Continuous-Flow Nanoprecipitation Method to Synthesize Degradable Hollow Mesoporous Organosilica Nanoparticles for Insecticide Delivery

Degradable mesoporous organosilica nanoparticles (MONPs) are attracting significant attention in the area of designing smart drug carriers mainly due to their excellent stability and multiple functions. However, the efficient, controllable, and large-scale production of MONPs still faces huge challenges. Herein, a novel and facile continuous-flow nanoprecipitation strategy was reported to synthesize hollow MONPs with highly uniform and tailored properties. The synthesized hollow MONPs possessed a large surface area (SBET > 1070.1 m2 g-1), narrow size distribution, large hollow cavity, and thin shell. Interestingly, the incorporation of organic moieties into silica cross-linked networks led to the timely degradation of nanocarriers with the desired responsiveness. Moreover, the applicability of the as-obtained hollow MONPs has been demonstrated in the loading and pH-responsive release of thiamethoxam (THI). The resultant THI-loaded MONPs possessed long-term storage stability at a low temperature and showed release behaviors in response to a basic environment. Benefiting from the shielding property of MONPs, THI-loaded MONPs manifested superior stability against the photolysis as compared to that of the THI technical. This work provides a new consideration for promoting the advancement of nanotechnology in agricultural fields.

A Comprehensive Study of Drug Loading in Hollow Mesoporous Silica Nanoparticles: Impacting Factors and Loading Efficiency

Although hollow mesoporous silica nanoparticles (HMSNs) have been intensively studied as nanocarriers, selecting the right HMSNs for specific drugs still remains challenging due to the enormous diversity in so far reported HMSNs and drugs. To this end, we herein made a comprehensive study on drug loading in HMSNs from the viewpoint of impacting factors and loading efficiency. Specifically, two types of HMSNs with negative and positive zeta potential were delicately constructed, and three categories of drugs were selected as delivery targets: highly hydrophobic and lipophobic (oily), hydrophobic, and hydrophilic. The results indicated that (i) oily drugs could be efficiently loaded into both of the two HMSNs, (ii) HMSNs were not good carriers for hydrophobic drugs, especially for planar drugs, (iii) HMSNs had high loading efficiency towards oppositely charged hydrophilic drugs, i.e., negatively charged HMSNs for cationic molecules and vice versa, (iv) entrapped drugs would alter zeta potential of drug-loaded HMSNs. This work may provide general guidelines about designing high-payload HMSNs by reference to the physicochemical property of drugs.

Hollow Mesoporous Silica Nanoparticles Gated by Chitosan-Copper Sulfide Composites as Theranostic Agents for the Treatment of Breast Cancer

The combination of chemotherapy and photothermal therapy (PTT) into a single formulation has attracted increasing attention as a strategy for enhancing cancer treatment. Here, hollow mesoporous silica nanoparticles (HMSNs) were used as a base carrier material, loaded with the anti-cancer drug doxorubicin (DOX), and surface functionalized with chitosan (CS) and copper sulfide (CuS) nanodots to give HMSNs-CS-DOX@CuS. In this formulation, the CuS dots act as gatekeepers to seal the surface pores of the HMSNs, preventing a burst release of DOX into the systemic circulation. S-S bonds connect the CuS dots to the HMSNs; these are selectively cleaved under the reducing microenvironment of the tumor, permitting targeted drug release. This, coupled with the PTT properties of CuS, results in a potent chemo/PTT platform. The HMSNs-CS-DOX@CuS nanoparticles have a uniform size (150 ± 13 nm), potent photothermal properties (η = 36.4 %), and tumor-targeted and near infrared (NIR) laser irradiation-triggered DOX release. In vitro and in vivo experimental results confirmed that the material has good biocompatibility, but is effectively taken up by cancer cells. Moreover, the CuS nanodots permit simultaneous thermal/photoacoustic dual-modality imaging. Treatment with HMSNs-CS-DOX@CuS and NIR irradiation caused extensive apoptosis in cancer cells both in vitro and in vivo, and could dramatically extend the lifetimes of animals in a murine breast cancer model. The system developed in this work therefore merits further investigation as a potential nanotheranostic platform for cancer treatment. STATEMENT OF SIGNIFICANCE: Conventional cancer chemotherapy is accompanied by unavoidable off-target toxicity. Combination therapies, which can ameliorate these issues, are attracting significant attention. Here, the anticancer drug doxorubicin (DOX) was encapsulated in the central cavity of chitosan (CS)-modified hollow mesoporous silica nanoparticles (HMSNs). The prepared system can target drug release to the tumor microenvironment. When exposed to near infrared laser (NIR) irradiation, CuS nanodots located at the surface pores of the HMSNs generate energy, accelerating drug release. In addition, a systematic in vitro and in vivo evaluation confirmed the HMSNs-CS-DOX@CuS platform to give highly effective synergistic chemotherapeutic-photothermal therapy and have effective thermal/photoacoustic dual-imaging properties. This work may open up a new avenue for NIR-enhanced synergistic therapy with simultaneous thermal/photoacoustic dual imaging.