Recently, inorganic nanomaterials have emerged as promising wettability modifiers to improve oil recovery. Among them, silica nanoparticles (SNPs) have gained a privileged place due to their outstanding properties. Several studies have reported the effectiveness of SNPs on this particular application. However, there is an increasing interest of understanding the parameters that may play an important role on oil recovery using nanofluids. The impact of particle size, particle concentration and types of nanoparticles on oil recovery have been reported. Nevertheless, to our knowledge, the influence of the surface charge has not been investigated. In this work, the effect of the surface charge of SNPs on oil recovery was studied. Silica nanoparticles with different charge profiles (negative, positive and slightly negative) were synthesized and characterized using transmission electron microscopy, FT-IR, dynamic light scattering and ζ-potential. Negatively charged nanoparticles (Neg-SNPs; − 33.45 ± 2.75) were obtained by following the Stöber process. The silanol groups present on the surface of the Neg-SNPs are responsible for the negative surface charge. Positively charged nanoparticles (AP-SNPs; + 42.25 ± 1.9) and slightly negatively charged nanoparticles (MeO-PEG-SNPs; − 12.20 ± 0.42) were obtained by grafting (3-aminopropyl) triethoxysilane and methoxy polyethylene glycol (MeO-PEG 2K) onto the surface of Neg-SNPs, respectively. The impact of silica materials with different charge profiles on wettability alteration and oil displacement at different concentrations (100 or 200 mg/L) was evaluated by contact angle estimation and spontaneous imbibition experiments. The results demonstrated that the surface charge of SNPs transformed the wettability of the sandstone cores and impacted oil recovery in a different extent. While MeO-PEG-SNPs showed the best performance at a low concentration, Neg-SNPs were the most effective in changing the rock wettability and removing oil from sandstone cores at a higher concentration. Overall, our results not only allowed to identify the impact of surface charge on oil recovery but also the effect of SNPs concentration on the suitability of the treatment for enhancing the oil recovery process.

Invasive candidiasis (IC) remains as a major cause of morbidity and mortality in critically ill patients. Amphotericin B (AmB) is one of the most effective antifungal agents commonly used to treat this infection. However, it induces severe side effects such as nephrotoxicity, cardiac alterations, nausea, fever, and liver damage. The utilization of drug delivery systems has been explored to overcome these limitations. Several AmB lipid formulations have been developed and are currently available in the market. Although they have the ability to reduce the main side effects of free AmB, their high cost, necessity of repeated intravenous injections for successful treatment, and incidence of pulmonary toxicity have limited their use. In the last decades, alginate has gained significant interest in drug delivery applications as a cost-effective strategy to improve the safety and therapeutic effect of toxic drugs. In this work, the clinically relevant drug AmB was encapsulated into alginate microparticles using the emulsification/external gelation method. We hypothesize that this synthesis strategy may positively impact the antifungal efficacy of AmB-loaded MCPs toward Candida albicans cells while reducing the toxicity in human lung cells. To prove this hypothesis, the ability of the microplatform to disrupt the cellular membrane potential was tested and its antifungal effectiveness toward Candida albicans cells was evaluated using the cell counting and plate count methods. Moreover, the toxicity of the microplatform in human lung cells was evaluated using CellTiter 96® AQueous cell viability assay and qualitative diffusion analysis of acridine orange. Our results demonstrated that the platform developed in this work was able to induce antifungal toxicity against Candida albicans yeast cells at the same level of free AmB with minimal toxicity to lung cells, which is one of the main side effects induced by commercial drug delivery systems containing AmB. Overall, our data provides convincing evidence about the effectiveness of the alginate-based microplatform toward Candida albicans cells. In addition, this vehicle may not require several infusions for a successful treatment while reducing the pulmonary toxic effect induced by commercial lipid formulations.