pH-Responsive Dual Cargo Delivery from Mesoporous Silica Nanoparticles with a Metal-Latched Nanogate

Abstract

A nanogate composed of two iminodiacetic acid (IDA) and a metal ion latch was designed, synthesized and assembled on mesoporous silica nanoparticles. This gating mechanism is capable of storing and releasing metal ions and molecules trapped in the pores. Pore openings derivatized with IDA can be latched shut by forming a bis-IDA chelate complex with a metal ion. This system was tested by loading with Hoechst 33342 as the probe cargo molecule, and latching with cobalt, nickel or calcium metal ions. No cargo release was observed in a neutral aqueous environment, but both cargoes were delivered after acid stimulation and/or the addition of a competitively binding ligand.

Template Synthesis of Iminodiacetic Acid Polysiloxane Immobilized Ligand Systems and their Metal Uptake Capacity

“…CTAB was extracted from the material by refluxing with ethanol. The [11,21,22] Diethyliminodiacetate polysiloxane material (P-DIDA-I) was prepared by adding diethyliminodiacetate (9.45 g 0.05 mol) to (10 g, 0.032 mol) of iodopolysiloxane (A-D) ( Table 1) in (50 ml, 0.610 mol) of THF. The mixture was stirred and refluxed at 95 • C for 48 hours.…”

“…i Preparation of polysiloxane-immobilized diethyliminodiacetate (P-DIDA-I) (A-D) by the reaction of diethyliminodiacetate with iodopolysiloxane (P-I) in THF, Scheme 1 [11,21,22]. ii Hydrolysis of P-DIDA-I using hydrochloric acid to form polysiloxane-immobilized iminodiacetic acid (P-IDA-I) (A-D) as given in Scheme 1.…”

“…In previous research, iminodiacetic acid (IDA) functionalized polysiloxane ligand systems were prepared by the sol-gel process in the absence of surfactants [15] or by modification of silica with an IDA-functionalized silane coupling agent [19,20]. More recently IDAfunctionalized mesoporous silica was prepared by treatment of iodopolysiloxane or iodofunctionalized mesoporous silica with diethyliminodiacetate [11,21,22].…”

Colloidal and spherical mesoporous silica particles: synthesis and new technologies for delivery applications

“…Some of the last reports in surface functionalization of MSP obtained from a TEOS sol-gel process are summarized in Table 2. It may be seen that most of the particles are type MCM-41 [78,79,[94][95][96][97][98][99], and few of them are from MCM-48 [100] or HMM [84]. All the others are catalogued as MSN [101][102][103][104][105][106][107][108], showing proof of mesostructured matrices with 2-4 nm average pore size, with exceptional sizes of 8 and 13 nm for HMM.…”

“…Snap-top cap molecules such as b-cyclodextrin (b-CD) are proposed to be photoresponsive [87], while i-motif quadruplex DNA [101] capped-MSN have been proposed for pH-switchable nanocontainers, as well as metal-latched nanogates [96] that can trap or release molecules upon pH variation from Lewis base chelating groups. Others pH-responsive mechanisms include rhodamine B/benzidine conjugates that act as nanopistons [94] in the cylindrical space of b-CD rings placed around the orifices of the pores, or L-cysteine functionalized gold nanoparticles [78] attached to the MSN surface by ligand bonds through Cu 2?…”