Hollow silica spheres with nested iron oxide particles

#Related aspects of this technology are described by Akhtar, et al., J. Saudi Chemical Society (available online Sep. 22, 2018), which is incorporated by reference for all purposes.

#The invention pertains to the fields of medicine and biopolymer chemistry, especially to use of hollow silica spheres (“HSS”) for treatment of neoplasms such as colorectal cancer.

#The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present disclosure.

#A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings below.

#FIGS. 1A-1C: Substrates and sol-gel process (FIG. 1A) used to prepare Fe3O4 nanoparticles incorporated hollow silica spheres or Fe-HSS (FIG. 1B). A photo of the prepared product is shown in FIG. 1C.

#FIGS. 2A-2F. Morphology and size analysis of the Fe3O4 nanoparticles and hollow silica spheres (HSS). (FIG. 2A) TEM image and (FIG. 2B) size histogram of Fe3O4 particles. The average diameter of the particles is ˜14 nm. (FIG. 2C) SAED pattern of the Fe3O4 nanoparticles, showing the polycrystalline nature, the first 5-rings of the pattern started from the inner ring are indexed as, (220), (311), (400), (511) and (440). SEM micrograph of (FIG. 2D) u-HSS, (FIG. 2E) c-HSS and (FIG. 2F) Fe-HSS.

#As explained above the inventors have now synthesized and compared uncalcined-hollow silica spheres (u-HSS), calcined hollow silica spheres (c-HSS) and Fe3O4-hollow silica spheres (Fe-HSS). Calcination was used to remove phenyl groups. Further detail about the substrates for HSS and the steps of producing and analyzing anti-cancer properties of HSS are provided below.

#Silica Spheres. When referencing hollow silica spheres, “hollow” refers to a central area (i.e., a core portion) of a particle which has a lower density of silica compared to the surrounding structure (i.e., the shell portion). While the definition of “hollow” may encompass a continuous void that is completely free of silica, this is not a requirement, and some silica may be disposed within the core portion. By way of example, a silica particle which has a substantially continuous density of silica from one point on the particle though the center of the particle to a point directly across from it would be considered solid herein and not hollow, whereas a silica particle that has 60-80 wt. % of a total silica content located in the shell portion, with the remaining 20-40 wt. % of a total silica content located in the central area would be considered hollow herein.

#The “degree of hollowness” of the hollow silica spheres as used herein is an indicator of the density differential between the silica-containing shell and the core, with higher degrees of hollowness being associated with an increased capacity for storage (e.g., of pharmaceutical or cosmetic payloads), adsorption, etc. The degree of hollowness is defined as a maximum peak intensity of the core divided by a minimum peak intensity of the silica-containing shell, each of which are measured by transmission electron microscopy. That is, given the higher density of silica in the silica-containing shell than in the core, it is more difficult for a beam of electrons to pass through the silica-containing shell, resulting in intensity profiles that can be used to quantify this silica density disparity. The degrees of hollowness can then be calculated for the individual hollow silica spheres and averaged. In some embodiments, the hollow silica spheres produced herein have an average degree of hollowness of 3, 4, 5, 6, 7 to 8, preferably 3.2 to 7.5, preferably 3.4 to 7.0, preferably 3.6 to 6.5, preferably 3.8 to 6.0, preferably 4.0 to 5.5, preferably about 4.06. Such a degree in hollowness is much higher (i.e., more hollow) than silica spheres which have not been calcined, which have an average degree of hollowness of about 2.3.