Silver has a wide range of antibacterial and fungicidal activities as well as the ability to coordinate with various ligands and macromolecules in microbial cells and is the noblest metal in the manufacture of nanoparticles. Silver is also widely used in inhibiting microbial proliferation and improving wound healing due to its anti-inflammatory effect. Silver nanoparticles have created new strands in medical protocols, and this has been attributed to their larger volume due to the apparent reaction of silver nanoparticles to the surface [13, 14]. In the present study, a biological method was used to produce silver nanoparticles using phycocyanin extracted from Spirulina platensis. Due to the revival of silver ions and the production of nanoparticles, the color of the samples has changed from blue to dark brown. This discoloration is due to the interaction of phycocyanin and the solution. Silver salt is considered the first indication of the production of silver nanoparticles. The discoloration occurs for the silver nanoparticles due to the oscillation of free electrons in the reaction mixture of the nanoparticles. After 24 h of incubation, the reaction mixture showed that the dark brown dye indicates complete synthesis of the nanoparticles [15]. The peak absorption spectrum of nanoparticles in the spectrophotometer is about 420 nm and confirms the production of silver nanoparticles, which is similar to the results of previous studies [16].
FTIR analysis was performed to investigate the potential organic compounds present in the nanoparticles. After reacting with silver nitrate, some displacements occur at the location and height of the peaks. These displacements are in 3452, 2361, 1152, which are related to the NH, and (H–C=O, C≡N) and C–O tensile strength. Silver salts and precursor proteins reduce silver ions and stabilize silver nanoparticles. The FTIR spectrum supports the presence of a protein on the surface of biosynthesized AgNPs, which causes the metabolic proteins produced to act as coatings during production, reducing the accumulation of silver particles. It has been suggested that the stability of AgNPs may be due to the presence of a protein cap agent that encloses them and forms a layer that protects the nanoparticles from aggregation [16,17,18,19]. The excitation wavelength of PC-AgNPs was 580 nm and the maximum emission peak was 625 nm. In another research, fluorescence spectrum analysis of the synthesized DNA-Ag nanoparticles showed that the maximum excitation wavelength was at 560 nm and the emission wavelength was 650 nm [20]. A similar study showed that nanosilver synthesized with short hydrogen-based peptides has an excitation wavelength at 530 nm and a diffusion wavelength of 634 nm [21].
In the present study, the antibacterial effect of synthesized silver nanoparticles on standard strains (Entercoccus faecalis, Escherichia coli, Serratia marceseus and Staphylococcus aureus) was investigated.
Biosynthesized AgNPs significantly inhibit the growth of Gram-positive and Gram- negative bacteria pharmacologically. The antibacterial activity of silver nanoparticles by breaking the plasma membrane or blocking the respiration associated with oxygen and sulfhydryl groups in the cell wall leads to bacterial cell death. Phycocyanin pigments were evaluated against bacterial species which in the case of the antibacterial activity against Staphylococcus aureus, this result is almost consistent with previous studies. The release of Ag may inactivate the production of certain enzymes and cellular proteins necessary for the synthesis of adenosine triphosphate (ATP) or the replication of bacterial DNA. Other research has suggested that silver ions may impair the function of restricted membrane enzymes in the respiratory chain. The antibacterial activity of silver nanoparticles is affected by particle size, and the smaller the particle size, the greater the antibacterial effect [22, 23].
Toxicological studies have shown that consumption of medicinal plants or medicines can alter the level of normal hematology [24]. Thus, hematological parameters can be a tool for investigating the effects of drugs [25]. In this study, RBC parameters such as Hb, MCV, MCH and MCHC in rats were studied. It was found that phycocyanin had an additive effect on RBC level and improvement of its parameters. It can be concluded that it can be effective in the treatment of anemia. PC-AgNp had less effect on these parameters. White blood cells (WBCs) kill foreign substances. A number of WBCs have been known to enhance the immune mechanism against toxins [26]. Leukocytes have been reported to be activated by AGEs (Advance Glycated End products), oxidative stress, angiotensin II, and anti-inflammatory cytokines [27]. In this study, rats treated with PC showed more leukocytosis than control and PC-AgNp treated rats.
The number of platelets is directly related to the number of WBCs, indicating a common mechanism. Increased platelet counts are commonly seen in infectious diseases and inflammatory reactions [28]. In the present study, there was an increase in platelet count in phicocyanin-treated rats and a decrease in platelet counts in phycocyanin nanoparticles-treated rats compared to control rats. Therefore, nanoparticle particles influence the coagulation process, which depends on the size, charge, shape and composition of Np [29].
Liu et al. found that intravenous injection of hydroxyapatite nanoparticles increased AST, ALT, and ALP in rabbits [30]. However, intraperitoneal injection does not alter these factors in rat serum, but induces apoptosis in liver and kidney cells [31]. In a similar study, Susan et al. reported that the different effects of nanoparticles are directly related to their diameter and dispersion in body tissues [32]. In fact, free radicals of silver nanoparticles attack liver cells and release their stored ATP into the bloodstream, and through the immune response to an exogenous factor in mice, the number of white blood cells increases and silver nanoparticles are destroyed. [33]. In evaluating the effect of silver nanoparticles in wistar rats, it was found that PC accumulates mainly in the liver, but in oral Np consumption, the levels of AST, ALT and Alp were different and showed partial inactivation of these enzymes [34]. In the present study, both ALT and AST levels were increased in the oral PC and PC-Np injection, but the ALK level was decreased, which was relatively high in the PC-Np group. In separate studies, the potential of silver nanoparticles to modulate enzyme activity depended on thiols [35, 36].
