The use of quercetin as a bioflavonoid is becoming increasingly common in food industries even though poor water solubility, instability, absorption, and permeability have limited its application. The oil-in-water single-emulsion solvent evaporation method to synthesize highly stable and soluble quercetin-encapsulated nanoparticles (NPs), in which the reaction yield, particle size, and polydispersity of the NPs are varied greatly within the process parameters of the synthesis method, has been optimized. NPs with different initial quercetin amounts were used to determine how the quercetin amount affected nanoparticle properties and antimicrobial efficiency. Listeria monocytogenes, Salmonella typhimurium, Escherichia coli, and Staphylococcus aureus were chosen as model bacteria due to their being foodborne pathogens. The results of antimicrobial activity evaluated by three different methods showed that the antimicrobial activity of both quercetin NPs and free quercetin was effective on gram-positive strains (L. monocytogenes and S. aureus). Additionally, it was detected that Q31 NPs have more effective antimicrobial activity than other synthesized quercetin nanoparticles depending on the amount of substance and release. Furthermore, on the basis of assessing the antibacterial effects by scanning electron microscopy, it was detected that bacteria cells lost their integrity and became pale with the release of cytoplasm and decomposed after treatment with Q31 NPs.

IntroductionCoronaviruses belonging to the family Coronaviridae from the members of the order Nidovirales are spherical, enveloped, and single-stranded positive RNA viruses within the diameter range of 60-220 nm, which have rodshaped glycoprotein extensions in their outer surfaces and carry a genome size of 26-32 kb (King et al., 2011;Shereen et al., 2020). Among the coronaviruses, which are classified into four subgroups: alpha (α), beta (β), gamma (γ), and delta (δ) (Kin et al., 2015), the strains that currently infect humans are seven; HCoV229E, HCoV-OC43, SARS-CoV, HCoV-NL63, HCoV-HKU1, MERS-CoV, and SARS-CoV-2 (severe acute respiratory syndrome coronavirus) (Nomura et al., 2004).Following the severe acute respiratory syndrome (SARS-CoV) that occurred in China in 2002, MERS-CoV caused endemic in the Middle East countries in 2013 (Brian and Baric, 2005), while SARS-CoV-2 created pandemics in 2020 1 . The SARS-1 WHO has declared COVID-19 as a pandemic. [online] Website: https://www.who.int/dg/speeches/detail/who-director-general-s-opening-remarks-at-the-media-briefing-on-covid-19---11-march-2020 [accessed date 25.05.2020]CoV-2, which caused the COVID-19 pandemic, belongs to the group of betacoronavirus and its clinical manifestations are evaluated in three different stages: i) mild; weakness, fever, dry cough, fatigue, and upper respiratory tract infections, ii) moderate; shortness of breath, severe cough, diarrhea, iii) severe; severe pneumonia, acute lung injury (ALI), and acute respiratory distress syndrome (ARDS), sepsis and septic shock (Cascella et al., 2020). Currently, there is no specific antiviral therapy developed against SARS-CoV-2.Based on previous experiences in SARS-CoV and MERS-CoV outbreaks, some treatment strategies have been developed (Cascella et al., 2020;Mehta et al., 2020;. These strategies include antiviral treatments or combinations of these that have been known to be safe for humans and used in previous viral outbreaks,

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Coronavirus disease 2019 (COVID-19) is today's most serious epidemic disease threatening the human race. The initial therapeutic approach of SARS-CoV-2 disease is based upon the binding the receptor-binding site of the spike protein to the host cell's ACE-2 receptor on the plasma membrane. In this study, it is aimed to develop a biocompatible and biodegradable polymeric drug delivery system that is targeted to the relevant receptor binding site and provides controlled drug release. Oseltamivir phosphate (OP) is an orally administered antiviral prodrug for primary therapy of the disease in biochemically activated carboxylate form (oseltamivir carboxylate OC). In the presented study, model drug OP loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) targeted with spike-binding peptide 1 (SBP1) of SARS-CoV-2 were designed to be used as an efficient and prolonged released antiviral drug delivery system. RY, EE, and DL values of the OP-loaded NPs produced by the solvent evaporation method were calculated to be 59.3%, 61.4%, and 26.9%, respectively. The particle size of OP-loaded NPs and OP-loaded NPs targeted with SBP1 peptide were 162.0±11.0 and 226.9±21.4 nm, respectively. While the zeta potential of the produced OP-loaded NPs was achieved negatively −23.9±1.21 mV), the result of the modification with SBP1 peptide this value approached zero as −4.59±0.728 mV. Morphological features of the OP-loaded NPs were evaluated using FEG-SEM. The further characterization and surface modification of the NPs were analyzed by FT-IR. In-vitro release studies of NPs showed that sustained release of OP occurred for two months that fitting the Higuchi kinetic model. By evaluating these outputs, it was reported that surface modification of OP-loaded NPs was significantly effective on characteristics such as size, zeta potential values, surface functionality, and release behavior. The therapeutic model drug-loaded polymeric formulation targeted with a specific peptide may serve as an alternative to more effective and controlled release pharmaceuticals in the treatment of COVID-19 upon an extensive investigation.

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