Engineering Laboratory for Tarim Animal Diseases Diagnosis and Control, College of Animal Science, Tarim University, Alar 843300, China.
Key Laboratory of Tarim Animal Husbandry & Science Technology of Xinjiang Production & Construction Corps, Alar 843300, China.
J Vet Sci. 2022 May;23(3):e48. doi: 10.4142/jvs.21292.
The poor intracellular concentration of enrofloxacin might lead to treatment failure of cow mastitis caused by small colony variants (SASCVs).
In this study, enrofloxacin composite nanogels were developed to increase the intracellular therapeutic drug concentrations and enhance the efficacy of enrofloxacin against cow mastitis caused by intracellular SASCVs.
Enrofloxacin composite nanogels were formulated by an electrostatic interaction between gelatin (positive charge) and sodium alginate (SA; negative charge) with the help of CaCl (ionic crosslinkers) and optimized by a single factor test using the particle diameter, zeta potential (ZP), polydispersity index (PDI), loading capacity (LC), and encapsulation efficiency (EE) as indexes. The formation mechanism, structural characteristics, bioadhesion ability, cellular uptake, and the antibacterial activity of the enrofloxacin composite nanogels against intracellular SASCVs strain were studied systematically.
The optimized formulation was comprised of 10 mg/mL (gelatin), 5 mg/mL (SA), and 0.25 mg/mL (CaCl). The size, LC, EE, PDI, and ZP of the optimized enrofloxacin composite nanogels were 323.2 ± 4.3 nm, 15.4% ± 0.2%, 69.6% ± 1.3%, 0.11 ± 0.02, and -34.4 ± 0.8 mV, respectively. Transmission electron microscopy showed that the enrofloxacin composite nanogels were spherical with a smooth surface and good particle size distributions. In addition, the enrofloxacin composite nanogels could enhance the bioadhesion capacity of enrofloxacin for the SASCVs strain by adhesive studies. The minimum inhibitory concentration, minimum bactericidal concentration, minimum biofilm inhibitory concentration, and minimum biofilm eradication concentration were 2, 4, 4, and 8 μg/mL, respectively. The killing rate curve had a concentration-dependent bactericidal effect as increasing drug concentrations induced swifter and more radical killing effects.
This study provides a good tendency for developing enrofloxacin composite nanogels for treating cow mastitis caused by intracellular SASCVs and other intracellular bacterial infections.
恩诺沙星的细胞内浓度较低可能导致小菌落变异体（SASCVs）引起的奶牛乳腺炎治疗失败。
本研究旨在开发恩诺沙星复合纳米凝胶，以增加细胞内治疗药物浓度，并增强恩诺沙星对细胞内 SASCVs 引起的奶牛乳腺炎的疗效。
采用静电相互作用，在 CaCl 的帮助下，用明胶（正电荷）和海藻酸钠（SA；负电荷）制备恩诺沙星复合纳米凝胶，并通过单因素试验以粒径、Zeta 电位（ZP）、多分散指数（PDI）、载药量（LC）和包封率（EE）为指标进行优化。系统研究了恩诺沙星复合纳米凝胶的形成机制、结构特征、生物黏附能力、细胞摄取以及对细胞内 SASCVs 菌株的抗菌活性。
优化后的配方由 10mg/mL（明胶）、5mg/mL（SA）和 0.25mg/mL（CaCl）组成。优化后的恩诺沙星复合纳米凝胶的粒径、LC、EE、PDI 和 ZP 分别为 323.2±4.3nm、15.4%±0.2%、69.6%±1.3%、0.11±0.02 和-34.4±0.8mV。透射电子显微镜显示，恩诺沙星复合纳米凝胶呈球形，表面光滑，粒径分布均匀。此外，通过黏附研究，恩诺沙星复合纳米凝胶可以增强恩诺沙星对 SASCVs 菌株的生物黏附能力。最小抑菌浓度、最小杀菌浓度、最小生物膜抑制浓度和最小生物膜清除浓度分别为 2、4、4 和 8μg/mL。杀菌率曲线呈浓度依赖性杀菌作用，随着药物浓度的增加，杀菌效果更快、更彻底。
本研究为开发治疗细胞内 SASCVs 引起的奶牛乳腺炎和其他细胞内细菌感染的恩诺沙星复合纳米凝胶提供了良好的趋势。
