Structural analysis of the interaction between free, glycated and fructated hemoglobin with propolis nanoparticles: A spectroscopic study

Improving the stability of myofibrillar proteins undergoing hemoglobin-mediated oxidation by rosmarinic acid or chlorogenic acid: Insights into the underlying mechanisms

In this study, rosmarinic acid (RA) and chlorogenic acid (CGA) were used to improve the stability of myofibrillar protein (MP) undergoing hemoglobin (Hb)-mediated oxidation. Hb-mediated oxidation caused changes in MP's secondary and tertiary structures. RA or CGA suppressed effectively Hb-induced MP oxidation, and maintained MP's spatial conformational stability through interacting with MP's amino acid side chains to form phenolic-protein complexes. Further investigations by multi-spectroscopic techniques, isothermal titration calorimetry, and molecular docking and dynamics simulation revealed the interaction of RA or CGA with Hb through binding to Hb's central hydrophobic cavity via one binding site. The RA/CGA-Hb binding was an enthalpy-driven spontaneous and exothermic process, involving hydrogen bonds and van der Waals forces as the main interactive forces. The Hb-CGA binding might be more stable than Hb-RA binding. This study provides a theoretical basis for the application of RA and CGA in improving meat products quality by regulating Hb-mediated protein oxidation.

Advances of nanoparticle derived from food in the control of α-dicarbonyl compounds-A review

α-Dicarbonyl compounds (α-DCs) are predominantly generated through the thermal processing of carbohydrate and protein-rich food. They are pivotal precursors to hazard formation, such as advanced glycation end products (AGEs), acrylamide, and furan. Their accumulation within the body will be genotoxicity and neurotoxicity. Recently, significant advancements have been made in nanotechnology, leading to the widespread utilization of nanomaterials as functional components in addressing the detrimental impact of α-DCs. This review focuses on the control of α-DCs through the utilization of nanoparticle-based functional factors, which were prepared by using edible components as resources. Four emerging nanoparticles are introduced including phenolic compounds-derived nanoparticle, plant-derived nanoparticle, active peptides-derived nanoparticle, and functional minerals-derived nanoparticle. The general control mechanisms as well as the recent evidence pertaining to the aforementioned aspects were also discussed, hoping to valuable helpful references for the development of innovative α-DCs scavengers and identifying the further scope of research.

Structural changes in hemoglobin and glycation

Hemoglobin (Hb) is a hemeprotein found inside erythrocytes and is crucial in transporting oxygen and carbon dioxide in our bodies. In erythrocytes (Ery), the main energy source is glucose metabolized through glycolysis. However, a fraction of Hb can undergo glycation, in which a free amine group from the protein spontaneously binds to the carbonyl of glucose in the bloodstream, resulting in the formation of glycated hemoglobin (HbA1c), widely used as a marker for diabetes. Glycation leads to structural and conformational changes, compromising the function of proteins, and is intensified in the event of hyperglycemia. The main changes in Hb include structural alterations to the heme group, compromising its main function (oxygen transport). In addition, amyloid aggregates can form, which are strongly related to diabetic complications and neurodegenerative diseases. Therefore, this chapter discusses in vitro protocols for producing glycated Hb, as well as the main techniques and biophysical assays used to assess changes in the protein's structure before and after the glycation process. This more complete understanding of the effects of glycation on Hb is fundamental for understanding the complications associated with hyperglycemia and for developing more effective prevention and treatment strategies.

Development of propolis, hyaluronic acid, and vitamin K nano-emulsion for the treatment of second-degree burns in albino rats

Burns are the fourth most common type of injury worldwide. Many patients also suffer numerous infections and complications that impair the burn healing process, which makes the treatment of burns a challenge. This study aimed to prepare and characterize nano-emulsion (NE) of propolis, hyaluronic acid, and vitamin K for treatment of second-degree burns. High-Pressure Liquid Chromatography (HPLC) was used for the qualitative assessment of the phenolic and flavonoid contents in crude propolis. The structural, optical, and morphological characterization, besides the antimicrobial, antioxidant, cytotoxicity, in-vitro, and in-vivo wound healing activities were evaluated. For in-vivo study, 30 adult male albino rats were divided randomly into control and treated groups, which were treated with normal saline (0.9%), and NE, respectively. The wounds were examined clinicopathologically on the 3rd, 7th, and 14th days. The NE revealed the formation of a mesh-like structure with a size range of 80-180 nm and a 21.6 ± 6.22 mV zeta potential. The IC50 of NE was 22.29 μg/ml. Also, the NE showed antioxidant and antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The in-vitro investigation of the NE on normal human skin fibroblasts using scratch assay proved an acceleration for wound healing. The treated rats showed improved wound healing clinically and pathologically and wound contraction percent (WC %) was 98.13% at 14th day, also increased epithelization, fibrous tissue formation, collagen deposition, and angiogenesis compared to the control. It could be concluded that the prepared NE possesses antimicrobial, antioxidant, and healing effect in the treatment of second-degree burns.

Structural characterization and stability analysis of phosphorylated nitrosohemoglobin

Phosphorylation modification by sodium tripolyphosphate (STP) on nitrosohemoglobin (NO-Hb) and its effect on the protein structure and stability were studied. Phosphate groups were found to bridge to NO-Hb via C-O-P bonds through serine and tyrosine residues. Hydrothermal treatment with STP maintained the α-helix stability of NO-Hb, and this change in secondary structure improved the proteins stability. Compared to NO-Hb, phosphorylated NO-Hb (P-NO-Hb) was more stable with respect to light (outdoor light, indoor light, and dark conditions), oxidant (hydrogen peroxide), high temperature, and non-neutral pH. The absorbance of P-NO-Hb was nearly twice those of Hb and NO-Hb (P < 0.05), and the absorbance of P-NO-Hb decreased more slowly over time than those of Hb and NO-Hb. The results confirm that the presence of phosphate groups can increase the stability of Hb through structural changes.

From propolis to nanopropolis: An exemplary journey and a paradigm shift of a resinous substance produced by bees

Propolis, a natural resinous mixture produced by honey bees is poised with diverse biological activities. Owing to the presence of flavonoids, phenolic acids, terpenes, and sesquiterpenes, propolis has garnered versatile applications in pharmaceutical industry. The biopharmaceutical issues associated with propolis often beset its use as being too hydrophobic in nature; it is not absorbed in the body well. To combat the problem, various nanotechnological approaches for the development of novel drug delivery systems are generally applied to improve its bioavailability. This paradigm shift and transition of conventional propolis to nanopropolis are evident from the literature wherein a multitude of studies are available on nanopropolis with improved bioavailability profile. These approaches include preparation of gold nanoparticles, silver nanoparticles, magnetic nanoparticles, liposomes, liquid crystalline formulations, solid lipid nanoparticles, mesoporous silica nanoparticles, etc. Nanopropolis has further been explored to assess the potential benefits of propolis for the development of futuristic useful products such as sunscreens, creams, mouthwashes, toothpastes, and nutritional supplements with improved solubility, bioavailability, and penetration profiles. However, more high-quality clinical studies assessing the effects of propolis either alone or in combination with synthetic drugs as well as natural products are warranted and its safety needs to be firmly established.

Investigation on the interaction between Ag+ and bovine hemoglobin using spectroscopic methods

Silver ions (Ag⁺) can be released by silver nanoparticles (AgNPs) which are widely used in diverse fields. Ag⁺ can exist inside cells to produce cytotoxicity. This report uses spectroscopic methods to reveal the interactions between Ag⁺ and bovine hemoglobin (BHb). The results of the quenching rate constant (K_q) and the fluorescence lifetime detection showed that the quenching mechanism of BHb by Ag⁺ was static. Thermodynamic investigations indicated that Ag⁺ can interact with BHb with one binding site to form complex mainly through van der Waals interactions and hydrogen bonds. The UV-vis absorption and synchronous fluorescence spectra showed that Ag⁺ changed the conformation of BHb, which may affect protein functions. This research is favorable for understanding the molecular toxic mechanism of Ag⁺ in vivo.

Development of antimicrobial films based on poly(lactic acid) incorporated with Thymus vulgaris essential oil and ethanolic extract of Mediterranean propolis

Antimicrobial films based on polylactic acid (PLA) were developed by incorporating Thymus vulgaris essential oil (TV-EOs) with different concentrations of ethanolic extract of Mediterranean propolis (EEP) (5 wt% and 10 wt% based on PLA). The antimicrobial activities of EEP were performed by the agar disc diffusion method. The EEP exhibited high antimicrobial properties with inhibition zone diameter of 12.1 and 11.58 mm against Staphylococcus aureus and Penicillium sp., respectively. The addition of TV-EOs to films containing 5 and 10 wt% of EEP decrease the elastic modulus from 1292 MPa to 1084 MPa and 911.1 MPa to 794 MPa compared with films containing 5 and 10% of EEP alone, respectively. However, the elongation at break increased by 64% after the addition of TV-EOs to the film containing 10 wt% of EEP. Thermal stability of films improvement by the addition of TV-EOs and EEP. Antimicrobial activity of the films showed that films containing 10 wt% EEP inhibited the growth of Candida albicans and the combination of EEP and TV-EOs in the PLA matrix showed a synergistic effect against Escherichia coli. The developed PLA-based films with antimicrobial activity have a potential application in food packaging to increase the shelf life of packaged food.

Effectiveness of chitosan-propolis nanoparticle against Enterococcus faecalis biofilms in the root canal

Background

The successful outcome of endodontic treatment depends on controlling the intra-radicular microbial biofilm by effective instrumentation and disinfection using various irrigants and intracanal medicaments. Instrumentation alone cannot effectively debride the root canals specially due to the complex morphology of the root canal system. A number of antibiotics and surfactants are being widely used in the treatment of biofilms however, the current trend is towards identification of natural products in disinfection. The aim of the study was to determine the antibacterial effect of chitosan-propolis nanoparticle (CPN) as an intracanal medicament against Enterococcus faecalis biofilm in root canal.

Methods

240 extracted human teeth were sectioned to obtain 6 mm of the middle third of the root. The root canal was enlarged to an internal diameter of 0.9 mm. The specimens were inoculated with E. faecalis for 21 days. Following this, specimens were randomly divided into eight groups (n = 30) according to the intracanal medicament placed: group I: saline, group II: chitosan, group III: propolis100 µg/ml (P100), group IV: propolis 250 µg/ml (P250), group V: chitosan-propolis nanoparticle 100 µg/ml (CPN100), group VI: chitosan-propolis nanoparticle 250 µg/ml (CPN250), group VII: calcium hydroxide(CH) and group VIII: 2% chlorhexidine (CHX) gel. Dentine shavings were collected at 200 and 400 μm depths, and total numbers of CFUs were determined at the end of day one, three and seven. The non-parametric Kruskal Wallis and Mann–Whitney tests were used to compare the differences in reduction of CFUs between all groups and probability values of p < 0.05 were set as the reference for statistically significant results. The scanning electron microscope (SEM) and confocal laser scanning microscopy (CLSM) were also performed after exposure to CPNs. The effectiveness of CPNs were also evaluated against E. faecalis isolated obtained from patients having failed root canal treatment.

Results

The treatments of chitosan, P100, P250, CPN100, CPN250, CH and 2% CHX reduced the CFUs significantly compared to saline (p < .05). On day one and three, at 200 and 400-μm, CPN250 showed significant reduction of CFUs compared to all other groups (p < .05), while CPN100 was significantly better than other groups (p < .05) except CPN250 and 2% CHX. On day seven, at 200-μm CPN250 showed significant reduction of CFUs compared to all other groups (p < .05) except CPN100 and CHX, while at 400 μm CPN250 showed similar effectiveness as CPN100, CH and 2% CHX. SEM images showed root canal dentin treated with CPN250 had less coverage with E. faecalis bacteria similarly, CLSM images also showed higher percentage of dead E. faecalis bacteria with CPN250 than to CPN100.

Conclusion

CPN250 was the most effective in reducing E. faecalis colonies on day one, three at both depths and at day seven CPN250 was equally effective as CPN100 and 2% CHX.

Propolis nanoparticle enhances the potency of antimicrobial photodynamic therapy against Streptococcus mutans in a synergistic manner

Less invasive removal approaches have been recommended for deep caries lesions. Antimicrobial photodynamic therapy (aPDT) and propolis nanoparticle (PNP) are highlighted for the caries management plan. Evidence is lacking for an additive effect of combination PNP with photosensitizer (PS) in aPDT. This study aimed to investigate the individual and synergistic effects of chlorophyllin-phycocyanin mixture (PhotoActive⁺) and toluidine blue O (TBO) as PSs in combination with PNP in the aPDT process (aPDT^plus) against major important virulence factors of Streptococcus mutans. Following characterization, biocompatibility of the PSs alone, or in combination with PNP were investigated on human gingival fibroblast cell. The in vitro synergy of PhotoActive⁺ or TBO and PNP was evaluated by the checkerboard method. The bacteria's virulence properties were surveyed in the presence of the PSs, individually as well as in combination. When the PSs were examined in combination (synergistic effect, FIC Index < 0.5), a stronger growth inhibitory activity was exhibited than the individual PSs. The biofilm formation, as well as genes involved in biofilm formation, showed greater suppression when the PSs were employed in combination. Overall, the results of this study suggest that the combination of PhotoActive⁺ or TBO with PNP with the least cytotoxicity effects and the highest antimicrobial activites would improve aPDT outcomes, leading to synergistic effects and impairing the virulence of S. mutans.

Toxicity of thimerosal in biological systems: Conformational changes in human hemoglobin, decrease of oxygen binding capacity, increase of protein glycation and amyloid's formation

Thimerosal (TH), an organomercurial compound, is used as a preservative in vaccines and cosmetics. Its interaction with human hemoglobin (Hb) was investigated under physiological conditions using biophysical and biological assays, aiming to evaluate hazardous effects. TH interacts spontaneously with Hb (stoichiometry 2:1, ligand-protein), preferably by electrostatic forces, with a binding constant of 1.41 × 10⁶ M^-1. Spectroscopic data allows to proposing that TH induces structural changes in Hg, through ethylmercury transfer to human Hb-Cys93 residues, forming thiosalicylic acid, which, in turn, interacts with the positive side of the amino acid in the Hb-HgEt adduct chain. As a consequence, inhibition of Hb-O₂ binding capacity up to 72% (human Hb), and 50% (human erythrocytes), was verified. Dose-dependent induction of TH forming advanced glycation end products (AGE) and protein aggregates (amyloids) was additionally observed. Finally, these results highlight the toxic potential of the use of TH in biological systems, with a consequent risk to human health.

Propolis nanoparticles prevent structural changes in human hemoglobin during glycation and fructation

Nowadays diabetes, as a metabolic disorder, is increasing at an alarming rate. Glycation and production of advanced glycation end products (AGEs) is the most important factor involved in diabetic complications. Due to the side effects of synthetic drugs, the demand for natural anti-diabetic herbal medicines has increased. Propolis is a natural and resinous material, which iscollected by honeybees. Due to the impact of nanotechnology in medicine and the advantageous role of nanoparticles in treatment, nano-propolis particles (PNP) were prepared. The anti-glycation effect of PNP at various concentrations was investigated on human hemoglobin (Hb) glycation and fructation and compared with aspirin as a common anti-glycation agent using glycation specific AGE fluorescence, AGE-specific absorbance and circular dichroism (CD) methods. Fluorescence spectroscopy results showed that PNP inhibited the formation of AGEs in Hb glycation and fructation by glucose and fructose, respectively. CD results revealed that PNP caused an increase in Hb beta-sheet content while decreasing the alpha helical content. Additionally, the results of UV-Vis spectroscopy and fluorescence emission of heme degradation products revealed the protective effect of PNP on heme during glycation and fructation of human Hb. It is notable that the synergistic effects of combined propolis nanoparticles and aspirin is more than either of them alone. However, having said that, PNP as a natural product has a potential to be an effective drug in the treatment of diabetes.