs) and curcumin-loaded ACRU/CS nanoparticles (Cur-ACRU/CS NPs) were homogenized spherical with average sizes of 200-450 nm and zeta potential of +15 mV. Encapsulation and loading efficiencies were 72% and 5.4%, respectively. In vitro release study using simulated gastro (SGF) and intestinal fluids (SIF) showed controlled release of curcumin in 6 h of exposure. Additionally, the Cur-ACRU/CS NPs are nontoxic to cultured Caco-2 cells, and the permeability assay indicated that Cur-ACRU/CS NPs had improved permeability efficiency of free curcumin through the Caco-2 cell monolayer. The findings suggest that ACRU/CS NPs can be used for encapsulation and delivery of curcumin in functional foods.

Improvement of Oral Bioavailability of Curcumin upon Microencapsulation with Methacrylic Copolymers

Curcumin (diferuloymethane; CUR) is a yellow pigment used in traditional medicine throughout history for its anti-inflammatory activity. In the last years, the scientific research has demonstrated that CUR effects are related to the modulation of crucial molecular targets, related to several pathologies including cancer, arthritis, diabetes, Crohn’s disease. In this paper, two formulations of microencapsulated CUR obtained by coevaporation with polymethacrylate polymers (Eudragit^® Retard) were investigated in vitro, ex vivo, and in vivo, and results were compared by laser confocal microscopy analysis. The permeation of microencapsulated CUR through CaCo-2 monolayers was evaluated in vitro. The mucoadhesion and bioadhesion of the CUR-loaded microparticles were evaluated in vitro, using E12 and CaCo-2 human intestinal cells, and ex vivo, by means of excised rat intestinal mucosa. After oral administration to rats, microencapsulated CUR showed a sevenfold increase of bioavailability in respect to the neat drug, with a concomitant reduction of the T_max and a five-fold plasma concentration peak increase.