Background: Mesoporous calcium-silicate nanoparticles (MCSNs) have good prospects in the medical field due to their great physicochemical characteristics, antibacterial activity and drug delivery capacity. This study was to analyze the antibiofilm activity and mechanisms of silver (Ag) and zinc (Zn) incorporated MCSNs (Ag/Zn-MCSNs) with different percentages of Ag and Zn. Methods: Ag/Zn(1:9, molar ratio)-MCSNs and Ag/Zn(9:1, molar ratio)-MCSNs were prepared and characterized. Endocytosis of nanoparticles by Enterococcus faecalis (E. faecalis) treated with Ag/Zn-MCSNs was observed using TEM to explore the antibacterial mechanisms. The antibiofilm activity of Ag/Zn-MCSNs with different ratios of Ag and Zn was tested by E. faecalis biofilm model in human roots. The human roots pretreated by different Ag/Zn-MCSNs were cultured with E. faecalis. Then, SEM and CLSM were used to observe the survival of E. faecalis on the root canal wall. Cytotoxicity of the nanoparticles was tested by CCK8 kits. Results: The Ag/Zn-MCSNs release Ag + and destroy the cell membranes to kill bacteria. The MCSNs containing Ag showed antibacterial activity against E. faecalis biofilms in different degrees, and they can adhere to dentin surfaces to get a continuous antibacterial effect. However, MTA, MCSNs and Zn-MCSNs could not disrupt the bacterial biofilms obviously. MCSNs, Ag/Zn(1:1, molar ratio)-MCSNs and Ag/Zn(1:9)-MCSNs showed no obvious cytotoxicity, while Ag-MCSNs and Ag/Zn(9:1)-MCSNs showed cytotoxicity. Zn-MCSNs can slightly promote cell proliferation. Conclusion: Ag/Zn-MCSNs have good antibiofilm activity. They might achieve an appropriate balance between the antibacterial activity and cytotoxicity by adjusting the ratio of Ag and Zn. Ag/Zn-MCSNs are expected to be a new type of root canal disinfectant or sealer for root canal treatment.

Hierarchical HZSM-5 membranes were prepared on the inner wall of stainless steel tubes, using amphiphilic organosilane (TPOAC) and mesitylene (TMB) as a meso-porogen and a swelling agent, respectively. The mesoporosity of the HZSM-5 membranes were tailored via formulating the TPOAC/Tetraethylorthosilicate (TPOAC/TEOS) ratio and TMB/TPOAC ratio, in synthesis gel, and the prepared membranes were systematically characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), N2 adsorption–desorption, N2 permeation, inductively coupled plasma (ICP), in situ fourier transform infrared (FT-IR), ammonia temperature-programmed desorption (NH3-TPD), etc. It was found that the increase of the TPOAC/TEOS ratio promoted a specific surface area and diffusivity of the HZSM-5 membranes, as well as decreased acidity; the increase of the TMB/TPOAC ratios led to an enlargement of the mesopore size and diffusivity of the membranes, but with constant acid properties. The catalytic performance of the prepared HZSM-5 membranes was tested using the catalytic cracking of supercritical n-dodecane (500 °C, 4 MPa) as a model reaction. The hierarchical membrane with the TPOAC/TEOS ratio of 0.1 and TMB/TPOAC ratio of 2, exhibited superior catalytic performances with the highest activity of up to 13% improvement and the lowest deactivation rate (nearly a half), compared with the microporous HZSM-5 membrane, due to the benefits of suitable acidity, together with enhanced diffusivity of n-dodecane and cracking products.

Novel structured catalysts of meso-HZSM-5/MCM-41 composite coatings were synthesized via a two-step process: washcoating HZSM-5 powder on the internal surface of a stainless steel tube and subsequently converting SiO2 binder into MCM-41 by sequential desilication and recrystallization. Additional Fe and Al species were incorporated into the MCM-41 framework for increasing the active sites. It was found that the adherence strength of composite coating was remarkably improved, as a result of encapsulation of HZSM-5 crystals into the successive MCM-41 network. Catalytic cracking of supercritical n-dodecane (500 °C and 4 MPa) was employed to test the catalytic performance of the coatings. The ZC-Al/Fe coating with both Fe and Al species incorporated into the MCM-41 framework showed an excellent catalytic performance, with the initial conversion of n-dodecane enhancement by 50.6%, the deactivation rate reduction by 64.5%, and the heat sink improvement by 14.5%, compared to the parent HZSM-5 coating. The performance enhancement for ZC-Al/Fe coating may result from the sequential precracking–cracking–dehydrogenation reaction process catalyzed by acid sites in MCM-41, acid sites in meso-HZSM-5, and redox sites in MCM-41, respectively.

Background: Silver (Ag) and/or zinc (Zn) incorporated mesoporous calcium-silicate nanoparticles (MCSNs) have good physicochemical characteristics and can be advanced materials for root canal filling. This study was to analyze the antibacterial properties and mechanism of Ag/Zn-MCSNs with different percentage of Ag and Zn.Methods: The antibacterial properties and the cytotoxicity of them were evaluated. Human root canals were inoculated with E. faecalis for 4 weeks to establish bacterial biofilm model. The E. faecalis biofilms were treated with MCSNs, Ag-MCSNs, Zn-MCSNs, Ag/Zn-MCSNs, calcium hydroxide (CH) and mineral trioxide aggregate (MTA) for 7 days. The ultrastructure and distribution of viable bacteria of the specimens were evaluated using SEM and CLSM. Human root canals were pretreated with CH, MCSNs, Ag-MCSNs, Zn-MCSNs and Ag/Zn-MCSNs, then the root canals were immersed in E. faecalis suspension for 7 days. The adhesion and colonization of E. faecalis on the root canal walls were observed using SEM and CLSM. Endocytosis of E. Faecalis treated by Ag-MCSNs and Ag/Zn-MCSNs were observed using TEM. Results: The MCSNs containing Ag showed better antibacterial properties than MCSNs and Zn-MCSNs (P<0.05). MCSNs, Ag/Zn(1:1)-MCSNs and Ag/Zn(1:9)-MCSNs showed no obvious cytotoxicity (P>0.05), while Ag-MCSNs and Ag/Zn(9:1)-MCSNs showed cytostatic effects. Zn-MCSNs slightly promote cell proliferation (P<0.05). The MCSNs containing Ag showed antibacterial abilities against E. faecalis biofilm in different degree, and can adhere to dentin surfaces to get a continuous antibacterial effect, but MTA, MCSNs and Zn-MCSNs could not disrupt the bacterial biofilm obviously. The Ag-MCSNs and Ag/Zn-MCSNs release Ag+ and destroy the cell membranes to kill bacteria. Conclusions: The antibacterial effects and cytotoxicity of Ag/Zn-MCSNs are related to Ag content, while Zn reduce cytotoxicity and promote cell proliferation.

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