Dispersing hydrophilic nanoparticles in hydrophobic polymers: HDPE/ZnO nanocomposites by a novel template-based approach

The efficiency of a novel template-based approach for the dispersion of hydrophilic nanoparticles within hydrophobic polymer matrices is investigated. The procedure envisages the permeation of a well dispersed nanoparticle suspension inside a micro-porous matrix, obtained through selective extraction of a sacrificial phase from a finely interpenetrated co-continuous polymer blend. Specifically, a blend of high density polyethylene (HDPE) and polyethylene oxide (PEO) at 50/50 wt% is prepared by melt mixing. The addition of small amounts of organo-clay promotes the necessary refinement of the blend morphology. Once removed the PEO, the micro-porous HDPE matrix is dipped in a colloidal suspension of zinc oxide nanoparticles which exhibits low interfacial tension with HDPE. A system prepared by traditional melt mixing is used as reference. Melt- and solid-state viscoelastic measurements reveal a good quality of the filler dispersion despite the uneven distribution on micro-scale. The latter can be capitalized to minimize the filler content to attain a certain improvement of the material properties or to design nano-structured polymer composites. © BME-PT

Improving osteoblasts cells proliferation via femtosecond laser surface modification of 3D-printed poly-ε-caprolactone scaffolds for bone tissue engineering applications

Synthetic polymer biomaterials incorporating cells are a promising technique for treatment of orthopedic injuries. To enhance the integration of biomaterials into the human body, additional functionalization of the scaffold surface should be carried out that would assist one in mimicking the natural cellular environment. In this study, we examined poly-epsilon-caprolactone (PCL) fiber matrices in view of optimizing the porous properties of the constructs. Altering the porosity of a PCL scaffold is expected to improve the material's biocompatibility, thus influencing its osteoconductivity and osteointegration. We produced 3D poly-epsilon-caprolactone (PCL) matrices by a fused deposition modeling method for bone and cartilage tissue engineering and performed femtosecond (fs) laser modification experiments to improve the surface properties of the PCL construct. Femtosecond laser processing is one of the useful tools for creating a vast diversity of surface patterns with reproducibility and precision. The processed surface of the PCL matrix was examined to follow the effect of the laser parameters, namely the laser pulse energy and repetition rate and the number (N) of applied pulses. The modified zones were characterized by scanning electron microscopy (SEM), confocal microscopy, X-ray computed tomography and contact angle measurements. The results obtained demonstrated changes in the morphology of the processed surface. A decrease in the water contact angle was also seen after fs laser processing of fiber meshes. Our work demonstrated that a precise control of material surface properties could be achieved by applying a different number of laser pulses at various laser fluence values. We concluded that the structural features of the matrix remain unaffected and can be successfully modified through laser postmodification. The cells tests indicated that the micro-modifications created induced MG63 and MC3T3 osteoblast cellular orientation. The analysis of the MG63 and MC3T3 osteoblast attachment suggested regulation of cells volume migration

Nanoformulation Composed of Ellagic Acid and Functionalized Zinc Oxide Nanoparticles Inactivates DNA and RNA Viruses

The COVID-19 pandemic has strongly impacted daily life across the globe and caused millions of infections and deaths. No drug therapy has yet been approved for the clinic. In the current study, we provide a novel nanoformulation against DNA and RNA viruses that also has a potential for implementation against COVID-19. The inorganic–organic hybrid nanoformulation is composed of zinc oxide nanoparticles (ZnO NPs) functionalized with triptycene organic molecules (TRP) via EDC/NHS coupling chemistry and impregnated with a natural agent, ellagic acid (ELG), via non-covalent interactions. The physicochemical properties of prepared materials were identified with several techniques. The hybrid nanoformulation contained 9.5 wt.% TRP and was loaded with up to 33.3 wt.% ELG. ELG alone exhibited higher cytotoxicity than both the ZnO NPs and nanoformulation against host cells. The nanoformulation efficiently inhibited viruses, compared to ZnO NPs or ELG alone. For H1N1 and HCoV-229E (RNA viruses), the nanoformulation had a therapeutic index of 77.3 and 75.7, respectively. For HSV-2 and Ad-7 (DNA viruses), the nanoformulation had a therapeutic index of 57.5 and 51.7, respectively. In addition, the nanoformulation showed direct inactivation of HCoV-229E via a virucidal mechanism. The inhibition by this mechanism was > 60%. Thus, the nanoformulation is a potentially safe and low-cost hybrid agent that can be explored as a new alternative therapeutic strategy for COVID-19

Synthesis and characterization of precipitation hardened amorphous matrix composite by mechanical alloying and pulse plasma sintering of Al<SUB>65</SUB>Cu<SUB>20</SUB>Ti<SUB>15</SUB>

This study reports synthesis of Al65Cu20Ti15 amorphous alloy by mechanical alloying and consolidation of the powder mass by pulsed plasma sintering. During sintering, several intermetallic phases precipitate from the amorphous matrix and cause a significant increase in nano-hardness and elastic modulus. Microstructure in as-milled and sintered conditions was characterized by X-ray diffraction, scanning/transmission electron microscopy and differential scanning calorimetric. Among various conditions of sintering, the composites pulse plasma, sintered at 500&#176;C, show the high compression strength (1745 MPa) and high indentation fracture toughness (4.96 MPa m&#189; ); although, the maximum density (3.73 Mg/in3), nano-hardness (14 GPa) and Young's modulus (208 GPa) in the present alloy have been obtained in the composites pulse plasma sintered at 600&#176;C

Highly biocompatible, nanocrystalline hydroxyapatite synthesized in a solvothermal process driven by high energy density microwave radiation

Dariusz Smolen1, Tadeusz Chudoba1, Iwona Malka1, Aleksandra Kedzierska1, Witold Lojkowski1, Wojciech Swieszkowski2, Krzysztof Jan Kurzydlowski2, Malgorzata Kolodziejczyk-Mierzynska3, Malgorzata Lewandowska-Szumiel31Polish Academy of Science, Institute of High Pressure Physics, Warsaw, Poland; 2Faculty of Materials Engineering, Warsaw University of Technology, Warsaw, Poland; 3Department of Histology and Embryology, Center of Biostructure Research, Medical University of Warsaw, Warsaw, PolandAbstract: A microwave, solvothermal synthesis of highly biocompatible hydroxyapatite (HAp) nanopowder was developed. The process was conducted in a microwave radiation field having a high energy density of 5 W/mL and over a time less than 2 minutes. The sample measurements included: powder X-ray diffraction, density, specific surface area, and chemical composition. The morphology and structure were investigated by scanning electron microscopy as well as transmission electron microscopy (TEM). The thermal behavior analysis was conducted using a simultaneous thermal analysis technique coupled with quadruple mass spectrometry. Additionally, Fourier transform infrared spectroscopy tests of heated samples were performed. A degradation test and a biocompatibility study in vitro using human osteoblast cells were also conducted. The developed method enables the synthesis of pure, fully crystalline hexagonal HAp nanopowder with a specific surface area close to 240 m2/g and a Ca/P molar ratio equal to 1.57. TEM measurements showed that this method results in particles with an average grain size below 6 nm. A 28-day degradation test conducted according to the ISO standard indicated a 22% loss of initial weight and a calcium ion concentration at 200 &amp;micro;mol/dm3 in the tris(hydroxymethyl)aminomethane hydrochloride test solution. The cytocompatibility of the obtained material was confirmed in a culture of human bone derived cells, both in an indirect test using the material extract, and in direct contact. A quantitative analysis was based on the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide. Viability assay as well as on DNA content measurements in the PicoGreen test. Indirect observations were performed at one point in time according to the ISO standard for in vitro cytotoxicity (ie, after 24 hours of cell exposure to the extracts). The direct contact tests were completed at three time points: after 24 hours, on day 7, and on day 14 of a culture in an osteogenic medium. All of the tests revealed good tolerance of cells toward the material; this was also shown by means of live/dead fluorescent staining. Both quantitative results and morphological observations revealed much better cell tolerance toward the obtained HAp compared to commercially available HAp NanoXIM, which was used as a reference material.Keywords: bone regeneration, bone substitute, microwave, HA

The utilization of electrical conductivity for evaluation of the plant tissue freezing/thawing process

Celem pracy była analiza możliwości wykorzystania przewodności elektrycznej właściwej do oceny przebiegu procesu zamrażania oraz rozmrażania, a także wybranych parametrów jakościowych rozmrożonej tkanki roślinnej. W tym celu próbki marchwi, ziemniaka oraz jabłka poddano zamrażaniu owiewowemu (–20°C), owiewowo-szokowemu (–20 lub –40°C) oraz immersyjnemu (–20°C), a następnie rozmrażano w temperaturze pokojowej (konwekcja naturalna) oraz wyznaczono czasy trwania poszczególnych etapów tych procesów. Po rozmrożeniu wyznaczono ubytek masy, przewodność elektryczną właściwą i zawartość suchej substancji tkanki. Stwierdzono, że zamrażanie, a następnie rozmrażanie prowadziło do wzrostu przewodności elektrycznej, przy czym wielkość tych zmian zależała przede wszystkim od rodzaju materiału. Na podstawie analizy statystycznej (przeprowadzonej metodą analizy skupień) wyników badań udowodniono, że przewodność elektryczna może być zgrupowana w jednej kategorii z zawartością suchej substancji, czasem przemiany fazowej podczas zamrażania, rozmrażania oraz z całkowitym czasem rozmrażania.The kinetics of freezing/thawing and quality of frozen-thawed materials depend on many factors which are linked to the processing method, features of the raw material and the pretreatment conditions. Therefore, it could be stated that there exist a need to develop a tool which could be helpful in the analysis of the course of the freezing process and which will help to evaluate the quality of freeze-thawed material. Measurement of electrical properties of the tissue, which are related to the integrity of the intercellular structure of the material, could provide a helpful data in both freezing process evaluation and optimization. The aim of this work was to analyze the dependence between the electrical conductivity and some parameters linked to the kinetics of freezing/thawing and physical parameters of frozen-thawed plant tissue. Apple, carrot and potato samples were used in the investigation. Plant materials were frozen by the means of air-freezing (–20°C), shock-air-freezing (–20 and –40°C) and immersion freezing (–20°) and thawed at the room temperature (free convection; 20 ±1°C). After such processing in the samples, electrical conductivity, dry matter content and the mass loss were determined. The shortest total freezing time was noticed for the shock-air-freezing method regardless of the processed raw material wherein the lower freezing temperature resulted in shorter freezing time. Thawing lasted at least two times longer than freezing and the longest total thawing time was observed in the case of carrots frozen by the means of shock-air-freezing at –40°C. Freezing and thawing generally reduced the dry matter content up to 26.1% in comparison to an unprocessed material. Furthermore, the lowest value of mass loss after thawing was observed in the case of samples which were processed by the immersion freezing regardless of the kind of the plant tissue. All thawed samples exhibited higher electrical conductivity than the unfrozen, raw tissues. The value of this parameter was even 7 times higher in the case of freeze-thawed potato frozen by the means of air-freezing (–20°C). Such situation was caused by the disintegration of the cell membrane as a consequence of ice crystal formation and thawing. Cluster analysis showed that the electrical conductivity can be aggregated in the same group with the dry matter content, phase transition time during freezing, phase transition time during thawing and total thawing time and thus it can facilitate the interpretation of the data