Polysaccharide-Modified MMT/ Modified MMT/ Polysaccharide – MNP, Lignin-Modified MMT Nanocomposites Verses Polyethyleneimineimine- Modified MMT-: A Comparative Analysis of Sustained Pesticide Delivery

The substance properties can change drastically at the nanoscale. Materials can demonstrate new properties with just a reduction in size and no alteration in the substance itself. In this paper, modified montmorillonite (M MMT) and a variety of different hybrid naturalbased nanocomposites were systematically investigated by combining a suspension of (M MMT) as a nanofiller with polymers comprising either chitosan (CS), starch (S), β-cyclodextrin (β-CD), polyethyleneimine (PEI), while in other cases polysaccharides such as chitosan (CS), carboxymethyl-β-cyclodextrin (CM-β-CD) served as the macroscopic polymer matrix while magnetite (MNP) constituted the nanoparticles thereby resulting in the polysaccharide-MNP nanocomposite. In the third case, the macroscopic polymer matrix of lignin mixed with M MMT suspension as nanofiller was analysed as controlled release formulations and the efficiencies of PLE and SPR for chlorpyrifos (ChP) pesticides were compared with gas chromatography mass spectrometry (GC-MS) and corrected with inductively coupled plasma mass spectrometry (ICP MS). Overall, owing to the smaller sized particles collected under optimum conditions, all inorganic and hybrid composites displayed decent to excellent PLE. However, L-M MMT displayed an impressive median PLE of 98 % relative to other Polysaccharide-M MMTs (50-80 %), polysaccharide-MNPs (72-75 %), PEI-M MMT (61-76 %) among the hybrid composites tested together with M MMT (49 %). However, compared to other composites with SPR results of ChP of 98 % in 12 days, S-M MMT displayed comparatively better results while other synthesized inorganic and nanocomposites showed 2681 % release. We expect that this description will help researchers choose the right approach for designing pesticides and achieving better pesticide delivery.


INTRODUCTION
Nanotechnology has risen to prominence in the last decade as a potential game-changer in agricultural practices. [1][2][3] Nanoscale particles have revolutionary properties that can increase pesticide efficiency and make the delivery system smart in terms of pesticide distribution. [4][5] Pesticides, like nano-drugs, can be administered in a regulated and targeted manner using a smart delivery system. [6][7] Nanoclays, such as montmorillonite (MMT), serve as nanofillers in polymer matrixes such as polysaccharides. [8][9] Clay gallery swelling is induced by MMT alteration, which improves polysaccharide chain intercalation and clay dispersion in the polysaccharide gallery. Via modification and compounding with a polysaccharide, the silicate layers of MMT can be delaminated, resulting in a nanocomposite with improved tensile properties. 10-12 When MNP is used instead of MMT as a nanofiller, the polysaccharide coating on MNP not only offers stability, but also reduces the toxicity of bare MNP, allowing the formulation to reach the target directly. 13 The incorporation of nanofillers such as M MMT into the PEI results in a substantial improvement in the elasticity module, increased thermal resilience or greater fire retardancy factor. [14][15][16] PEIs and macroscopic polymer such as, lignin greatly improve a range of physicochemical properties needed in new fields of application. (Figure 1). [17][18][19]

Figure 1. Types of system evaluated for pesticide encapsulation and release
In combination with nanotechnology, carbohydrates appear to be promising candidates for increasing E.E. We synthesized a sequence of hybrid M MMTs/MNPs of polysaccharides (chitosan, 20 starch 21 β-cyclodextrin 22 CM-β-cyclodextrin 23 lignin, 24 PEIs 25 forming hybrid nanocomposites by wet impregnation 27 , gelation 28 and coprecipitation 29 32 CM-β-CD-MNP 33 and compared with their EE % & PLE %age of chlorpyrifos. Finally, spectrophotometrically, sustained pesticide release (SPR) was determined wherein time-dependent release of chlorpyrifos from the above synthesized formulations was compared. (Figure 1). Because of its phenol groups, which are capable of scavenging free radicals, 34 Lignin was tried as it can serve as a stabilizer against UV degradation or thermo-oxidation ( Figure 1). Although the macro-to-nano-particles were discussed in a significant number of papers, it was shown that particle size reduction to nano shows pronounced E.E and SPR values due to more spaces (surface area) for insecticide molecules to be trapped. 35 Another main aim of this research is to figure out which is the better nanotechnology (MNP vs M MMT). This is the first systematic relative account of E.E %, PLE wt % and polysaccharides vs. lignin vs. PEI aqueous release activity of chlorpyrifos using M MMT/MNP nanomaterials. Dialyzer tubes (MWCO 1KDa) were procured from G-Biosciences. Carboxymethyl-βcyclodextrin was synthesized from microcrystalline β-cyclodextrin as per literature procedure 36 2.2 Analytical methods. X-ray Diffraction (XRD) was performed using Bruker D-8 advanced diffractometer in the 2θ range of 10 to 90 °C. The average crystallite size with and without surface coating was estimated using the Scherrer equation. Fourier transform infrared (FT-IR) spectra were recorded on Agilent Cary 660 spectrometer using the KBr pellet technique in a range of 4000-400 cm -1 . Thermogravimetric analysis (TGA) was performed to determine the degradation/decomposition behavior of samples using thermogravimetric (TG) analyzer-(Perkin Elmer STA 8000) at a N2 flow rate of 10 mL/min and heating rate of 10 °C/min. Atomic The supernatants, which had excess chitosan, were discarded after five washes with distilled water. After that, the solids were dried in a vacuum oven at 50 0 C. 39

2.3.(i)e: Preparation of the β-CD-M MMT nanocomposite
With minor modifications, the β-cyclodextrin -M MMT solution was synthesized according to the literature. 40 To produce a homogeneous mixture, β-cyclodextrin (1g) was dissolved in 25 ml acetic acid solution (1%) and stirred for 4 h. A suspension of 2% M MMT (500 mg) in acetic acid solution (1%, 25 ml) was also prepared. The suspension was added into the resulting gel. To produce a homogeneous β-CD-M MMT suspension, the mixture was stirred at 50°C for 2 days and then freeze dried.

(i)f: Preparation of the CM-β-CD-MNP
With minor modifications, CM-β-CD was synthesized as described in the literature. 41 A solution of 16.3 percent monochloroacetic acid (2.7 ml) was used to treat a mixture of β-CD (1 g) and NaOH (0.93 g) in water (3.7 ml) at 50 0 C for 5 h. The pH values were modified in the range of 6-7 after the temperature of the reaction mixture was decreased to 25 °C. The obtained neutral solution was mixed with 10 mL of methanol to create a white carboxymethylated-β-cyclodextrin precipitate, which was purified and dried in a 50 °C oven.
With minor modifications, CM-β-CD-MNP was synthesized according to published methods. 41 With rapid stirring at a speed of 1200 rpm, 0.57 g FeCl2.4H2O, 1.57 g FeCl3.6H2O, and 1 g CM-β-CD were dissolved in 26.7 ml distilled water. As the reaction mixture reached 90 °C, 3.5 mL liquid ammonia (25%) was added in drops. The reaction was held at 90 °C for 1 hour with continuous stirring. The nanoparticles were then washed in distilled water to eliminate any unreacted contaminants before being dried in a 70 °C oven.

(i)g: Preparation of the CS-MNP
The chitosan-coated MNP were made by in situ co-precipitation of iron salts, as described in the literature, but with a few tweaks 42  The supernatant was taken to determine the free and entrapped pesticide concentrations.

Quantification of Pesticide Loading Efficiency (PLE) and Entrapment Efficiency
(E.E). Using gas chromatography mass spectrometry (GC-MS) analysis with a retention period of 19.8 min, the amount of free pesticide present in the supernatant was measured (Section B in the SI). In MeOH, the calibration curve of ChP was prepared ( Figure S12 & S13 in SI).
Using the following equations, PLE (wt %) and E.E % were computed and the results are shown in The pesticide loading study was carried out with the same volume for all the NCs (90 mg).
Using ICP-MS (GC MS/ICP-MS data available in Section B3, B4, Table S3 in SI), the %age of iron oxide content present in hybrid NCs such as CS-MNP and CM-β-CD-MNP was calculated at 4.14 and 2.49 %, respectively.

Samples of PEI-M MMT / Polysaccharide-M MMT/ Polysaccharide-MNPs/L-M
MMT hybrid and inorganic (M MMT) of known weights (20 mg) were placed in a glass vial containing 15 ml of phosphate buffer at pH 6.5 at ambient temperature for slow release studies of loaded Chp loaded NCs. 45 The set-up was gently shaken and the was weighed, pH was measured (Table S6 in SI) and 1 ml of the liquid was removed for examination and supplemented with a fresh 1 ml of the medium to preserve the sink state. After syringe-filtering the aliquot, a UV-Vis spectrometer was used to investigate the release and correlate the concentration emitted with the Chp calibration map.
Statistical analysis: All of the measurements were repeated at least three times (n = 3) to ensure that the results were repeatable, and the data were summarized as mean T s.d., with error bars shown in the data points in some of the figures.     The DLS was measured using water as dispersant with RI of 1.330 at 25 0 C. (Figure S10 and S11 in SI).

Comparison of PLE and E.E for M MMT and hybrid-NCs.
After efficient loading of chlorpyrifos (chp) pesticide on the M MMTs/hybrid MMTs and hybrid MNPs, pesticide loading efficiency (PLE, wt %)) and encapsulation efficiency (E.E %) were quantified using gas chromatography-mass spectrometry (GC-MS) study and corrected with inductively coupled plasma mass spectrometry (ICP MS). (Table 1, Table S3, S4 in SI).  Based on the absorption of ChP monitored using UV/Vis spectroscopy, time-dependent pesticide release concentration profiles were determined with the initial measurement of pH (   Table S6 in    We anticipate that this description will aid researchers in selecting the best technique for developing pesticides and improving pesticide delivery.