Nanoformulations of curcumin and quercetin with silver nanoparticles for inactivation of bacteria

Mehran Alavi , Nareen Arif Adulrahman, Azad Abduljabar Haleem, Ahmed Diyar Hussein AlRâwanduzi, Ameer Khusro, Mohamed A Abdelgawad, Mohammed M. Ghoneim, Gaber El-Saber Batiha, Danial Kahrizi , Fleming Martinez , Niranjan Koirala Nanobiotechnology Department, Faculty of Innovative Science and Technology, Razi University, Kermanshah, Iran Family and Community Medicine Department, College of Medicine, University of Duhok, Duhok, Iraq Pediatric Department, College of Medicine, University of Duhok, Duhok, Iraq Cicilav Medical Facilities, Brayati, Erbil, Iraq Collage of Medicine, Hawler Medical University, Erbil. Iraq Research Department of Plant Biology and Biotechnology, Loyola College, Nungambakkam, Chennai-600034, Tamil Nadu, India Department of Pharmaceutical Chemistry, College of Pharmacy, Jouf University, Sakaka, Al Jouf 72341, Saudi Arabia Department of Pharmacy Practice, Faculty of Pharmacy, AlMaarefa University, Ad Diriyah 13713, Saudi Arabia Department of Pharmacology and Therapeutics, Faculty of Veterinary Medicine, Damanhour University, Damanhour 22511, AlBeheira, Egypt Grupo de Investigaciones Farmacéutico-Fisicoquímicas, Departamento de Farmacia, Facultad de Ciencias, Universidad Nacional de Colombia, Sede Bogotá, Colombia Department of Natural Products Research, Dr. Koirala Research Institute for Biotechnology and Biodiversity, Kathmandu 44600, Nepal


Introduction
Turmeric with the scientific name of Curcuma longa is a plant of the ginger family that has dried rhizomes. It is used for food and medicine and is native to the warm regions of Asia like India, Pakistan and Indonesia. Turmeric throughout history, also as a medicine and has been used as food by people and in Traditional medicine is also used as an herbal remedy for various infections. Curcumin is the active ingredient in turmeric, which has its chemical name of diferuloylmethane with the chemical formula (C21H20O6) (1). As shown in Figures 1a-b, there are two main forms of enol and keto for curcumin. It should be mentioned that the enol form is more energetically stable compared to the keto one (2,3). Moreover, this plant species has numerous chemical compounds including essential oils, alpha and beta turmeric, ginger, glucose, fructose, arabinose, and starch. The color of turmeric is also related to dyes such as curcumin, des-methoxy curcumin, and bisdemethoxycurcumin. In addition, antioxidant activity, curcumin, has anti-inflammatory, woundhealing (by increasing the growth of blood vessel density, fibroblasts, and regeneration of skin), anticancer, and antimicrobial properties ( Figure 2) (4).  (Figure 1c), which can be found at different contents in various plant species such as green tea leaves, dill, broccoli and raw onions (Table 1). Anticancer and antimicrobial properties are reported for this metabolite or its derivatives (5). For instance, the antibacterial activity of starch aldehyde-quercetin conjugate was found against Listeria monocytogenes, Staphylococcus aureus, and Escherichia coli species (6). Antibiotic resistance as a major hindrance in combat bacterial pathogens is increasing owing to acquisition resistance mechanisms in new bacterial strains (8,9). Nanotechnology by presenting numerous nanomaterials with unrivaled physicochemical properties has obtained high attention (10). Nanoparticles specifically metal or metal oxide nanoparticles have a large surface area-to-volume ratio and more reactivity relative to bulk materials appropriate to therapeutic applications such as antibacterial or anticancer agents (11). In this regard, silver (Ag), gold (Au), copper/copper oxide (Cu/CuO), zinc oxide (ZnO2), titanium dioxide (TiO2), and platinum (Pt) are common metallic nanoparticles (12). Among these nanoparticles, AgNPs have shown prominent antibacterial capacity with disadvantages of cytotoxicity in higher doses (13,14). In this way, conjugation or combination of AgNPs with plant materials particularly curcumin and quercetin has been presented as an effective strategy. Therefore, this review has discussed this issue in recent years for getting a novel comprehensive scope of future studies.

AgNPs-curcumin
As shown in Figure 3a, curcumin compound can form AgNPs by reducing the reaction of Ag+ ions in colloidal solution resulting from several possible sites of carbon and oxygen atoms for electrophilic attack (3). As noted in the introduction section, AgNPs at high concentrations are toxic for eukaryotic cells. Therefore, using other biocompatible materials to modify NPs and reduce cytotoxicity is an indispensable affair. In a comparative study, AgNO3, AgNPs, AgNPs-curcumin, curcumin, kanamycin, and chloramphenicol exhibited minimum bactericidal concentration (MBC) values of 2.5, 20, 10, 280, 4, and 12.5 mg/L toward S. aureus ATCC 9144, respectively. The concentration for inhibition 90% of the cells (IC90) of AgNPs-curcumin against human keratinocytes was 156 mg/L less than 5 mg/L of minimum inhibition concentration (MIC) for S. aureus (18). In order to the formulation of AgNPscurcumin for healing of infected wounds, other supporter materials such as polymers can offer new advantages of stability and sustained drug release in physiological conditions. Gelatin derived from collagen is an example of natural polymers suitable for obtaining stable nanocomposites based on AgNPscurcumin-gelatin under ultraviolet (UV) irradiation owing to the conversion of amine groups of gelatin structure to nitrite via the metal ion-induced oxidation. According to different concentration (1.25%, 1%, 0.75%, and 0.5%) of gelatin solution, MBCs against Pseudomonas aeruginosa were 250, 125, 125, and 250 µL/mL, respectively with desirable biocompatibility at 125 µL/mL (19).
It is worth noting that curcumin-AgNPs can induce mutagenic effects as the recovered abilities to fabricate histidine amino acid in TA98 and TA100 strains of Salmonella typhimurium at the presence of S9, a liver extract that simulates the hepatic metabolism (20). Curcumin-AgNPs can be more functionalized using natural and synthetic polymers. In this regard, the monomer 2-(2methoxyethoxy)ethyl methacrylate (MEO2MA), crosslinking monomer of tetraethylene glycol dimethacrylate (TEGDMA), and reducer/stabilizer agent of trisodium citrate dehydrate were applied to functionalize curcumin-AgNPs to obtain Ag@curcumin-P(MEO2MA) NPs with core-shell morphology and a size range of 34-64 nm dependent on curcumin weight % (1.05-3.80%) (21).

AgNPs-quercetin
Metal and metal oxide NPs can cause the deformation and destruction of bacterial cells via direct and indirect interactions. Adhesion of NPs or metallic ions to the bacterial membrane or cell wall is found as direct interaction, while production of reactive oxygen species (ROS) such as superoxide radicals and damaging biological macromolecules in the bacterial medium are indirect antibacterial effects for these NPs (23). As shown in Figure 3b, quercetin as a plant flavonoid can contribute to the synthesis of AgNPs by reduction of Ag + ions in the redox reaction. In addition to synergistic antibacterial activity against Gram-negative and Gram-positive bacteria, the increased antioxidant property is expected for a combination of AgNPs with quercetin, as antioxidant capacity of 82.3% at a concentration of 400 ppm was led by AgNPs-quercetin with the mean size of 20 nm (24). Quercetin may be used directly to synthesize AgNPs. A combination of quercetin as an efficient free radical scavenger and AgNO3 at 40 ○ C for 60 minutes was employed to fabricate AgNPs with spherical shape and mean size of 11 nm. P. aeruginosa and S. aureus displayed 2 and 4 µg/mL MBC values upon quercetin-AgNPs, respectively (25).
Quercetin isolated from methanolic extract of Clitoria ternatea plant species was able to synthesize AgNPs with spherical shape and the mean size of 65 nm, which revealed ~70% inhibition of exopolysaccharide synthesis at 100 ppm against S. aureus with ~4.5% hemolytic activity at 120 ppm (26). It should be noted that, synergistically, modification of AgNPs by plant secondary metabolite of quercetin may be more efficient than a green synthesis of AgNPs using plant extract. For example, MBC amounts for AgNPs-quercetin towards ESbL (+) E. coli, ESbL (+) P. aeruginosa, methicillin-sensitive S. aureus, and methicillin-resistant S. aureus strains were 60, 60, 70, 70 ppm compared to AgNPs phytosynthesized by yellow bell pepper extract with MBCs of 80, 80, 100, 100 ppm, respectively (27). In a lower diameter, AgNPs can inhibit bacteria more efficient than larger ones, as quercetin-synthesized AgNPs with a size of 8 nm displayed a minimum inhibitory concentration (MIC) value of 1 ppm toward E. coli in comparison with AgNPs (size of 20 nm) by the MIC of 2.5 ppm (28). Small interference RNA (siRNA) or silencing RNA is non-coding double-stranded RNA with 19-25 base pairs (29). siRNA was employed for surface modification of AgNPs-quercetin to prepare siRNA/AgNPs-quercetin with a mean size of ~ 40 nm in a spherical shape, which exhibited significant bacterial inactivation as MIC value of 2.1 ppm compared to AgNPs and AgNPs-quercetin by MIC amounts of 16.4 and 13.2 ppm, respectively against antibiotic-resistant B. subtilis. Moreover, this nanoformulation showed reduced bacteremia symptoms in mice specimens after 7 days of treatment (30).

Conclusions
Pathogenic bacterial strain with obtaining antibiotic resistance can sidestep the plethora of conventional antibiotics. Recently, metal or metal oxide nanoparticles specifically silver nanoparticles (AgNPs) have been used efficiently to inhibit antibiotic-resistant Gram-negative and Gram-positive bacteria. AgNPs at high concentrations is toxic for eukaryotic cells, application of other biocompatible materials such as natural phenolic compounds of curcumin and quercetin to reduce cytotoxicity is an indispensable affair. These phenolic compounds can contribute to the synthesis of AgNPs by reduction of Ag + ions in the redox reaction. In addition to synergistic antibacterial activity against Gramnegative and Gram-positive bacteria, increased antioxidant property is expected for combination of AgNPs with curcumin and quercetin bioactive metabolites. As a critical point, curcumin-AgNPs complex can stimulate mutagenic in TA98 and TA100 strains of S. typhimurium at the presence of S9 by the recovered abilities to fabricate histidine. Finally, future investigations should meet the increased biocompatibility of AgNPs by other phenolic compounds similar to curcumin for an efficient formulation, suitable for physiological conditions.

Acknowledgement
The authors deeply acknowledge the Researchers Supporting Program (TUMA-Project-2021-6), AlMaarefa University, Riyadh, Saudi Arabia for supporting steps of this work.

Interest conflict
The authors declare no conflict of interest.