Inside the Protein Corona: From Binding Parameters to Unstained Hard and Soft Coronas Visualization.

Proteins spontaneously adsorb on nanoparticle surfaces when injected into the bloodstream. It drastically modifies the nanoparticle's fate and how they interact with organs and cells. Although this protein layer (protein corona) has been widely studied, the robustness of the most employed characterization methods and the visualization of its unstained fractions remain open questions. Here, synchrotron-based small-angle X-ray scattering was used to follow the corona formation and estimate binding parameters. At the same time, transmission electron microscopy under cryogenic conditions associated with cross-correlation image processing and energy-filtered transmission electron microscopy allowed to determine protein corona morphology and thickness together with the visualization of its unstained hard and soft fractions. The above-presented strategy shows tremendous potential for deciphering fundamental protein corona aspects and can contribute to rational medical nanoparticle engineering.

Shielding and stealth effects of zwitterion moieties in double-functionalized silica nanoparticles.

Surface functionalization of silica nanoparticles (SiO2NPs) has been considered as a promising strategy to develop target-specific nanostructures. However, finding a chemical functionalization that can be used as an active targeting moiety while preserving the nanoparticles colloidal stability in biological fluids is still challenging. We present here a dual surface modification strategy for SiO2NPs where a zwitterion (ZW) and a biologically active group (BAG) (amino, mercapto or carboxylic functionalities) are simultaneously grafted on the nanoparticles' surface. The rationale behind this strategy is to generate colloidally stable nanoparticles and avoid the nonspecific protein adsorption due to ZW groups insertion, while the effective interaction with biosystems is guaranteed by the BAGs presence. The biological efficacy was tested against VERO cells, E. coli bacteria and Zika viruses and a similar trend was observed for all tested particles. The desirable "stealth property" to prevent nonspecific protein adhesion also generated a ZW shielding effect of the BAG functionality hindering their proper interaction and activity in cells, bacteria and viruses.

Tailoring the Antimicrobial Response of Cationic Nanocellulose-Based Foams through Cryo-Templating.

To shed light on novel sustainable materials with antimicrobial functionality, in this contribution, we describe the use of cationic nanocellulose to produce foams featuring antibacterial activity against the powerful human pathogen Escherichia coli. Dialdehyde cellulose was cationized with Girard's reagent T (GRT), mechanically disintegrated into nanofibrillated cellulose (NFC), and shaped into foams through different protocols. All steps were carried out in aqueous media and in the absence of hazardous chemicals. While evaporative drying led to compact films (density of 1.3 g cm-3), freeze-casting (i.e., freezing and freeze-drying) produced monolithic cryogels with low densities (<50 mg cm-3) and porosities of ca. 98%. Although highly porous, the cryogels obtained through rapid freezing remarkably presented smaller pores than those that were previously frozen in a slow fashion. The quaternary ammonium groups of GRT-cationized NFC removed E. coli to different extents depending upon sample morphology. We demonstrated in an innovative manner that porosity, which is directly associated with surface area, and pore size play an essential role on the antimicrobial performance. This outcome arises from the inaccessibility of bacterial cells to cationic surfaces inside monoliths composed of small pores. We herein present an uncomplicated, environmentally friendly protocol for fine-tuning the porosity and pore size of all-cellulose materials through cryo-templating. Controlling these morphometric parameters allowed us to achieve a ca. 85% higher anti-E. coli activity when comparing samples made up of the very same material (i.e., the same NFC concentration and degree of substitution) but presented as dense films. These findings bear clear implications for the pursuit of sustainable materials presenting multifunctionality.

Antimicrobial Imidazolium Ionic Liquids for the Development of Minimal Invasive Calcium Phosphate-Based Bionanocomposites.

Biofilm formation is one of the main obstacles that occur during in vivo implantation, which compromises the implant functionality and patients' health. This is the inspiration for the development of novel implant materials that contain broad-spectrum antimicrobial activity, including antibacterial and antifungal, and enable the local release of antimicrobial agents. Here, multifunctional calcium phosphate-ionic liquid (IL) materials, possessing antimicrobial and repair/regeneration features plus injectability, are proposed as implants in minimally invasive surgery. This approach was based on the loading of 1-alkyl-3-alkylimidazolium chloride ionic liquids (ILs) (C nMImCl ( n = 4, 10, 16) and (C10)2MImCl) during the in situ sol-gel synthesis of calcium phosphates (CaP) and study of their effects on CaP crystallization and biological properties. Physical, morphological, and biological investigations were performed to evaluate the bionanocomposites' properties. The IL N-alkyl chain length influenced the crystallization of CaP and, consequently, the biological properties, which afforded bionanocomposites (when loaded with C16MImCl or (C10)2MImCl) that, (i) inhibit both in vitro bacterial and fungal growth; (ii) reduce the in vitro inflammatory response; (iii) induce osteogenic differentiation in the basal medium of human mesenchymal stem cells; and (iv) are injectable. This will enable the design of multifunctional injectable implants with antimicrobial, anti-inflammatory, and regenerative properties to be used in minimally invasive surgery of bone and maxillofacial defects.

Infrared and Raman spectroscopic characterization of some organic substituted hybrid silicas.

Nine hybrid silicas bearing the organic substituent groups methyl, octyl, octadecyl, vinyl, phenyl, mercaptopropyl, isocyanatopropyl, chloropropyl and glycidoxypropyl were synthesized by an acid-catalyzed, hydrolytic sol-gel process. The resulting solid materials were characterized by their absorbance and attenuated total reflection (ATR) IR and Raman spectra. The latter technique proved to be particularly useful in the identification of the organic moieties in the hybrid silicas. The effect of the presence of the organic groups on the silica networks was also investigated - there were increases observed in both the SiOSi bond angles and bond lengths. Moreover, deconvolution of the IR-active antisymmetric SiOSi stretching bands permitted detection of the four- and six-membered siloxane rings present in the silicas. There proved to be a greater number of four-membered rings on the surfaces of the particles. Both IR and Raman spectroscopy proved to be invaluable in the characterization of these hybrid materials.

Determination of titanium and vanadium in Ziegler-Natta catalysts by inductively coupled plasma atomic emission spectrometry.

A method for the determination of Ti and V using inductively coupled plasma atomic emission spectrometry (ICP OES) in Ziegler-Natta polymerization catalysts is proposed. The concentrations of both Ti and V are efficiently determined after catalyst acid digestion with a mixture of HNO3 + HCl + HF and heating (160 degrees C for 6 h) or with 10% (v/v) H2SO4 and heating (160 degrees C for 6 h) or with 10% (v/v) H2SO4 and sonication (during 2 min). The V and Ti detection limits are 0.002% and 0.08%, respectively, using 0.20 g of catalyst sample in 50 ml. The method is validated by a comparison with the Rutherford backscattering spectrometry (RBS) technique. In this case, catalyst samples are only pressed as pellets before analyte determination. Despite the fact that both the V and Ti concentrations cannot be determined individually by means of RBS, because the atomic numbers of Ti and V are very close, the sum of the V and Ti contents is in accordance with that attained by means of ICP OES. According to scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) it is observed that the Ti distribution on the catalyst grain is not homogenous.