Mesoporous Silica Microparticles Research Articles

Different rheological behaviors of reinforced poly(methylvinylsiloxane) by mesoporous and spherical silica microparticles

To elucidate the mechanism underlying the high performance of mesoporous silica aerogel microparticle (SAG) in reinforcing polymers, the hydrodynamic effect and reinforcement effect of SAG microparticle in Poly-methylvinylsiloxane (PMVS) were investigated. For comparison, regular spherical silica particles (SS) with a comparable particle size and smooth surface were also incorporated into the study as a contrasting filler. It was found that SAG tended to form aggregates with high aspect ratio (shape factor f values between 16-20) and highly branched backbone structures (x = 1.95). However, these aggregates are more loosely packed (df = 1.7) and easily break into smaller flocs under the influence of shear forces. The load-bearing mechanism of the spatial network formed by these aggregates as nodes was akin to physical gels controlled by bond-bending forces (BBFs), with a scaling exponent of G*r with φe-φc of ν = 3.84, close to the theoretical value of the BBFs model. In contrast, the SS particles formed more compact aggregates (f value approximately 1.6) in PMVS, with load-bearing characteristics of the spatial network formed by them closer to chemical gels controlled by central forces (CFs). The scaling exponent of G*r with φe-φc for SS/PMVS was found to be ν = 2.15, close to the theoretical value of the CFs model.

Large-scale production of chiral nematic microspheres.

The membrane emulsification technique enables the self-assembly of cellulose nanocrystals (CNCs) confined within a spherical geometry for large-scale production. The resulting solid microspheres show long-range ordering with chiral nematic structures, and this fascinating hierarchical architecture can even be transferred to mesoporous carbon or silica microparticles by a sacrificial template method.

Chitosan-coated mesoporous silica particles as a plastic-free platform for photochemical suppression and stabilization of organic ultraviolet filters.

Photochemical instability and reactivity of organic ultraviolet (UV) filters not only degrade the performance of sunscreen formulations but also generate toxic photodegradation products and reactive oxygen species (ROS). Although the encapsulation of organic UV filters into synthetic polymer particles has been widely investigated, synthetic plastics were recently banned for personal care and cosmetic products due to marine and coastal pollution issues. Here we present a plastic-free, photochemically stable and inactive UV filter platform based on chitosan-coated mesoporous silica microparticles, denoted 'mSOCPs', incorporating octyl methoxycinnamate (OMC) as a sunscreen agent. Sunlight induced the degradation of ∼80% free OMC in artificial sweat in 1h at room temperature, while only 20% of OMC degraded for 3h when encapsulated within mSOCPs. Moreover, mSOCPs efficiently suppressed the photochemical generation of ROS by about 99% through the combined effects of the mesoporous silica structure and chitosan coating. Accordingly, mSOCPs substantially increased the cell viability of fibroblasts exposed to UV irradiation. This work demonstrates that the biopolymer coatings of mesoporous inorganic particles can be a promising approach to the plastic-free encapsulation of organic UV filters for suppressing their photochemical reactivity and degradation.

PLGA-modified Syloid®-based microparticles for the ocular delivery of terconazole: in-vitro and in-vivo investigations

The eye is an invulnerable organ with intrinsic anatomical and physiological barriers, hindering the development of a pioneer ocular formulation. The aim of this work was to develop an efficient ocular delivery system that can augment the ocular bioavailability of the antifungal drug, terconazole. Mesoporous silica microparticles, Syloid® 244 FP were utilized as the carrier system for terconazole. Preliminary studies were carried out using different drug:Syloid® weight ratios. The optimum weight ratio was mixed with various concentrations (30 and 60%w/w) of poly (lactic-co-glycolic acid) (PLGA), ester or acid-capped and with different monomers-ratio (50:50 and 75:25) using the nano-spray dryer. Results revealed the superiority of drug:Syloid® weight ratio of 1:2 in terms of yield percentage (Y%), SPAN and drug content percentage (DC%). Furthermore, incorporation of PLGA with lower glycolic acid monomer-ratio significantly increased Y%. In contrast, increasing the glycolic acid monomer-ratio resulted in higher DC% and release efficiency percentage (RE%). Additionally, doubling PLGA concentration significantly reduced Y%, DC%, drug loading percentage (DL%) and RE%. Applying desirability function in terms of increasing DC%, DL% besides RE% and decreasing SPAN, the selected formulation was chosen for DSC, XRD and SEM investigations. Results confirmed the successful loading of amorphized terconazole on PLGA-modified Syloid® microparticles. Moreover, pharmacokinetic studies for the chosen formulation on male Albino rabbits’ eyes revealed a 2, 6.7 and 25.3-fold increase in mean residence time, Cmax and AUC0–24-values, respectively, compared to the drug suspension. PLGA-modified Syloid® microparticles represent a potential option to augment the bioavailability of ocular drugs.

Fabrication of Antibacterial, Osteo-Inductor 3D Printed Aerogel-Based Scaffolds by Incorporation of Drug Laden Hollow Mesoporous Silica Microparticles into the Self-Assembled Silk Fibroin Biopolymer.

In this study, the novel biomimetic aerogel-based composite scaffolds through a synergistic combination of wet chemical synthesis and advanced engineering approaches have successfully designed. To this aim, initially the photo-crosslinkable methacrylated silk fibroin (SF-MA) biopolymer and methacrylated hollow mesoporous silica microcapsules (HMSC-MA) as the main constituents of the novel composite aerogels were synthesized. Afterward, by incorporation of drug-loaded HMSC-MA into the self-assembled SF-MA, printable gel-based composite inks are developed. By exploiting micro-extrusion-based three-dimensional (3D) printing, SF-MA-HMSC composite gels are printed by careful controlling their viscosity to provide a means to control the shape fidelity of the resulted printed gel constructs. The developed scaffold has shown a multitude of interesting biophysical and biological performances. Namely, thanks to the photo-crosslinking of the gel components during the 3D printing, the scaffolds become mechanically more stable than the pristine SF scaffolds. Also, freeze-casting the printed constructs generates further interconnectivity in the printed pore struts resulting in the scaffolds with hierarchically organized porosities necessary for cell infiltration and growth. Importantly, HMSC incorporated scaffolds promote antibacterial drug delivery, cellular ingrowth and proliferation, promoting osteoblastic differentiation by inducing the expression of osteogenic markers and matrix mineralization. Finally, the osteoconductive, -inductive, and anti-infective composite aerogels are expected to act as excellent bone implanting materials with an extra feature of local and sustained release of drug for efficient therapy of bone-related diseases.

In vitro toxicological evaluation of mesoporous silica microparticles functionalised with carvacrol and thymol

The cytotoxicity of carvacrol- and thymol-functionalised mesoporous silica microparticles (MCM-41) was assessed in the human hepatocarcinoma cell line (HepG2). Cell viability, lactate dehydrogenase (LDH) activity, reactive oxygen species (ROS) production, mitochondrial membrane potential (ΔΨm), lipid peroxidation (LPO) and apoptosis/necrosis analyses were used as endpoints. The results showed that both materials induced cytotoxicity in a time- and concentration-dependent manner, and were more cytotoxic than free essential oil components and bare MCM-41. This effect was caused by cell-particle interactions and not by degradation products released to the culture media, as demonstrated in the extract dilution assays. LDH release was a less sensitive endpoint than the MTT (thiazolyl blue tetrazolium bromide) assay, which suggests the impairment of the mitochondrial function as the primary cytotoxic mechanism. In vitro tests on specialised cell functions showed that exposure to sublethal concentrations of these materials did not induce ROS formation during 2 h of exposure, but produced LPO and ΔΨm alterations in a concentration-dependent manner when cells were exposed for 24 h. The obtained results generally support the hypothesis that the carvacrol- and thymol-functionalised MCM-41 microparticles induced toxicity in HepG2 cells by an oxidative stress-related mechanism that resulted in apoptosis through the mitochondrial pathway.

Lactose-Gated Mesoporous Silica Particles for Intestinal Controlled Delivery of Essential Oil Components: An In Vitro and In Vivo Study.

Mesoporous silica microparticles functionalized with lactose for the specific release of essential oil components (EOCs) in the small intestine are presented. In vitro and in vivo intestinal models were applied to validate the microparticles (M41-EOC-L), in which the presence of lactase acts as the triggering stimulus for the controlled release of EOCs. Among the different microdevices prepared (containing thymol, eugenol and cinnamaldehyde), the one loaded with cinnamaldehyde showed the most significant Caco-2 cell viability reduction. On the other hand, interaction of the particles with enterocyte-like monolayers showed a reduction of EOCs permeability when protected into the designed microdevices. Then, a microdevice loaded with cinnamaldehyde was applied in the in vivo model of Wistar rat. The results showed a reduction in cinnamaldehyde plasma levels and an increase in its concentration in the lumen of the gastrointestinal tract (GIT). The absence of payload release in the stomach, the progressive release throughout the intestine and the prolonged stay of the payload in the GIT-lumen increased the bioavailability of the encapsulated compound at the site of the desired action. These innovative results, based on the specific intestinal controlled delivery, suggest that the M41-payload-L could be a potential hybrid microdevice for the protection and administration of bioactive molecules in the small intestine and colon.

PH-Dependent Molecular Gate Mesoporous Microparticles for Biological Control of Giardia intestinalis.

Giardiasis is a parasitism produced by the protozoa Giardia intestinalis that lives as trophozoite in the small intestine (mainly in the duodenum) attached to the intestinal villus by means of billed discs. The first line treatment is metronidazole, a drug with high bioavailability, which is why to obtain therapeutic concentrations in duodenum, it is necessary to administer high doses of drug to patients with the consequent occurrence of side effects. It is necessary to developed new therapeutical approaches to achieve a local delivery of the drug. In this sense, we have developed gated mesoporous silica microparticles loaded with metronidazole and with a molecular gate pH dependent. In vitro assays demonstrated that the metronidazole release is practically insignificant at acidic pHs, but in duodenum conditions, the metronidazole delivery from the microparticles is effective enough to produce an important parasite destruction. In vivo assays indicate that this microparticulate system allows to increase the concentration of the drug in duodenum and reduce the concentration in plasma avoiding systemic effects. This system could be useful for other intestinal local treatments in order to reduce doses and increase drug availability in target tissues.

A microparticulate based formulation to protect therapeutic enzymes from proteolytic digestion: phenylalanine ammonia lyase as case study

Phenylketonuria is a genetic disorder affecting the metabolism of phenylalanine (phe) due to a deficiency in the enzyme phenylalanine hydroxylase. This disorder is characterized by an elevated phe blood level, which can lead to severe intellectual disabilities in newborns. The current strategy to prevent these devastating consequences is limited to a life-long phe-free diet, which implies major lifestyle changes and restrictions. Recently, an injectable enzyme replacement therapy, Pegvaliase, has been approved for treating phenylketonuria, but is associated with significant side-effects. In this study a phe-metabolizing system suitable for oral delivery is designed to overcome the need for daily injections. Active phenylalanine ammonia-lyase (PAL), an enzyme that catalyses phe metabolism, is loaded into mesoporous silica microparticles (MSP) with pore sizes ranging from 10 to 35 nm. The surface of the MSP is lined with a semipermeable barrier to allow permeation of phe while blocking digestive enzymes that degrade PAL. The enzymatic activity can be partially preserved in vitro by coating the MSP with poly(allylamine) and poly(acrylic acid)-bowman birk (protease inhibitor) conjugate. The carrier system presented herein may provide a general approach to overcome gastro-intestinal proteolytic digestion and to deliver active enzymes to the intestinal lumen for prolonged local action.

T cell force-responsive delivery of anticancer drugs using mesoporous silica microparticles

A cellular force-responsive platform for controlled release of anticancer drugs.

Towards 99mTc- and Re-Based Multifunctional Silica Platforms for Theranostic Applications

Taking advantage of the radiation properties of 99mTc and 186/188Re and the photophysical characteristics of the {M(CO)3}+ moiety (M = Re), we developed a multifunctional silica platform with the theranostic pair 99mTc/Re with high potential for (nano)medical applications. Starting with a general screening to evaluate the most suitable mesoporous silica construct and the development of appropriate chelate systems, multifunctional mesoporous silica microparticles (SBA-15) were synthesized. These particles act as a model towards the synthesis of the corresponding nanoconstructs. The particles can be modified at the external surface with a targeting function and labeled with the {M(CO)3}+ moiety (M = 99mTc, Re) at the pore surface. Thus, a silica platform is realized, whose bioprofile is not altered by the loaded modalities. The described synthetic procedures can be applied to establish a target-specific theranostic nanoplatform, which enables the combination of fluorescence and radio imaging, with the possibility of radio- and chemotherapy.

Nanoporous Silica of Some Egyptian Diatom Frustules as a Promising Natural Material

Background:Diatoms are a large unique group of unicellular microalgae with a significant ornamented cell wall made of hydrated silica, which is called "frustule". Their ornamented siliceous shells are usually composed of multi-layer structures with multi-scale porosity, which can be used as a promising source to obtain hierarchical macro and mesoporous silica microparticles. The present study is one step forward through a long road seeking for green nanofabrication techniques of such porous materials that will be economically more efficient with large design flexibility.Materials and Methods:For seeking different porosity scales, architectures, and distribution patterns, a total of 237 diatom species and varieties belonging to 68 genera were identified from 59 samples, which were collected from different Egyptian habitats and environments. Of these eight species were selected to study their frustules' ultra-structures in details, including; Aulacoseira granulata (Ehrenberg) Simonsen, Actinocyclus octonarius Ehrenberg, Cyclotella meneghiniana Kützing, Pleurosira laevis (Ehrenberg) Compére, Synedra ulna (Nitzsch) Ehrenberg, Achnanthes brevipes Agardh, Nitzschia amphibia Grunow and Nitzschia palea (Kützing) W. Smith. Nitzschia palea (Kützing) W. Smith was also isolated and cultivated.Results:The ultrastructure and porosity of all studied species had been revealed. The porosity scale was ranged from 5 to 500 nm in diameter.Conclusion:The obtained results showed the potential of diatom frustules in nanotechnology as a source of natural silica microparticles with macro and mesoporous structures could be of a large interest for applications including ultra, micro and nanofiltration, drug delivery systems, optoelectronics, or other novel nanotechnology applications.

Application of Lecithin-templated Mesoporous Silica Microparticles for the Specific and Selective Removal of Phospholipids

Phospholipids are among the many components of algae bio oil, and they harbor the trans-esterification process by poisoning the catalyst, hence the need for they removal prior to this process is crucial. Mesoporous silica materials are feasible and viable candidates for the selective removal of phospholipids by tailoring their surface morphology using different surfactants (templates) for specific and selective adsorption. In this study, the adsorption of phospholipids using lecithin template mesoporous silica microparticles (Leci-MSM) was investigated. Comparative studies using cetyltriammoniumbromide mesoporous microparticles (CTAB-MSM) were also carried out. Both Leci-MSM and CTAB-MSM were synthesized via sol-gel process, packed into mini columns and used for column breakthrough adsorption studies. Scanning electron micrographs revealed a particle size of 5.0 µm for Leci-MSM and 2.95 µm for CTAB-MSM. Textural analysis by BET and BJH exhibited a surface area of 425 and 1210 m2/g for Leci-MSM and CTAB-MSM, respectively. A pore volume of 1.59 and 2.77 cc/g for Leci-MSM and CTAB-MSM, respectively, were also obtained. In addition, Leci-MSM revealed a column breakthrough volume of 28 mL at 41 min, while for the CTAB-MSM was 46 mL at 53 min. The actual adsorption capacity recorded by Leci-MSM was 11.34 mg/g and 8.71 mg/g for CTAB-MSM.

Spray-drying water-based assembly of hierarchical and ordered mesoporous silica microparticles with enhanced pore accessibility for efficient bio-adsorption

The fast and scalable spray-drying-assisted evaporation-induced self-assembly (EISA) synthesis of hierarchically porous SBA-15-type silica microparticles from a water-based system is demonstrated. The SBA-15-type silica microparticles has bowl-like shapes, uniform micro-sizes (∼90 µm), large ordered mesopores (∼9.5 nm), hierarchical meso-/macropores (20–100 nm) and open surfaces. In the synthesis, soft- and hard-templating approaches are combined in a single rapid drying process with a non-ionic tri-block copolymer (F127) and a water-insoluble polymer colloid (Eudragit RS, 120 nm) as the co-templates. The RS polymer colloid plays three important roles. First, the RS nanoparticles can be partially dissolved by in-situ generated ethanol to form RS polymer chains. The RS chains swell and modulate the hydrophilic-hydrophobic balance of F127 micelles to allow the formation of an ordered mesostructure with large mesopore sizes. Without RS, only worm-like mesostructure with much smaller mesopore sizes can be formed. Second, part of the RS nanoparticles plays a role in templating the hierarchical pores distributed throughout the microparticles. Third, part of the RS polymer forms surface “skins” and “bumps”, which can be removed by calcination to enable a more open surface structure to overcome the low pore accessibility issue of spray-dried porous microparticles. The obtained materials have high surface areas (315–510 m2 g−1) and large pore volumes (0.64–1.0 cm3 g−1), which are dependent on RS concentration, HCl concentration, silica precursor hydrolysis time and drying temperature. The representative materials are promising for the adsorption of lysozyme. The adsorption occurs at a >three-fold faster rate, in a five-fold larger capacity (an increase from 20 to 100 mg g−1) and without pore blockage compared with the adsorption of lysozyme onto spray-dried microparticles of similar physicochemical properties obtained without the use of RS.

Anisotropic Hybrid Hydrogels with Superior Mechanical Properties Reminiscent of Tendons or Ligaments

AbstractMimicking the hierarchically anisotropic structure and excellent mechanical properties of natural tissues, such as tendons and ligaments, using biomaterials is challenging. Despite recent achievements with anisotropic hydrogels, limitations remain because of difficulties in achieving both structural and mechanical characteristics simultaneously. A simple approach for fabricating hybrid hydrogels with a hierarchically anisotropic structure and superior mechanical properties that are reminiscent of tendons or ligaments is proposed. Alginate–polyacrylamide double‐network (DN) hydrogels incorporated with high aspect ratio mesoporous silica microparticles are stretched and fixed via subsequent drying and ionic crosslinking to achieve multiscale structures composed of an anisotropically aligned polymer network embedded with aligned microparticles. The mechanical properties of hydrogels can be further controlled by the degree of stretching, quantities, and functional groups of inorganic microparticles, and types of crosslinking cations. The subsequent reswelling results in a high water content (>80%) similar to that of natural tendons while high strength, modulus, and toughness are maintained. The optimized anisotropic hybrid hydrogel exhibits a tensile modulus of 7.2 MPa, strength of 1.3 MPa, and toughness of 1.4 MJ m−3 even in the swollen state, which is 451‐, 27‐, and 2.2 times higher than that observed in the non‐swollen tough DN hydrogel. This study suggests a new strategy for fabricating anisotropic hydrogels with superior mechanical properties to develop new biomaterials for artificial tendons or ligaments.

Double Drug Delivery Using Capped Mesoporous Silica Microparticles for the Effective Treatment of Inflammatory Bowel Disease.

Silica mesoporous microparticles loaded with both rhodamine B fluorophore (S1) or hydrocortisone (S2), and capped with an olsalazine derivative, are prepared and fully characterized. Suspensions of S1 and S2 in water at an acidic and a neutral pH show negligible dye/drug release, yet a notable delivery took place when the reducing agent sodium dithionite is added because of hydrolysis of an azo bond in the capping ensemble. Additionally, olsalazine fragmentation induced 5-aminosalicylic acid (5-ASA) release. In vitro digestion models show that S1 and S2 solids are suitable systems to specifically release a pharmaceutical agent in the colon. In vivo pharmacokinetic studies in rats show a preferential rhodamine B release from S1 in the colon. Moreover, a model of ulcerative colitis is induced in rats by oral administration of 2,4,6-trinitrobenzenesulfonic acid (TNBS) solutions, which was also used to prove the efficacy of S2 for colitis treatment. The specific delivery of hydrocortisone and 5-ASA from S2 material to the colon tissue in injured rats markedly lowers the colon/body weight ratio and the clinical activity score. Histological studies showed a remarkable reduction in inflammation, as well as an intensive regeneration of the affected tissues.

Functionalized Large-Pore Mesoporous Silica Microparticles for Gefitinib and Doxorubicin Codelivery.

Large-pore coralline mesoporous silica microparticles (CMS) were synthesized using the triblock polymer PEG-b-PEO-b-PEG and a hydrothermal method. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the coralline morphology of the fabricated materials. The Brunauer–Emmett–Teller (BET) method and the Barrett–Joyner–Halenda (BJH) model confirmed the existence of large pores (20 nm) and of a tremendous specific surface area (663.865 m2·g−1) and pore volume (0.365 cm3·g−1). A novel pH-sensitive multiamine-chain carboxyl-functionalized coralline mesoporous silica material (CMS–(NH)3–COOH) was obtained via a facile “grafting-to” approach. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR) validated the effective interfacial functionalization of CMS with carboxyl and multiamine chains. The encapsulation and release behavior of the dual drug (gefitinib (GB) and doxorubicin (DOX)) was also investigated. It was found that CMS–(NH)3–COOH allows rapid encapsulation with a high loading capacity of 47.36% for GB and 26.74% for DOX. Furthermore, the release profiles reveal that CMS–(NH)3–COOH can preferably control the release of DOX and GB. The accumulative release rates of DOX and GB were 32.03% and 13.66%, respectively, at a low pH (pH 5.0), while they reduced to 8.45% and 4.83% at pH 7.4. Moreover, all of the modified silica nanoparticles exhibited a high biocompatibility with a low cytotoxicity. In particular, the cytotoxicity of both of these two drugs was remarkably reduced after being encapsulated. CMS–(NH)3–COOH@GB@DOX showed tremendously synergistic effects of the dual drug in the antiproliferation and apoptosis of A549 human cancer cells in vitro.

Efficacy of budesonide-loaded mesoporous silica microparticles capped with a bulky azo derivative in rats with TNBS-induced colitis

A colon targeted drug delivery system for inflammatory bowel diseases (IBD), consisting in budesonide loaded mesoporous silica microparticles functionalized with a selective azo-molecular gate (M-Bud), has been evaluated for in vivo efficacy. Experimental colitis in male Wistar rats was induced by rectal instillation of 2,4,6-trinitrobenzenesulfonic acid (TNBS). M-Bud was orally administered to the rats as a suspension in water. Colon/body weight ratio, clinical activity score, and histological evaluation were used as inflammatory indices to measure the performance of the microparticles. The formulation was compared with a suspension prepared from the commercial drug Entocord®. Statistical analyses of all scores indicate that the controlled release of budesonide in colon from M-Bud showed efficacy similar to that of Entocord in the healing of induced colitis in rats.

Abstract B119: DC-recruiting biomaterial vaccine to enhance antitumor immunity

Abstract Biomaterials have shown substantial potential to integrate synergistically with current cancer vaccine strategies and enhance their effectiveness. We recently developed an injectable biomaterial vaccine via spontaneous assembly of mesoporous silica (MPS) microparticles into a 3D scaffold in vivo. When formulated with GM-CSF and the TLR-9 agonist CpG, the MPS vaccine modulates host dendritic cell (DC) activation and trafficking. Here we demonstrate that a single injection of the MPS vaccine induced persistent germinal center B cell activity for over 30 days. Consequently, when immunized with a small linear Her2/neu peptide within the Trastuzumab binding domain, the MPS vaccine elicited over 2 orders of magnitude higher IgG1 and IgG2a antibody titer compared to a traditional bolus vaccine, and the antibody exhibited immunoreactivity on the native Her2 structure on breast cancer cells. To further enhance CTL responses against tumor antigens, we co-presented the antigen with polyethylenimine (PEI) in the MPS vaccine. PEI increased antigen cross-presentation in murine DCs, and TNF-a and IL-6 production in both murine and human DCs in vitro. Compared to the MPS vaccine, the MPS-PEI vaccine enhanced activated and antigen+ DCs in the vaccine and the vaccine draining lymph node by ~2 fold. Systemically, using both OVA and a HPV-E7 peptide as antigens, the MPS-PEI vaccine induced ~2.5 fold higher IFN-y producing antigen specific circulating CD8+ T-cells compared to the MPS vaccine. Impressively, using a HPV-E7 expressing tumor model, we demonstrated that a single injection of the MPS-PEI vaccine completely eradicated large established tumors in over 80% of mice. Finally, when immunized with a pool of recently sequenced B16 melanoma neoantigen peptides, the MPS-PEI vaccine induced potent therapeutic tumor growth control and synergy with anti-CTLA4 checkpoint blockade therapy. These findings suggest that the MPS vaccine may serve as a facile multifunctional and multi-epitope platform to modulate host immune cell function and augment personalized antitumor immunity. Citation Format: Aileen W. Li, Maxence O. Dellacherie, Miguel Sobral, Omr O. Ali, Jaeyun Kim, David J. Mooney. DC-recruiting biomaterial vaccine to enhance antitumor immunity [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B119.

Mesoporous silica microparticles gated with a bulky azo derivative for the controlled release of dyes/drugs in colon.

Mesoporous silica microparticles were prepared, loaded with the dye safranin O (M-Saf) or with the drug budesonide (M-Bud) and capped by the grafting of a bulky azo derivative. Cargo release from M-Saf at different pH values (mimicking those found in the gastrointestinal tract) in the absence or presence of sodium dithionite (a reducing agent mimicking azoreductase enzyme present in the colon) was tested. Negligible safranin O release was observed at pH 6.8 and 4.5, whereas a moderate delivery at pH 1.2 was noted and attributed to the hydrolysis of the urea bond that linked the azo derivative onto the external surface of the inorganic scaffold. Moreover, a marked release was observed when sodium dithionite was present and was ascribed to the rupture of the azo bond in the molecular gate. Budesonide release from M-Bud in the presence of sodium dithionite was also assessed by ultraviolet-visible spectroscopy and high performance liquid chromatography measurements. In addition, preliminary in vivo experiments with M-Saf carried out in mice indicated that the chemical integrity of the microparticles remained unaltered in the stomach and the small intestine, and safranin O seemed to be released in the colon.