A facilely controlled length, cytotoxicity, length-dependent and cell type-dependent cellular uptake of silica nanotubes and their applications in the delivery of immunostimulatory CpG oligodeoxynucleotides

Abstract

A controllable length of inorganic nanotubes as a drug delivery system is crucial to understanding internalization mechanisms and designing new biomedical applications. In this study, silica nanotubes (SiNTs) with controlled length ranging from several hundred nanometers to several micrometers were firstly fabricated via a facile and effective acid-degradation collagen template route and then functionalized with chitosan (ChSiNTs) to deliver immunostimulatory cytosine-phosphodiester-guanine oligodeoxynucleotides (CpG ODNs). It was found that the length of SiNTs could be well controlled through the adjustment of the acid-treatment temperature. Cytotoxic assessment indicated that SiNTs exhibited good biocompatibility when separately incubated with four types of cell lines: 293XL-hTLR9, A549, NIH3T3, and C2C12. The cellular uptake of SiNTs was strongly affected by their length and cell type. A decrease in the length led to an increase in the cellular uptake of SiNTs, while a significantly higher cellular uptake by C2C12 cells was observed in comparison with A549 and NIH3T3 cells. An immunochemical assay revealed that SiNTs were located in the endolysosomes after cellular internalization. ChSiNTs were positive and well complexed with negative CpG ODNs to produce a ChSiNT/CpG ODN complex (CpG-ChSiNT) via electric force. ChSiNTs were located in the endolysosomes after internalization and enhanced the cellular uptake of CpG-ODNs. CpG ODNs could be released from CpG-ChSiNTs in a sustained way and specifically recognized by the TLR9 receptor in 293XL-hTLR9 cells. The amount of interleukin-6 cytokine stimulated by CpG-ChSiNT against peripheral blood mononuclear cells was higher than that by free CpG ODNs and ChSiNTs significantly enhanced the immunostimulatory response of CpG ODNs.

Silica-Based Gene Delivery Systems: From Design to Therapeutic Applications

“…The most common approach for synthesizing SNTs is the template method, which entails the synthesis or deposition of the material within the cylindrical nanopores of a template membrane that can be dissolved away afterward [ 9 , 25 ]. This method is very popular, since the properties of tubular structures are well directed by the template and can be easily customized by adjusting the template structure [ 26 ]. It has been used to prepare solid (nanorods or nanowires) and hollow structures (nanotubes) composed not only of silica but also different types of materials, such as polymers or carbon [ 25 ].…”

“…It has been used to prepare solid (nanorods or nanowires) and hollow structures (nanotubes) composed not only of silica but also different types of materials, such as polymers or carbon [ 25 ]. Anodic aluminum oxide [ 22 , 23 ] and collagen [ 26 ] membranes have been used as templates, on which a silica layer is deposited through sol–gel reactions [ 9 ]. Building upon this concept, Yu and colleagues [ 27 ] developed a mechanical capping method of SNTs using an alumina microbead hammering treatment, which could be used to encapsulate functional molecules into the nanotubes.…”

“…In this study, the outer surface of the developed nanotubes was functionalized with chitosan (ChSNT), another cationic polymer, which was used to deliver immunostimulatory cytosine-phosphodiester-guanine oligodeoxynucleotides (CpG ODNs). The developed system was found in the endolysosomes after cellular internalization and significantly enhanced both the cellular uptake and immunostimulatory response of CpG ODNs [ 26 ].…”

“…It has been used to prepare solid (nanorods or nanowires) and hollow structures (nanotubes) composed not only of silica but also different types of materials, such as polymers or carbon [25]. Anodic aluminum oxide [22,23] and collagen [26] membranes have been used as templates, on which a silica layer is deposited through sol-gel reactions [9]. Building upon this Reproduced from [22], with permission from John Wiley and Sons.…”

Organic and Inorganic Template Assisted Synthesis of Silica Nanotubes and Evaluation of Its Properties for Drug Targeting

“…The important property of silica nanotube is biocompatibility, superior mechanical property, excellent hydrophilic in nature especially easy acceptability of surface functionalization on both inner and outer wall due to presence of silane group and adjustable pore size and large surface area [5,7]. Mostly the synthesis of metal inorganic single-wall nanotubes by several routes such as thermal evaporation, centrifugal jet spinning, and template-directed sol-gel [8][9][10][11]. Among them, the template-directed sol-gel pathway is a very favorable method to prepare the facilely adjusted silica nanotube using the suitable templates [12], especially the long-chain organic surfactants offer to get unique inorganic oxide nanotubes with uniform porosity [13].…”