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  • 1. Afonso, Damien
    et al.
    Valetti, Sabrina
    Fraix, Aurore
    Bascetta, Claudia
    Petralia, Salvatore
    Conoci, Sabrina
    Feiler, Adam
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Sortino, Salvatore
    Multivalent mesoporous silica nanoparticles photo-delivering nitric oxide with carbon dots as fluorescence reporters2017Inngår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, nr 36, s. 13404-13408Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Amino-terminated mesoporous silica nanoparticles embedding carbon dots (MSCD) formed by calcination were functionalized with a nitric oxide (NO) photodonor (1) to give a robust MSCD-1 conjugate. The intense fluorescence of MSCDs was strongly quenched in MSCD-1 by effective energy transfer. Visible light excitation of MSCD-1 liberates NO, suppresses the energy transfer mechanism and leads to concomitant fluorescence restoration of the MSCD scaffold, which acts as an optical reporter for the released NO. The MSCD-1 hybrid is also able to encapsulate the highly hydrophobic photosensitizer temoporfin, preserving the fluorescence reporting function.

  • 2. Angiolini, L.
    et al.
    Valetti, S.
    Cohen, B.
    Feiler, Adam
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. Nanologica AB, Södertälje, Sweden.
    Douhal, A.
    Fluorescence imaging of antibiotic clofazimine encapsulated within mesoporous silica particle carriers: Relevance to drug delivery and the effect on its release kinetics2018Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, nr 17, s. 11899-11911Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the encapsulation of the antibiotic clofazimine (CLZ) within the pores of mesoporous silica particles having hydrophilic (CBET value of 137) and more hydrophobic (CBET value of 94 after calcination at 600 °C) surfaces. We studied the effect of pH on the released amount of CLZ in aqueous solutions and observed a maximum at pH 4.1 in correlation with the solubility of the drug. Less release of the drug was observed from the more hydrophobic particles which was attributed to a difference in the affinity of the drug to the carrier particles. Fluorescence lifetime imaging microscopy, emission spectra, and fluorescence lifetimes of single drug loaded particles provided detailed understanding and new knowledge of the physical form of the encapsulated drug and the distribution within the particles. The distribution of CLZ within the particles was independent of the surface chemistry of the particles. The confirmation of CLZ molecules as monomers or aggregates was revealed by controlled removal of the drug with solvent. Additionally, the observed optical "halo effect" in the fluorescent images was interpreted in terms of specific quenching of high concentration of molecules. The emission lifetime experiments suggest stronger interaction of CLZ with the more hydrophobic particles, which is relevant to its release. The results reported in this work demonstrate that tuning the hydrophilicity/hydrophobicity of mesoporous silica particles can be used as a tool to control the release without impacting their loading ability.

  • 3.
    Feiler, Adam A.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Jenkins, Paul
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Effect of relative humidity on adhesion and frictional properties of micro- and nano-scopic contacts2005Inngår i: Atomic Force Microscopy in Adhesion Studies, Leiden-Boston: VSP , 2005, s. 491-505Kapittel i bok, del av antologi (Fagfellevurdert)
  • 4.
    Feiler, Adam
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Stiernstedt, Johanna
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Theander, Katarina
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Jenkins, Paul
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Effect of capillary condensation on friction force and adhesion2007Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 2, s. 517-522Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Friction force measurements have been conducted with a colloid probe on mica and silica (both hydrophilic and hydrophobized) after long (24 h) exposure to high-humidity air. Adhesion and friction measurements have also been performed on cellulose substrates. The long exposure to high humidity led to a large hysteresis between loading and unloading in the friction measurements with separation occurring at large negative applied loads. The large hysteresis in the friction - load relationship is attributed to a contact area hysteresis of the capillary condensate which built up during loading and did not evaporate during the unloading regime. The magnitude of the friction force varied dramatically between substrates and was lowest on the mica substrate and highest on the hydrophilic silica substrate, with the hydrophobized silica and cellulose being intermediate. The adhesion due to capillary forces on cellulose was small compared to that on the other substrates, due to the greater roughness of these surfaces.

  • 5.
    Pettersson, Torbjörn
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Nordgren, Niklas
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Feiler, Adam
    Department of Physical and Analytical Chemistry, Surface Biotechnology, Uppsala University.
    Comparison of different methods to calibrate torsional spring constant and photodetector for atomic force microscopy friction measurements in air and liquid2007Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 78, nr 9, s. 093702-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A number of atomic force microscopy cantilevers have been exhaustively calibrated by a number of techniques to obtain both normal and frictional force constants to evaluate the relative accuracy of the different methods. These were of either direct or indirect character-the latter relies on cantilever resonant frequencies. The so-called Sader [Rev. Sci. Instrum. 70, 3967 (1999)] and Cleveland [Rev. Sci. Instrum. 64, 403 (1993)] techniques are compared for the normal force constant calibration and while agreement was good, a systematic difference was observed. For the torsional force constants, all the techniques displayed a certain scatter but the agreement was highly encouraging. By far the simplest technique is that of Sader, and it is suggested in view of this validation that this method should be generally adopted. The issue of the photodetector calibration is also addressed since this is necessary to obtain the cantilever twist from which the torsional force is calculated. Here a technique of obtaining the torsional photodetector sensitivity by combining the direct and indirect methods is proposed. Direct calibration measurements were conducted in liquid as well as air, and a conversion factor was obtained showing that quantitative friction measurements in liquid are equally feasible provided the correct calibration is performed.

  • 6.
    Stjern, Louise
    et al.
    KTH.
    Voittonen, Sandra
    KTH.
    Weldemichel, Rahel
    KTH.
    Thuresson, Sofia
    Agnes, Marco
    Benkovics, Gabor
    Fenyvesi, Eva
    Malanga, Milo
    Yannakopoulou, Konstantina
    Feiler, Adam
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Valetti, Sabrina
    Cyclodextrin-mesoporous silica particle composites for controlled antibiotic release. A proof of concept toward colon targeting2017Inngår i: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 531, nr 2, s. 595-605Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cyclodextrins (CDs) and mesoporous silica particles (MSPs) have been combined as composite carriers for controlled antibiotic release. CDs were employed as "gatekeeper" agents and grafted onto MSPs to retain drug molecules inside the MSP carrier. A variety of CDs (unfunctionalized, positively charged and carboxymethylated) and three different coupling strategies (covalent binding, electrostatic adsorption and inclusion complexation) were systematically investigated for their ability to control the release of two antibiotic drugs, metronidazole and clofazimine. The drugs had significantly different physicochemical properties (metronidazole - small hydrophilic, clofazimine-large hydrophobic). We report for the first time on the encapsulation and characterization of metronidazole-loaded-MSP. Each CD coating strategy reduced the drug release rate in phosphate buffer compared to unmodified MSP (from 20% to 100% retained drug). Covalent binding and inclusion complex approaches were significantly more effective than electrostatically adsorbed CD. In particular, the novel inclusion complex based on host/guest interaction between benzyl-modified silica surface and alpha-CD proved to be very effective (60-100% retained drug amount). Using pharmaceutical manufacturing processes, our study shows that CD-MSP composites can retain both hydrophobic and hydrophilic antibiotic compounds with potential translation to triggered release formulation targeting bacterial infections in the colon and lower intestine.

  • 7. Valetti, Sabrina
    et al.
    Feiler, Adam
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Trulsson, Martin
    Bare and Effective Charge of Mesoporous Silica Particles2017Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, nr 29, s. 7343-7351Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We develop and combine a novel numerical model, within the Poisson-Boltzmann framework, with classical experimental titration techniques for mesoporous silica particles to study the charging behavior as both pH and the amount of monovalent salt are varied. One key finding is that these particles can be considered to have an effectively or apparent electroneutral inner core with an effectively charged rim. As a consequence, the total apparent charge of the particle is several orders of magnitude smaller than that of the bare silica charge, which accounts only for the charged silanol groups of the mesoporous silica particles and which has its major contribution from the interior. Hence, the interior dictates the mesoporous silicas' bare charge while the rim its effective charge. We furthermore report density, charge, and accumulated charge profiles across the particle's interface.

  • 8. Valetti, Sabrina
    et al.
    Wankar, Jitendra
    Ericson, Marica B.
    Feiler, Adam
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Manet, Ilse
    Mesoporous silica particles as a lipophilic drug vehicle investigated by fluorescence lifetime imaging2017Inngår i: Journal of materials chemistry. B, ISSN 2050-750X, E-ISSN 2050-7518, Vol. 5, nr 17, s. 3201-3211Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three types of new label-free fluorescent mesoporous silica micro- and nanoparticles were prepared by controlled thermal decomposition of carboamino groups linked on the surface without compromising the drug loading capacity of the silica particles. Clofazimine, a lipophilic antibiotic drug with excellent in vitro activity against mycobacterium tuberculosis, was encapsulated inside these fluorescent particles to obtain multifunctional drug carriers of interest in the field of theranostics. The morphological features together with the photophysical properties of both powders and aqueous suspensions are described. The photophysical properties seem to be independent of the mesoporosity features but correlate with the residual carboamino functionalization. The particles are endowed with emission in the visible region and have fluorescence lifetimes of up to 9.0 ns that can be easily discriminated from intrinsic biological fluorescence. Furthermore, their fluorescence lifetime offers a promising tool to follow the release of the encapsulated drug which is not possible by means of simple fluorescence intensity. We report here a novel attractive theranostic platform enabling monitoring of drug release in biological environments by means of fluorescence lifetime.

  • 9. Valetti, Sabrina
    et al.
    Xia, Xin
    Costa-Gouveia, Joana
    Brodin, Priscille
    Bernet-Camard, Marie-Francoise
    Andersson, Margareta
    Feiler, Adam
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Clofazimine encapsulation in nanoporous silica particles for the oral treatment of antibiotic-resistant Mycobacterium tuberculosis infections2017Inngår i: Nanomedicine, ISSN 1743-5889, E-ISSN 1748-6963, Vol. 12, nr 8, s. 831-844Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aim: First extensive reformulation of clofazimine (CLZ) in nanoporous silica particles (NSPs) for tackling antibiotic-resistant tuberculosis (TB) infections. Materials & methods: Solid-state characterization of several CLZ-encapsulated NSP formulations was followed by in vitro drug solubility, Caco-2 intestinal cells drug permeability and TB antibacterial activity. Results: NSPs stabilize the amorphous state of CLZ (shelf stability > 6 months) and dramatically increase the drug solubility in simulated gastric fluid (up to 20-fold) with different dissolution kinetics depending on the NSPs used. CLZ encapsulation in NSP substantially enhances the permeation through model intestinal cell layer, achieving effective antimicrobial concentrations in TB-infected macrophages. Conclusion: Promising results toward refurbishment of an approved marketed drug for a different indication suitable for oral anti-TB formulation.

  • 10. Valle-Delgado, J. J.
    et al.
    Molina-Bolivar, J. A.
    Galisteo-Gonzalez, F.
    Galvez-Ruiz, M. J.
    Feiler, Adam
    KTH, Tidigare Institutioner, Kemi.
    Rutland, Mark W
    KTH, Tidigare Institutioner, Kemi.
    Interaction forces between BSA layers adsorbed on silica surfaces measured with an atomic force microscope2004Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 108, nr 17, s. 5365-5371Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interaction forces between bovine serum albumin (BSA) layers adsorbed on silica surfaces have been measured using an atomic force microscope (AFM) in Conjunction with the colloid probe technique. Measurements of force-distance curves were made at different pH values and electrolyte concentrations (NaCl and CaCl2). The interaction at long range is dominated by electrical double-layer forces, while at short surface separations an additional repulsion due to the compression of the adsorbed protein layers appears. However, prior to this steric interaction, when the pH is above the isoelectric point of the protein and at high salt concentration, a non-DLVO repulsive interaction is observed. This behavior is explained if the presence of hydration forces in the system is assumed. Theoretical predictions including a hydration term in the DLVO theory fit the experimental results satisfactorily. The results presented in this article provide a direct confirmation that the AFM colloid probe technique can provide a useful way of directly quantifying the interaction of biological macromolecules.

  • 11. Valle-Delgado, J. J.
    et al.
    Molina-Bolivar, J. A.
    Galisteo-Gonzalez, F.
    Galvez-Ruiz, M. J.
    Feiler, Adam
    KTH, Tidigare Institutioner, Kemi.
    Rutland, Mark W.
    KTH, Tidigare Institutioner, Kemi.
    Interactions between bovine serum albumin layers adsorbed on different substrates measured with an atomic force microscope2004Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 6, nr 7, s. 1482-1486Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By the aid of an atomic force microscope (AFM) and the colloid probe technique, the interaction forces between bovine serum albumin (BSA) layers adsorbed on different substrates (silica and polystyrene) have been measured directly as a function of pH and salt concentration. Electrostatic and steric forces dominate the interactions at low salt concentrations. At high salt concentrations, when electrostatic interactions are screened, a very strange behaviour is found as a function of pH. The behaviour around the i.e.p. of the protein is also very striking: the interaction is attractive at low salt concentration, but it is repulsive at high salt concentration. These results could be explained if the presence of hydration forces is assumed. Theoretical predictions including a hydration term in the DLVO theory fit the experimental results satisfactorily.

  • 12. Valle-Delgado, J. J.
    et al.
    Molina-Bolivar, J. A.
    Galisteo-Gonzalez, F.
    Galvez-Ruiz, M. J.
    Feiler, Adam
    KTH, Tidigare Institutioner, Kemi.
    Rutland, Mark W
    KTH, Tidigare Institutioner, Kemi.
    Measurement of interactions between protein layers adsorbed on silica by atomic force microscopy2004Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 16, nr 26, s. S2383-S2392Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present work, using an atomic force microscope and the colloid probe technique, investigates the interaction forces between bovine serum albumin (BSA) layers and between apoferritin layers adsorbed on silica surfaces. The measurements have been carried out in an aqueous medium at different pH values and NaCl concentrations. Similar behaviours have been found with both proteins. Electrostatic and steric forces dominate the interactions between the protein layers at low NaCl concentrations. However, a very strange behaviour is found as a function of pH at high NaCl concentrations. The results obtained under these conditions could be explained if the presence of hydration forces in these systems is assumed.

  • 13. Zhou, Chunfang
    et al.
    Afonso, Damien
    Valetti, Sabrina
    Feiler, Adam
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Nanologica AB, Sweden.
    Cardile, Venera
    Graziano, Adriana C. E.
    Conoci, Sabrina
    Sortino, Salvatore
    Targeted Photodynamic Therapy with a Folate/Sensitizer Assembly Produced from Mesoporous Silica2017Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, nr 32, s. 7672-7676Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mesoporous silica material prepared by using folic acid (FA) as a template enables the effective encapsulation of meso-tetrakis(4-carboxyphenyl) porphyrin (TCPP) in its interior. Combination of steady-state and time-resolved absorption and emission spectroscopy demonstrate that FA and TCPP are released from the silica material to the aqueous phase in the form of a non-covalent assembly. This assembly does not form by simple mixing of the two components in the absence of silica, suggesting the key role of the material in the assembling process. The FA/TCPP assembly exhibits dual color fluorescence in the visible region, good photosensitization capability of singlet oxygen, and enhanced photo-induced mortality in KB cancer cells overexpressing folate receptor, if compared with the free components.

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