Photocatalytic and Biological Activities of Spherical Shape Cellulose/Silver Nanocomposites Using Xenostegia tridentata (L.) Leaf Extract

A novel green synthesis of cellulose/Ag nanocomposites (Cell/XTLL Ag NCs) with in situ generated silver nanoparticles using Xenostegia tridentata (L.) leaf extracts (XTLL). Te synthesized nanocomposites have been appreciably characterized by SEM, TEM, FT-IR, XRD, UV-Vis spectrometer, AFM, DRS, XPS, TGA, and ICP-OES. Te Ag nanoparticles found for the Cell/XTLL 60 mM AgNO 3 have an average particle size of 33.78nm. Moreover, Cell/XTLL Ag NC flm, prepared with 60mM AgNO 3 , suggests greater antioxidant activity. Te most potent cell/XTLL 60mM AgNO 3 against Escherichia coli , Staphylococcus aureus , Trichoderma viride, and Fusarium oxysporum has strong antimicrobial activity and the best antimicrobial properties due to the fact that because the concentration of AgNO 3 solution increased, the zone of inhibition additionally accelerated. Te Cell/XTLL 60 mM becomes examined in vitro for its ability of human tumor cell growth inhibitory impact on human breast cancer cell line MCF-7 using MTT assay. Te catalytic activity of Cell/XTLL 60mM AgNO 3 was assessed by the photocatalytic degradation of methylene blue and compared with bare cellulose. Te Ag NPs are homogeneously unfolded out in Cell/XTLL 60mM AgNO 3 which leads to low electron-hole recombination and accelerated dye adsorption. In particular, 100mg of Cell/XTLL 60mM AgNO 3 , as catalyst, showed excellent photocatalytic activity with the efciency of 91% degradation of methylene blue (MB).


Introduction
Silvernanoparticles with electrochemical, chemical reduction, and biological techniques have been combined over the past few years [1,2]. Te biosynthesis of silver nanoparticles had advanced the use of microorganisms and chemical reduction method by using plant extracts [3,4]. In this method, plants, being easily available, provide rapid and simple silver nanoparticle synthesis, due to the presence of metabolites consisting of terpenoids, vitamins, alkaloids, amino acids, enzymes, proteins, etc., which act as both stabilizing and capping agents [5,6]. Te review of research studies revealed the generation of silver nanoparticles within the polymer network utilizing plant extract, notwithstanding biocompatible cellulose silver nanocomposites for antimicrobial, fabric, and therapeutic applications [7][8][9]. Te Xenostegia tridentata (L.) possesses good diuretic, antiallergic, bitter, astringent, calefacient, laxative, purgative, fever, snake bite, tonic, and spasmolytic characteristics [10,11]. Xenostegia tridentata (L.) leaf has been found to contain 3,5-cafeoylquinic acid, quercetin-3-o-rhamnoside, kaempferol-3-o-rhamnoside, luteolin-7-o-glucoside, β-sterol, and stigma sterol compounds that can be capping and reducing agents (XTLLs) which can easily reduce the silver nitrate solution to Ag ions in cellulose matrix [12][13][14]. In previous studies, the radical scavenging activities of silver nanoparticles and cellulose silver nanocomposites have been reported as a free radical scavenger in in vivo and in vitro systems [15][16][17]. Te literature suggests that silver nanoparticles and cellulose silver nanocomposites can treat cancer via alterations in cell morphology, cell viability, and lower metabolic activity [18][19][20]. In the past few decades, the fast development of the industry worldwide has critical environmental issues, especially water and soil contamination, which has harmed the biosphere [21]. Recently, Fan et al. prepared a self-assembled cellulose flm having uniform Ag and tungsten oxide nanoparticles in cellulose matrix with the nanoparticles obtained by the reduction of polydopamine (PDA), previously deposited on cellulose for better adhesion of oxide nanoparticles. Te fexible fber showed excellent photocatalytic degradation of RB-19 dye with 93% efciency under solar irradiation [22]. Te nonsolvent-induced phase separation and in situ deposition technique was used to fabricate cellulose-Ag@AgCl-cellulose acetate/silk fbroin flm, which showed excellent catalytic performance in the degradation of methyl orange dye. Ag nanoparticles enhanced the catalytic activity of the Ag@AgCl-CA/SF flm [23,24]. Junjie Wu et al. adopted an ecofriendly route to prepare porous cellulose/silver nanoparticle composite from NaOH/thiourea aqueous solution through sol-gel synthesis [25]. In this manuscript, we present an investigation on the in situ preparation of AgNPs in cellulose matrix to prepare cellulose silver nanocomposites Cell/XTLL/Ag NCs. Te prepared Cell/XTLL/Ag NCs were characterized by TEM, SEM, FT-IR, XRD, UV-Vis spectroscopy, AFM, DRS, and TGA. ICP-OES was used for the measurements of silver nanoparticle concentration in the cellulose matrix. Eventually, this study investigates the antimicrobial cell viability test against human breast cancer cell line MCF-7, photocatalysis, and free radical scavenging properties of the novel Cell/XTLL/Ag NCs.
Te XTLL extraction leaves have been dried in the laboratory for six days at room temperature and then crushed into small pieces. Te 20 g of XTLL (Figure 2(a)) was mixed with 300 ml of deionized water and heated to 82°C for 25 minutes, and then the solution was fltered and used ( Figure 2(b)).

Dissolution of Cellulose.
Te technique described through [8,26] was adopted; the aqueous solution was made up of mixing 8 wt% NaOH and 15 wt% of CO(NH) 2 , with subsequent cooling to − 13.0°C. Tis precooled solution was supplied with 5 wt% cotton linter pulp and was continuously stirred at high speed at room temperature. A clear solution of cellulose obtained under 3 min of stirring to the undissolved cellulose was removed by centrifugation at 7150 rpm and a temperature of 6°C for 15 min. Te clear cellulose solution obtained was stored at 6°C for additional use.

Preparation of Cellulose/XTLL Composite Films.
Te XTLL was dried in a warm air oven to remove the moisture; the dried leaf was added to cellulose solution and mixed thoroughly with the help of a mechanical stirrer. Te cellulose solution was degassed to remove any air bubbles. Glass plates have been used for casting cellulose and cellulose/XTLL solution. Te dried glass plates had been suspended in water and pH adjusted with  sulfuric acid; the regenerated composite flms were washed thoroughly and kept immersed in the water bath until further use.

Preparation of Cellulose/XTLL Ag NC Composite Films.
Te silver nitrate solutions at exclusive concentrations of 20, 40, and 60 mM were prepared; each of these solutions was kept taken separately and wet cellulose/XTLL composite flms were immersed in each beaker and the whole arrangement was mixed thoroughly for 25 h. Te color change of the wet flms from light color to dark brown indicated the in situ generation of silver nanoparticles on the cellulose flms. Te wet flms were washed and dried at room temperature and stored in desiccators for further use. To obtain FT-IR spectra, KBr and the nanocomposite have been pressure pressed to produce a disk, which was analyzed in the Avatar 330 FT-IR spectrophotometer. Te size of silver nanoparticles was found using an AFM (model: Innova), Bruker AXS Pvt., Ltd., USA. A Termo Fisher Scientifc spectrometer using nonmonochromatic Al K radiation 1486.5 eV run at 15 kV and 10 mA as an X-ray source was used to obtain the photoelectron spectra of the synthesized nanocomposites. Te thermal gravimetric analyzer (TGA, Q50) was used to measure the weight loss and thermal behavior of the cellulose nanocomposite. Te silver contents in the samples have been quantifed by the usage of an inductively coupled plasma optical emission spectrophotometer with a cross-fow nebulizer and a Ryton Scott chamber.

Preparation of Pathogens
. Te pathogens to be tested had been spread on plates and a well with a 6 mm diameter made in the agar. Te samples had been loaded in the concentration range from 45 to 55 μg/well compared with sterile antibiotics, which were loaded at the concentration of 22 μg/well. Te samples had been incubated for 25 h, following which the zone of inhibition was measured and was regarded as the antimicrobial activity.

Free Radical Scavenging
Activity. Te in vitro free radical scavenging activity of the nanocomposites with different silver concentrations was used: DPPH (2,2-diphenyl-1picrylhydrazyl) and ABTS (2,2-azino-bis(3-etylbenzothiazoline-6-sulfonic acid) assays. Te radical form of DPPH has an absorption band at 514 nm, which shall disappear upon reduction with the samples, demonstrating the antioxidant property. Te photometric assay was settled by distributing the samples in diferent volumes in multiple test tubes. Te total volume was adjusted to 10 μL using methanol; 5 mL of 0.1 methanolic solutions of DPPH was added and shaken vigorously. Te solutions were equilibrated at 27°C. A control was also prepared with the procedure outlined above, but for the samples. Ascorbic acid (C 6 H 8 O 6 ) was used as an internal standard. Te absorbance was measured at 516 nm and the percentage decolorization of the samples was calculated using the following formula, scavenging activity (%) � [(A517 of control -A517 of Cell/XTLL 20, 40, and 60 mM AgNO 3 )/A51 of control] × 100. ABTS + , 2, 2′-Azino-bis(3-ethylbenzothiazoline-6--sulfonic acid) scavenging activity: the assay was prepared by reacting a 7 mmol aqueous solution of ABTS + , with 2.4 mM potassium persulfate in the dark for 12-16 h at 27°C. Care was taken to the prepared free radical solution to be stable for more than two days when stored in the dark at room temperature. During the absorbance measurement, 2 mL of the diluted free radical solution is added to the nanocomposite samples. Water was chosen as blank. After an incubation time of 36 minutes at room temperature, the absorbance was recorded at 732 nm and compared with ascorbic acid, the internal standard. Te percentage of inhibition was calculated.
2.11. Anticancer Activity. Subculturing of cells: ahead of the experiment, the culture medium and TPVG (trypsin, PBS, Versene, and glucose solution) were brought to ordinary temperature. Te tissue culture fask was pragmatic for cell degradation, pH, and turbidity, and a suitable fask was selected for splitting. In vitro evaluations were carried out using MCF-7 cell lines purchased from the National Centre for Cell Science (NCCS), Pune, and were used in this study. Te subsequent procedure of progression is as follows: (1) the mouth of the fask was wiped with cotton soaked in spirit.
(2) Te medium was discarded and the cells had been washed twice, with MEM medium. (3)4 mL of TVPG (prewarmed to 37°C) was added over the cells. (4) TPVG was allowed to act for 45 s -1 minute. (5) TPVG was discarded and 5 mL of 10% MEM was added. (6) Te cell clusters were broken by gently pipetting (passaging the cells) back and forth. (7)20 mL of growth medium was added to the tissue culture fask and the cells were transferred into 96 well plates. Te calculation of the cell viability is carried out as % MCF-7 cell viability � absorbance at 540 of treated cells/ absorbance at 540 of control cells × 100%.

Statistical Analysis.
Te antibacterial, antifungal, DPPH, ABBTS, and cytotoxicity tests were performed in triplicate and repeated three times (mean ± SE). Statistical analysis was performed using the analysis of variance (ANOVA) method with Tukey's multiple comparison tests (Prism, version 5.0). Te diference observed between samples was considered to be signifcant at P < 0.05 [27]. In the present work, Ag nanoparticles were produced in situ using Xenostegiatridentata (L.) leaf extract by changing the silver nitrate concentration (Cell/XTLL/20, 40, and 60 mM AgNO 3 ) in a polymer matrix.

Results and Discussion
Tese Cell/XTLL and Cell/XTL samples were examined using scanning electron microscopy and were exposed to 20, 40, and 60 mM AgNO shows the combination of mostly spherical Ag nanoparticles, located on the surface of the cellulose matrix; Figure 3(a) suggests the absence of spherical Ag nanoparticles on the cellulose matrix. Te EDAX spectra were utilized to indicate that Ag metal was present in the Cell/XTLL20, 40, and 60 mM AgNO3 flms, as shown in Figure 3(e) [9,28]. Te TEM image of Cell/XTLL 60 mM AgNO 3 had been observed to be a spherical shape as shown in Figures 4(a) and 4(b). Te diameters of the silver nanoparticles were found to be around 33.78 nm, as presented in a histogram of particle size distribution (Figure 4(d)). Te bright circular spots in the selected area electron difraction (SAED) pattern (Figure 4(c)) show circular rings that can reveal the crystalline nature of the silver nanoparticles formed in cellulose matrix. Figure 4 reveals that the spherical Ag nanoparticles might be dispersed homogeneously on the surface of the cellulose matrix. In this case, the cellulose matrix (Cell/XTLL) serves as a capping, stabilizing, and reducing agent to the nanosized silver particles [29][30][31].
An FT-IR spectrum had been shown with the aid of using the presence of silver nanoparticles in the cellulose, XTL (leaf ), as shown in Figures 6(a)-6(f ). Cell/XTLLAgNO3 and Cell/XTL 20, 40, and 60 mMAgNO3 were the reactants used in the frst reaction. In the XTLL extract and difused cellulose, distinguished bands had been located at around 2258, 1719, 1625, 1557, and 1073 cm − 1 . Te observed bands account for C− O− C, C− O, and C=C organic functional groups. Tese bands can be attributed to 3,5-dicafeoylquinic acid, quercetin-3-o-rhamnoside, kaempferol-3-o-rhamnoside, luteolin-7-o-glucoside, β-sterol, and stigmasterol compounds which might be considerably found in Xenostegia tridentata (L.) leaf extract [12][13][14] and are responsible for the reduction of silver ion to silver nanoparticles in the cellulose matrix.
It can be seen that an additional band at 1730 cm − 1 was observed for the Cell/XTLL 60 mM AgNO 3 which was assigned to the C�O vibration as shown in Figure 6(c). It is evident that the carbonyl groups of XTLL were involved in the reduction of silver nitrate into silver nanoparticles in cellulose matrix. Te cellulose used in this study has a high amount of hydroxyl (OH) groups as well as substantial interand intramolecular hydrogen (H) bonding interactions, characteristic of Cell/XTLL Ag NCs. Tese functional groups could be involved in the Ag NPs by anchoring Ag ions to the cellulose matrix and stabilizing the silver nanoparticles due to the interaction between cellulose hydrogen (H) bonds and the silver nanoparticles [9,34,35].
Te XPS spectra evaluation is carried out further to confrm the chemical state of the cellulose silver nanoparticle composite. Te survey spectra in Figure 7(a) clearly show the presence of oxygen (O1s) and carbon (C1s) from cellulose in nanocomposites. As shown in the inset of Figure 7(a), the XPS spectra clearly reveal the elemental status of Ag3d, which are doublet peaks formed by spin orbital coupling, Ag3d3/2 (371.51 eV) and Ag3d5/2 (366.3 eV). A high resolution analysis of Ag3d was performed for further investigation and the core level spectrum is shown in Figure 7(b). Te spectrum deconvolutes into three components with binding energies of 368.3 eV (Ag 2 O), 367.4 eV (AgO), and 366.3 eV (Ag 0 ), which can be assigned to Ag 0 corroborating the formation of silver nanoparticles on the surface of the cellulose [36][37][38].
Primarily, thermal stability of Cell/XTLL and Cell/XTLL Ag NCs was performed by TG for Cell/XTLL; there are mainly two weight loss stages below 160°C and 290 to 360°C (Figure 8) in which the frst weight-loss stage corresponds to the evaporation of physically adsorbed water XTLL leaf extract which behaves as a reducing agent. Te organic functional groups reduce their afnity toward moisture absorption. As a result, a small quantity of water was absorbed by the surface of Cell/XTLL Ag NCs evaporated from the surface at a much lower temperature. In the second stage thermogram, the weight loss of about 87% is due to the decomposition of cellulose followed by carbonization. Te nanocomposite (Cell/XTLL 60 mM AgNO 3 ) shows an overall weight loss of 64%, while the Cell/XTLL showed 97% decomposition. Hence, the deposition of silver nanoparticles resulted in a more thermal resistant material.
Using the frst reaction mixture and the UV-Vis spectra of Cell/XTLL 20, 40, and 60 mM AgNO 3 , it was observed that Ag nanoparticles are shown in Figure 9. It was demonstrated by the formation of a characteristic surface plasmon resonance absorption band at 415 to 425 nm; at this peak, it was confrmed that Ag ions present in the silver nitrate solution were reduced to silver nanoparticles. As the silver content increased, the peak intensity increased suggesting that the concentration of the silver nanoparticles also increased. Te cellulose matrix is band-free, and the color shift from pale yellow to grey is all that is visible (Figure 10), indicative of redox reaction between the silver salt and carbonyl groups of XTLL. Tis grey color was persistent in the Cell/XTLL Ag NCs compound during four months of realization of the remaining experiments, suggesting that the cellulose used in this study provides good stability to the synthesized silver nanoparticles [39]. Both the solutions were withdrawn and further diluted to measure the Ag NP content using inductively coupled plasma optical emission spectroscopy and are listed in Table 1. It is observed that as the concentration of AgNO 3 solution increases, so does the formation of silver nanoparticles. Te UV-Vis refection spectra of cellulose/XTLL and Cell/XTLL 20, 40, and 60 mM AgNO 3 are shown in        absorption coefcient versus band gap energy Cell/XTLL 60 mM AgNO 3 . Te band potentials of silver nanoparticles Ag (0) in the cellulose matrix were calculated theoretically and showed 3.40 eV at Cell/XTLL 60 mM AgNO 3 ( Figure 11) [40]. Te top morphology of the Cell/XTLL 60 mM AgNO 3 flm was also characterized by atomic force microscopy. Figure 12 shows a 3D AFM image of the Cell/XTLL 60 mM AgNO 3 surface. Te presence of silver nanoparticles on the cellulose surface can be observed as additional supporting evidence related to the surface roughness of Cell/XTLL 60 mM AgNO 3 at 33.78 nm which was evaluated ( Figure 12). Tis result may indicate good adhesion and dispersion of Ag nanoparticles on the cellulose surface [41].
Te antibacterial efects of cellulose, Cell/XTLL, Cell/ AgNO 3 , and Cell/XTLL 20, 40 mM AgNO 3 , and Cell/XTLL-60 mM AgNO 3 against bacterial and fungal strains by disc difusion tests are shown in Figures 13-16. It has been verifed. It was observed that as the concentration of the silver nitrate solution increased, Ag NPs in the cellulose matrix increased and the inhibition zone also increased. Escherichia coli, Staphylococcus aureus, Trichoderma viride, and Fusarium oxysporum showed higher activity than the other microorganisms tested. Terefore, from the current approach, the developed Cell/XTLL 60 mM AgNO 3 can be regarded as an excellent antibacterial agent efective in killing microorganisms. It can also be concluded that the developed Cell/XTLL 60 mM AgNO 3 nanocomposites have a larger inhibition zone compared to other prepared nanocomposites. Cellulose-silver nanocomposites penetrate more efectively into bacterial and fungal cells, damaging cell nuclei and killing fungi faster. Te primed Cell/XTLL Ag NCs can penetrate the bacterial cell wall and induce cell death. Cell/XTLL Ag NCs can increase the permeability of cell membranes. Te production of reactive oxygen species releases Ag ions and interferes with the replication of deoxyribonucleic acid [42][43][44].
Te cancer activity of Cell/XTLL 20, 40, and 60 mM AgNO 3 on MCF-7 cells was determined by the MTT assay [46], when MCF-7 cells (1 × 105/well) were plated in 0.2 ml        (Table 4). In this process, silver nanoparticles in the Cell/XTLL Ag NCs bind and penetrate the negatively charged cancer cell to disturb metabolic and membrane activity leading to cell death. Te Cell/XTLL Ag NCs also release positively charged (Ag + ) cation which leads to the destruction of the cell wall. Te prepared Cell/XTLL Ag NCs are endocytosed into MCF-7 cells; this can release their cargo to exert a therapeutic efect. However, the strength of this interaction depends not only on the rate of endocytosis but also on the residence time and accumulation of the silver nanoparticles inside cells [47].
Photocatalytic activity of cellulose-silver nanocomposites: the absorption intensity of MB at 525 nm decreased with increasing irradiation time, indicating that the concentration of MB dye also decreased with increasing irradiation time as shown in Figures 20(a) and 20(b). When exposed to light, photon absorption occurs, and (eh + ) charge loss occurs due to the excitation of electrons (e -) from the valence band of silver nanoparticles and the abandonment of the conduction band opening to do a band of silver nanoparticles [48][49][50][51]. Photocatalytic tests have shown that UV light and catalytic activity are required to efectively destroy MB. Te pure Cell/XTLL and Cell/XTLL 60 mM AgNO 3 nanocomposites were used under equivalent conditions with only 49% and 91% degradation, respectively. Tis shows that the Cell/XTLL 60 mM AgNO 3 nanocomposite process can handle MB degradation better than other prepared nanocomposites. Degradation was more successful with Cell/XTLL 60 mM AgNO 3 nanocomposites, but we investigated the efects of valid parameters in this process and found optimal conditions. In catalytic decomposition, the pseudofrst-order rate constants (plot ln (C/C 0 ) vs. time t) show a linear relationship, as shown in Figure 20(c), where C is the concentration of MB dye. When integrated within the range of C/C 0 at t = 0, C 0 is the equilibrium concentration of the bulk solution of the MB dye, and the formula (ln (C/C 0 ) = k t ) is obtained, where C 0 is the equilibrium concentration of the dye. Solution, C = concentrations and t = time; therefore, the equation has the following form ln (C 0 /C) = K App t, where K App (min − 1 ) is the frst-order pseudodynamics of the velocity constant shown Figure 18 14 Journal of Chemistry be k = 0.9723 and k = 0.94242, respectively. Te proposed mechanism of photocatalytic activity of the cell/XTLL 60 mM AgNO 3 heterojunction nanocomposites is outlined in Figure 21 as charge transfer and energy position. Cellulose is common, has a large surface area, and has a loose porous structure, so it can absorb large amounts of contaminants in a dark environment and balance absorption and desorption. Tis is because the photo-generated electrons on the Ag conduction band can be transferred to the conductive network system on the Cell/XTLL composite due to the conductivity that prevents the photo-generated electrons and holes from binding. As a result, the addition of AgNO 3 to the fabric signifcantly improved the photocatalytic properties. In addition, the introduction of AgNO 3 nanoparticles separates electrons and holes by absorbing visible light through the SPR efect. In addition, electrons or holes transferred to the nanostructure Cell/XTLL 60 mM AgNO 3 active surface are directly involved in the redox reaction. In this reaction, the electrons reduce the dissolved oxygen to mimic the superoxide anion (O 2 -), and the H 2 Othe molecule is oxidized to provide hydroxyl radical (OH). Organic dye contaminants (MBs) are eventually oxidized to CO 2 and H 2 O products by these highly elastic species. Apart from hydroxyl radicals, holes have been identifed as the most important active species in the Cell/XTLL 60 mM AgNO 3 system [52,53]. Te grafted silver nanoparticles can act as preferred hole channels and receptors for efcient separation of photo-excited electrons and holes, thereby enhancing the photocatalytic properties of Cell XTLL 60 mM AgNO 3 shown as follows: Cell(h + VB) + MB ⟶ degraded products.

Conclusion
In summary, Xenostegia tridentata (L.) leaf extract is used as a reducing agent and silver nitrate is used as a silver precursor, environmentally friendly green synthesis, to produce silver nanoparticles (in situ) in a cellulose matrix. Te SEM and TEM results show that the spherical shape silver nanoparticles are evenly dispersed in the Cell/XTLL matrix. Te XPS spectra observed that the Ag 3 d 5/2 peak was composed at 368.82 eV, which can be assigned to Ag 0 . Among these are the XRD patterns of face-centered cubic silver in cellulose matrix (3 1 1), (2 2 0), (2 0), and (1 1 1). Te FT-IR spectra were concluded that C-O-C, C-O, and C = C functional groups reducing silver ion to Ag nanoparticles. Te most potent have been synthesized Cell/XTLL 60 mM AgNO3 against Escherichia coli, Staphylococcus aureus, Trichoderma viride, and Fusarium oxysporum have strong antimicrobial activity, DPPH, ABTS+ scavengers, and MTT assay for its highly inhibitory efect on human tumor cell proliferation in MCF-7 cervical cancer cell lines. In this cellulose-silver nanocomposite heterojunction nanostructure, Ag may (i) enhance the composite's response to visible light and (ii) enhance fast electron transfer and inhibit charge recombination. Consequently, the synthesis of highly photocatalytic 1D cellulose silver nanocomposites opens up a wider range of applications which can be efectively used as a photocatalyst to decompose organic pollutants in aqueous bodies, thereby helping to restore the environment.

Data Availability
Te data used to support the study are available from the corresponding author upon request.

Conflicts of Interest
Te authors declare that there are no conficts of interest.