Dual Enzyme-Triggered Controlled Release on Capped Nanometric Silica Mesoporous Supports

The development of nanoscopic hybrid materials equipped with “molecular gates” showing the ability of releasing target entrapped guests upon the application of an external trigger has attracted great attention and has been extensively explored during recent years. These nanodevices are composed of two subunits, namely, a suitable support and certain capping entities grafted on the surface of the scaffolding. The support is used as a suitable reservoir in which certain chemicals can be stored whereas the molecules grafted in the outer surface act as a “gate” and can control the release of the entrapped molecules at will. Both components are carefully selected and arranged in order to achieve a wide range of required functionalities. As support, mesoporous silica nanoparticles (MSN) have been widely used due to their unique properties, such as large load capacity, biocompatibility, high surface area and wellknown functionalization procedures. Moreover, gated MSN have recently been used for the development of on-command delivery nanodevices by using several physical and chemical triggers. For instance, MSN displaying controlled-release features with the use of light, redox reactions, and pH changes have been described. In contrast, gated nanomaterials able to deliver the cargo triggered by biomolecules are scarce although some illustrative examples that use antigen– antibody interactions, hybridisation of single stranded oligonucleotides, and enzymes have been reported. In particular, the use of enzymes is especially appealing taking into account the possibility to synthesise tailor-made enzyme-specific sequences as molecular caps. However, in spite of these interesting features there are few examples that use enzymes in opening protocols. The first enzyme-responsive gate in a mesoporous support was described by Stoddart and co-workers. In that work, a [2]rotaxane ended with a bulky adamantyl ester stopper that acted as molecular gate was removed by porcine liver esterase treatment. Further hybrid systems involving avidin–biotin, lactose, starch, b-cyclodextrins and peptide sequences as capping groups have been reported. These examples offer a chemically simple approach that can benefit from the vast knowledge on enzyme–substrate pairs for the design of versatile systems for controlled release. A further step in the field should take into account that the flow of defined biological processes rely on biochemical networks with the participation of multiple enzyme-dependent stages. It would be then useful to define future applications with the development of dual or multiple enzyme-triggered systems by using capped mesoporous supports. This would require the design of capping threads containing different enzyme-specific hydrolysable linkers located at defined positions on the external surface of MSN. The whole design will provide highly versatile and specific-release nanodevices the delivery profiles of which could be controlled and fine-tuned by defined combinations of enzymes. As a first-of-its-kind proof-of-concept, we have prepared an MSN support capped with the molecular entity 1 that contains amide and urea linkages, and we have evaluated it as a multi-enzyme-tuned delivery system (Scheme 1). As inorganic carrier vehicle we selected mesoporous MCM41 silica nanoparticles of about 100 nm in diameter, which were prepared following well-known procedures using TEOS as hydrolytic inorganic precursor and hexadecyltrimethylammonium bromide (CTABr) as porogen species. The structure of the nanoparticulated calcined MCM-41 starting material was confirmed by X-ray diffraction (Figure 1), TEM and SEM microscopy. The N2 adsorption–desorption isotherms showed a typical type IV curve with a specific surface of 999.6 mg , and a pore volume of 0.79 cmg . From the XRD, porosimetry and TEM studies, the a0 cell parameter (4.44 nm), the pore diameter (2.46 nm) and a value for the wall thickness (1.99 nm) were calculated. For the preparation of S1, the calcinated MSN was first loaded with [Ru(bipy)3]Cl2, which was used as dye for monitoring the enzyme-triggered protocol, and then treated with the capping molecule 1. The derivative 1 was synthesised following a two-step procedure from diethylentriamine. In a [a] A. Agostini, Dr. L. Mondrag n, Dr. C. Coll, Dr. E. Aznar, Dr. M. D. Marcos, Prof. R. Mart nez-M Çez, Dr. F. Sancen n, Dr. J. Soto Centro de Reconocimiento Molecular y Desarrollo Tecnol gico Unidad Mixta Universidad Polit cnica de Valencia Universidad de Valencia (Spain) [b] A. Agostini, Dr. L. Mondrag n, Dr. C. Coll, Dr. M. D. Marcos, Prof. R. Mart nez-M Çez, Dr. F. Sancen n, Dr. J. Soto Departamento de Qu mica, Universidad Polit cnica de Valencia Camino de Vera s/n, 46022, Valencia (Spain) E-mail : [email protected] [c] Dr. L. Mondrag n, Dr. C. Coll, Dr. E. Aznar, Dr. M. D. Marcos, Prof. R. Mart nez-M Çez, Dr. F. Sancen n CIBER de Bioingenier a Biomateriales y Nanotecnolog a (CIBER-BNN, Spain) [d] Prof. E. P rez-Pay Centro de Investigaci n Pr ncipe Felipe Laboratorio de P ptidos y Prote nas Avda. Autopista al Saler, 16, 46012, Valencia (Spain) [e] Prof. P. Amor s Institut de Ci ncia dels Materials (ICMUV), Universitat de Valencia P.O. Box 2085, 46071, Valencia (Spain) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/open.201200003. 2012 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.