Herodotou Stephania, Lissenden Natalie, Skinley Kevin, Nimmo Derric, Snetselaar Janneke, Guy Amy, Myers Peter, Ryazanskaya Svetlana
Innovative Vector Control Consortium, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
Department of Chemistry, University of Liverpool, Liverpool L69 3BX, UK.
Insects. 2025 Sep 5;16(9):937. doi: 10.3390/insects16090937.
The efficacy of indoor residual spray (IRS) products is affected by various factors, such as the substrate on which they are sprayed and the surface concentration and bioavailability of the insecticide. This study investigated the potential of bespoke silica particles (hereafter referred to as 'X-tec silica') as a unique carrier for insecticides to reduce the insecticide content in an IRS formulation by improving pickup by mosquitoes and optimising the physical state of the insecticide while maintaining its residual biological activity on a surface. Molecular computer modelling was used to define the critical crystallisation size of clothianidin, and silica particles were manufactured with pore diameters smaller than this length to maintain the insecticide in an amorphous state. Silica carriers were then formulated to incorporate clothianidin inside their pores, and a full material characterisation was conducted to assess the clothianidin coating position on/in the silica particles, their concentration, and their physical form. The clothianidin-formulated silica (10%) was sprayed at three different application rates (30, 60, and 90 mg active ingredient (a.i.)/m) onto two surfaces: glazed and unglazed tiles. The tiles were tested for bioefficacy against the insecticide-susceptible s.s. Kisumu mosquito strain at 1 week and 8 months post-spray application. At 1 week post-spray application, at 60 and 90 mg a.i./m application rates, 100% mortality was observed on both surfaces within 48 h. For the lowest concentration (30 mg a.i./m), 100% mortality was reached within 72 h on glazed tiles; however, for unglazed tiles, due to the surface irregularity and porosity, it remained below 60%. At 8 months post-spray application, on glazed tiles, 100% mortality was reached within 24 h at 60 and 90 mg a.i./m application rates and within 48 h at 30 mg a.i./m. On unglazed tiles, 96 h mortality was not measured; however, 100% mortality was reached within 72 h (90 mg a.i./m) and 120 h (60 mg a.i./m) at higher concentrations. At the lowest concentration (30 mg a.i./m) at 120 h, mortality only reached 25%. The lowest application rate tested (30 mg a.i./m) is ten times lower than that of current products on the market and demonstrates the potential of this approach. Preliminary findings from this study suggest that X-tec silica particles may enhance the effectiveness of IRS using clothianidin. However, further extensive research is needed to confirm this.
室内滞留喷洒（IRS）产品的功效受多种因素影响，如喷洒的底物、杀虫剂的表面浓度和生物利用度。本研究调查了定制二氧化硅颗粒（以下简称“X-tec二氧化硅”）作为杀虫剂独特载体的潜力，通过提高蚊子的摄取量并优化杀虫剂的物理状态，同时保持其在表面的残留生物活性，来降低IRS制剂中的杀虫剂含量。使用分子计算机建模来确定噻虫胺的临界结晶尺寸，并制造孔径小于该长度的二氧化硅颗粒，以使杀虫剂保持无定形状态。然后将二氧化硅载体配制成在其孔隙内包含噻虫胺，并进行全面的材料表征，以评估噻虫胺在二氧化硅颗粒上/内的包覆位置、浓度及其物理形态。将含噻虫胺的二氧化硅（10%）以三种不同的施用量（30、60和90毫克活性成分（a.i.）/平方米）喷洒在两种表面上：釉面和未釉面瓷砖。在喷洒后1周和8个月，对瓷砖进行针对杀虫剂敏感的基苏木按蚊品系的生物功效测试。在喷洒后1周，施用量为60和90毫克a.i./平方米时，在48小时内两种表面上均观察到100%的死亡率。对于最低浓度（30毫克a.i./平方米），在釉面瓷砖上72小时内达到100%的死亡率；然而，对于未釉面瓷砖，由于表面不规则和多孔性，死亡率仍低于60%。在喷洒后8个月，在釉面瓷砖上，施用量为60和90毫克a.i./平方米时，24小时内达到100%的死亡率，30毫克a.i./平方米时48小时内达到。在未釉面瓷砖上，未测量96小时的死亡率；然而，在较高浓度下，72小时（90毫克a.i./平方米）和120小时（60毫克a.i./平方米）内达到100%的死亡率。在最低浓度（30毫克a.i./平方米）下120小时，死亡率仅达到25%。测试的最低施用量（30毫克a.i./平方米）比市场上现有产品低十倍，证明了这种方法的潜力。本研究的初步结果表明，X-tec二氧化硅颗粒可能会提高使用噻虫胺的IRS的有效性。然而，需要进一步广泛研究来证实这一点。
