Surface electrochemistry of mesoporous silicas as a key factor in the design of tailored delivery devices

Amorphous stabilization of BCS II drugs using mesoporous silica

This study aimed to investigate the amorphous stabilization of BCS Class II drugs using mesoporous silica as a carrier to produce amorphous solid dispersions. Ibuprofen, fenofibrate, and budesonide were selected as model drugs to evaluate the impact of molecular weight and partition coefficient on the solid state of drug-loaded mesoporous silica (MS) particles. The model drugs were loaded into three grades of MS, SYLYSIA SY730, SYLYSIA SY430, and SYLYSIA SY350, with pore diameters of 2.5 nm, 17 nm, and 21 nm, respectively, at 1:1, 2:1, and 3:1, carrier to drug ratios, and three different loading concentrations using solvent immersion and spray drying techniques. Differential scanning calorimetry (DSC) thermograms of SY430 and SY350 samples exhibited melting point depressions indicating constricted crystallization inside the pores, whereas SY730 samples with melting points matching the pure API may be a result of surface crystallization. Powder x-ray diffraction (PXRD) diffractograms showed all crystalline samples matched the diffraction patterns of the pure API indicating no polymorphic transitions and all 3:1 ratio samples exhibited amorphous halo profiles. Response surface regression analysis and Classification and Regression Tree (CART) analysis suggest carrier to drug ratios, followed by molecular weight, have the most significant impact on the crystallinity of a drug loaded into MS particles.

PGC1α-Inducing Senomorphic Nanotherapeutics Functionalized with NKG2D-Overexpressing Cell Membranes for Intervertebral Disc Degeneration

Cellular senescence is a significant contributor to intervertebral disc aging and degeneration. However, the application of senotherapies, such as senomorphics targeting senescence markers and the senescence-associated secretory phenotype (SASP), remains limited due to challenges in precise delivery. Given that the natural killer group 2D (NKG2D) ligands are increased on the surface of senescent nucleus pulposus (NP) cells, the NKG2D-overexpressing NP cell membranes (NNPm) are constructed, which is expected to achieve a dual targeting effect toward senescent NP cells based on homologous membrane fusion and the NKG2D-mediated immunosurveillance mechanism. Then, mesoporous silica nanoparticles carrying a peroxisome proliferator-activated receptor-ɣ coactivator 1α (PGC1α)inducer (SP) are coated with NNPm (SP@NNPm) and it is found that SP@NNPm selectively targets senescent NP cells, and the SP cores exhibit pH-responsive drug release. Moreover, SP@NNPm effectively induces PGC1α-mediated mitochondrial biogenesis and mitigates senescence-associated markers induced by oxidative stress and the SASP, thereby alleviating puncture-induced senescence and disc degeneration. This dual-targeting nanotherapeutic system represents a novel approach to delivery senomorphics for disc degeneration treatment.

Silica-based nanosystems against antibiotic-resistant bacteria and pathogenic viruses

Today, with the intensity of antibiotic abuse and self-medication, the need for the use of novel systems with high efficiency and biosafety for targeted drug delivery against antibiotic-resistant bacteria and their infections should be highly considered by researchers. Silica-based nanosystems with unique physicochemical properties such as large surface area, tuneable pore diameter, drug loading capacity, controlled particle size/morphology, and good biocompatibility are attractive candidates against antibiotic-resistant bacteria and pathogenic viruses. They can be loaded with antiviral and antimicrobial drugs or molecules through their exclusive internal porous structures or different surface linkers. In this context, smart nanosystems can be produced via suitable surface functionalization/modification with a variety of functional groups to act against different clinical pathogenic microbes or viruses, offering great opportunities for controlling and treating various infections. However, important criteria such as the ability to degrade, biocompatibility, biodegradability, cytotoxicity, stability, clearance from targeted organs should be systematically analysed to develop nanosystems or nanocarriers with high efficiency and multifunctionality. Herein, recent advancements pertaining to the application of silica-based nanosystems against antibiotic-resistant bacteria and pathogenic viruses are deliberated, focussing on important challenges and future perspectives.

A bifunctional zoledronate sustained-release system in scaffold: Tumor therapy and bone repair

It is of great challenges to repair bone defect and prevent tumor recurrence in bone tumors postoperative treatment. Bone scaffolds loaded with zoledronate (ZOL) are expected to solve these issues due to its osteogenesis and anti-tumor ability. Furthermore, ZOL needs to be sustained release to meet the requirement of long-term therapy. In this study, ZOL was loaded into amination functionalized mesoporous silicon (SBA15NH₂), and then incorporated into poly (L-lactic acid) to prepare PLLA/SBA15NH₂-ZOL scaffold via selective laser sintering technology. On one hand, ZOL of local release not only can inhibit growth and proliferation of bone tumor cells but also inhibit osteoclast differentiation through competitive binding of receptor activator of nuclear factor (NF)-kB (RANK) in osteoclast precursors. On the other hand, amination function could change the surface charge of mesoporous silica to positive charge to enhance the absorption of ZOL, mesoporous structure and abundant amino groups of SBA15NH₂ play a barrier role and form hydrogen bond with phosphate groups of ZOL, respectively, thereby achieving its sustained release. The results showed that the loading amount of ZOL was 236.53 mg/g, and the scaffold could sustainedly release ZOL for more than 6 weeks. The scaffold inhibited proliferation of osteosarcoma cells through inducing apoptosis and cell cycle arrest. TRAP staining and F-actin ring formation experiment showed the scaffold inhibited differentiation and mature of osteoclast. Pit formation assay indicated that bone resorption activity was inhibited strongly.

Recent Advances in Mesoporous Silica Nanoparticle-Mediated Drug Delivery for Breast Cancer Treatment

Breast cancer (BC) currently occupies the second rank in cancer-related global female deaths. Although consistent awareness and improved diagnosis have reduced mortality in recent years, late diagnosis and resistant response still limit the therapeutic efficacy of chemotherapeutic drugs (CDs), leading to relapse with consequent invasion and metastasis. Treatment with CDs is indeed well-versed but it is badly curtailed with accompanying side effects and inadequacies of site-specific drug delivery. As a result, drug carriers ensuring stealth delivery and sustained drug release with improved pharmacokinetics and biodistribution are urgently needed. Core-shell mesoporous silica nanoparticles (MSNPs) have recently been a cornerstone in this context, attributed to their high surface area, low density, robust functionalization, high drug loading capacity, size-shape-controlled functioning, and homogeneous shell architecture, enabling stealth drug delivery. Recent interest in using MSNPs as drug delivery vehicles has been due to their functionalization and size-shape-driven versatilities. With such insights, this article focuses on the preparation methods and drug delivery mechanisms of MSNPs, before discussing their emerging utility in BC treatment. The information compiled herein could consolidate the database for using inorganic nanoparticles (NPs) as BC drug delivery vehicles in terms of design, application and resolving post-therapy complications.

Development of Proanthocyanidin-Loaded Mesoporous Silica Nanoparticles for Improving Dental Adhesion

Dentin biomodification is a promising approach to enhance dental tissue biomechanics and biostability for restorative and reparative therapies. One of the most active dentin tissue biomodifiers is proanthocyanidin (PAC)-rich natural extracts, which are used in the dental bonding procedure in combination with resin-based adhesives (RBAs). This study aimed to investigate the use of mesoporous silica nanoparticles (MSNs) for the sustained delivery of PACs for dentin biomodification as a novel drug-delivery system for dental applications. The effects of the incorporation of MSN functionalized with 3-aminopropyltriethoxysilane (APTES) and loaded with PAC into an experimental RBA were assessed by characterizing the material mechanical properties. In addition, the immediate and long-term bonding performance of an experimental resin-based primer (RBP) containing MSN-APTES loaded with PAC was also evaluated. For that, different formulations of RBA and RBP were prepared containing 20% w/v MSN-APTES loaded with PAC before or after functionalization (MSN-PAC-APTES and MSN-APTES-PAC, respectively). The incorporation of MSN-APTES-PAC did not negatively impact the degree of conversion or the overall mechanical properties of the RBA. However, adding MSN-PAC-APTES resulted in inferior mechanical properties of the experimental RBA. In the adhesion studies, APTES-functionalized MSN was successfully added to an experimental RBP for drug-delivery purposes without compromising the bond strength to the dentin or the failure mode. Interestingly, the sequence of surface functionalization with APTES resulted in differences in the bonding performance, with better long-term results for RBP containing MSN loaded with PAC after functionalization.

Structural insights into the binding of zoledronic acid with RANKL via computational simulations

Zoledronic acid (ZOL) inhibits receptor activator of nuclear factor-κB ligand (RANKL) and reduces bone turnover. This plays an important role in the development of bisphosphonate-related osteonecrosis of the jaw (BRONJ). Previous reports have shown that ZOL binds to the enzyme farnesyl pyrophosphate synthase (FPPS) to block its activity. However, the mechanism of action of ZOL and its interaction with RANKL is still unclear. In this study, we confirmed that ZOL significantly suppressed the bone remodeling in ZOL-treated rats, investigated whether ZOL could bind to RANKL and examined the interactions between these molecules at the atomic level. Surface plasmon resonance (SPR) assay was performed to validate that ZOL could directly bind to RANKL in a dose dependent manner, and the equilibrium constant was calculated (K_D = 2.28 × 10⁻⁴ M). Then, we used molecular docking simulation to predict the binding site and analyze the binding characteristics of ZOL and RANKL. Through molecular dynamics simulation, we confirmed the stable binding between ZOL and RANKL and observed their dynamic interactions over time. Binding free energy calculations and its decomposition were conducted to obtain the binding free energy −70.67 ± 2.62 kJ/mol for the RANKL–ZOL complex. We identified the key residues of RANKL in the binding region, and these included Tyr217(A), Val277(A), Gly278(A), Val277(B), Gly278(B), and Tyr215(C). Taken together, our results demonstrated the direct interaction between ZOL and RANKL, indicating that the pharmacological action of ZOL might be closely related to RANKL. The design of novel small molecules targeting RANKL might reduce the occurrence of BRONJ.

Characterization of a Mesoporous Silica Nanoparticle Formulation Loaded with Mitomycin C Lipidic Prodrug (MLP) and In Vitro Comparison with a Clinical-Stage Liposomal Formulation of MLP

Nanomedicines have revolutionized the treatment of certain types of cancer, as is the case of doxil, liposomal formulation with doxorubicin encapsulated, in the treatment of certain types of ovarian cancer, AIDS-related Kaposi sarcoma, and multiple myeloma. These nanomedicines can improve the performance of conventional chemotherapeutic treatments, with fewer side effects and better efficiency against cancer. Although liposomes have been used in some formulations, different nanocarriers with better features in terms of stability and adsorption capabilities are being explored. Among the available nanoparticles in the field, mesoporous silica nanoparticles (MSNP) have attracted great attention as drug delivery platforms for the treatment of different diseases. Here, a novel formulation based on MSNP loaded with a potent antitumor prodrug that works in vitro as well as in a clinically evaluated liposomal formulation has been developed. This novel formulation shows excellent prodrug encapsulation efficiency and effective release of the anticancer drug only under certain stimuli typical of tumor environments. This behavior is of capital importance for translating this nanocarrier to the clinic in the near future.

Engineering mesoporous silica nanoparticles for drug delivery: where are we after two decades?

The present review details a chronological description of the events that took place during the development of mesoporous materials, their different synthetic routes and their use as drug delivery systems. The outstanding textural properties of these materials quickly inspired their translation to the nanoscale dimension leading to mesoporous silica nanoparticles (MSNs). The different aspects of introducing pharmaceutical agents into the pores of these nanocarriers, together with their possible biodistribution and clearance routes, would be described here. The development of smart nanocarriers that are able to release a high local concentration of the therapeutic cargo on-demand after the application of certain stimuli would be reviewed here, together with their ability to deliver the therapeutic cargo to precise locations in the body. The huge progress in the design and development of MSNs for biomedical applications, including the potential treatment of different diseases, during the last 20 years will be collated here, together with the required work that still needs to be done to achieve the clinical translation of these materials. This review was conceived to stand out from past reports since it aims to tell the story of the development of mesoporous materials and their use as drug delivery systems by some of the story makers, who could be considered to be among the pioneers in this area.

Superparamagnetic Iron Oxide Nanoparticles Decorated Mesoporous Silica Nanosystem for Combined Antibiofilm Therapy

A crucial challenge to face in the treatment of biofilm-associated infection is the ability of bacteria to develop resistance to traditional antimicrobial therapies based on the administration of antibiotics alone. This study aims to apply magnetic hyperthermia together with controlled antibiotic delivery from a unique magnetic-responsive nanocarrier for a combination therapy against biofilm. The design of the nanosystem is based on antibiotic-loaded mesoporous silica nanoparticles (MSNs) externally functionalized with a thermo-responsive polymer capping layer, and decorated in the outermost surface with superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs are able to generate heat upon application of an alternating magnetic field (AMF), reaching the temperature needed to induce a change in the polymer conformation from linear to globular, therefore triggering pore uncapping and the antibiotic cargo release. The microbiological assays indicated that exposure of E. coli biofilms to 200 µg/mL of the nanosystem and the application of an AMF (202 kHz, 30 mT) decreased the number of viable bacteria by 4 log10 units compared with the control. The results of the present study show that combined hyperthermia and antibiotic treatment is a promising approach for the effective management of biofilm-associated infections.

A versatile multicomponent mesoporous silica nanosystem with dual antimicrobial and osteogenic effects

In this manuscript, we propose a simple and versatile methodology to design nanosystems based on biocompatible and multicomponent mesoporous silica nanoparticles (MSNs) for infection management. This strategy relies on the combination of antibiotic molecules and antimicrobial metal ions into the same nanosystem, affording a significant improvement of the antibiofilm effect compared to that of nanosystems carrying only one of these agents. The multicomponent nanosystem is based on MSNs externally functionalized with a polyamine dendrimer (MSN-G3) that favors internalization inside the bacteria and allows the complexation of multiactive metal ions (MSN-G3-Mⁿ⁺). Importantly, the selection of both the antibiotic and the cation may be done depending on clinical needs. Herein, levofloxacin and Zn²⁺ ion, chosen owing to both its antimicrobial and osteogenic capability, have been incorporated. This dual biological role of Zn²⁺ could have and adjuvant effect thought destroying the biofilm in combination with the antibiotic as well as aid to the repair and regeneration of lost bone tissue associated to osteolysis during infection process. The versatility of the nanosystem has been demonstrated incorporating Ag⁺ ions in a reference nanosystem. In vitro antimicrobial assays in planktonic and biofilm state show a high antimicrobial efficacy due to the combined action of levofloxacin and Zn²⁺, achieving an antimicrobial efficacy above 99% compared to the MSNs containing only one of the microbicide agents. In vitro cell cultures with MC3T3-E1 preosteoblasts reveal the osteogenic capability of the nanosystem, showing a positive effect on osteoblastic differentiation while preserving the cell viability. STATEMENT OF SIGNIFICANCE: A simple and versatile methodology to design biocompatible and multicomponent MSNs based nanosystems for infection management is proposed. These nanosystems, containing two antimicrobial agents, levofloxacin and Zn²⁺, have been synthetized by external functionalization of MSNs with a polycationic dendrimer (MSNs-G3), which favours its internalization inside the bacteria and lead the complexation with metal ions through the amines of the dendrimer. The nanosystems offer a notable improvement of the antibiofilm effect (above 99%) than both components separately as well as osteogenic capability with positive effect on the osteoblastic differentiation and preserved cell viability.

Nanoantibiotics Based in Mesoporous Silica Nanoparticles: New Formulations for Bacterial Infection Treatment

This review focuses on the design of mesoporous silica nanoparticles for infection treatment. Written within a general context of contributions in the field, this manuscript highlights the major scientific achievements accomplished by professor Vallet-Regí's research group in the field of silica-based mesoporous materials for drug delivery. The aim is to bring out her pivotal role on the envisage of a new era of nanoantibiotics by using a deep knowledge on mesoporous materials as drug delivery systems and by applying cutting-edge technologies to design and engineer advanced nanoweapons to fight infection. This review has been divided in two main sections: the first part overviews the influence of the textural and chemical properties of silica-based mesoporous materials on the loading and release of antibiotic molecules, depending on the host-guest interactions. Furthermore, this section also remarks on the potential of molecular modelling in the design and comprehension of the performance of these release systems. The second part describes the more recent advances in the use of mesoporous silica nanoparticles as versatile nanoplatforms for the development of novel targeted and stimuli-responsive antimicrobial nanoformulations for future application in personalized infection therapies.

Adsorption and Release of Sulfamethizole from Mesoporous Silica Nanoparticles Functionalised with Triethylenetetramine

Mesoporous silica nanoparticles (MSN) were synthesised and functionalised with triethylenetetramine (MSN-TETA). The samples were fully characterised (transmission electron microscopy, small angle X-ray scattering, Fourier transform infrared spectroscopy, thermogravimetric analysis, zeta potential and nitrogen adsorption/desorption isotherms) and used as carriers for the adsorption of the antimicrobial drug sulphamethizole (SMZ). SMZ loading, quantified by UV-Vis spectroscopy, was higher on MSN-TETA (345.8 mg g-1) compared with bare MSN (215.4 mg g-1) even in the presence of a lower surface area (671 vs. 942 m2 g-1). The kinetics of SMZ adsorption on MSN and MSN-TETA followed a pseudo-second-order model. The adsorption isotherm is described better by a Langmuir model rather than a Temkin or Freundlich model. Release kinetics showed a burst release of SMZ from bare MSN samples (k1 = 136 h-1) in contrast to a slower release found with MSN-TETA (k1 = 3.04 h-1), suggesting attractive intermolecular interactions slow down SMZ release from MSN-TETA. In summary, the MSN surface area did not influence SMZ adsorption and release. On the contrary, the design of an effective drug delivery system must consider the intermolecular interactions between the adsorbent and the adsorbate.

Comparative release kinetics of small drugs (ibuprofen and acetaminophen) from multifunctional mesoporous silica nanoparticles

Multifunctional mesoporous silica nanoparticles (MSNs) can confer dynamically varied release kinetics depending on the intermolecular interactions between model drugs and functional decorations on the MSNs. Herein, brush-like fluorescent conjugates were grafted on the pore walls of pristine MSNs for high drug loading and to impart fluorescence properties. The fluorescent MSNs (FMSNs) were further coated with polydopamine (PDA) and graphene oxide (GO) double layer, designated FMSNs@PDA and FMSNs@PDA@GO, respectively. The FMSNs@PDA@GO exhibited highly consistent drug release over one week (∼7 days) because of the consolidated PDA/GO double layer at neutral pH (7.4). However, the release rate of FMSN-Ibu@PDA@GO was increased at acidic pH (5.5) because the PDA/GO double layer was partially disrupted due to weakened π-π stacking and electrostatic interactions. The release kinetics of the FMSNs-based NPs (FMSNs, FMSNs@PDA, and FMSNs@PDA@GO) were systematically investigated using negatively charged hydrophobic ibuprofen and neutral hydrophilic acetaminophen at pH 7.4. In the FMSN-drug system, the release rate of acetaminophen was higher than that of ibuprofen because of the higher solubility of acetaminophen in aqueous solution. In addition, ibuprofen has a bulky molecular structure compared to acetaminophen, leading to its slower transmission through the porous channels of FMSNs. In the FMSNs-drug@PDA system, acetaminophen exhibited a slower release rate than ibuprofen, owing to the π-π stacking interactions in the transmission of neutral acetaminophen by the PDA coating layer. On the other hand, the FMSNs-drug@PDA@GO exhibited a slower ibuprofen release rate than acetaminophen, owing to the electrostatic repulsion effect of the negative GO layer. Our drug delivery system was demonstrated as an advanced delivery platform, in which the transmission rate is controlled by intermolecular interactions between the diffusing drugs and functional decorations on the nanocarrier.

Impact of the antibiotic-cargo from MSNs on Gram-positive and Gram-negative bacterial biofilms

Mesoporous silica nanoparticles (MSNs) are promising drug nanocarriers for infection treatment. Many investigations have focused on evaluating the capacity of MSNs to encapsulate antibiotics and release them in a controlled fashion. However, little attention has been paid to determine the antibiotic doses released from these nanosystems that are effective against biofilm during the entire release time. Herein, we report a systematic and quantitative study of the direct effect of the antibiotic-cargo released from MSNs on Gram-positive and Gram-negative bacterial biofilms. Levofloxacin (LVX), gentamicin (GM) and rifampin (RIF) were separately loaded into pure-silica and amino-modified MSNs. This accounts for the versatility of these nanosystems since they were able to load and release different antibiotic molecules of diverse chemical nature. Biological activity curves of the released antibiotic were determined for both bacterial strains, which allowed to calculate the active doses that are effective against bacterial biofilms. Furthermore, in vitro biocompatibility assays on osteoblast-like cells were carried out at different periods of times. Albeit a slight decrease in cell viability was observed at the very initial stage, due to the initial burst antibiotic release, the biocompatibility of these nanosystems is evidenced since a recovery of cell viability was achieved after 72 h of assay. Biological activity curves for GM released from MSNs exhibited sustained patterns and antibiotic doses in the 2-6 μg/mL range up to 100 h, which were not enough to eradicate biofilm. In the case of LVX and RIF first-order kinetics featuring an initial burst effect followed by a sustained release above the MIC up to 96 h were observed. Such doses reduced by 99.9% bacterial biofilm and remained active up to 72 h with no emergence of bacterial resistance. This pioneering research opens up promising expectations in the design of personalized MSNs-based nanotherapies to treat chronic bone infection.

Delivery of Natural Agents by Means of Mesoporous Silica Nanospheres as a Promising Anticancer Strategy

Natural prodrugs derived from different natural origins (e.g., medicinal plants, microbes, animals) have a long history in traditional medicine. They exhibit a broad range of pharmacological activities, including anticancer effects in vitro and in vivo. They have potential as safe, cost-effective treatments with few side effects, but are lacking in solubility, bioavailability, specific targeting and have short half-lives. These are barriers to clinical application. Nanomedicine has the potential to offer solutions to circumvent these limitations and allow the use of natural pro-drugs in cancer therapy. Mesoporous silica nanoparticles (MSNs) of various morphology have attracted considerable attention in the search for targeted drug delivery systems. MSNs are characterized by chemical stability, easy synthesis and functionalization, large surface area, tunable pore sizes and volumes, good biocompatibility, controlled drug release under different conditions, and high drug-loading capacity, enabling multifunctional purposes. In vivo pre-clinical evaluations, a significant majority of results indicate the safety profile of MSNs if they are synthesized in an optimized way. Here, we present an overview of synthesis methods, possible surface functionalization, cellular uptake, biodistribution, toxicity, loading strategies, delivery designs with controlled release, and cancer targeting and discuss the future of anticancer nanotechnology-based natural prodrug delivery systems.

Mesoporous Silica Nanoparticles as a Potential Platform for Vaccine Development against Tuberculosis

The increasing emergence of new strains of Mycobacterium tuberculosis (Mtb) highly resistant to antibiotics constitute a public health issue, since tuberculosis still constitutes the primary cause of death in the world due to bacterial infection. Mtb has been shown to produce membrane-derived extracellular vesicles (EVs) containing proteins responsible for modulating the pathological immune response after infection. These natural vesicles were considered a promising alternative to the development of novel vaccines. However, their use was compromised by the observed lack of reproducibility between preparations. In this work, with the aim of developing nanosystems mimicking the extracellular vesicles produced by Mtb, mesoporous silica nanoparticles (MSNs) have been used as nanocarriers of immunomodulatory and vesicle-associated proteins (Ag85B, LprG and LprA). These novel nanosystems have been designed and extensively characterized, demonstrating the effectiveness of the covalent anchorage of the immunomodulatory proteins to the surface of the MSNs. The immunostimulatory capacity of the designed nanosystems has been demonstrated by measuring the levels of pro- (TNF) and anti-inflammatory (IL-10) cytokines in exposed macrophages. These results open a new possibility for the development of more complex nanosystems, including additional vesicle components or even antitubercular drugs, thus allowing for the combination of immunomodulatory and bactericidal effects against Mtb.

Biomimicked and CPMV-Imprinted Hollow Porous Zinc Phosphate Nanocapsules and Their Therapeutic Efficiency

Hollow zinc phosphate nanocapsules (hZPNCs) are an alloplastic biomaterial that has been synthesized to deliver chemotherapeutic drugs in a sustained manner. A very simple one-pot synthesis approach has been employed to synthesize hZPNCs by using cowpea mosaic virus (CPMV) in the presence of phosphate buffer (PBS) (0.01 M PBS, pH ∼7.2) with zinc acetate precursor. The synthesis mechanism of hZPNCs relies on the basis of biomineralization, where the precursor molecules initiate mineralization with the help of amino acid residues present on the CPMV capsid. The synthesized hollow nanocapsules were of diameter ∼50-60 nm and porous shell with thickness of ∼4 nm. The cavity performed as a reservoir for the anticancer drugs (DOX and IM). The release kinetic studies show the positive aspect of hZPNCs to be labeled as drug delivery cargo for sustained delivery. In vitro cytotoxic studies of hZPNCs and hZPNCs-chemo drugs on HEK293, HEPG2, and K562 cells were performed. The cytotoxic studies show that hZPNCs-DOX and hZPNCs-IM arrest the cell cycle of carcinoma cells (HEPG2 and K562 cells) at relatively low IC₅₀ and that the inhibition efficiency is dosage dependent. Furthermore, through HRTEM, in vitro cellular interactions of carcinoma cells with hZPNCs and chemo drug-loaded hZPNCs were confirmed by the cryo-sectioning of cells before and after the incubation. These studies revealed the likely endocytic pathway for the nanocapsules entering the cell and executing the specific action of delivering the anticancer drugs. Together, these results reveal the hZPNCs as potential sustained drug delivery agents.

Synthesis and characterization of a modified surface of SBA-15 mesoporous silica for a chloramphenicol drug delivery system

In this work, the potential of the modified SBA-15 surface was examined as a sorbent to load the drug from an aqueous solution; this was done using a post-synthesis function procedure. Several means were used to identify the material characterization before and after functionalization, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface area, Fourier transform infrared (FTIR) spectroscopy and thermal gravimetric analysis (TGA). To obtain the effect of different variables on the efficacy of chloramphenicol drug load, batch adsorption experiments have been performed in a single adsorption system. These variables were the dosage of NH₂-SBA-15 (10–120) mg, contact time (0–72 h) and initial concentration (10–120 mg/L). The results of these experiments showed the significant and active effect of the functional amino group in increasing the drug's load capacity. The results of these experiments showed that the functional amino group had a significant and active effect in increasing the drug's capacity. Also, the loading capacity is inversely proportional to the initial concentration, but directly proportional to the NH₂-SBA-15 dose and contact time. The best results at 1 hour for the release were 41%. It was found that the load efficiency of chloramphenicol was 51%.

Mixed-charge pseudo-zwitterionic mesoporous silica nanoparticles with low-fouling and reduced cell uptake properties

The design of drug delivery systems needs to consider biocompatibility and host body recognition for an adequate actuation. In this work, mesoporous silica nanoparticles (MSNs) surfaces were successfully modified with two silane molecules to provide mixed-charge brushes (-NH3⊕/-PO3⊝) and well evaluated in terms of surface properties, low-fouling capability and cell uptake in comparison to PEGylated MSNs. The modification process consists in the simultaneous direct-grafting of hydrolysable short chain amino (aminopropyl silanetriol, APST) and phosphonate-based (trihydroxy-silyl-propyl-methyl-phosphonate, THSPMP) silane molecules able to provide a pseudo-zwitterionic nature under physiological pH conditions. Results confirmed that both mixed-charge pseudo-zwitterionic MSNs (ZMSN) and PEG-MSN display a significant reduction of serum protein adhesion and macrophages uptake with respect to pristine MSNs. In the case of ZMSNs, this reduction is up to a 70-90% for protein adsorption and c.a. 60% for cellular uptake. This pseudo-zwitterionic modification has been focused on the aim of local treatment of bacterial infections through the synergistic effect between the inherent antimicrobial effect of mixed-charge system and the levofloxacin antibiotic release profile. These findings open promising future expectations for the effective treatment of bacterial infections through the use of mixed-charge pseudo-zwitterionic MSNs furtive to macrophages and with antimicrobial properties. STATEMENT OF SIGNIFICANCE: Herein a novel antimicrobial mixed-charge pseudo-zwitterionic MSNs based system with low-fouling and reduced cell uptake behavior has been developed. This chemical modification has been performed by the simultaneous grafting of short chain organosilanes, containing amino and phosphonate groups, respectively. This nanocarrier has been tested for local infection treatment through the synergy between the antimicrobial effect of mixed-charge brushes and the levofloxacin antibiotic release profile.

Mesoporous Silica Nanoparticles: A Comprehensive Review on Synthesis and Recent Advances

Recent advancements in drug delivery technologies utilizing a variety of carriers have resulted in a path-breaking revolution in the approach towards diagnosis and therapy alike in the current times. Need for materials with high thermal, chemical and mechanical properties have led to the development of mesoporous silica nanoparticles (MSNs). These ordered porous materials have garnered immense attention as drug carriers owing to their distinctive features over the others. They can be synthesized using a relatively simple process, thus making it cost effective. Moreover, by controlling the parameters during the synthesis; the morphology, pore size and volume and particle size can be transformed accordingly. Over the last few years, a rapid increase in research on MSNs as drug carriers for the treatment of various diseases has been observed indicating its potential benefits in drug delivery. Their widespread application for the loading of small molecules as well as macromolecules such as proteins, siRNA and so forth, has made it a versatile carrier. In the recent times, researchers have sorted to several modifications in the framework of MSNs to explore its potential in drug resistant chemotherapy, antimicrobial therapy. In this review, we have discussed the synthesis of these multitalented nanoparticles and the factors influencing the size and morphology of this wonder carrier. The second part of this review emphasizes on the applications and the advances made in the MSNs to broaden the spectrum of its use especially in the field of biomedicine. We have also touched upon the lacunae in the thorough understanding of its interaction with a biological system which poses a major hurdle in the passage of this carrier to the clinical level. In the final part of this review, we have discussed some of the major patents filed in the field of MSNs for therapeutic purpose.

Mesoporous silica nanoparticles decorated with polycationic dendrimers for infection treatment

This work aims to provide an effective and novel solution for the treatment of infection by using nanovehicles loaded with antibiotics capable of penetrating the bacterial wall, thus increasing the antimicrobial effectiveness. These nanosystems, named "nanoantibiotics", are composed of mesoporous silica nanoparticles (MSNs), which act as nanocarriers of an antimicrobial agent (levofloxacin, LEVO) localized inside the mesopores. To provide the nanosystem of bacterial membrane interaction capability, a polycationic dendrimer, concretely the poly(propyleneimine) dendrimer of third generation (G3), was covalently grafted to the external surface of the LEVO-loaded MSNs. After physicochemical characterization of this nanoantibiotic, the release kinetics of LEVO and the antimicrobial efficacy of each released dosage were evaluated. Besides, internalization studies of the MSNs functionalized with the G3 dendrimer were carried out, showing a high penetrability throughout Gram-negative bacterial membranes. This work evidences that the synergistic combination of polycationic dendrimers as bacterial membrane permeabilization agents with LEVO-loaded MSNs triggers an efficient antimicrobial effect on Gram-negative bacterial biofilm. These positive results open up very promising expectations for their potential application in new infection therapies.

STATEMENT OF SIGNIFICANCE

Seeking new alternatives to current available treatments of bacterial infections represents a great challenge in nanomedicine. This work reports the design and optimization of a new class of antimicrobial agent, named "nanoantibiotic", based on mesoporous silica nanoparticles (MSNs) decorated with polypropyleneimine dendrimers of third generation (G3) and loaded with levofloxacin (LEVO) antibiotic. The covalently grafting of these G3 dendrimers to MSNs allows an effective internalization in Gram-negative bacteria. Furthermore, the LEVO loaded into the mesoporous cavities is released in a sustained manner at effective antimicrobial dosages. The novelty and originality of this manuscript relies on proving that the synergistic combination of bacteria-targeting and antimicrobial agents into a unique nanosystem provokes a remarkable antimicrobial effect against bacterial biofilm.

Bifunctional Cage-Type Cubic Mesoporous Silica SBA-1 Nanoparticles for Selective Adsorption of Dyes

Bifunctional SBA-1 mesoporous silica nanoparticles (MSNs) with carboxylic acid and amino groups (denoted as CNS-10-10) have been successfully synthesized, characterized, and employed as adsorbents for dye removal. Adsorbent CNS-10-10 shows high affinity towards cationic and anionic dyes in a wide pH range, and exhibits selective dye removal of a two-dye mixture system of cationic methylene blue and anionic eosin Y. By changing the pH of the medium, the selectivity of the adsorption behavior can be easily modulated. For comparison purposes, the counterparts, that is, pure silica SBA-1 MSNs (CS-0) and those with either carboxylic acid or amino functional groups (denoted as CS-10 and NS-10, respectively) were also prepared to evaluate their dye-adsorption behaviors. As revealed by the zeta-potential measurements, the electrostatic interaction between the adsorbent surface and the dye molecule plays an important role in the adsorption mechanism. Adsorbent CNS-10-10 can be easily regenerated and reused, and maintains its adsorption efficiency up to 80 % after four cycles.

Adsorption and release of ampicillin antibiotic from ordered mesoporous silica

In this work the adsorption and the release of ampicillin - a β-lactam penicillin-like antibiotic - from MCM-41, SBA-15, and (amino functionalized) SBA-15-NH₂ ordered mesoporous silica (OMS) materials were investigated. The silica matrices differ for their pore size (SBA-15 vs. MCM-41) mainly, and also for surface charge (SBA-15 and MCM-41, vs. SBA-15-NH₂). OMS samples were characterized through small-angle X-rays scattering (SAXS), transmission electron microscopy (TEM), N₂ adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and potentiometric titrations. The quantification of immobilized and released ampicillin was monitored by mean of UV-Vis spectroscopy. Experimental adsorption isotherms evidenced that ampicillin's loading is not related to the pore size (d_BJH) of the adsorbent. Indeed the maximal loadings were 237mg/g for SBA-15 (d_BJH=6.5nm), 278mg/g for MCM-41 (d_BJH=2.2nm), and 333mg/g for SBA-15-NH₂ (d_BJH=5.6nm). Loading seems, instead, to be related to the surface charge density (σ) of the sorbent surface. Indeed, at pH 7.4 ampicillin drug is negatively charged and likely prefers to interact with SBA-15-NH₂ (σ_SBA-15-NH2=+0.223Cm^-2) rather than the slightly negatively charged silicas (σ_SBA-15=-0.044Cm^-2 and σ_MCM-41=-0.033Cm^-2). Similarly, ampicillin release is affected by interfacial interactions. Indeed, we found a burst release from pure silica samples (SBA-15 and MCM-41), whereas a sustained one from SBA-15-NH₂ sample. We explain this behavior as a result of an attractive interaction between the protonated amino group of SBA-15-NH₂ and the negatively charged carboxylate group of ampicillin. In summary, in order to obtain a sustained drug release, the chemical nature of the matrix's surface plays a role which is more important than its textural features. SBA-15-NH₂ matrix is hence a suitable candidate for local sustained release of antibiotic drugs.

Functionalized Silica Nanoparticles As an Alternative Platform for Targeted Drug-Delivery of Water Insoluble Drugs

The selective action of drugs in tumor cells is a major problem in cancer therapy. Most chemotherapy drugs act nonspecifically and damage both cancer and healthy cells causing various side effects. In this study, the preparation of a selective drug delivery system, which is able to act as a carrier for hydrophobic and anticancer drugs is reported. Amino-functionalized silica nanoparticles loaded with curcumin were successfully synthesized via sol-gel approach and duly characterized. Thereafter, the targeting ligand, folate, was covalently attached to amino groups of nanoparticle surface through amide bond formation. The cytotoxic effect of nanoparticles on prostate cancer cells line was evaluated and compared to normal cells line (prostate epithelial cell). Cytotoxicity experiments demonstrated that folate-functionalized nanoparticles were significantly cytotoxic to tumor cells, whereas normal cells were much less affected by the presence of these structures.

Controllable morphology transition from vesicular to worm-like to vesicular multilamellar mesoporous silica induced by β-cyclodextrin

Morphological changes of mesoporous silica from vesicular to worm-like to vesicular multilamellar were induced by adding appropriate amounts of β-CD to mixed CTAB/DDAB surfactant aggregates.

Silaffins in Silica Biomineralization and Biomimetic Silica Precipitation

Biomineralization processes leading to complex solid structures of inorganic material in biological systems are constantly gaining attention in biotechnology and biomedical research. An outstanding example for biomineral morphogenesis is the formation of highly elaborate, nano-patterned silica shells by diatoms. Among the organic macromolecules that have been closely linked to the tightly controlled precipitation of silica in diatoms, silaffins play an extraordinary role. These peptides typically occur as complex posttranslationally modified variants and are directly involved in the silica deposition process in diatoms. However, even in vitro silaffin-based peptides alone, with and without posttranslational modifications, can efficiently mediate biomimetic silica precipitation leading to silica material with different properties as well as with encapsulated cargo molecules of a large size range. In this review, the biomineralization process of silica in diatoms is summarized with a specific focus on silaffins and their in vitro silica precipitation properties. Applications in the area of bio- and nanotechnology as well as in diagnostics and therapy are discussed.

Fabrication of mesoporous silica nanospheres with radially oriented mesochannels by microemulsion templating for adsorption and controlled release of aspirin

The MSN spheres with narrow size distribution and radially oriented mesoporous channels were prepared using an O/W microemulsion system, consisting of CTAB (or PVP), ethanol, cyclohexane and water as template.

Effects of functional groups on the structure, physicochemical and biological properties of mesoporous bioactive glass scaffolds

Functionalization of biomaterials with specific functional groups is one of the most straightforward strategies to induce specific cell responses to biomaterials.

Adsorption of lysozyme on hyaluronic acid functionalized SBA-15 mesoporous silica: a possible bioadhesive depot system

Silica-based ordered mesoporous materials are very attractive matrices to prepare smart depot systems for several kinds of therapeutic agents. This work focuses on the well-known SBA-15 mesoporous silica and lysozyme, an antimicrobial protein. In order to improve the bioadhesion properties of SBA-15 particles, the effect of hyaluronic acid (HA) functionalization on lysozyme adsorption was investigated. SBA-15 samples having high (H-SBA) and low (L-SBA) levels of functionalization were analyzed during the three steps of the preparations: (1) introduction of the -NH2 groups to obtain the SBA-NH2 samples; (2) functionalization with HA to obtain the SBA-HA matrices; (3) adsorption of lysozyme. All silica matrices were characterized through N2-adsorption/desorption isotherms, small-angle X-ray scattering, transmission electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The whole of the experimental data suggests that a high level of functionalization of the silica surface allows for a negligible lysozyme adsorption mainly due to unfavorable electrostatic interactions (H-SBA-NH2) or steric hindrance (H-SBA-HA). A low degree of functionalization of the silica surface brings about a very good performance toward lysozyme adsorption, being 71% (L-SBA-NH2) and 63% (L-SBA-HA) respectively, compared to that observed for original SBA-15. Finally, two different kinetic models--a "pseudo-second order" and a "intraparticle diffusion"--were compared to fit lysozyme adsorption data, the latter being more reliable than the former.

Confinement effects on drugs in thermally hydrocarbonized porous silicon

Thermally hydrocarbonized porous silicon (THCPSi) microparticles were loaded with indomethacin (IMC) and griseofulvin (GSV) using three different payloads between 6.2-19.5 and 6.2-11.4 wt %, respectively. The drug loading parameters were selected to avoid crystallization of the drug molecules on the external surface of the particles that would block the pore entrances. The successfulness of the loadings was verified with TG, DSC, and XRPD measurements. The effects of the confinement of IMC and GSV into the small mesopores of THCPSi were analyzed with helium pycnometry, FTIR, and NMR spectroscopy. The results showed the density of the THCPSi loaded drugs to be ca. 10% lower than the bulk crystalline forms, while a melt quenched amorphous drugs showed a density reduction of 3-7.5%. DSC and FTIR results confirmed that the drugs reside in an amorphous form within the THCPSi pores. Similar results were obtained with NMR, which also indicated that IMC may reside as both amorphous clusters and individual molecules within the pores. The (1)H transverse relaxation times (T2) of amorphous and THCPSi loaded drugs showed IMC relaxation times of 0.28 ms for both the cases, whereas for GSV the values were 0.32 and 0.39 ms, respectively, indicating similar limited mobility in both cases. The results indicated that strong drug-carrier interactions were not necessary for stabilizing the amorphous state of the adsorbed drug. Dissolution tests using biorelevant media, fasted state simulated intestinal fluid (FaSSIF) and simulated gastric fluid (SGF), showed that THCPSi-loaded IMC and GSV were rapidly released in FaSSIF with comparable rates to the amorphous forms, whereas in SGF the THCPSi reduced the pH dependency in the dissolution of IMC.

Interactions at the silica-peptide interface: the influence of particle size and surface functionality

The variety of interactions that can occur at the silica/aqueous interface makes silica nanoparticles (SiNPs) attractive materials for technological applications. Despite their importance, interfacial interactions are not fully understood. In this contribution, we investigate the effect of (1) particle size and (2) surface functionalization on the adsorption of small biomolecular binders on SiNPs. Small silica binding peptides with different properties (charge, pI, and amino acid composition) were used as binders, while a range of fully characterized SiNPs of diameters ranging between 28 and 500 nm (pristine silica) and SiNPs of ca. 500 nm functionalized with cationic 3-aminopropyl groups and hydrophobic methyl groups was used as binding substrates. Adsorption and binding affinity were investigated by a fluorimetric assay at pH 7.4. A detailed characterization of the surface chemistry of the particles showed that the extent of surface functionalization on modified silica was well below monolayer coverage [by X-ray photoelectron spectroscopy (XPS), ca. 2 and 18 atomic % for the amino- and methyl-modified surfaces, respectively]. Although peptide binding is generally moderated by the physicochemical characteristics of the adsorbing peptide, the introduction of such a small degree of functionality onto silica particles was sufficient to produce drastic changes in adsorption at the silica/aqueous interface. In addition, an increase in peptide adsorption with an increasing particle size, independent of the nature and properties of the peptide, was observed. This particle size effect is attributed to a shift of the dominant binding mechanism toward electrostatic interactions on larger SiNPs. The data presented demonstrate that particle size and surface functionality are both parameters that can substantially influence (bio)molecule uptake via modulation or selection of specific binding modes at the silica/peptide interface. These results are applicable to the design and development of interfaces with specific adsorption/affinity response for biomedical applications, where uptake is important, such as drug delivery. Further, they provide important insights on how peptide affinity and selection during biopanning can be determined by small changes in surface chemistry of the surface of a target that can, in some instances, be associated with the presence of impurities.

A novel zwitterionic bioceramic with dual antibacterial capability

A novelzwitterionicbioceramic is developed, capable of lowering the relative bacterial adhesion from 100% to below 0.1%, as derived fromin vitroassays usingS. aureus. This matrix can release antibiotics over a long time and provides new insights in the treatment of bone implant infections.

pH and ion strength modulated ionic species loading in mesoporous silica nanoparticles

Mesoporous silica nanoparticles (MSN) have emerged as appealing host materials to accommodate guest molecules for biomedical applications, and recently various methods have been developed to modulate the loading of guest molecules in the silica matrix. Herein, it was demonstrated that pH and ion strength showed great influence on the loading of charged species into the nanoparticles, taking MCM-41 as a host MSN model and methylviologen (MV(2+)) and 1,5-naphthalene disulfonate (NDS(2-)) as typical charged ionic guest molecules. As the pH increased from 3.0 to 8.0, the loading amount of MV(2+) increased gradually, while on the contrary, it decreased gradually for NDS(2-), for the solution pH changed the electrostatic interaction between the silica matrix and the ionic guest molecules. Additionally, the adding of NaCl reduced the electrostatic interaction, which resulted in a decreasing of the electrostatic rejection and electrostatic accumulation for the molecules carrying the same and the opposite charge to the particle respectively. Thus, pH and ion strength can be employed as simple approaches to modulate the loading of charged molecules and permselectivity in MSN. This work has a definite guidance function for molecule loading, transport modulation, controlled release as well as sensors based on MSN.

Amine modification of thermally carbonized porous silicon with silane coupling chemistry

Thermally carbonized porous silicon (TCPSi) microparticles were chemically modified with organofunctional alkoxysilane molecules using a silanization process. Before the silane coupling, the TCPSi surface was activated by immersion in hydrofluoric acid (HF). Instead of regeneration of the silicon hydride species, the HF immersion of silicon carbide structure forms a silanol termination (Si-OH) on the surface required for silanization. Subsequent functionalization with 3-aminopropyltriethoxysilane provides the surface with an amine (-NH(2)) termination, while the SiC-type layer significantly stabilizes the functionalized structure both mechanically and chemically. The presence of terminal amine groups was verified with FTIR, XPS, CHN analysis, and electrophoretic mobility measurements. The overall effects of the silanization to the morphological properties of the initial TCPSi were analyzed and they were found to be very limited, making the treatment effects highly predictable. The maximum obtained number of amine groups on the surface was calculated to be 1.6 groups/nm(2), corresponding to 79% surface coverage. The availability of the amine groups for further biofunctionalization was confirmed by successful biotinylation. The isoelectric point (IEP) of amine-terminated TCPSi was measured to be at pH 7.7, as opposed to pH 2.6 for untreated TCPSi. The effects of the surface amine termination on the cell viability of Caco-2 and HT-29 cells and on the in vitro fenofibrate release profiles were also assessed. The results indicated that the surface modification did not alter the loading of the drug inside the pores and also retained the beneficial enhanced dissolution characteristics similar to TCPSi. Cellular viability studies also showed that the surface modification had only a limited effect on the biocompatibility of the PSi.