Document Type : Research Paper
Authors
1 Department of Chemistry, College of Sciences for Women, Babylon University, Hilla, Iraq
2 Department of Chemistry, College of Education, University of Al-Qadisiyah, Al-Qadisiyah, Iraq
Abstract
Keywords
INTRODUCTION
Adsorption is one of the most successful technologies for purification and separation processes, and it is employed on such a huge scale in our manufacturing economy and in our daily lives that adsorption procedures are found in almost every industry today [1, 2]. According to literature studies, adsorption on porous surfaces represents an effective method for the removal of organic and inorganic contaminants from air and distilled water [3-12]. Polymeric nanoparticles have gotten a lot of attention as nano carriers because of their capacity to protect the bioactive ingredient while also allowing it to be released in a regulated manner [13, 14]. Researchers have been paying close attention to polymeric nanoparticles because of their stability and ease of surface modification, and Nano composite materials combine the features of inorganic and biopolymer materials [15-19]. In the fields of biology and medicine, cytostatic potential of nanoparticles of zinc oxide (ZnO-NPs) towards cancerous cells, their potential against microbes as well as fungi, their capacity to expedite curing wound, their application in bio-imaging owing to chemiluminescent characteristics of nanoparticles along with their potential against diabetes widely studied [9-13]. Sodium Alginate has sparked a lot of interest in the pharmaceutical industry because of its promising qualities like biodegradability, biocompatibility, and antibacterial characteristics Tumors and viruses , Because of these intriguing qualities, sodium alginate along with its byproducts find uses for different pharmaceutical purposes [18, 20-23].
Objective of this study is to investigate and analyze the characteristics of SA-g-P(AAc-co-Am) hydrogel post-loading by zinc oxide nanoparticles, including morphological, structural, and functional properties. Additionally, the study aims to evaluate the biological activity of the prepared composite against various bacterial and fungal pathogens, examining the potential inhibitory effects on their growth.
MATERIALS AND METHODS
Chemicals and materials
The materials utilized in the study were obtained from a variety of suppliers. Acryl amide was secured from Himedia, located in India. Potassium persulfate (KPS, employed as initiator), was procured from Merck (Germany). The N, N’- methylene bisacrylamide (NMBA), a multifunctional crosslinker, procured from Fluka (Germany). Alpha Chemika supplied sodium chloride while ZnO purchased from Sigma-Aldrich, Germany.
Preparation of SA-g-P(AAc-co-Am)
SA-g-P(AAc-co-Am) was prepared utilizing a series of solutions. Initially, a 1% v/v solution of AAC was prepared. Concurrently, 1.0 g of sodium alginate was dissolved in 60 mL of AAc, stirred for 50 min (45ºC). KPS solution was then created by dissolving 0.4 g of it in 4 mL of distilled water, while an Acrylamide (AM) solution was formed by dissolving 4 g of AM in 4 mL of distilled water. Additionally, a linking solution was prepared from MBA by dissolving its 0.1g in 4 mL water. Subsequently, KPS solution added to sodium alginate solution (in drop-way manner) while stirring, followed by addition of AM solution, while stirr for 5 min. The MBA (N,N-Methylene-Bisacrylamide) was then added while stirring and infusing nitrogen gas for 3 min. This prepared solution was then transferred to water bath (50°C) for 3 h. With distilled water, resulting polymer then purified followed by drying at 60°C [14]. The equations for hydrogel synthesis are visually represented in Fig. 1.
Loading of zinc nanoparticles
The equilibrium time for nano zinc oxide loading was determined, keeping all parameters including temperature, pressure, solution concentration, and surface weight constant, thereby making time the sole variable. Ten samples of 10ml zinc oxide solution, each with a concentration of 100ppm, were prepared. These samples were individually placed in a 25ml conical flask, to each of which 0.05g of the adsorbent surface was added. Following this, they were placed in a shaker and samples were extracted at various time intervals (1-240 minutes). These samples were then centrifuged at a speed of 6000 rpm for 15 minutes. Each sample’s absorbance was quantified at a peak wavelength of λmax=370nm. From these absorbance values, an equilibrium time of 120 minutes was inferred.
Antimicrobial Activity
Three different solutions of nano Zinc Oxide (ZnO-NPs) were prepared at different concentrations (1-15 mg/mL) and adsorbed onto the surface of CH-g-P(AA–co–Am) using both distilled water and DMSO solvent. Biological activity was evaluated for each solution over a range of 5-15 hours to determine optimal adsorption timing against two pathogenic bacteria strains: Staphyococus.auerus (a Gram-positive Bacteria) and Escherichia coli (a Gram-negative Bacteria). Additionally, a strain of the fungus Aspergillus Niger was studied to determine the inhibitory impact of this composite on the growth of these organisms.
RESULTS AND DISCUSSION
Characterization
FTIR
The FTIR analysis of SA-g-P(AAc-co-Am) depicted in Fig. 2 illustrates the interaction of the hydroxyl group (3320 cm-1) having group of amine (3423 cm-1), resulting from existing H-bond between them. Band at (2928 cm-1) corroborates presence of R-groups, peak at (1618 cm-1) highlight -C=O of amide group. However, peak at (1643 cm-1) signifies -C=O of -COOH group. Peak (1314 cm-1) corresponds to carbon-nitrogen bond. Owing to the hydrogen binding to active groups on hydrogel surface, these groups’ absorption packs are displaced and reduced post adsorption of zinc oxide[24, 25]. The radiation spectrum indicated that ZnO adsorption onto surface resulted in the displacement and diminution of ionic groups’ adsorption peaks on the hydrogel surface. Peaks within the range of 520-750 cm-1 represent the vibrational stretching of ZnO nanoparticles, as metal oxides typically manifest in regions below 1000 cm-1. This signifies that ZnO nanoparticles are present and are intermingled with the hydrogel [26-36].
FE-SEM
FE-SEM of SA-g-P(AAc-co-Am) revealed spongy structures, indicating good adsorption sites and a shell-like composite membrane structure. This porous interconnection is attributed to attachment of polymer chains via some cross-linker, thereby enhancing swelling of hydrogel. Post-adsorption, surface findings depict increased smoothness of the prepared surface (Fig. 3). This is a consequence of the surface pores being filled with zinc oxide particles, resulting in a crusty layer that could be single or multi-layered. The presence of zinc oxide particles on the surface confirms the occurrence of the process[37, 38].
TEM
TEM was applied to the Hydrogel SA-g-P(AA-co-Am) before and after loading it with zinc oxide. Fig. 4 illustrates different magnifications of the surface. These images distinctly suggest the presence of uniformly distributed, small granules organized in a regular clumping pattern, attributed to the sodium alginate matrix. Fig. 4 reveals the Hydrogel SA-g-P(AA-co-Am) covered by heterogeneous, spherically shaped nanoparticles that are uniformly distributed zinc oxide (ZnO-NPs) particles [39].
The structural properties of the composition, crystal size, and interplanar distances of the hydrogel were investigated via X-ray diffraction (XRD). Broad band depicted in Fig. 5 suggests that the hydrogel possesses an amorphous structure[40-42].
Debye-Scherer expression used for calculating size of crystal for prepared hydrogel:
Since d represents the spacing amongst the plane of crystallinity, n referring to an integer (1,2,3, ……), Table 1 shows diffraction angel, values of d-spacing, as well as relative intensity of the beams and Hydrogel[43].
After loading zinc oxide, the results showed a clear adsorption ZnO on the surface of the Hydrogel, as shown in the Fig. 6 through the visible beams at 2θ equal to (25.2, 35.3, 38.3, 55.4, 65.3), which belong to the zinc oxide[44].
Biological Activity
The inhibitory diameter (in mm) was measured for both bacterial and fungal types, where the symbol (R) indicates resistance of bacteria and fungi to inhibition. Findings revealed that inhibition of fungus Aspergillus Niger increased with both an increase in concentration of Zinc Oxide solution and time (Fig. 7). As for the bacteria S.aureus and E.coli, both types of bacteria showed resistance to inhibition at a concentration of 1mg/mL of Zinc Oxide solution (Fig. 8). Upon increasing the concentration to 5mg/mL, inhibition of bacteria and fungi was observed because increasing the concentration leads to enhanced activity due to partial solubility in distilled water. However, upon increasing the concentration to 15mg/mL, the bacteria showed minimal inhibition compared to the fungi, which showed good inhibition. This could be attributed to the differences in the biological nature of each organism. When DMSO solvent was used at concentrations of 1-5mg/mL, these concentrations showed inhibitory effect on bacteria and fungi due to the high solubility of ZnO in DMSO, which damages the outer envelope of the bacteria and thereby inhibits them[45-47].
CONCLUSION
Based on the FTIR analysis, it can be concluded that various functional groups, including hydroxyl, amine, and carbonyl groups, are present in the hydrogel and exhibit changes upon zinc oxide absorption, indicating active interactions between the hydrogel and zinc oxide nanoparticles. SEM and TEM analyses reveal a porous structure of the hydrogel, which provides ample sites for zinc oxide adsorption, and confirm the successful loading of zinc oxide particles on the hydrogel surface. XRD data indicate an amorphous structure of hydrogel, with additional peaks after ZnO loading pointing to the successful incorporation of ZnO on hydrogel surface. The biological activity analysis suggests that the zinc oxide-loaded hydrogel exhibits considerable antimicrobial activity, with a stronger inhibitory effect on fungi than bacteria. This effect appears to be concentration and time-dependent. Overall, the zinc oxide-loaded SA-g-P(AAc-co-Am) hydrogel presents promising potential for biomedical and biological applications due to its excellent absorption properties and antimicrobial activity.
CONFLICT OF INTEREST
The authors declare that there is no conflict of interests regarding the publication of this manuscript.
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