Hydroxyethyl cellulose: Uses, Interactions, Mechanism of Action

Figure 1 reveals the spectral analysis of HEC, M, HECM1, HECM2, and HECM3. The results showed that the characteristic functional bands assigned to HEC are OH-stretching&#;&#;&#;&#;cm&#;&#;1, anti-symmetric and symmetric CH2-stretching&#;&#;&#; and &#;cm&#;&#;1, anti-symmetric and symmetric stretching vibrations of COO&#; &#; and &#;cm&#;&#;1, C=C&#;&#;&#;&#;cm&#;&#;1, C&#;O=C&#;&#;&#;&#;cm&#;&#;1, C&#;O&#;C&#;&#;&#;&#;cm&#;&#;1, C&#;O&#;&#;&#;&#;cm&#;&#;1 [16,17,18]. On the other hand, FTIR of M showed that OH-stretching&#;&#;&#;&#;cm&#;&#;1, CH2-stretching&#;&#;&#;&#;cm&#;&#;1, C=O in aldehyde and ketone&#;&#;&#;, &#;cm&#;&#;1, and C=C&#;&#;&#;&#;cm&#;&#;1 [19]. Furthermore, the grafting of HEC was marked by increased intensity of the characteristic peaks of oxygen functionalities (νO&#;H, and νC=O). Since the band at &#;cm&#;&#;1 is attributed to C&#;H stretching, this band can be used as an internal standard to determine the relative absorbance (RA) [20]. The RAs of the O&#;H were 0.82, 0.93, 0.93, and 0.94, while the RAs of the C=O were 0.67, 0.85, 0.93, and 0.97 for HEC, HECM1, HECM2, and HECM3, respectively. It is clear that the RAs of the O&#;H and C=O groups enormously increased by increasing the concentration of M compared to that of HEC.

The increase in crystallinity )LOI) and H-bonding (MHBS) of HECM3, as shown in Table 1, might be due to the decomposition of the amorphous parts of HEC during modification [20].

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FTIR spectra of HEC, M, HECM1, HECM2, and HECM3, respectively

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X-ray diffraction patterns of HEC, M, HECM1, HECM2, and HECM3 are presented in Fig. 2. Table 2 shows that the crystallinity indexes calculated for HEC, M, HECM1, HECM2, and HECM3 were 17.44, 18.49, 5.84, 17.25, and 25.92%, respectively. Cr.l (%) and d (nm) of the blended films (i.e., HECM1, HECM2, and HECM3) increased gradually due to the M concentration increase, which affects HEC film. The XRD crystallinity values agree with the MHBS values calculated from the IR spectra in the case of HECM1, HECM2, and HECM3.

XRD analysis of a HEC, b M, c HECM1, d HECM2, and e HECM3, respectively

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The matrix&#;s structure, morphology, and homogeneity can affect the permeability of films. SEM was used to characterize the morphology of the composite films. SEM in Fig. 3 shows that HEC1, HEC2, and HEC3 appear more smooth and wavy than HEC blank. In addition, HEC3 is wavier than other modified films. The film&#;s porosity was calculated from the SEM figures and introduced in Table 3; the porosity was increased at higher M addition.

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SEM images of a HEC, c HECM1, d HECM2 and e HECM3, respectively

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Since tensile properties are essential for many applications, HEC matrix is blended with different M ratios. The tensile tests of HEC films with various loadings of M were investigated. Table 4 represents tensile strength (TS) at maximum load, elongation at break (EB%), and Young&#;s modulus (YM) of HEC, HECM1, HECM2, and HECM3, respectively.

According to the obtained results, the tensile properties of pristine HEC film have been remarkably affected by blending with varied M concentrations. Mechanical properties of pure HEC film, TS of 2.10&#;MPa, EB% of 147.69%, and YM of 2.98&#;MPa, are significantly changed after blending with 2.5, 5.0, and 10% of M. Upon loading of 10% M (i.e., HECM3); HEC film mechanical properties have primarily deteriorated. Percolation of a high concentration of M has destroyed the HEC polymer. YM is also affected by increasing the M content and reaches its maximum value of 7.39&#;MPa at HECM3 loading. YM enhancements can indicate homogeneous M dispersion through HEC matrix with HECM1, HECM2, and HECM3. These higher values observed for HECM1, HECM2, and HECM3 films in comparison with pristine HEC suggest the attenuation of the existing H-bonds between HEC by percolation of M and the establishment of new bonds between HEC and M in the film [21]. However, there was no conformity between the data of TS and MHBS. This was probably due to the type (intra- and inter-molecular), and degree of H-bonding.

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From Table 4, an enhancement of YM values after M loading can be observed. YM increases with increasing M content from 2.5 to 10%. The remarkable increase in YM of the prepared films may be attributed to the formation of a more bonded network generated by adding M within the HEC matrix. This network results from strong electrostatic interactions and the H-bonding between M and HEC polymers. On the other hand, the EB% of films decreased considerably when loaded with M. The EB% of HECM1 does not change much from pristine HEC film. One possible reason can be attributed to the restricted motion of the HECM1 matrix by incorporating M in terms of the strong interactions between the fillers and the biopolymer matrix [21].

The most important medical discovery of the 20th century was the discovery of potent, relatively harmless antibacterial drugs. Antimicrobial agents&#; modes of action against human, animal, and plant pathogens fall into one of four groups based on their action location. Inhibition of cell wall formation, protein synthesis, nucleic acid synthesis, and cell membrane integrity was among them [22]. Figure 4 shows that mango peel powder and its prepared samples have excellent antimicrobial activity against gram-positive bacteria (Micrococcus leutus, which shows a specific anti-gram-positive bactericidal spectrum). The prepared samples do not have any antibacterial and antifungal activity against two pathogenic gram-negative bacteria (Escherichia coli & Pseudomonas aeruginosa) and pathogenic fungal yeast (Candida albicans) respectively. In addition, they have modest antibacterial activity against gram-positive bacteria (Staphylococcus aureus).

The mode of action of mango peel powder and its prepared samples causes inhibition of bacterial cell walls, which is a mucopolysaccharide component called peptidoglycan (murein). So many actions take place toward gram-positive such as inhibition cell wall biosynthesis, inhibition biosynthesis of proteins, disrupt membranes, inhibition nucleic acid synthesis, mycobacterial adenosine triphosphate (ATP) synthase inhibitor, interact directly with PBPs and inhibit trans peptidase activity. These large molecules bind to the peptide chain of peptidoglycan subunits, blocking transglycosylation and transpeptidation and blocking the transport of peptidoglycan subunits across the cytoplasmic membrane. All these actions lead to the bactericidal effect of the sample (mango peel powder and its prepared films) against gram-positive bacteria (Micrococcus leutus). The effect of these samples (mango peel powder and its prepared films) on the cell wall of gram-positive is due to the presence of M powder, which enters inside the bacterial cell and ceases many cascades of action through inhibition of nucleic acid synthesis, which led to protein synthesis inhibition and followed the inhibition of all other bacterial metabolism activities. Also, they have this antimicrobial activity against pathogenic gram-positive bacteria Staphylococcus aureus, which is the skin-infected strain that causes many skin infections such as abscesses, wound infections, burning infections, and other skin infections, so the mango peel powder and its prepared samples, give a wide range of many application, such wound coatings, pharmaceutical and food packing.

Antimicrobial activity of the prepared samples.

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Finally, the prepared samples have excellent antimicrobial activity toward gram-positive bacteria (Micrococcus leutus), which was improved by adding mango peel powder. Furthermore, antimicrobial activity was enhanced from 0.0 to 18.0&#;mm inhibition zone range, finally showing a promising specific anti-gram positive bacterial agent. Mangiferin is rich with a phenolic compound resemple to curcumin, and improved the antimicrobial properties of HEC films on the same way of cellulose, chitosan and collagen improvement by curcumin to fit wound healing applications [23]. Acutallly, chitosan shows some more prounnced results owing to its natural positively charge. It was proven that wound dressings based on natural polymer such as functionalized cellulose have an appropriate properties such as anti-adhesion, antimicrobial and skin reconstruction properties that can accelerate wound healing and inhibt eliminate microbial infections [24].

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