Peroxidase-like activity of hemoglobin-based hybrid materials against different substrates and their enhanced application for H2O2 detection

ABSTRACT. Organic-inorganic hybrid nanoflowers method with unique properties are preferred than conventional immobilization methods for the past decade. Hereemoglobin-based hybrid material (HbNFs@Cu) was synthesized under different experimental conditions (pH 5.0-9.0 and 0.01-0.50 mgmL-1 of hemoglobin) obtaining a material size of 9-10 µm. The encapsulation percentage and weight yield of HbNFs@Cu were determined as 100% and 6.7%, respectively. The peroxidase-like activities of the material against different substrates (ABTS and Guaiacol) were compared to free hemoglobin. The HbNFs@Cu hybrid structure exhibited Vmax of 3.6995 EU/mg and a Michaelis-Menten constant (KM) of 0.1357 mM/mL. The HbNFs@Cu hybrid material was then used to catalyze the oxidation of a peroxidase substrate ABTS to the pigmented product, which provided a colorimetric and spectrophotometric detection of H2O2. The linear operating range, detectable colorimetrically as H2O2 sensor, is 0.005-0.0042 mM, while the linear operating range, detectable spectrometically, is 0.003-0.0042 mM. The limits of detection of colorimetric and spectrophotometric sensors were 0.005 mM and 0.003 mM, respectively. Collectively, these results showed that HbNFs@Cu can be used as colorimetric biosensor for H2O2 in potential applications such as pharmaceutical food, biomedical, environmental, and industrial.                     KEY WORDS: Hydrogen peroxide, Hemoglobin, Hybrid Material, Colorimetric assay   Bull. Chem. Soc. Ethiop. 2021, 35(3), 537-550.  DOI: https://dx.doi.org/10.4314/bcse.v35i3.

Health worker densities and immunization coverage in Turkey: a panel data analysis

<p>Abstract</p> <p>Background</p> <p>Increased immunization coverage is an important step towards fulfilling the Millennium Development Goal of reducing childhood mortality. Recent cross-sectional and cross-national research has indicated that physician, nurse and midwife densities may positively influence immunization coverage. However, little is known about relationships between densities of human resources for health (HRH) and vaccination coverage within developing countries and over time. The present study examines HRH densities and coverage of the Expanded Programme on Immunization (EPI) in Turkey during the period 2000 to 2006.</p> <p>Methods</p> <p>The study is based on provincial-level data on HRH densities, vaccination coverage and provincial socioeconomic and demographic characteristics published by the Turkish government. Panel data regression methodologies (random and fixed effects models) are used to analyse the data.</p> <p>Results</p> <p>Three main findings emerge: (1) combined physician, nurse/midwife and health officer density is significantly associated with vaccination rates – independent of provincial female illiteracy, GDP per capita and land area – although the association was initially positive and turned negative over time; (2) HRH-vaccination rate relationships differ by cadre of health worker, with physician and health officers exhibiting significant relationships that mirror those for aggregate density, while nurse/midwife densities are not consistently significant; (3) HRH densities bear stronger relationships with vaccination coverage among more rural provinces, compared to those with higher population densities.</p> <p>Conclusion</p> <p>We find evidence of relationships between HRH densities and vaccination rates even at Turkey's relatively elevated levels of each. At the same time, variations in results between different empirical models suggest that this relationship is complex, affected by other factors that occurred during the study period, and warrants further investigation to verify our findings. We hypothesize that the introduction of certain health-sector policies governing terms of HRH employment affected incentives to provide vaccinations and therefore relationships between HRH densities and vaccination rates. National-level changes experienced during the study period – such as a severe financial crisis – may also have affected and/or been associated with the HRH-vaccination rate link. While our findings therefore suggest that the size of a health workforce may be associated with service provision at a relatively elevated level of development, they also indicate that focusing on per capita levels of HRH may be of limited value in understanding performance in service provision. In both Turkey and elsewhere, further investigation is needed to corroborate our results as well as gain deeper understanding into relationships between health worker densities and service provision.</p

Amino acid-metal phosphate hybrid nanoflowers (AaHNFs): their preparation, characterization and anti-oxidant capacities

Reactive oxygen species like hydrogen peroxide have positive roles in vivo systems such as phagocytosis, intercellular signal transfer, regulation of cell growth, and the synthesis of important biological compounds. Nanostructures can exhibit increased redox and radical scavenging activities compared to the free form with peroxidase-like activities. This work presents the synthesis and characterization of amino acid-metal phosphate hybrid nanoflowers (AaHNFs) and their potential as a radical scavenger and anti-oxidant. The AaHNFs were synthesized using some metal ions (Cu2+, Mn2+, Ni2+, Co2+, and Zn2+) and selected amino acids (His, Cys, Asn, and Asp) which contain an imidazole ring, sulfhydryl, carboxamide, and carboxylate groups. Synthesized AaHNFs were characterized by their morphology and chemical point of view by using different techniques such as SEM, EDX, FTIR and XRD. Their peroxidase like activities were determined. Using the principle of Fenton's reaction, AaHNFs were found to be exhibitinga more effective peroxidase-like activity than free amino acids. We applied different analytical measurement methods such as hydrogen peroxide scavenging activity assay of AaHNFs and the assays of DPPH and ABTS radical scavenging activities to determine the anti-oxidant capacities of AaHNFs. AaHNFs can be evaluated as an effective anti-oxidant scavenger material due to their superior properties. This new type of HNFs can be exploited as a natural anti-oxidant in various potential applications related to fields such as biosensing, bioassay, biomedicine, pharmaceutics and biocatalysis

Anti-microbial, anti-oxidant and wound healing capabilities of Aloe vera-incorporated hybrid nanoflowers

© 2023 The Society for Biotechnology, JapanThe active ingredients of Aloe vera have attracted attention for their potential use in nanotechnology-based medical applications and biomaterial production. It has many therapeutic applications in modern world. This study used Aloe vera extract in different concentrations to synthesize Aloe vera-incorporated hybrid nanoflowers (AV-Nfs). The most uniform morphology in the nanoflowers obtained was at a concentration of 2 mL. The AV-Nfs were well characterized by scanning electron microscopy, X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction (XRD). The highest peroxidase-mimicking activity of the components was 1.488 EU/mg at 60°C and pH 6. The DPPH assay determined the antioxidant activity of the components and the MTT assay tested on CCD-1072Sk fibroblast cell line determined the effect of AV-Nfs on cell proliferation. Separate treatment of AV-Nfs with Cu3(PO4)2·3H2O significantly increased cell proliferation according to free Aloe vera and CuSO4. In vitro wound healing results showed that AV-Nfs could significantly close wounds compared to free Aloe vera. In this study, AV-Nfs showed antimicrobial activity against Staphylococcus epidermidis, Enterococcus faecalis, Escherichia coli and Klebsiella pneumoniae at minimum inhibitory concentration of 625 μg/mL, suggesting that AV-Nfs may be used in wound healing applications with enhanced biological properties. AV-Nfs showed no activity against the yeast Candida albicans