Modification of AgNP-Decorated PET: A Promising Strategy for Preparation of AgNP-Filled Nuclear Pores in Polymer Membranes.

Polymer-based membranes represent an irreplaceable group of materials that can be applied in a wide range of key industrial areas, from packaging to high-end technologies. Increased selectivity to transport properties or the possibility of controlling membrane permeability by external stimuli represents a key issue in current material research. In this work, we present an unconventional approach with the introduction of silver nanoparticles (AgNPs) into membrane pores, by immobilising them onto the surface of polyethyleneterephthalate (PET) foil with subsequent physical modification by means of laser and plasma radiation prior to membrane preparation. Our results showed that the surface characteristics of AgNP-decorated PET (surface morphology, AgNP content, and depth profile) affected the distribution and concentration of AgNPs in subsequent ion-track membranes. We believe that the presented approach affecting the redistribution of AgNPs in the polymer volume may open up new possibilities for the preparation of metal nanoparticle-filled polymeric membranes. The presence of AgNPs on the pore walls can facilitate the grafting of stimuli-responsive molecules onto these active sites and may contribute to the development of intelligent membranes with controllable transport properties.

Nano-assembly of cytotoxic amides of moronic and morolic acid.

Moronic acid and morolic acid, less frequently studied plant triterpenoids, were subjected to derivation with several structural modifiers, namely, piperazine-, pyrazine-, 1H-indole- and L-methionine-based compounds. Derivation was targeted to design and prepare novel compounds capable of nano-assembling and/or displaying cytotoxicity. Formation of nanostructures has been proven for several novel target compounds that formed different types of nanostructures, either in chloroform or in water. Isometric nanoparticles with broad size distributions (12 and 25), distorted single sheets (23) or very large thin warped films (13) were formed in chloroform solutions. Sheet-like nanostructures (12 and 23), and sphere-like nanostructures (hydrogen bonding connected nanoparticles; 3, 5, 13, 21 and 25) were formed in water suspensions. Cytotoxicity was also investigated and compared with that of the parent triterpenoids, showing enhanced effect of 18 that was the most successful derivative of the prepared series with sufficient balance between its cytotoxicity in CEM (IC50 = 11.7 ± 2.4 µM), HeLa (IC50 = 9.0 ± 0.7 µM) and G-361 (IC50 = 10.6 ± 5.5 µM) cancer cell lines, and toxicity in BJ (IC50 = 43.3 ± 1.5 µM). The calculated selectivity index values for 18 are SI = 3.9 (CEM), 4.8 (HeLa) and 4.4 (G-361). Additional compounds displaying cytotoxicity were 5, 7, 9 and 15, all of them showed comparable cytotoxicity with 18, in the investigated cancer cell lines; however, they were more toxic in BJ than 18.

Cryopreservation of apheresis platelets treated with riboflavin and UV light.

BACKGROUND: Pathogen reduction technology (PRT) is increasingly used in the preparation of platelets for therapeutic transfusion. As the Czech Republic considers PRT, we asked what effects PRT may have on the recovery and function of platelets after cryopreservation (CP), which we use in both military and civilian blood settings. STUDY DESIGN AND METHODS: 16 Group O apheresis platelets units were treated with PRT (Mirasol, Terumo BCT, USA) before freezing; 15 similarly collected units were frozen without PRT as controls. All units were processed with 5-6% DMSO, frozen at - 80 °C, stored > 14 days, and reconstituted in thawed AB plasma. After reconstitution, all units were assessed for: platelet count, mean platelet volume (MPV), platelet recovery, thromboelastography, thrombin generation time, endogenous thrombin potential (ETP), glucose, lactate, pH, pO2, pCO2, HCO3, CD41, CD42b, CD62, Annexin V, CCL5, CD62P, and aggregates > 2 mm and selected units for Kunicki score. RESULTS: PRT treated platelet units had lower platelet number (247 vs 278 ×109/U), reduced thromboelastographic MA (38 vs 62 mm) and demonstrated aggregates compared to untreated platelets. Plasma coagulation functions were largely unchanged. CONCLUSIONS: Samples from PRT units showed reduced platelet number, reduced function greater than the reduced number would cause, and aggregates. While the platelet numbers are sufficient to meet the European standard, marked platelets activation with weak clot strength suggest reduced effectiveness.

Surface Engineering of AgNPs-Decorated Polyetheretherketone.

Metal nanostructure-treated polymers are widely recognized as the key material responsible for a specific antibacterial response in medical-based applications. However, the finding of an optimal bactericidal effect in combination with an acceptable level of cytotoxicity, which is typical for metal nanostructures, prevents their expansion from being more significant so far. This study explores the possibility of firmly anchoring silver nanoparticles (AgNPs) into polyetherether ketone (PEEK) with a tailored surface morphology that exhibits laser-induced periodic surface structures (LIPSS). We demonstrated that laser-induced forward transfer technology is a suitable tool, which, under specific conditions, enables uniform decoration of the PEEK surface with AgNPs, regardless of whether the surface is planar or LIPSS structured. The antibacterial test proved that AgNPs-decorated LIPSS represents a more effective bactericidal protection than their planar counterparts, even if they contain a lower concentration of immobilized particles. Nanostructured PEEK with embedded AgNPs may open up new possibilities in the production of templates for replication processes in the construction of functional bactericidal biopolymers or may be directly used in tissue engineering applications.

Anionically Functionalized Glycogen Encapsulates Melittin by Multivalent Interaction.

We developed acid-functionalized glycogen conjugates as supramolecular carriers for efficient encapsulation and inhibition of a model cationic peptide melittin─the main component of honeybee venom. For this purpose, we synthesized and characterized a set of glycogens, functionalized to various degrees by several different acid groups. These conjugates encapsulate melittin up to a certain threshold amount, beyond which they precipitate. Computer simulations showed that sufficiently functionalized conjugates electrostatically attract melittin, resulting in its efficient encapsulation in a broad pH range around the physiological pH. Hemolytic assays confirmed in vitro that the effective inhibition of melittin's hemolytic activity occurs for highly functionalized samples, whereas no inhibition is observed when using low-functionalized conjugates. It can be concluded that functional glycogens are promising carriers for cationic molecular cargos or antidotes against animal venoms under conditions, in which suitable properties such as biodegradability and biocompatibility are crucial.

Novel cytotoxic 1,10-phenanthroline-triterpenoid amphiphiles with supramolecular characteristics capable of coordinating 64Cu(II) labels.

1,10-Phenanthroline was decorated with triterpenoid-based substituents bearing additional spermine units to form amphiphilic molecules. The synthetic procedure designed for the new phenanthroline-triterpenoid amphiphiles is described in detail. Besides 1,10-phenanthroline, all target structures bear 1,4-disubstituted 1,2,3-triazole rings. The target compounds self-assembled into either helical-like or sheet-like nanostructures, depending on the structure of the target molecule, either based on betulinic acid or oleanolic acid, and on the way of binding spermine subunits to the rest of the molecules. They also proved their ability to coordinate 64Cu(II) ions. Finally, the target compounds showed cytotoxicity that was partly dependent on the formation of nanostructures.

Thermo- and ROS-Responsive Self-Assembled Polymer Nanoparticle Tracers for 19F MRI Theranostics.

Fluorine-19 magnetic resonance imaging (19F MRI) enables detailed in vivo tracking of fluorine-containing tracers and is therefore becoming a particularly useful tool in noninvasive medical imaging. In previous studies, we introduced biocompatible polymers based on the hydrophilic monomer N-(2-hydroxypropyl)methacrylamide (HPMA) and the thermoresponsive monomer N-(2,2-difluoroethyl)acrylamide (DFEA). These polymers have abundant magnetically equivalent fluorine atoms and advantageous properties as 19F MRI tracers. Furthermore, in this pilot study, we modified these polymers by introducing a redox-responsive monomer. As a result, our polymers changed their physicochemical properties once exposed to an oxidative environment. Reactive oxygen species (ROS)-responsive polymers were prepared by incorporating small amounts (0.9-4.5 mol %) of the N-[2-(ferrocenylcarboxamido)ethyl]acrylamide (FcCEA) monomer, which is hydrophobic and diamagnetic in the reduced electroneutral (Fe(II), ferrocene) state but hydrophilic and paramagnetic in the oxidized (Fe(III), ferrocenium cation) state. This property can be useful for theranostic purposes (therapy and diagnostic purposes), especially, in terms of ROS-responsive drug-delivery systems. In the reduced state, these nanoparticles remain self-assembled with the encapsulated drug but release the drug upon oxidation in ROS-rich tumors or inflamed tissues.

Magnetic cobalt oxide nanosheets: green synthesis and in vitro cytotoxicity.

Cobalt oxide nanoparticles were prepared via green chemistry route and fully characterized by Field Emission Scanning Electron Microscope (FESEM), Energy-dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM) and Transmission electron microscopy (TEM) analyses; the CoO and Co3O4 nanoparticles, in sheet-shaped cobalt oxide form, ensued simultaneously in one step. The varying concentrations of NPs were analyzed via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test on the cancer cell line (U87) which revealed that with increasing concentration of cobalt oxide nanoparticles, the survival rate of U87 tumor cells decreases; IC50 of nanoparticles being ~ 55 µg/ml-1.

Optomechanical Processing of Silver Colloids: New Generation of Nanoparticle-Polymer Composites with Bactericidal Effect.

The properties of materials at the nanoscale open up new methodologies for engineering prospective materials usable in high-end applications. The preparation of composite materials with a high content of an active component on their surface is one of the current challenges of materials engineering. This concept significantly increases the efficiency of heterogeneous processes moderated by the active component, typically in biological applications, catalysis, or drug delivery. Here we introduce a general approach, based on laser-induced optomechanical processing of silver colloids, for the preparation of polymer surfaces highly enriched with silver nanoparticles (AgNPs). As a result, the AgNPs are firmly immobilized in a thin surface layer without the use of any other chemical mediators. We have shown that our approach is applicable to a broad spectrum of polymer foils, regardless of whether they absorb laser light or not. However, if the laser radiation is absorbed, it is possible to transform smooth surface morphology of the polymer into a roughened one with a higher specific surface area. Analyses of the release of silver from the polymer surface together with antibacterial tests suggested that these materials could be suitable candidates in the fight against nosocomial infections and could inhibit the formation of biofilms with a long-term effect.

Controlled Tuning of the Size of Ag-Hydrosol Nanoparticles by Nonstabilized THF and Detection of Peroxides in THF.

Surface plasmon extinction (SPE) spectra of plasmonic nanoparticles (NPs) are sensitive indicators of their composition, size, shape, interparticle interactions, and of the dielectric constant of their ambient. In this study, rapid changes in SPE spectra of Ag NPs suggesting variations in NP size and concentration were detected after addition of aged tetrahydrofuran (THF). Using time-dependent UV/vis spectroscopy combined with factor analysis, transmission electron microscopy imaging, selected-area electron diffraction, and energy-dispersive X-ray analysis, we observed that an over-limit amount of aged THF fully dissolved Ag NPs with no plasmon recovery. By contrast, an under-limit amount led to incomplete dissolution of Ag NPs and, after reaching the turnover point, to spontaneous recrystallization on residual Ag nuclei, as demonstrated by the SPE band intensity recovery to the original or even higher values. The newly formed Ag NPs were isometric, and their diameter was dependent on the added amount of THF. Furthermore, both Ag NP dissolution and recrystallization were caused by THF peroxides and their reduction products. Therefore, the dissolution of Ag NPs and the resulting hydrosol bleaching may be used as an indicator of the presence of peroxides in THF. Moreover, the reaction of aged THF with Ag NPs can be employed as a tool for tuning the size of Ag NPs in hydrosols.

Monolithic intercalated PNIPAm/starch hydrogels with very fast and extensive one-way volume and swelling responses to temperature and pH: prospective actuators and drug release systems.

Remarkable monolithic (non-porous) hydrogels based on poly(NIPAm-co-sodium methacrylate) intercalated by starch were prepared, and were found to display very fast and extensive one-way solvent (water) release, induced by both pH and temperature. With centimeter-sized 3D specimens, the achieved response times were as short as 4 min (for 70% water release), in combination with very large volume responses (shrinking ratios up to 15). The response time can be tuned from minutes, over tens of minutes, up to hours. The pH-induced deswelling is always slower than the temperature-induced one, but at the highest starch content, ca. 5.5 min are needed for 70% completion of the pH-triggered process. Simultaneous temperature- and pH-stimuli expectedly also lead to very fast water release. The unique intercalated structure and the temperature-dependent hydrogen bridging between the intercalated phases, as well as between these phases and water, were found to play the key role in the ability of the gels to rapidly release water and shrink, which was deeper elucidated in this work. The hydrogels are of interest as soft actuators, but also for chemical release systems or for drug release applications. The latter was successfully tested with theophylline as the drug.

Self-Assembled Thermoresponsive Polymeric Nanogels for 19F MR Imaging.

Magnetic resonance imaging using fluorinated contrast agents (19F MRI) enables to achive highcontrast in images due to the negligible fluorine background in living tissues. In this pilot study, we developed new biocompatible, temperature-responsive, and easily synthesized polymeric nanogels containing a sufficient concentration of magnetically equivalent fluorine atoms for 19F MRI purposes. The structure of the nanogels is based on amphiphilic copolymers containing two blocks, a hydrophilic poly[ N-(2-hydroxypropyl)methacrylamide] (PHPMA) or poly(2-methyl-2-oxazoline) (PMeOx) block, and a thermoresponsive poly[ N(2,2difluoroethyl)acrylamide] (PDFEA) block. The thermoresponsive properties of the PDFEA block allow us to control the process of nanogel self-assembly upon its heating in an aqueous solution. Particle size depends on the copolymer composition, and the most promising copolymers with longer thermoresponsive blocks form nanogels of suitable size for angiogenesis imaging or the labeling of cells (approximately 120 nm). The in vitro 19F MRI experiments reveal good sensitivity of the copolymer contrast agents, while the nanogels were proven to be noncytotoxic for several cell lines.

Formation of core/corona nanoparticles with interpolyelectrolyte complex cores in aqueous solution: insight into chain dynamics in the complex from fluorescence quenching.

Formation of interpolyelectrolyte complexes (IPECs) of poly(methacrylic acid) (PMAA) bearing a fluorescent label (umbelliferone) at the chain end and poly[3,5-bis(trimethyl ammoniummethyl)-4-hydroxystyrene iodide]-block-poly(ethylene oxide) (QNPHOS-PEO) acting as a fluorescence quencher, was followed using a combination of scattering, calorimetry, microscopy and fluorescence spectroscopy techniques. While scattering and microscopy measurements indicated formation of spherical core/corona nanoparticles with the core of the QNPHOS/PMAA complex and the PEO corona, fluorescence measurements showed that both static and dynamic quenching efficiency were increased in the nanoparticle stability region. As the dynamic quenching rate constant remained unchanged, the quenching enhancement was caused by the increase in the local concentration of QNPHOS segments in the microenvironment of the label. This finding implies that the local dynamics of PMAA end chains affecting the interaction of the label with QNPHOS segments was independent of both PMAA and QNPHOS chain conformations.

Arrays of Ag and Au Nanoparticles with Terpyridine- and Thiophene-Based Ligands: Morphology and Optical Responses.

The assembly of Ag and Au nanoparticles (NPs) into nanoparticulate arrays mediated by terpyridine (tpy), 4'-(2-thienyl)terpyridine (T-tpy), and short α,ω-bis(tpy)oligothiophene ligands has been accomplished at the interface between the Ag or Au NP hydrosol and a solution of the molecular species in dichloromethane. The relationship between the morphology and the optical responses of the arrays has been investigated by advanced methods of TEM (transmission electron microscopy) image analysis and surface plasmon extinction (SPE) spectra. It has been established that the size of islands of closely spaced NPs rather than the average interparticle distance affects the extent of delocalization of the surface plasmon excitations and thus also the SPE spectra. Furthermore, the structure of surface-adsorbate complexes formed in these arrays has been investigated by SERS spectral measurements carried out as a function of the excitation wavelength. Photoinduced charge transfer (CT) transitions from the neutral Ags0 and Aus0 adsorption sites on metal NPs to antibonding orbitals of the adsorbates have been identified for Ag/tpy, Ag/T-tpy, Au/tpy, and Au/T-tpy nanoparticulate arrays. Although the surface-adsorbate complexes displaying a photoinduced CT are known for Ag NPs, the Aus0 surface complexes with this CT are newly reported. Bis(tpy)oligothiophenes were found to be attached to both Ag and Au NPs via the tpy group(s). The match between the interparticle distances within the NP islands and the lengths of the oligomers molecules indicates that the molecules act as interparticle linkers. In this case, unequivocal spectral marker band evidence of the Ags0 as well as Aus0 surface complex formation has not been obtained.

Insight into the cryopolymerization to form a poly(N-isopropylacrylamide)/clay macroporous gel: structure and phase evolution.

The cryopolymerization and formation of a macroporous poly(N-isopropylacrylamide) (PNIPA)/clay cryogel were investigated. The mechanism of the cryopolymerization and cryogel formation was elucidated. Two processes, cryostructuration and cryopolymerization, proceed simultaneously and their relative rates determine the structure evolution and the cryogel morphology - porosity. The cryostructuration in the PNIPA/clay system during freezing, controlled by the freezing temperature and the rate of cooling, includes both water and NIPA crystallization, formation of a highly concentrated non-frozen liquid phase (NFLP) and clay aggregation. The rate of cryopolymerization and gelation is governed by the following effects: by a low polymerization temperature and after freezing, by the high cryoconcentration and a steric confinement, manifested by a reduced reagent mobility. Moreover, it depends on the cooling rate and the evolution of cryostructuration. The progress of cryostructuration and cryopolymerization during freezing was described and experimentally proved step by step. Both the phase development during freezing and the progress of cryopolymerization including gelation were monitored in situ by NMR, DSC, chemorheology and SAXS. The morphology and porosity of the cryogels were characterized by SEM and TEM.

Influence of Corona Structure on Binding of an Ionic Surfactant in Oppositely Charged Amphiphilic Polyelectrolyte Micelles.

Interaction of polystyrene-block-poly(methacrylic acid) micelles (PS-PMAA) with cationic surfactant N-dodecylpyridinium chloride (DPCl) in alkaline aqueous solutions was studied by static and dynamic light scattering, SAXS, cryogenic transmission electron microscopy (cryo-TEM), isothermal titration calorimetry (ITC), and time-resolved fluorescence spectroscopy. ITC and fluorescence measurements show that there are two distinct regimes of surfactant binding in the micellar corona (depending on the DPCl content) caused by different interactions of DPCl with PMAA in the inner and outer parts of the corona. The compensation of the negative charge of the micellar corona by DPCl leads to the aggregation of PS-PMAA micelles, and the micelles form colloidal aggregates at a certain critical surfactant concentration. SAXS shows that the aggregates are formed by individual PS-PMAA micelles with intact cores and collapsed coronas interconnected with surfactant micelles by electrostatic interactions. Unlike polyelectrolyte-surfactant complexes formed by free polyelectrolyte chains, the PMAA/DPCl complex with collapsed corona does not contain surfactant micelles.

[UHMWPE - polyethylene for articulating surfaces of joint replacements]. / UHMWPE - polyethylen pro artikulacní povrchy kloubních náhrad.

The introduction of artificial joint replacement constitutes a breakthrough method of treatment for severe joint disease for millions of people worldwide.Annual increase in the number of primary replacement and also increasing demands on the longevity of joint replacements are leading to increased demands on wear resistance of articular surface. Ultra-high molecular weight polyethylene (UHMWPE) is still most commonly used material for the production of articular surface. It was introduced into clinical practice in the 60s of the 20th century. Physical-chemical properties of UHMWPE are subject of many studies. These lead gradually to its improvement in terms of higher wear resistance while maintaining the stability against oxidative degradation.The main objective of this review is to summarize the basic properties of high-molecular weight polyethylene which are important for its use in orthopaedic practice and to explain the possibilities of its modification and sterilization. Knowledge of the latest trends about this material helps to orthopaedic surgeons get oriented in the issues and then to choose for their patients implants with the highest implant longevity.

Macroporous Biodegradable Cryogels of Synthetic Poly(α-amino acids).

We present an investigation of the preparation of highly porous hydrogels based on biodegradable synthetic poly(α-amino acid) as potential tissue engineering scaffolds. Covalently cross-linked gels with permanent pores were formed under cryogenic conditions by free-radical copolymerization of poly[N(5)-(2-hydroxyethyl)-L-glutamine-stat-N(5)-(2-methacryloyl-oxy-ethyl)-L-glutamine] (PHEG-MA) with 2-hydrohyethyl methacrylate (HEMA) and, optionally, N-propargyl acrylamide (PrAAm) as minor comonomers. The morphology of the cryogels showed interconnected polyhedral or laminar pores. The volume content of communicating water-filled pores was >90%. The storage moduli of the swollen cryogels were in the range of 1-6 kPa, even when the water content was >95%. The enzymatic degradation of a cryogel corresponded to the decrease in its storage modulus during incubation with papain, a model enzyme with specificity analogous to wound-healing enzymes. It was shown that cryogels with incorporated alkyne groups can easily be modified with short synthetic peptides using azide-alkyne cycloaddition "click" chemistry, thus providing porous hydrogel scaffolds with biomimetic features.

Quantification of structural changes of UHMWPE components in total joint replacements.

BACKGROUND: At present time the number of implantations of joint replacements as well as their revisions increases. Higher demands are required on the quality and longevity of implants. The aim of this work was to determine the degree of oxidative degradation and the amount of free/residual radicals in selected ultra-high molecular weight polyethylene (UHMWPE) components of the joint replacements and demonstrate that the measured values are closely connected with quality and lifetime of the polymer components. METHODS: We tested both new (4 samples) and explanted (4 samples) UHMWPE polymers for total joint replacements. The samples were characterized by infrared spectroscopy (IR), electron spin resonance (ESR) and microhardness (MH) test. The IR measurements yielded the values of oxidation index and trans-vinylene index. The ESR measurements gave the free radicals concentration. RESULTS: In the group of new polyethylene components, we found oxidation index values ranging from 0.00-0.03 to 0.24. The trans-vinylene index values ranged from 0.044 to 0.080. The value of free radical concentration was zero in virgin and also in sample of Beznoska Company and non-zero in the other samples. In the group of explanted components, the measured values were associated with their history, micromechanical properties and performance in vivo. CONCLUSIONS: We demonstrated that measuring of oxidative damage may help the orthopaedic surgeon in estimating the quality of UHMWPE replacement component and thus radically to avoid early joint replacement failure due to worse polyethylene quality.