Cristina de la Torre

Enzyme‐Responsive Intracellular‐Controlled Release Using Silica Mesoporous Nanoparticles Capped with ε‐Poly‐L‐lysine

The synthesis and characterization of two new capped silica mesoporous nanoparticles for controlled delivery purposes are described. Capped hybrid systems consist of MCM-41 nanoparticles functionalized on the outer surface with polymer ε-poly-L-lysine by two different anchoring strategies. In both cases, nanoparticles were loaded with model dye molecule [Ru(bipy)3](2+). An anchoring strategy involved the random formation of urea bonds by the treatment of propyl isocyanate-functionalized MCM-41 nanoparticles with the lysine amino groups located on the ε-poly-L-lysine backbone (solid Ru-rLys-S1). The second strategy involved a specific attachment through the carboxyl terminus of the polypeptide with azidopropyl-functionalized MCM-41 nanoparticles (solid Ru-tLys-S1). Once synthesized, both nanoparticles showed a nearly zero cargo release in water due to the coverage of the nanoparticle surface by polymer ε-poly-L-lysine. In contrast, a remarkable payload delivery was observed in the presence of proteases due to the hydrolysis of the polymers amide bonds. Once chemically characterized, studies of the viability and the lysosomal enzyme-controlled release of the dye in intracellular media were carried out. Finally, the possibility of using these materials as drug-delivery systems was tested by preparing the corresponding ε-poly-L-lysine capped mesoporous silica nanoparticles loaded with cytotoxic drug camptothecin (CPT), CPT-rLys-S1 and CPT-tLys-S1. Cellular uptake and cell-death induction were studied. The efficiency of both nanoparticles as new potential platforms for cancer treatment was demonstrated.

Gated Mesoporous Silica Nanoparticles for the Controlled Delivery of Drugs in Cancer Cells

In recent years, mesoporous silica nanoparticles (MSNs) have been used as effective supports for the development of controlled-release nanodevices that are able to act as multifunctional delivery platforms for the encapsulation of therapeutic agents, enhancing their bioavailability and overcoming common issues such as poor water solubility and poor stability of some drugs. In particular, redox-responsive delivery systems have attracted the attention of scientists because of the intracellular reductive environment related to a high concentration of glutathione (GSH). In this context, we describe herein the development of a GSH-responsive delivery system based on poly(ethylene glycol)- (PEG-) capped MSNs that are able to deliver safranin O and doxorubicin in a controlled manner. The results showed that the PEG-capped systems designed in this work can be maintained closed at low GSH concentrations, yet the cargo can be delivered when the concentration of GSH is increased. Moreover, the efficacy of the PEG-capped system in delivering the cytotoxic agent doxorubicin in cells was also demonstrated.

Temperature-controlled release by changes in the secondary structure of peptides anchored onto mesoporous silica supports

Changes in the conformation of a peptide anchored onto the external surface of mesoporous silica nanoparticles have been used to design novel temperature-controlled delivery systems.

Azobenzene Polyesters Used as Gate‐Like Scaffolds in Nanoscopic Hybrid Systems

The synthesis and characterisation of new capped silica mesoporous nanoparticles for on-command delivery applications is reported. Functional capped hybrid systems consist of MCM-41 nanoparticles functionalised on the external surface with polyesters bearing azobenzene derivatives and rhodamine B inside the mesopores. Two solid materials, Rh-PAzo8-S and Rh-PAzo6-S, containing two closely related polymers, PAzo8 and PAzo6, in the pore outlets have been prepared. Materials Rh-PAzo8-S and Rh-PAzo6-S showed an almost zero release in water due to steric hindrance imposed by the presence of anchored bulky polyesters, whereas a large delivery of the cargo was observed in the presence of an esterase enzyme due to the progressive hydrolysis of polyester chains. Moreover, nanoparticles Rh-PAzo8-S and Rh-PAzo6-S were used to study the controlled release of the dye in intracellular media. Nanoparticles were not toxic for HeLa cells and endocytosis-mediated cell internalisation was confirmed by confocal microscopy. Furthermore, the possible use of capped materials as a drug-delivery system was demonstrated by the preparation of a new mesoporous silica nanoparticle functionalised with PAzo6 and loaded with the cytotoxic drug camptothecin (CPT-PAzo6-S). Following cell internalisation and lysosome resident enzyme-dependent gate opening, CPT-PAzo6-S induced CPT-dependent cell death in HeLa cells.

Amidase-responsive controlled release of antitumoral drug into intracellular media using gluconamide-capped mesoporous silica nanoparticles

MCM-41 silica nanoparticles were used as inorganic scaffolding to prepare a nanoscopic-capped hybrid material S1, which was able to release an entrapped cargo in the presence of certain enzymes, whereas in the absence of enzymes, a zero release system was obtained. S1 was prepared by loading nanoparticles with Safranine O dye and was then capped with a gluconamide derivative. In the absence of enzymes, the release of the dye from the aqueous suspensions of S1 was inhibited as a result of the steric hindrance imposed by the bulky gluconamide derivative, the polymerized gluconamide layer and the formation of a dense hydrogen-bonded network around the pore outlets. Upon the addition of amidase and pronase enzymes, delivery of Safranine O dye was observed due to the enzymatic hydrolysis of the amide bond in the anchored gluconamide derivative. S1 nanoparticles were not toxic for cells, as demonstrated by cell viability assays using HeLa and MCF-7 cell lines, and were associated with lysosomes, as shown by confocal microscopy. Finally, the S1–CPT material loaded with the cytotoxic drug camptothecin and capped with the gluconamide derivative was prepared. The HeLa cells treated with S1–CPT underwent cell death as a result of material internalization, and of the subsequent cellular enzyme-mediated hydrolysis and aperture of the molecular gate, which induced the release of the camptothecin cargo.

Encapsulation of folic acid in different silica porous supports: A comparative study

Although folic acid is essential to numerous bodily functions, recent research indicates that a massive exposition to the vitamin could be a double-edged sword. In this study, the capacity of different caped mesoporous silica particles (i.e. Hollow Silica Shells, MCM-41, SBA-15 and UVM-7) to dose FA during its passage through the gastrointestinal tract has been evaluated. Results confirmed that the four capped materials were capable to hinder the delivery of FA at low pH (i.e. stomach) as well as able to deliver great amounts of the vitamin at neutral pH (i.e. intestine). Nevertheless, the encapsulation efficiency and the deliver kinetics differed among supports. While supports with large pore entrance exhibited an initial fast release, MCM-41, showed a sustained release along the time. This correlation between textural properties and release kinetics for each of the supports reveals the importance of a proper support selection as a strategy to control the delivery of active molecules.

Polyglutamic Acid-Gated Mesoporous Silica Nanoparticles for Enzyme-Controlled Drug Delivery

Mesoporous silica nanoparticles (MSNs) are highly attractive as supports in the design of controlled delivery systems that can act as containers for the encapsulation of therapeutic agents, overcoming common issues such as poor water solubility and poor stability of some drugs and also enhancing their bioavailability. In this context, we describe herein the development of polyglutamic acid (PGA)-capped MSNs that can selectively deliver rhodamine B and doxorubicin. PGA-capped MSNs remain closed in an aqueous environment, yet they are able to deliver the cargo in the presence of pronase because of the hydrolysis of the peptide bonds in PGA. The prepared solids released less than 20% of the cargo in 1 day in water, whereas they were able to reach 90% of the maximum release of the entrapped guest in ca. 5 h in the presence of pronase. Studies of the PGA-capped nanoparticles with SK-BR-3 breast cancer cells were also undertaken. Rhodamine-loaded nanoparticles were not toxic, whereas doxorubicin-loaded nanoparticles were able to efficiently kill more than 90% of the cancer cells at a concentration of 100 μg/mL.

Caspase 3 Targeted Cargo Delivery in Apoptotic Cells Using Capped Mesoporous Silica Nanoparticles

Excessive apoptotic cell death is at the origin of several pathologies, such as degenerative disorders, stroke or ischemia-reperfusion damage. In this context, strategies to improve inhibition of apoptosis and other types of cell death are of interest and may represent a pharmacological opportunity for the treatment of cell-death-related disorders. In this scenario new peptide-containing delivery systems (solids S1 -P1 and S1 -P2 ) are described based on mesoporous silica nanoparticles (MSNs) loaded with a dye and capped with the KKGDEVDKKARDEVDK (P1 ) peptide that contains two repeats of the DEVD target sequence that are selectively hydrolyzed by caspase 3 (C3). This enzyme plays a central role in the execution-phase of apoptosis. HeLa cells electroporated with S1 -P1 are able to deliver the cargo in the presence of staurosporin (STS), which induces apoptosis with the consequent activation of the cytoplasmic C3 enzyme. Moreover, the nanoparticles S1 -P2 , containing both a cell-penetrating TAT peptide and P1 also entered in HeLa cells and delivered the cargo preferentially in cells treated with the apoptosis inducer cisplatin.

A new fluorescent "turn-on" chemodosimeter for the detection of hydrogen sulfide in water and living cells

A new fluorescent turn-on probe for the selective detection of hydrogen sulfide in water and living cells based on a 8-hydroxyquinoline fluorophore functionalized with a 2,6-dinitrophenyl ether moiety has been developed.

Neoglycoenzyme-Gated Mesoporous Silica Nanoparticles: Toward the Design of Nanodevices for Pulsatile Programmed Sequential Delivery

We report herein the design of a stimulus-programmed pulsatile delivery system for sequential cargo release based on the use of a lactose-modified esterase as a capping agent in phenylboronic acid functionalized mesoporous silica nanoparticles. The dual-release mechanism was based on the distinct stability of the cyclic boronic acid esters formed with lactose residues and the long naturally occurring glycosylation chains in the modified neoglycoenzyme. Cargo delivery in succession was achieved using glucose and ethyl butyrate as triggers.