A Sustained Release Anchored Biocide System Utilizing the Honeycomb Cellular Structure of Expanded Perlite

Abstract

The development of a sustained-release biocide system, involving an anchored quaternary ammonium salt (AQAS) embedded in expanded perlite (EP) substrate, is reported. Scanning electron microscopy (SEM) images reveal the well-defined honeycomb cells that are a feature of EP. These honeycomb cells exhibit a variety of polygon shapes, which are filled with the AQAS molecules as evidenced by SEM data. The aqueous leaching of the AQAS from the EP honeycomb cells is monitored by the Fourier transform infrared CH stretching absorbance maxima at 2920 and 2850 cm–1. Solid-state NMR data indicate the formation of three dominant oligomeric forms of the AQAS biocide molecules formed within the EP network by condensation reactions at curing temperatures (160 °C). The various oligomeric species involve different numbers of SiO chains bonded to a central Si atom within the AQAS anchoring groups. Assays confirm the potency of the AQAS oligomers against Staphylococcus aureus and Escherichia coli bacteria.

Study on Sustained-Release Pesticides Blended with Fosthiazate-Stearic Acid/Expanded Perlite

“…EP does not show a specific shape or crystal structure, but looked like a thin sheet. The interior of EP material had a well-defined polygonal honeycomb structure (sometimes referred to as "popcorn" structure) surrounded by a relatively smooth outer surface (sometimes referred to as "eggshell") [17]. These characteristics were considered to be caused by the high internal pressure generated by the water vapor in the original perlite minerals at the EP transition temperature (850°C).…”

“…Perlite is a natural, common, non-toxic and cheap raw material. EP has the characteristics of lightweight, thermal stability and chemical inertia [17]. Compared with other common synthetic zeolite, nano clay, amorphous silicon and so on, EP has a large load, and has the natural abundance and economic feasibility, so it will hopefully replace other synthetic adsorbents.…”

“…The results showed that the release rate of 5-aminosalicylic acid in the buffer decreased with the increase of the content of the coupling agent 3-(trimethoxy-methylsilyl-propyl methacrylate) in the composite. Using the cellular structure of EP, Rachel et al [19] developed a sustained-release biocide system, involving an anchored quaternary ammonium salt (AQAS) embedded in EP substrate. The results showed that the honeycomb cellular microstructure of EP enables the adsorption and accumulation of AQAS monomeric species from methanol solution and acts as a substrate for the formation of oligomeric species after curing, which slowed down the dissolution rate of AQAS, so that AQAS could be released continuously for a long time.…”

The antibacterial potency and antibacterial mechanism of a commercially available surface-anchoring quaternary ammonium salt (SAQAS)-based biocide in vitro

“…This intimate interaction is proposed to lead to the denaturation of proteins in the bacterial cell membrane (McDonnell & Russell, 1999;Oblak et al, 2019) and disturbs the electrical balance and osmotic pressure of the bacterial membrane leading to cell lysis (Daood & Yiu, 2018;Xu et al, 2012). Other studies suggest that killing occurs through an ion-exchange mechanism in the bacterial cell membrane (Crismaru et al, 2011;Mathew, Cooney, Zujovic, et al, 2018).…”

“…The antimicrobial activity of 3‐(trimethoxysilyl)‐propyldimethyloctadecyl ammonium chloride, (CAS 27668–52‐6; C 26 H 58 ClNO 3 Si), an organosilicon quaternary ammonium compound (Si‐QAC), was first investigated by Isquith et al ( 1972 ). The Si‐QAC silane group condenses with free hydroxyl groups on the surface (Sambhy et al, 2008 ), and intermolecular siloxane (Si‐O‐Si) linkages (Legido‐Quigley et al, 2003 ) form to stably anchor the biocide at the surface (Mathew, Cooney, Malmstrom, et al, 2018 ; Mathew, Cooney, Zujovic, et al, 2018 ), giving rise to the name surface anchoring quaternary ammonium salt (SAQAS). The antimicrobial mechanism is assigned to the positively charged quaternary amine (N+ atom) that attracts the negatively charged microbes onto the needle‐like C18 structure of the hydrophobic chain, which penetrates the cell envelope of micro‐organisms.…”