Decreasing Pore Size Research Articles

Fractal Features of the Catalytic Performances of Bimodal Mesoporous Silica‐Supported Organocatalysts Derived from Bipyridine‐Proline for Asymmetric Aldol Reaction

AbstractThe three bipyridine‐proline chiral ligands (Z) with different structural units as highly active species were successfully introduced on Zn‐modified bimodal mesoporous silicas (BMMs). The representative heterogeneous catalysts (ZZnBMMs‐n) containing different molar ratios of Z/Zn (5, 20, 50, 100, 200%) were prepared, and their catalytic performances were evaluated in the asymmetric aldol reactions between p‐nitrobenzaldehyde and cyclohexanone, showing the satisfactory activities (yields) and good stereoselectivity (dr and ee). Meanwhile, their microstructural features and physicochemical properties were characterized by various methods. Particularly, the fractal evolution, the pair distance distribution function, and the Porod plots of the ZZnBMMs catalysts were demonstrated by SAXS analysis. The results revealed that the interfacial layer thickness and their mass fractal (Dm) value gradually increased with the enhanced molar ratios of Z/Zn, along with the decrease of pore size and densification of volume, suggesting the successful Z‐grafting into the mesoporous channels of Zn‐modified matrixes. The essential relationships between the fractal features and their catalytic performance (yield, dr and ee) were explored, showing the larger the Dm values, the better catalytic performance. Besides, the uniform distributions of Zn and S elements in ZZnBMMs catalysts and the formation of enamine‐imine intermediates during the asymmetric aldol reactions were confirmed.

MICROPLASTICS IN LANDFILL LEACHATES IN THREE NORDIC COUNTRIES

We investigated the occurrence of microplastics (size range 5,000-50 µm) in leachates at 11 landfills of different age and operational status in Finland, Iceland and Norway. Collective sampling was carried out by pumping leachate with a stainless-steel submergible pump through a custom-made, stainless-steel filter unit containing filter plates with decreasing pore sizes (5,000, 417 and 47 µm, respectively). Samples were pre-treated and split into particles size classes above 500 μm and above 50 μm, and screened for occurrence of microplastics made of PE, PP, PVC, PS, PET, PA, PU, PC, PMMA, POM, SBR (rubber) or PMB (polymer modified bitumen). Samples were analysed by FT-IR spectroscopy, both to identify and to count microplastic particles (SBR and PMB were merely identified). Most samples tested positive for multiple microplastics. Three leachates, including drinking water (blank), tested positive for SBR particles and/or PMB only. Treated leachate samples exhibited lower total microplastic’s counts than untreated, up to several orders of magnitude. National waste management practices over time, landfill age or operational status do not seem to explain differences in microplastic abundance or counts between leachates. Particle count and calculated loads of microplastic emissions through leachates differed several orders of magnitude between landfills. Results indicate that landfill leachates might be a relatively small source of microplastics (>50 µm) to surface waters compared to untreated and treated sewage or road runoff. Continued data acquisition, improved sample preparation and understanding of variability of microplastics in landfill leachate are necessary, including particles smaller than 50 µm.

Effect of sugar reduction and addition of corn fibre and polydextrose on pore size and syneresis of yoghurt

This study investigated the effect of sugar reduction and replacement by corn fibre and polydextrose on yoghurt gel pore size and syneresis. Five yoghurt formulations were produced with 9, 4.5 and 0% sucrose, and also 4.5% with added 2% corn fibre or polydextrose. The increasing demand for sugar reduction in dairy products justifies studies on new formulations such as fibre addition. Sucrose reduction from 9% to 0% led to a decrease in average matrix pore size and increased syneresis. Fibre or polydextrose addition effectively reduced syneresis, despite bigger matrix pore sizes. Fermentation profile, acidity and pH values were not significantly affected by compositional changes.

Research on preparation and characterization of Ti-Ti5Si3 gradient composite porous material via in-situ reactive process

Gradient composite porous material can reach a high filtering accuracy with larger filtration flux, and the filter elements applied in separation equipment can enhance the filtration efficiency and reduce the energy consumption. Ti-Ti5Si3 gradient composite porous material was successfully prepared by in-situ reaction process with the raw materials of Ti powder and high purity quartz tablets. Microstructures and filtration properties prepared under different synthesized conditions have been studied, including the parameters of pressure sintering (additional loads and temperatures) and powder particle sizes. The synthesized granules on the membrane are well distributed with the size of ∼1.0 µm, and the thickness of the membrane is 3.0∼6.3 µm. The relative air permeability coefficient of porous membrane reduces raptly compared to the sample matrix due to the decrease of pore size. The all synthesized membranes show the presence of Ti and Ti5Si3 phases. There are two distinct layers observed in the membrane layers prepared by fine powder due to in-situ over-reaction.

Influence of 17-4 PH stainless steel powder recycling on properties of SLM additive manufactured parts

Metal Additive Manufacturing (AM) processes are developing quickly. These processes have several attractive qualities, however, the quality of manufactured parts still remains a major issue that needs to be addressed if it is to become a prevalent technology in the industry. In some powder bed fusion techniques, such as Selective Laser Melting (SLM), there is a portion of initial powder that does not melt and it can be recycled to ensure the economic and environmental viability of the process. In previous research, we demonstrated the morphological, chemical and microstructural change suffered by 17-4 PH stainless steel powder after reusing it in a SLM manufacturing process. In this work, the properties of 17-4 PH stainless steel parts, printed from powder in different recycling states (virgin powder (P0) and 20 times reused powder (P20)), were evaluated, in order to establish good recycling procedures and optimise the SLM process performance. Analyses of the properties revealed a slight decrease in roughness and pore size with powder recycling. The external porosity of the samples is similar in both powder states; however, internal porosity decreases by increasing the number of reuse cycles. Regarding the microstructural analysis, a slight increase in the γ-phase is observed with the powder recycling, which leads to a slight increase in ductility and decrease in hardness of the samples. Therefore, it is concluded that the 17-4 PH powder recycling process in SLM manufacturing is adequate and recommended to ensure the economic and environmental viability of the process without adversely affecting the properties of the parts.

Tuning the Transport Properties of Gases in Porous Graphene Membranes with Controlled Pore Size and Thickness

AbstractPorous graphene membranes have emerged as promising alternatives for gas‐separation applications due to their atomic thickness enabling ultrahigh permeance, but they suffer from low gas selectivity. Whereas decreasing the pore size below 3 nm is expected to increase the gas selectivity due to molecular sieving, it is rather challenging to generate a large number of uniform small pores on the graphene surface. Here, a pore‐narrowing approach via gold deposition onto porous graphene surface is introduced to tune the pore size and thickness of the membrane to achieve a large number of small pores. Through the systematic approach, the ideal combination is determined as pore size below 3 nm, obtained at the thickness of 100 nm, to attain high selectivity and high permeance. The resulting membrane shows a H2/CO2 separation factor of 31.3 at H2 permeance of 2.23 × 105 GPU (1 GPU = 3.35 × 10−10 mol s−1 m−2 Pa−1), which is the highest value reported to date in the 105 GPU permeance range. This result is explained by comparing the predicted binding energies of gas molecules with the Au surface, −5.3 versus −21 kJ mol−1 for H2 and CO2, respectively, increased surface–gas interactions and molecular‐sieving effect with decreasing pore size.

Gradient porous electrode-inducing bubble splitting for highly efficient hydrogen evolution

Designing highly efficient electrodes for the hydrogen evolution reaction (HER) has attracted enormous attention owing to the urgent demand to decrease greenhouse gas emissions. However, the enormous energy loss due to an insufficient exposure of active sites caused by sluggish bubble detachment has been proven to be a critical obstacle for further enhancing the HER performance. In this study, we developed a gradient porous electrode (SML-LMS-HE) with decreasing pore size from the middle of the electrode to the two sides. This electrode was fabricated by simply pressing stack-up gradient porous nickel foams and employing a solvothermal treatment to load hierarchically porous coral-shaped MoS2/Ni3S2 heteronanorod electrocatalysts. The as-prepared SML-LMS-HE electrode enabled a much smaller hydrogen bubble detachment size by inducing hydrogen bubble splitting as compared to another gradient porous electrode and homogeneous porous electrode, leading to a reduced reactant transfer resistance and a decreased ohmic drop within the electrode. As a result, SML-LMS-HE exhibited excellent HER activity with an overpotential as low as 83 mV at − 10 mA cm−2 and prominent durability.

Interphase Surface Stability in Liquid-Liquid Membrane Contactors Based on Track-Etched Membranes.

A promising solution for the implementation of extraction processes is liquid–liquid membrane contactors. The transfer of the target component from one immiscible liquid to another is carried out inside membrane pores. For the first time, highly asymmetric track-etched membranes made of polyethylene terephthalate (PET) of the same thickness but with different pore diameters (12.5–19 nm on one side and hundreds of nanometers on the other side) were studied in the liquid–liquid membrane contactor. For analysis of the liquid–liquid interface stability, two systems widely diverging in the interfacial tension value were used: water–pentanol and water–hexadecane. The interface stability was investigated depending on the following process parameters: the porous structure, the location of the asymmetric membrane in the contactor, the velocities of liquids, and the pressure drop between them. It was shown that the stability of the interface increases with decreasing pore size. Furthermore, it is preferable to supply the aqueous phase from the side of the asymmetric membrane with the larger pore size. The asymmetry of the porous structure of the membrane makes it possible to increase the range of pressure drop values between the phases by at least two times (from 5 to 10 kPa), which does not lead to mutual dispersion of the liquids. The liquid–liquid contactor based on the asymmetric track-etched membranes allows for the extraction of impurities from the organic phase into the aqueous phase by using a 1% solution of acetone in hexadecane as an example.

In Vitro Neuroprotective Effects of Macrophage Membrane-Derived Curcumin-Loaded Carriers against 1-Methyl-4-phenylpyridinium-Induced Neuronal Damage.

Curcumin (CUR) possesses neuroprotective effects. However, its clinical therapeutic efficacy is limited because of its low systemic bioavailability due to poor water solubility and fast metabolism. Herein, we designed biomimetic therapeutic nanovesicles (NVs) with enhanced performance and biocompatibility for the intracellular delivery of hydrophobic CUR. Cell membrane NVs were constructed to function as drug carriers by the serial extrusion of macrophages using filters with decreasing pore sizes. Various CUR loading strategies were also evaluated. Furthermore, the neuroprotective effects of the CUR-loaded NVs (NVs–CUR) against 1-methyl-4-phenylpyridinium (MPP+)-induced neuronal degeneration were studied thoroughly. CUR-loaded NVs were readily taken up by neurons in vitro, and the survival rate of MPP+-induced primary neurons increased from 65.37 ± 6.37 to 90.91 ± 3.18% after pretreatment with NVs–CUR. Compared with traditional Parkinson’s disease chemotherapeutic treatment, NV formulations can improve the bioavailability of this drug. NVs are expected to become a new and effective drug-delivery platform for further applications in the field of central nervous system therapy.

Atmospheric-pressure PECVD synthesis of polymer-supported molecular sieving silica membranes for gas separation: Effect of pore size of polymeric support

Molecular sieving silica-based membranes were prepared on porous polymeric supports by atmospheric-pressure plasma-enhanced chemical vapor deposition. The effect of polymeric support pore size on the gas permeation properties of polymer-supported silica-based membranes was investigated using nanofiltration (NF) and ultrafiltration membranes as polymeric supports. The silica-based layer was uniformly formed on the surfaces of the polymeric supports, irrespective of their different pore sizes. The selectivity of the resultant polymer-supported membranes was found to increased with decreasing support pore size. The NF-supported membrane exhibited an improved H2/N2 permeance ratio of > 40, which was comparable to those of ceramic-supported membranes, demonstrating the successful synthesis of molecular sieving silica-based membranes onto a porous polymeric support.

Production of Porous Agarose-Based Structures: Freeze-Drying vs. Supercritical CO2 Drying.

In this work, the effect of two processes, i.e., freeze-drying and supercritical CO2 (SC-CO2) drying, on the final morphology of agarose-based porous structures, was investigated. The agarose concentration in water was varied from 1 wt% up to 8 wt%. Agarose cryogels were prepared by freeze-drying using two cooling rates: 2.5 °C/min and 0.1 °C/min. A more uniform macroporous structure and a decrease in average pore size were achieved when a fast cooling rate was adopted. When a slower cooling rate was performed instead, cryogels were characterized by a macroporous and heterogenous structure at all of the values of the biopolymer concentration investigated. SC-CO2 drying led to the production of aerogels characterized by a mesoporous structure, with a specific surface area up to 170 m2/g. Moreover, agarose-based aerogels were solvent-free, and no thermal changes were detected in the samples after processing.

Microstructure and Mechanical Strength Properties of Chitosan Sponges Obtained from Polymer Solutions in Carbonic Acid

Polymer sponges based on chitosan are first obtained from chitosan solutions in carbonic acid and gels based on these solutions crosslinked by a noncytotoxic agent of natural origin, genipin. A comparative analysis of the structure and mechanical strength properties of sponges prepared from chitosan solutions in carbonic and acetic acids is carried out. It is shown that the addition of genipin in an amount of ~2 wt % to a chitosan solution in carbonic acid leads to a decrease in the average pore size by ~2.5 times and a significant increase in the strength characteristics of the material in comparison with the sponge prepared without genipin.

Ultra-permeable CNTs/PES membranes with a very low CNTs content and high H2/N2 and CH4/N2 selectivity for clean energy extraction applications

Polysulfone (PES) membranes are among the rare membranes that are capable of double filtration: a pre-filter layer captures agglomerates and a thin-dense layer is responsible for the main separation process. This work aims to enhance the permeability and H2/N2 and CH4/N2 of the dense layer of PES by mixing it with low concentrations of carbon nanotubes (CNTs: 0.01–0.03 wt.%) using solution casting and doctor blade techniques. The pore topology, microstructure, chemical, thermal, and mechanical properties of the synthesized CNTs/PES membranes were investigated using FTIR, XRD, TGA, and a universal testing machine, while permeability of single CO2, H2, N2, and CH4 permeability of the CNTs/PES membranes were tested under different temperatures (20–60 °C) and pressures (1–6 bar). Also, the effect of added CNTs, separation temperature, and pressure on the gas separation mechanism were investigated. The results showed that adding of CNTs contributed to increase in porosity from 81.7% (PES) to 88.4% (CNTs/PES) and decrease in pore sizes from 84 nm (PES) to 50 nm (CNTS/PES). Meanwhile, the thermal and mechanical analysis showed that CNTs/PES membranes had higher thermal stability and somewhat lower strength compared with neat membranes. Also, the permeability measurements showed a big increase when only 0.01 wt.% of CNTs had been added, where H2, CH4, N2, CO2 permeabilities were increased up to 28,553, 11,358, 7540, 6720 Barrer, respectively, vs 10.4, 4.6, 13.7, and 12.3 Barrer in case of PES membranes. In addition, CO2/N2, CH4/N2, and H2/N2 selectivity of CNTs/PES membranes were enhanced by 29%, 396%, and 426%, respectively, as a result of pores refining and increasing of free space in the prepared CNTs/PES membranes. According to these results, CNTs/PES membranes with small loading of CNTs have a tremendous ability to deal with separation of H2/N2 and CH4/N2, what make them promising candidates for clean energy extraction applications.

Injectable eggshell-derived hydroxyapatite-incorporated fibroin-alginate composite hydrogel for bone tissue engineering

Tissue engineering is a promising approach to repair and regenerate damaged or lost tissues or organs. In dental aspect, reconstruction of the resorbed alveolar bone after tooth extraction plays an important role in the success of dental substitution, especially in dental implant treatment. The hydroxyapatite (HA)-incorporated fibroin-alginate composite injectable hydrogel was fabricated to be used as scaffold for bone regeneration. HA was synthesized from eggshell biowaste. Fibroin was extracted from Bombyx mori cocoon. The synthesized HA, fibroin and alginate hydrogel were characterized. HA-incorporated fibroin-alginate hydrogel had decreased pore size and porosity compared with pure alginate hydrogel. Thermal analysis showed that hydrogel had a degradation peak of approximately 250 °C. Hydrogel could absorb water, with a swelling ratio of around 300% at 24 h. Hydrogel was degraded as time passed and almost completely degraded at day 7. Its compressive Young's modulus was approximately 0.04 ± 0.02 N/mm2 to 0.10 ± 0.02 N/mm2. Primary cytotoxicity test indicated non-toxic potential of the fabricated hydrogel. Increased ALP activity was observed in MC3T3-E1 cultured in HA-incorporated fibroin-alginate hydrogel. Results suggested the potential use of injectable HA fibroin-alginate hydrogel as dental scaffolding material. Further studies including in vivo examinations are needed prior to its clinical application.

Synthesis of SBA 15 graphene oxide composite membrane using phenol–formaldehyde resin pore modifier for CO2 separation

AbstractPresent study highlights the development of carbon‐loaded SBA 15 membrane on clay‐alumina tubular support and its performance on the CO2 separation efficiencies from different mixture gases. To modify the large pores of SBA 15 by graphitic carbon, low molecular weight phenol–formaldehyde (PF) resin was incorporated into the mesoporous channel followed by calcination under inert atmosphere. The modified ordered pore structure of the membrane has been characterized by low‐angle XRD, TEM, and pore size distribution analysis. The chemical state of the deposited carbon phase into the SBA 15 pores was analyzed by X‐ray photoelectron and Raman spectroscopy. Carbon having graphitic nature mainly in graphene oxide has been deposited into the mesopore of SBA 15 resulting decrease in pore size from 8.9 to 1.0 nm. Finally, the developed SBA 15 carbon membranes were characterized by CO2 permeation and separation selectivity of CO2/CH4, CO2/CO. Highest CO2/CH4 separation factor was achieved as 16.9 with CO2 permeance 13.6 × 10–8 mol/m2/s/Pa at 200 kPa feed pressure by the 20% resin with 2 times coated membrane. In flue gas analysis, highest CO2/CO separation factor of 32.8 was achieved. This study offers an observation on CO2 separation from simulated BF gas for the first time and the results show the potential of the developed SBA 15/C composite membranes in commercial application.

Towards High Energy Density Electrochemical Energy Storage Systems: Li- and Na-Ion-Based Ultrathick Electrodes with New Current Collector Architectures By Spark Plasma Sintering and Hard Templating Approach

High energy density electrodes are of great interest for the application in electrochemical energy storage systems as well as electric vehicles. While the vast majority of research is still focusing on crystallochemical search for the new high-voltage/high-capacity materials, the cell engineering approach goes relatively unnoticed. However, over the past couple of decades, more and more research activities are aimed at developing new battery configurations to further improve the energy density of Li- and Na-ion batteries without fundamentally changing the underlying chemistry. Some methods suggest the fabrication of (ultra)thick electrodes while others concentrate on the production of electrodes with a minimum amount of inactive materials (binder-free, conductive additive-free, integrated current collectors, etc). Owing to a rapid and highly efficient sintering process, Spark Plasma Sintering (SPS) offers the luxury of obtaining simultaneously binder-free and (ultra)thick electrodes which suffer no structural degradation.Combined with novel integrated current collector architectures, SPS-fabricated (ultra)thick electrodes could provide high active material accessibility while working at elevated current rates owing to the controlled pore network morphology and improved electronic conductivity. In 2018 Elango et. al reported a successful Spark Plasma Sintering of the LiFePO4 and Li4Ti5O12 electrodes with controlled porosity by hard templating method (NaCl leaching) [1]. Obtained by SPS and templating approach ultrathick electrodes (1 mm thick) showed remarkable electrochemical performance at C/20 against lithium metal delivering areal capacities 4 times higher than those of the conventional tape-casted electrodes. This study coming from our group demonstrated the proof-of-concept in the fabrication of Li-ion battery electrodes with an ultrathick design by means of SPS. A follow-up study on the correlation between the electrode’s architecture (porosity level and pore size) and its electrochemical performance has been conducted [6] showing that a moderate increase of porosity and decrease in pore size improves the rate capability of the (ultra)thick electrodes (1 mm thick) by reducing the pore tortuosity and promoting fuller electrolyte impregnation.Spark Plasma Sintering-based electrode fabrication technique is expected to be easily transferable to other battery types like Na-ion batteries. However, commonly used Na-ion battery materials are not as widely produced as their Li counterparts and still require long and tedious synthesis procedures. In our work, we have recently demonstrated that SPS could be used to synthesize a common Na-ion battery cathode material – Na3V2(PO4)2F3 – in under only 40 min [2] which resembles a phase-pure compound with a small particle size showing slightly enhanced electrochemical performance when compared to the solid-state synthesized NVPF. SPS-synthesized NVPF requires no further treatment and could be used directly as an active material component in the production of our thick binder-free electrodes.In this presentation, the detailed study on the correlation between the (ultra)thick electrode architecture (porosity, pore size/shape distribution, tortuosity, etc), synthesis/sintering parameters, nature of precursors, and the electrochemical performance will be discussed (both for Li- and Na-ion batteries). An insight into the fabrication of (ultra)thick electrodes with novel integrated current collector architectures and their impact on the structural integrity as well as the electrochemical performance of the electrode will be reported.[1] R. Elango et al., Advanced Energy Materials, Vol 8 Issue 15 (2018)[2] A. Nadeina et al., Energy Technol., 8: 1901304 (2020)[3] F. Lalère, et al, Journal of Power Sources, 247, 975-980 (2014)[4] G. Delaizir, et al., Adv. Funct. Mater., 22: 2140-2147 (2012)[5] A. Aboulaich, et al., Adv. Energy Mater., 1: 179-183 (2011)[6] R. Elango, A. Nadeina, et al., Journal of Power Sources, 488, 229402 (2021) Figure 1

Development of polysulfone ultrafiltration membranes with enhanced antifouling performance for the valorisation of side streams in the pulp and paper industry

One-stage method of polysulfone (PSf) membrane modification by the addition of polyacrylic acid (PAA, Mn = 250 kg·mol−1) to the coagulation bath during membrane preparation via non-solvent induced phase separation (NIPS) was proposed. The effect of PAA concentration on the membrane structure, hydrophilicity, zeta potential, separation performance and antifouling stability in ultrafiltration of lysozyme, polyvinylpyrrolidone (PVP K-30, Mn = 40 kg mol−1) and humic acid model solutions as well as thermomechanical pulp mill process (ThMP) water was studied. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), measurements of the tangential flow streaming potential and water contact angle were used for membrane characterization. It was found that addition of PAA into coagulation bath resulted in decreasing pore size and porosity of the selective layer as well as the formation of a thicker and denser selective layer. Water contact angle of the modified membranes was found to decrease significantly and zeta potential of the selective layer was shown to become more negative in the studied pH range 3–10, all compared to the reference membrane. It was revealed that pure water flux (PWF) decreased and lysozyme and PVP K-30 rejection increased with the increase in PAA concentration in the coagulation bath. It was found that membranes modified with PAA demonstrated better antifouling stability in ultrafiltration of humic acid solution and ThMP process water. Modified membranes were found to have higher flux, fouling recovery ratio and hemicelluloses rejection in ThMP process water ultrafiltration compared to the reference PSf membrane that allows application of these membranes for hemicelluloses concentration and purification.

Phosphorous and sulfur doped asphaltene derived activated carbon for supercapacitor application

It is important to develop alternative methods for obtaining hierarchical porous and heteroatoms-doped carbon for the fabrication of a high-performance supercapacitor that is both effective and inexpensive. In this research, asphaltene rich-sulfur derived activated carbon (As-AC) is prepared by one-step pyrolysis of asphaltene. But, further phosphorous doping Asphaltene derived activated carbon (P-As-AC) was fabricated with facile pyrolysis of As-AC at 300 °C in the presence of (NH4)2HPO4. The synthesized materials were characterized by XRD, BET, EDAX, XPS, TEM, FTIR, Raman and Zeta potential analysis. XRD diagram show two broad diffraction peaks for As-AC and P-As-AC samples were displayed at 2Ө values of around 24° and 42°, respectively. The total specific surface area (SSA) of As-AC was 425.7 m2 g−1 while that of P-As-AC that doped with phosphorus decreased sharply to 18.468 m2 g−1. The total pore volume decreased from 0.5 cm3 g−1 for As-AC to 0.023 cm3 g−1 for P-As-AC and the pore size decrease from 3.3 nm for As-AC to 2.3 nm for P-As-AC. The supercapacitive activity of As-AC and P-As-AC electrodes was studied by cyclic voltammetry (CV), Galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). The mechanism of energy storage and charge storage was discussed.

Ambient pressure drug loading on trimethylchlorosilane silylated silica aerogel in aspirin controlled-release system

Trimethylchlorosilane silylated silica aerogel (TS-SA) was loaded with a model drug, aspirin. TS-SA preparation, drug loading, and drying were performed through ambient pressure techniques in a safe and cheap manner. The sample structure, drug loading, and drug dissolution profiles were characterized by N2 adsorption and desorption analysis, FT-IR spectroscopy, UV absorption spectroscopy, FE-EM, EDX, XRD, and DSC. The characterization results indicated drug molecules are successfully loaded on the entire nanostructure of TS-SA. Specific surface area, total pore volume, and average pore size decrease with drug loading in TS-SA structure, as well as XRD and DSC results are indicating the amorphous state of loaded aspirin. Drug adsorption isotherm was measured and fitted well by the Freundlich model. Drug release kinetics from the samples were also evaluated in 0.1 N HCl (pH 1.2) and phosphate buffer (pH 7.4). The zero-order model, the first-order model, and the Higuchi model were employed to study the release kinetics. Better fitting to the Higuchi model showed that Fick's diffusion governs the aspirin release mechanism. The release rate of loaded samples was slower than the pure drug in both HCl and phosphate buffer. As pure aspirin dissolves totally in 0.1 N HCl and phosphate buffer within 40 min and 20 min, respectively, loaded drug dissolve 35% ± 4 and 80% ± 4 in 0.1 N HCl and phosphate buffer within 100 min. The ambient pressure drug loading on TS-SA could have interesting potential applications in controlled release drug delivery systems.

3D printed‐polylactic acid scaffolds coated with natural rubber latex for biomedical application

AbstractThree‐dimensional (3D) printing is a rapidly growing technology and plays an emerging role in several biomedical applications. Polylactic acid (PLA) is one of the most common materials in 3D printing, however, it is chemically inert due to the absence of reactive side chain groups. In this context, in this work, the PLA scaffolds with two different geometries were produced and coated with natural rubber latex (NRL) extracted from the rubber tree Hevea brasiliensis. NRL presents bioactive substances that are related to its biological properties. The results revealed scaffolds with interconnected pores and pores sizes from 600 to 1300 μm. The NRL coatings caused a decrease in pore size. Infrared spectra showed that 2 NRL layers were more efficient in coverage. Compressive strength values obtained are in agreement with the spongy bones value (22–24 MPa for crossbar and 20–22 MPa for roundbar cube). Finally, the hemolytic activity of the PLA scaffold was 3%, while the scaffolds coated with 1 and 2 NRL layers presented values of 0%, indicating a potential use in biomedical applications due to the absence of hemolytic effects.