Solubility and Thermal Degradation of Quercetin in CO2-Expanded Liquids

Nano Drug Delivery Strategies for an Oral Bioenhanced Quercetin Formulation

Quercetin, a naturally occurring flavonoid, has been credited with a wide spectrum of therapeutic properties. However, the oral use of quercetin is limited due to its poor water solubility, low bioavailability, rapid metabolism, and rapid plasma clearance. Quercetin has been studied extensively when used with various nanodelivery systems for enhancing quercetin bioavailability. To enhance its oral bioavailability and efficacy, various quercetin-loaded nanosystems such as nanosuspensions, polymer nanoparticles, metal nanoparticles, emulsions, liposomes or phytosomes, micelles, solid lipid nanoparticles, and other lipid-based nanoparticles have been investigated in in-vitro cells, in-vivo animal models, and humans. Among the aforementioned nanosystems, quercetin phytosomes are attracting more interest and are available on the market. The present review covers insights into the possibilities of harnessing quercetin for several therapeutic applications and a special focus on anticancer applications and the clinical benefits of nanoquercetin formulations.

Effects of Calcium Carbonate Microcapsules and Nanohydroxyapatite on Properties of Thermosensitive Chitosan/Collagen Hydrogels

Thermosensitive chitosan/collagen hydrogels are osteoconductive and injectable materials. In this study, we aimed to improve these properties by adjusting the ratio of nanohydroxyapatite particles to calcium carbonate microcapsules in a β-glycerophosphate-crosslinked chitosan/collagen hydrogel. Two hydrogel systems with 2% and 5% nanohydroxyapatite particles were studied, each of which had varying microcapsule content (i.e., 0%, 1%, 2%, and 5%). Quercetin-incorporated calcium carbonate microcapsules were prepared. Calcium carbonate microcapsules and nanohydroxyapatite particles were then added to the hydrogel according to the composition of the studied system. The properties of the hydrogels, including cytotoxicity and biocompatibility, were investigated in mice. The calcium carbonate microcapsules were 2-6 µm in size, spherical, with rough and nanoporous surfaces, and thus exhibited a burst release of impregnated quercetin. The 5% nanohydroxyapatite system is a solid particulate gel that supports homogeneous distribution of microcapsules in the three-dimensional matrix of the hydrogels. Calcium carbonate microcapsules increased the mechanical and physical strength, viscoelasticity, and physical stability of the nanohydroxyapatite hydrogels while decreasing their porosity, swelling, and degradation rates. The calcium carbonate microcapsules-nanohydroxyapatite hydrogels were noncytotoxic and biocompatible. The properties of the hydrogel can be tailored by adjusting the ratio of calcium carbonate microcapsules to the nanohydroxyapatite particles. The 1% calcium carbonate microcapsules containing 5% nanohydroxyapatite particle-chitosan/collagen hydrogel exhibited mechanical and physical strength, permeability, and prolonged release profiles of quercetin, which were superior to those of the other studied systems and were optimal for promoting bone regeneration and delivering natural flavonoids.

Quercetin-loaded chitosan nanoparticles as an alternative for controlling bacterial adhesion to urethral catheter

OBJECTIVES

The present study aimed to assess the antimicrobial and antiadhesion behavior of quercetin-loaded chitosan nanoparticles in Escherichia coli and Staphylococcus aureus multidrug-resistant isolates.

METHODS

The ionic gelation method was used to prepare chitosan nanoparticles loaded with quercetin. The antimicrobial and antibiofilm effects were observed by minimum inhibitory concentration (MIC), plate count, crystal violet assay, and the matrix exopolysaccharide dosages. The nanoparticles coated in silicone urethral catheters were evaluated by crystal violet assay and plating count method.

RESULTS

MIC ranged from 6.25 to 12.5 mg/ml. A reduction of at least 3.6 log CFU/ml and 6.2 log CFU/ml for, respectively, E. coli and S. aureus isolates was observed (p < 0.05). Under subinhibitory concentration (3.1 mg/ml) it was found a reduction of microbial adhesion and exopolysaccharide dosages in respectively 83.3% and 75% of the bacterial samples. The coated silicone urethral catheters showed a reduction of adhered cells in 25% of the isolates and biomass decreasing in 91.6% of them (p < 0.05).

CONCLUSIONS

The quercetin nanoparticles provided antimicrobial and antiadhesion effects in multidrug-resistant isolates.

Antioxidant Cardioprotection against Reperfusion Injury: Potential Therapeutic Roles of Resveratrol and Quercetin

Ischemia-reperfusion myocardial damage is a paradoxical tissue injury occurring during percutaneous coronary intervention (PCI) in acute myocardial infarction (AMI) patients. Although this damage could account for up to 50% of the final infarct size, there has been no available pharmacological treatment until now. Oxidative stress contributes to the underlying production mechanism, exerting the most marked injury during the early onset of reperfusion. So far, antioxidants have been shown to protect the AMI patients undergoing PCI to mitigate these detrimental effects; however, no clinical trials to date have shown any significant infarct size reduction. Therefore, it is worthwhile to consider multitarget antioxidant therapies targeting multifactorial AMI. Indeed, this clinical setting involves injurious effects derived from oxygen deprivation, intracellular pH changes and increased concentration of cytosolic Ca²⁺ and reactive oxygen species, among others. Thus, we will review a brief overview of the pathological cascades involved in ischemia-reperfusion injury and the potential therapeutic effects based on preclinical studies involving a combination of antioxidants, with particular reference to resveratrol and quercetin, which could contribute to cardioprotection against ischemia-reperfusion injury in myocardial tissue. We will also highlight the upcoming perspectives of these antioxidants for designing future studies.

Characteristics and biologic effects of thermosensitive quercetin-chitosan/collagen hydrogel on human periodontal ligament stem cells

Thermosensitive hydrogels could function as scaffolds and delivery vehicle of natural flavonoids. The current study aimed to investigate effects of chitosan/collagen ratios on properties of thermosensitive beta-glycerophosphate (bGP) chitosan/collagen hydrogels as delivery vehicle of quercetin and then examined effects of quercetin-hydrogels on growth and cell viability of human periodontal ligament stem cells (hPDLSCs). Microstructure and physical, mechanical and antioxidant properties and quercetin release profiles of the hydrogels were investigated. Fourier transform infrared spectroscopy and X-ray powder diffraction analyses were performed to examine gelation process of the hydrogels. Antioxidant assays were conducted to measure antioxidant capacity of quercetin-hydrogels. It was found that bGP-chitosan/collagen hydrogels exhibited porous structures with interconnected pore architecture and could sustain quercetin release. Chitosan content improved well defined porous structure, increased porosity of the hydrogels and decreased releasing rate of quercetin from the hydrogels. The quercetin-bGP-2:1 (wt/wt) chitosan/collagen hydrogels exhibited antioxidant capacity and were able to promote growth of hPDLSCs in a dose dependent manner. In conclusion, the thermosensitive quercetin-bGP-2:1 (wt/wt) chitosan/collagen hydrogel demonstrated optimal properties of scaffolds for bone tissue engineering and sustained release of natural flavonoids. Incorporating quercetin in the chitosan/collagen hydrogel enhanced bioactive microenvironment that supported stem cell encapsulation.