Influence of surface functionalization on the hydrophilic character of mesoporous silica nanoparticles.

We report the synthesis and surface functionalization of MCM-41-like mesoporous silica nanoparticles (MSNs) with spheroidal shape and particle size of 141 ± 41 nm. The success of surface functionalization with aminopropyl and sodium ethylcarboxylate groups (giving amino-MSN and carboxy-MSN, respectively) was ascertained by infrared spectroscopy and ζ potential measurements. The former showed the decrease of surface silanol groups and the corresponding appearance of signals related to NH2 bending mode (δNH2) at 1595 cm(-1) and COO(-) stretching (νas and νsym) at 1562 and 1418 cm(-1). The latter showed a change in surface charge, in that the isoelectric point (IEP) changed from pH 3-4.5 to 8.5 when the MSN was functionalized with the amino groups, while carboxy-MSN showed a more negative charge in the whole pH range with respect to MSN. The hydrophilic character of the prepared materials was ascertained by quantitative microgravimetric measurements, allowing the calculation of the average isosteric adsorption heat (q[combining macron]st). This was found to be 51 ± 3 kJ mol(-1), 61 ± 4, and 65 ± 3 kJ mol(-1) for MSN, amino-MSN, and carboxy-MSN samples, respectively. The increase in q[combining macron]st after functionalization can be ascribed to the specific interaction of water molecules with the functionalizing agents, in agreement with a higher basicity with respect to silanol groups. Moreover, the possibility of multiple H-bonding interactions of water molecules with the carboxylate anion is put forward to account for the higher water uptake with respect to parent MSN.

[1]  J. Hernandez,et al.  Speciation of silanol groups in precipitated silica nanoparticles by 1H MAS NMR spectroscopy , 2007 .

[2]  V. Rotello,et al.  The role of surface functionality in determining nanoparticle cytotoxicity. , 2013, Accounts of chemical research.

[3]  P. Gómez-Álvarez,et al.  Insights into the microscopic behaviour of nanoconfined water: host structure and thermal effects , 2015 .

[4]  Zongxi Li,et al.  Mesoporous silica nanoparticles in biomedical applications. , 2012, Chemical Society reviews.

[5]  Linlin Li,et al.  Mesoporous Silica Nanoparticles: Synthesis, Biocompatibility and Drug Delivery , 2012, Advanced materials.

[6]  M. Pinto,et al.  Characterization of the hydrophobicity of mesoporous silicas and clays with silica pillars by water adsorption and DRIFT. , 2008, Journal of colloid and interface science.

[7]  M. Sodupe,et al.  H-Bond Features of Fully Hydroxylated Surfaces of Crystalline Silica Polymorphs: A Periodic B3LYP Study , 2009 .

[8]  Darrell J Irvine,et al.  Drug delivery: One nanoparticle, one kill. , 2011, Nature materials.

[9]  Christy L Haynes,et al.  Impacts of mesoporous silica nanoparticle size, pore ordering, and pore integrity on hemolytic activity. , 2010, Journal of the American Chemical Society.

[10]  V. Inglezakis,et al.  Heat of adsorption, adsorption energy and activation energy in adsorption and ion exchange systems , 2012 .

[11]  F. Renzo,et al.  Morphological control of MCM-41 by pseudomorphic synthesis. , 2002, Angewandte Chemie.

[12]  B. Fubini,et al.  Surface heterogeneity on hydrophilic and hydrophobic silicas : Water and alcohols as probes for H-bonding and dispersion forces , 1997 .

[13]  M. Vallet‐Regí,et al.  A New Property of MCM-41: Drug Delivery System , 2001 .

[14]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[15]  C. Haynes,et al.  Stability of small mesoporous silica nanoparticles in biological media. , 2011, Chemical communications.

[16]  G. Richmond,et al.  From Head to Tail: Structure, Solvation, and Hydrogen Bonding of Carboxylate Surfactants at the Organic–Water Interface , 2011 .

[17]  María Vallet-Regí,et al.  Drug delivery from ordered mesoporous matrices , 2009, Expert opinion on drug delivery.

[18]  Weihong Tan,et al.  Fluorescent nanoparticles for multiplexed bacteria monitoring. , 2007, Bioconjugate chemistry.

[19]  Galo J. A. A. Soler-Illia,et al.  Mesoporous Aminopropyl-Functionalized Hybrid Thin Films with Modulable Surface and Environment-Responsive Behavior , 2008 .

[20]  J. Goupil,et al.  Quantification of water and silanol species on various silicas by coupling IR spectroscopy and in-situ thermogravimetry. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[21]  A. Walcarius,et al.  Rate of Access to the Binding Sites in Organically Modified Silicates. 2. Ordered Mesoporous Silicas Grafted with Amine or Thiol Groups , 2003 .

[22]  Bengt Herbert Kasemo,et al.  Biological surface science , 1998 .

[23]  Cecilia Sahlgren,et al.  Towards multifunctional, targeted drug delivery systems using mesoporous silica nanoparticles--opportunities & challenges. , 2010, Nanoscale.

[24]  J. Martens,et al.  In situ FT-IR investigation of etravirine speciation in pores of SBA-15 ordered mesoporous silica material upon contact with water. , 2013, Molecular pharmaceutics.

[25]  Zongxi Li,et al.  Engineered design of mesoporous silica nanoparticles to deliver doxorubicin and P-glycoprotein siRNA to overcome drug resistance in a cancer cell line. , 2010, ACS nano.

[26]  Shaobin Wang,et al.  Ordered mesoporous materials for drug delivery , 2009 .

[27]  J. Douillard,et al.  The difference between the surface reactivity of amorphous silica in the gas and liquid phase due to material porosity , 2010 .

[28]  A. Walcarius,et al.  Rate of Access to the Binding Sites in Organically Modified Silicates. 1. Amorphous Silica Gels Grafted with Amine or Thiol Groups , 2002 .

[29]  Miss A.O. Penney.  (b) , 1974, The New Yale Book of Quotations.

[30]  Howard I Maibach,et al.  Age and skin structure and function, a quantitative approach (I): blood flow, pH, thickness, and ultrasound echogenicity , 2005, Skin research and technology : official journal of International Society for Bioengineering and the Skin (ISBS) [and] International Society for Digital Imaging of Skin (ISDIS) [and] International Society for Skin Imaging.

[31]  Tian Xia,et al.  Physicochemical properties determine nanomaterial cellular uptake, transport, and fate. , 2013, Accounts of chemical research.

[32]  S. Coluccia,et al.  Functionalization of mesoporous MCM-41 with aminopropyl groups by co-condensation and grafting: a physico-chemical characterization , 2012, Research on Chemical Intermediates.

[33]  Piero Ugliengo,et al.  Structural and induced heterogeneity at the surface of some silica polymorphs from the enthalpy of adsorption of various molecules , 1993 .

[34]  Dong Chen,et al.  The effect of the shape of mesoporous silica nanoparticles on cellular uptake and cell function. , 2010, Biomaterials.

[35]  E. Bonifacio,et al.  INTERACTION OF ORGANIC PHOSPHORUS WITH CLAYS EXTRACTED FROM OXISOLS , 2008 .

[36]  T. Azaïs,et al.  Chemical Modification As a Versatile Tool for Tuning Stability of Silica Based Mesoporous Carriers in Biologically Relevant Conditions , 2012 .

[37]  R. J. Hunter,et al.  Zeta Potential in Colloid Science , 1981 .

[38]  Gianmario Martra,et al.  Hydrophilic and hydrophobic sites on dehydrated crystalline and amorphous silicas , 1991 .

[39]  S. Sapino,et al.  Mesoporous silica as topical nanocarriers for quercetin: characterization and in vitro studies. , 2015, European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V.

[40]  Tiehong Chen,et al.  Reactivity of the surface hydroxyl groups of MCM-41 towards silylation with trimethylchlorosilane , 2001 .

[41]  R. J. Hunter.  Zeta potential in colloid science : principles and applications , 1981 .

[42]  C. Chen,et al.  Superhydrophobic SiO2-based nanocomposite modified with organic groups as catalyst for selective oxidation of ethylbenzene , 2014 .

[43]  María Vallet-Regí,et al.  Mesoporous materials for drug delivery. , 2007, Angewandte Chemie.

[44]  Courtney R. Thomas,et al.  Synthesis of biomolecule-modified mesoporous silica nanoparticles for targeted hydrophobic drug delivery to cancer cells. , 2011, Small.

[45]  Chung-Yuan Mou,et al.  Mesoporous silica nanoparticles as nanocarriers. , 2011, Chemical communications.

[46]  L. Tavlarides,et al.  Kinetics of Water Vapor Adsorption on Single-Layer Molecular Sieve 3A: Experiments and Modeling , 2014 .

[47]  P. Midgley,et al.  Surface structure, hydration, and cationic sites of nanohydroxyapatite: UHR-TEM, IR, and microgravimetric studies , 2007 .

[48]  W. Marsden.  I and J , 2012 .

[49]  F. Renzo,et al.  Hydrophobic and hydrophilic behavior of micelle-templated mesoporous silica , 1997 .

[50]  Jeffrey I Zink,et al.  pH-responsive dual cargo delivery from mesoporous silica nanoparticles with a metal-latched nanogate. , 2013, Inorganic chemistry.

[51]  Juan L. Vivero-Escoto,et al.  Mesoporous silica nanoparticles as controlled release drug delivery and gene transfection carriers. , 2008, Advanced drug delivery reviews.

[52]  B. Ninham,et al.  Ion specific surface charge density of SBA-15 mesoporous silica. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[53]  P. Voort,et al.  Influence of water in the reaction of γ-aminopropyltriethoxysilane with silica gel. A Fourier-transform infrared and cross-polarisation magic-angle-spinning nuclear magnetic resonance study , 1992 .

[54]  G. Socrates,et al.  Infrared and Raman characteristic group frequencies : tables and charts , 2001 .

[55]  G. Caputo,et al.  The protective effect of the mesoporous host on the photo oxidation of fluorescent guests: a UV-Vis spectroscopy study. , 2014, Physical chemistry chemical physics : PCCP.

[56]  J. Rosenholm,et al.  Towards establishing structure-activity relationships for mesoporous silica in drug delivery applications. , 2008, Journal of controlled release : official journal of the Controlled Release Society.

[57]  C. Alba-Simionesco,et al.  Wall thickness determination of hydrophobically functionalized MCM-41 materials , 2012 .

[58]  T. Kenny,et al.  CORRIGENDUM: Quantum Limit of Quality Factor in Silicon Micro and Nano Mechanical Resonators , 2014, Scientific Reports.

[59]  P. Voort,et al.  The role of silanols in the modification of silica gel with aminosilanes , 1995 .

[60]  A. Myers,et al.  Comparison of Experimental Techniques for Measuring Isosteric Heat of Adsorption , 2000 .

[61]  M. Bayindir,et al.  Impact of mesoporous silica nanoparticle surface functionality on hemolytic activity, thrombogenicity and non-specific protein adsorption. , 2013, Journal of materials chemistry. B.

[62]  Xiue Jiang,et al.  Impact of shape and pore size of mesoporous silica nanoparticles on serum protein adsorption and RBCs hemolysis. , 2014, ACS applied materials & interfaces.

[63]  Huaiyong Zhu,et al.  Comprehensive study of surface chemistry of MCM-41 using 29Si CP/MAS NMR, FTIR, pyridine-TPD, and TGA , 1997 .

[64]  J. Zink,et al.  Development of Pharmaceutically Adapted Mesoporous Silica Nanoparticles Platform. , 2012, The journal of physical chemistry letters.

[65]  T. Asefa,et al.  Mesoporosity and functional group dependent endocytosis and cytotoxicity of silica nanomaterials. , 2009, Chemical research in toxicology.

[66]  T. Kühne,et al.  Study of water adsorption and capillary bridge formation for SiO(2) nanoparticle layers by means of a combined in situ FT-IR reflection spectroscopy and QCM-D set-up. , 2014, Physical chemistry chemical physics : PCCP.

[67]  E. Garrone,et al.  In situ infrared study of SBA-15 functionalized with carboxylic groups incorporated by a co-condensation route. , 2005, The journal of physical chemistry. B.

[68]  J. L. Hueso,et al.  Synthesis and Characterization of Zwitterionic SBA-15 Nanostructured Materials , 2010 .

[69]  Chung-Yuan Mou,et al.  Size effect on cell uptake in well-suspended, uniform mesoporous silica nanoparticles. , 2009, Small.

[70]  Xinglu Huang,et al.  The promotion of human malignant melanoma growth by mesoporous silica nanoparticles through decreased reactive oxygen species. , 2010, Biomaterials.

[71]  Li-Ming Yang,et al.  A fundamental understanding of catechol and water adsorption on a hydrophilic silica surface: exploring the underwater adhesion mechanism of mussels on an atomic scale. , 2014, Langmuir : the ACS journal of surfaces and colloids.

[72]  Jason L. Townson,et al.  Re-examining the size/charge paradigm: differing in vivo characteristics of size- and charge-matched mesoporous silica nanoparticles. , 2013, Journal of the American Chemical Society.

[73]  M. Sodupe,et al.  Cooperative effects at water-crystalline silica interfaces strengthen surface silanol hydrogen bonding. An ab initio molecular dynamics study. , 2012, Physical chemistry chemical physics : PCCP.

[74]  P. Ugliengo,et al.  Hydrophobic Behavior of Dehydroxylated Silica Surfaces: A B3LYP Periodic Study , 2010 .

[75]  Courtney R. Thomas,et al.  Mechanized silica nanoparticles: a new frontier in theranostic nanomedicine. , 2011, Accounts of chemical research.

[76]  J. Eriksson,et al.  Targeted intracellular delivery of hydrophobic agents using mesoporous hybrid silica nanoparticles as carrier systems. , 2009, Nano letters.

[77]  Remo Guidieri.  Res , 1995, RES: Anthropology and Aesthetics.

[78]  G. Magnacca,et al.  Microcalorimetric Characterization of Structural and Chemical Heterogeneity of Superacid SO4/ZrO2 Systems† , 1997 .

[79]  F. Renzo,et al.  Preferential grafting of alkoxysilane coupling agents on the hydrophobic portion of the surface of micelle-templated silica , 2000 .

[80]  A. Walcarius,et al.  Analytical investigation of the chemical reactivity and stability of aminopropyl-grafted silica in aqueous medium. , 2003, Talanta.

[81]  C. Lamberti,et al.  Calorimetric and IR spectroscopic study of the interaction of NH3 with variously prepared defective silicalites: Comparison with ab initio computational data , 2002 .

[82]  A. Luquín,et al.  Characterisation of hybrid xerogels synthesised in acid media using methyltriethoxysilane (MTEOS) and tetraethoxysilane (TEOS) as precursors , 2011 .

[83]  Victor S-Y Lin,et al.  A polyamidoamine dendrimer-capped mesoporous silica nanosphere-based gene transfection reagent. , 2004, Journal of the American Chemical Society.

[84]  M. Sodupe,et al.  Realistic Models of Hydroxylated Amorphous Silica Surfaces and MCM‐41 Mesoporous Material Simulated by Large‐scale Periodic B3LYP Calculations , 2008 .

[85]  S. Kozlova,et al.  Post-synthetic activation of silanol covering in the mesostructured silicate materials МСМ-41 and SBA-15 , 2010 .

[86]  S. Bocian,et al.  Study of hydration process on silica hydride surfaces by microcalorimetry and water adsorption. , 2014, Journal of colloid and interface science.

[87]  Aaas News,et al.  Book Reviews , 1893, Buffalo Medical and Surgical Journal.

[88]  D. Grosso,et al.  Alcohol-Assisted Water Condensation and Stabilization into Hydrophobic Mesoporosity , 2014 .

[89]  R. Gorte,et al.  A new calorimeter for simultaneous measurements of loading and heats of adsorption from gaseous mixtures , 1999 .

[90]  Jenny Andersson,et al.  Influences of Material Characteristics on Ibuprofen Drug Loading and Release Profiles from Ordered Micro- and Mesoporous Silica Matrices , 2004 .

[91]  M. Corno,et al.  Large-Scale B3LYP Simulations of Ibuprofen Adsorbed in MCM-41 Mesoporous Silica as Drug Delivery System , 2014 .

[92]  Andrew G. Glen,et al.  APPL , 2001 .

[93]  M. Jaroniec,et al.  Adsorption and Thermogravimetric Methods for Monitoring Surface and Structural Changes in Ordered Mesoporous Silicas Induced by their Chemical Modification , 1999 .

[94]  M. Anpo,et al.  States of H2O adsorbed on oxides: An investigation by near and mid infrared spectroscopy , 2006 .

[95]  D. Castner,et al.  Biomedical surface science: Foundations to frontiers , 2002 .

[96]  Zongjin Li,et al.  Molecular simulation of “hydrolytic weakening”: A case study on silica , 2014 .

[97]  K. Cychosz,et al.  Combining nitrogen, argon, and water adsorption for advanced characterization of ordered mesoporous carbons (CMKs) and periodic mesoporous organosilicas (PMOs). , 2013, Langmuir : the ACS journal of surfaces and colloids.

[98]  M. Jaroniec,et al.  Determination of Pore Size and Pore Wall Structure of MCM-41 by Using Nitrogen Adsorption, Transmission Electron Microscopy, and X-ray Diffraction , 2000 .