## 5 Conclusions  
We presented synthesis routes of silica flakes fabricated on two types of templates: on graphene oxide and Mg-Al layered double hydroxide. Both types of silica flakes have been functionalized by folic acid and anticancer drug (MTX). Detailed spectroscopic analyses allowed proving that the drug interacts with silica flakes not only via hydrogen bonding, but also via amide bond formation. Interestingly, different structural properties affected their drug release profiles.  
In all experiments there was at least 80 wt % drug release observed. The release, in water as well as in PBS solution, from mSiO\({}_{2}\) after GO was slower and more gradual than from mSiO\({}_{2}\) after LDH. For the first structure, the release stopped after 30 h, reaching 90 wt % in water and \(\approx\)99 wt % in PBS solution. Drug release from mSiO\({}_{2}\) after LDH Mg/Al occurred almost immediately in both media (water and PBS). The equilibrium was achieved in PBS after 2 h, while in H2O, it was achieved after 4 h, reaching 100 wt % and 80 wt %, respectively. This can be explained by the smaller pore volume of these structures allowing the drug adsorption only on the surface and not into the pores of the material detected. No additional silica structures were observed.  
Both kind of flakes also degraded differently in the solutions. In water, none of the petals showed the changes in morphology. In contrast, the PBS solution and medium significantly affected the structure of the flakes. However, mSiO\({}_{2}\) after GO placed in PBS and medium lost their porosity, and newly formed structures appeared. In the case of mSiO\({}_{2}\) after LDH Mg/Al, the overall shape of the flakes is maintained throughout the experiment, but a change in the porosity of the sample is also detected. The deformation appeared in the form of large holes in the nanoflakes structure. Accordingto the TEM analysis, the degradation occurs faster for the flakes made from GO. These differences can be noticed after 48 h.  
Analyzing the data, it can be assumed that mSiO\({}_{2}\) after GO can be more suitable as a drug delivery system due to the following: (i) the larger volume of pores in which the drug can be accumulated, and (ii) the smaller size of flakes that would more easily penetrate the cells. The obtained results are promising, but they require further research, primarily biological, to determine whether this folic acid functionalization combined with silica flakes will be effective in targeted anticancer therapies.  
The following are available online at [[http://www.mdpi.com/2076-3417/10/18/6465/s1](http://www.mdpi.com/2076-3417/10/18/6465/s1)]([http://www.mdpi.com/2076-3417/10/18/6465/s1](http://www.mdpi.com/2076-3417/10/18/6465/s1)), Figure S1: X-ray dispersion spectroscopy (EDX) elemental spectra of silica flakes and the templates; Figure S2: XRD patters of mSiO\({}_{2}\) after GO (A) and GO and mSiO\({}_{2}\) after LDH Mg/Al and LDH Mg/Al (B); Figure S3: Raman spectra of mSiO\({}_{2}\) after GO (A) and GO and mSiO\({}_{2}\) after LDH Mg/Al and LDH Mg/Al (B); Figure S4: BET isotherms (A) and diagrams of pore diameter distribution (B) of mSiO\({}_{2}\) after GO and mSiO\({}_{2}\) after LDH Mg/Al; Figure S5: Thermoquimeric analysis of silica flakes functionalized with folic acid.  
Conceptualization, M.T. and K.C.; methodology, M.T.; investigation, M.T. and W.K.; writing--original draft preparation, M.T.; writing--review and editing, E.M. and K.C.; supervision, M.T. and E.M.; All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Science Centre, Poland, grant number 2016/21/N/ST8/02397.  
The authors are grateful for the financial support of National Science Centre within PRELUDIUM 11 program (no. 2016/21/N/ST8/02397)  
The authors declare no conflict of interest.