Faster Degradation Rate Research Articles

Crude oil hydrocarbon degradation efficiency of indigenous bacterial strains isolated from contaminated sites in Nigeria

The crude oil degradation potential of bacterial isolates from three contaminated sites in Nigeria were investigated. Seven bacterial isolates namely Pseudomonas aeruginosa strain W15, Pseudomonas aeruginosa strain N3R, Serratia marcescens strain N4, Providencia vermicola strain W8, Serratia marcescens strain W13, Pseudomonas aeruginosa strain W11 and Pseudomonas protegens strain P7 were isolated and identified using molecular methods. Isolates N4, N3 and W13 showed higher % total petroleum hydrocarbon (TPH) degradation of 79.26%, 78.96% and 78.69% respectively than W15, P7, W8 and W11 with % TPH degradation of 68.96%, 62.14%, 59.75% and 59.00% respectively. W13 showed the fastest degradation rate with 78.72% within the first 14 days of incubation; however, after the 14th day, there was no progressive change in % TPH. W11 showed degradation of wider range of hydrocarbon components originally in the crude oil as well as the complete degradation of most intermediates formed. The isolates showed good degradation potentials for bioremediation applications.

O-266 Encapsulation of human preantral follicles in an optimized hydrogel with similar mechanical strength of reproductive-age ovarian tissue

Abstract Study question Could a hydrogel with similar mechanical properties of reproductive age ovarian cortex support the growth of human preantral follicles? Summary answer Yes, our optimized PEGylated fibrin hydrogel with tailored mechanical strength provides a suitable substrate for follicle survival and growth. What is known already The most challenging part of assembling an engineered ovary is developing an appropriate scaffold that can maintain follicle spatial architecture and allow them to have radial growth and development1-3. Fibrin is a promising biomaterial due to its biocompatibility and bioactivity. Although fibrin has been used as a scaffold in fabricating different tissues such as the ovary, it has a fast degradation rate resulting in loss of physical support for the isolated follicles4-6. Therefore, various approaches such as physical or chemical modifications have been investigated to overcome the fibrin limitation7-10. Study design, size, duration PEGylation as a chemical reaction was used to control fibrin degradation. Moreover, to create an appropriate scaffold for encapsulating human preantral follicles, the Response Surface Methodology was used to find a hydrogel formulation with similar mechanical properties to the reproductive-age ovarian cortex. The chosen hydrogel was used to in vitro culture isolated human preantral follicles for 7 days. Participants/materials, setting, methods Design-Expert® software was employed to optimize PEGylated fibrin formulation to match mechanical properties of human ovarian tissues. Preantral follicles isolated from reproductive age patients were embedded in the hydrogel and in vitro cultured for 7 days. Follicle viability and diameter were evaluated on days 1 and 7. Moreover, confocal microscopy analysis was performed on whole follicles to confirm their growth by Ki67 staining of granulosa cells. Main results and the role of chance In this study, the biomechanically optimized PEGylated fibrin formulation was obtained by mathematical modeling. The hydrogel formulation was established by setting the specific goal of targeting 3178 ± 245 Pa, Young’s modulus of ovarian tissue fragments in reproductive-age women11, in order to obtain the optimized concentration of PEGylated fibrinogen and thrombin. Our results showed that the optimum condition with the desirability of 97.5% occurred by the PEGylated fibrin hydrogel containing 39.06 mg/ml of PEGylated fibrinogen and 50.36 IU/ml of thrombin with Young’s modulus of 3512.31±656.97 pa. Isolated follicles cultured in our hydrogel significantly increased in their diameter from 48.5±10.8µm (day 1) to 222.5±84.5µm (day 7), indicating the suitability of the optimized PEGylated fibrin formulation to support radial follicle growth. Moreover, follicles survival on days 1 and 7 did not significantly differ (86.9±8.9% and 83.4±6.4%, respectively). Follicle growth was confirmed by the presence of Ki67-positive granulosa cells from follicles at day 7. Limitations, reasons for caution In this study, the optimized hydrogel was first evaluated only in vitro, which is different from the actual physiological condition. Therefore, it is essential to perform a study analyzing the follicles after their encapsulation in the optimized hydrogel and transplantation, which will be the next step of our study. Wider implications of the findings Our results introduced an appropriate biomaterial, which resembles Young’s modulus of ovarian tissues in reproductive age, for encapsulating human preantral follicles. The optimal concentration of PEGylated fibrin allowed follicles to maintain their viability and have radial growth. Moreover, PEGylation enhanced the fibrin stability and physical support of follicles. Trial registration number not applicable

Construction of composite separator with 3D hierarchical spinel structure in Lithium-Sulfur batteries

Lithium-sulfur (Li-S) batteries are considered the most promising candidate for achieving a low-cost high-energy–density system. One of the biggest deterrents during the practical application of Li-S batteries is the shuttle effect which causes fast capacity degradation and poor rate performance. 3D CoNi2S4 with 3D interconnected porous nitrogen doping carbon was prepared by sulfurizing the precursor Prussian blue analogues. The CoNi2S4 nanoparticles are confined in the carbon framework, affording interconnected macro-mesoporous channels. The constructed 3D CoNi2S4 modified separator effectively accommodates enough electrolytes and provides more exposed active sites that suppress the shuttle effect through trapping polysulfides and accelerating the lithiation of S8 to Li2S. Thus, Li-S batteries with 3D CoNi2S4-PP separators exhibit high-rate capacity and remarkable cycle stability. Furthermore, based on the modified separators, a high sulfur loading cathode delivers an areal capacity of 5.62 mAh cm−2. The separator size expands further to assemble the 1Ah Li-S pouch cell, confirming the practicality. This work provides an efficient strategy with a modified separator for high-performance Li-S batteries.

Mesoporous BiVO4/TiO2 heterojunction: enhanced photoabsorption and photocatalytic ability through promoted charge transfer.

BiVO4 has been constructed into heterojunctions with TiO2 to boost the photocatalytic ability under visible illumination. Here, mesoporous BiVO4/TiO2 nanocomposites have been fabricated by a facile sol-gel approach utilizing nonionic surfactant and addressed for morphological, optical, structural, and degradation of ciprofloxacin (CIP) in water under visible illumination as an antibiotic pollutant model. The TEM images demonstrated that the TiO2 NPs are homogenous in terms of shape and size (15 ± 5nm). The introduction of BiVO4 into mesoporous TiO2 could effectively enhance the rapid separation efficiency of the photoinduced carriers and optical absorption. The 3%BiVO4/TiO2 photocatalyst possessed the best degradation efficiency (100%) within 60min which was promoted 20-folds larger than TiO2 NPs (5%). 3%BiVO4/TiO2 nanocomposite exhibited the fastest degradation rate (2.15 × 10-2min-1), which was 40 times faster than bare TiO2 photocatalyst (0.05 × 10-2min-1). The enhanced photocatalytic ability originated from superior charge separation characteristics and high solar energy absorption in mesopore structures. The recombination rate and mobility of charge carriers were characterized utilizing photoluminescence (PL) and photoelectrochemical measurements. This work highlights the advantages of mesoporous heterojunction BiVO4/TiO2 nanocomposites for photocatalytic performances and provides a multilateral route to design an effective wide-spectrum response photocatalyst for the development of comparable materials. The photocatalytic mechanism for degradation CIP over BiVO4/TiO2 was discussed in detail..

In vitro degradation and erosion behavior of commercial PLGAs used for controlled drug delivery.

Copolymers of lactic (or lactide) and glycolic (or glycolide) acids (PLGAs) are among the most commonly used materials in biomedical applications, such as parenteral controlled drug delivery, due to their biocompatibility, predictable degradation rate, and ease of processing. Besides manufacturing variables of drug delivery vehicles, changes in PLGA raw material properties can affect product behavior. Accordingly, an in-depth understanding of polymer-related "critical quality attributes" can improve selection and predictability of PLGA performance. Here, we selected 19 different PLGAs from five manufacturers to form drug-free films, submillimeter implants, and microspheres and evaluated differences in their water uptake, degradation, and erosion during in vitro incubation as a function of L/G ratio, polymerization method, molecular weight, end-capping, and geometry. Uncapped PLGA 50/50 films from different manufacturers with similar molecular weights and higher glycolic unit blockiness and/or block length values showed faster initial degradation rates. Geometrically, larger implants of 75/25, uncapped PLGA showed higher water uptake and faster degradation rates in the first week compared to microspheres of the same polymers, likely due to enhanced effects of acid-catalyzed degradation from PLGA acidic byproducts unable to escape as efficiently from larger geometries. Manufacturer differences such as increased residual monomer appeared to increase water uptake and degradation in uncapped 50/50 PLGA films and poly(lactide) implants. This dataset of different polymer manufacturers could be useful in selecting desired PLGAs for controlled release applications or comparing differences in behavior during product development, and these techniques to further compare differences in less reported properties such as sequence distribution may be useful for future analyses of PLGA performance in drug delivery.

Bio-based poly(butylene diglycolate-co-furandicarboxylate) copolyesters with balanced mechanical, barrier and biodegradable properties: A prospective substitute for PBAT

Poly(butylene adipate-co-terephthalate) (PBAT) is a flexible aliphatic/aromatic copolyester commercialized for degradable plastics, while the slow degradation rates and poor barrier properties limit its applications. Consequently, it is highly desirable to develop materials with faster degradation rates and enhanced barrier properties. Here, we synthesized poly(butylene diglycolate-co-furandicarboxylate) (PBDF) copolyesters by transesterification and melt polycondensation. The NMR spectra confirmed their structure and composition. Besides, the thermal, mechanical, permeable and degradable properties were characterized thoroughly. It was found that the properties were dependent on chemical composition and crystallinity. Actually, the introduction of diglycolic acid (DGA) comonomer hinders the crystallization and all the copolyesters appear as semicrystalline polyesters except for PBDF80. Among them, PBDF40 possesses outstanding mechanical properties with an elastic modulus of 165 MPa, tensile strengths of 54 MPa, and elongations of break of 654%. Moreover, the CO2 and O2 barrier properties of PBDF40 are 68.6 and 45.9 times higher than those of PBAT. PBDFs also exhibit accelerated rates in hydrolysis and composting degradation, which could be attributed to the enhanced hydrophilicity due to the electronegativity of ether-oxygen atoms in DGA. In particular, the mass loss of PBDF40 reaches 46% and 42% after 28 days of CALB enzymatic degradation and 8 weeks of compost degradation, respectively. These results highlight that the synthesized polyesters, especially PBDF40, demonstrate potential application in food packaging.

Recent Advancements in Materials and Coatings for Biomedical Implants.

Metallic materials such as stainless steel (SS), titanium (Ti), magnesium (Mg) alloys, and cobalt-chromium (Co-Cr) alloys are widely used as biomaterials for implant applications. Metallic implants sometimes fail in surgeries due to inadequate biocompatibility, faster degradation rate (Mg-based alloys), inflammatory response, infections, inertness (SS, Ti, and Co-Cr alloys), lower corrosion resistance, elastic modulus mismatch, excessive wear, and shielding stress. Therefore, to address this problem, it is necessary to develop a method to improve the biofunctionalization of metallic implant surfaces by changing the materials’ surface and morphology without altering the mechanical properties of metallic implants. Among various methods, surface modification on metallic surfaces by applying coatings is an effective way to improve implant material performance. In this review, we discuss the recent developments in ceramics, polymers, and metallic materials used for implant applications. Their biocompatibility is also discussed. The recent trends in coatings for biomedical implants, applications, and their future directions were also discussed in detail.

High-performance epoxy covalent adaptable networks enabled by alicyclic anhydride monoesters

Transesterification-based covalent adaptable networks (CANs) exhibit malleability and reprocessability, yet are highly dependent on the addition of a large amount of catalysts to accelerate transesterification reactions. A strategy of dynamic transfer auto-catalysis has been proposed by pending dynamically transferable anhydride monoesters at the network, which will greatly enhance the auto-catalytic efficiency. Here two trifunctional acids from alicyclic five-membered cyclic anhydride and six-membered cyclic anhydride, were synthesized and cured with bisphenol A epoxy monomer, respectively. The reprocessability, degradability and mechanical properties of the obtained epoxy CANs can be readily tuned by changing the structure of the trifunctional acid. The conformational transition of the non-planar ring accelerated network rearrangement and the large steric hindrance slowed down the degradation rate and the rigid feature endowed high thermal and mechanical properties of the epoxy CANs. In addition, the kinetically slow formation of six-membered cyclic anhydride than that of five-membered cyclic anhydride, led to the lower dynamic transfer auto-catalytic efficiency of its monoester. However, its good solubility in water gave it a fast degradation rate.

Poly(lactic acid)/artificially cultured diatom frustules nanofibrous membranes with fast and controllable degradation rates for air filtration.

The worldwide pandemic, coronavirus COVID-19, has been posing a serious threat to the global economy and security in last 2 years. The monthly consumption and subsequent discarding of 129 billion masks (equivalent to 645,000 tons) pose a serious detrimental impact on environmental sustainability. In this study, we report a novel type of nanofibrous membranes (NFMs) with supreme filtration performance and controllable degradation rates, which are mainly composed of polylactic acid (PLA) and artificially cultured diatom frustules (DFs). In this way, the filtration efficiency of particular matter (PM) and the pressure drop were significantly improved in the prepared PLA/DFs NFMs as compared with the neat PLA NFM. In specific, with incorporation of 5% DFs into fibers, PM0.3 removal with a filtration efficiency of over 99% and a pressure drop of 109 Pa were achieved with a membrane thickness of only 0.1 mm. Moreover, the yield strength and crystallinity degree of the PLA/DFs5 NFMs were sharply increased from 1.88 Mpa and 26.37% to 2.72 Mpa and 30.02%. Besides those unique characters, the PLA/DFs5 presented excellent degradability, accompanied by the degradation of 38% in 0.01 M sodium hydroxide solution after 7 days and approximately 100% in natural condition after 42 days, respectively. Meanwhile, the environmentally friendly raw materials of the composite polylactic acid and artificially cultured diatom frustules could be extracted from corn-derived biomass and artificially cultivated diatoms, ensuring the conformance to carbon neutrality and promising applications in personal protection.Graphical abstract Supplementary informationThe online version contains supplementary material available at 10.1007/s42114-022-00474-7.

Hydroxyl Group-Targeted Conjugate and Its Self-Assembled Nanoparticle of Peptide Drug: Effect of Degree of Saturation of Fatty Acids and Modification of Physicochemical Properties.

PurposeTo conjugate different degree of saturation of C18 fatty acids (stearic acid, oleic acid, and linoleic acid) with the hydroxyl groups of leuprolide acetate (LEU acetate) and to investigate the controlled release and enhanced permeability through self-assembled nanoparticles (L18FNs).MethodsYamaguchi esterification with benzoyl chloride and DMAP (4-Dimethylaminopyridine) allowed the conjugation of the fatty acid to the hydroxyl group of LEU. The three conjugates were then designated as stearic acid-conjugated LEU, LSC, oleic acid-conjugated LEU, LOC, and linoleic acid-conjugated LEU, LLC, respectively. The conjugates (L18FCs) were purified using preparative HPLC (Prep-HPLC) and identified through various instrumental analyses.ResultsThe zeta potential, particle size, and morphology of each L18FNs were evaluated. In the case of LSNs, the zeta potential value was relatively low and the particle size was larger than LONs and LLNs owing to the higher hydrophobicity of saturated fatty chain, while the LLNs showed a higher zeta potential and smaller particle size. In human plasma, LLC showed the fastest degradation rate with the highest accumulative drug release. The permeability of L18FNs was analyzed through the Franz diffusion cell experiment, confirming that the degree of saturation of fatty acids affects the permeability of LFNs. While the permeability of LSNs was not significantly enhanced due to higher particle size after nanonization, LONs and LLNs increased 1.56 and 1.85 times in permeation, respectively, compared to LEU.ConclusionUtilization of different degree of saturation of fatty acids to conjugate a peptide drug could provide pharmaceutical versatility via self-assembly and modification of physicochemical properties.

Improved corrosion resistance on Mg-2Ca alloy with TiO2 nanoparticles embedded in a polycaprolactone (PCL) coating

When seeking bone healing applications, calcium (Ca) is the preferred element for Magnesium (Mg) alloying. Unfortunately, the fast degradation rate of these alloys limits their applicability as bioresorbable implants. Biodegradable polymeric coatings based on polycaprolactone (PCL) were prepared to overcome this limitation. TiO2 nanoparticles (NPs) were further embedded in the polymeric matrix to increase the protectiveness and biocompatibility of such coatings. The degradation rate, assessed by electrochemical impedance technique (EIS) in cell culture medium, proved the superior protectiveness of the PCL-TiO2 coating. The corrosion layer was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). In the bare and PCL coated samples, the corrosion layer was composed of brucite, carbonates, and magnesium oxychloride, whereas in the PCL-TiO2 coated sample, the additional precipitation of apatites occurred. This data advances important insights on Mg-2Ca alloys and discusses the role of bioactive coatings on the degradation of this alloy.

A silicate-loaded MgAl LDH self-healing coating on biomedical Mg alloys for corrosion retardation and cytocompatibility enhancement

Clinical application of magnesium (Mg) alloys such as bone fracture fixation is hindered by the fast degradation rate under physiological conditions. In this work, a magnesium‑aluminum layered double hydroxide coating intercalated with silicate (LDH-SiO3) is fabricated on the anodized AZ31B Mg alloy by a hydrothermal technique and anion exchange process to tailor the corrosion rate and cytocompatibility. The LDH-SiO3 coating comprising a porous outer layer and compact inner layer adheres strongly to the anodized Mg alloy substrate. Electrochemical tests reveal that the LDH-SiO3 coating reduces the corrosion current density by 266 times to 0.8 ± 0.1 μA cm−2 in addition to yielding a large charge transfer resistance of 4.98 × 104 Ω cm2 in the simulated body fluid (SBF), revealing decreased corrosion because of inhibition of diffusion of aggressive ions through the compact and adherent inner LDH layer on the Mg alloy substrate. Immersion tests in SBF for 360 h reveal that the LDH-SiO3 coating mitigates corrosion propagation, Mg release, hydrogen evolution, and pH variation, indicating the notable long-term protection ability resulting from the self-healing LDH-SiO3 coating after localized corrosion occurs on the Mg alloy substrate. The self-healing mechanism mainly stems from SiO32− released from the LDH coating in conjunction with Mg leaching during natural degradation, resulting in the formation of Mg silicate precipitate that covers the corroded areas. Biologically, the LDH-SiO3 coating enhances attachment and proliferation of MC3T3-E1 pre-osteoblasts suggesting good cytocompatibility stemming from the favorable outcome including inhibited Mg leaching and alkalization as a result of the LDH-SiO3 coating. The self-healing LDH-SiO3 coating is very promising in expanding the clinical application of Mg-based implants by offering a viable approach to control corrosion and improve cytocompatibility.

Synthesis, Herbicidal Activity, Crop Safety and Soil Degradation of Pyrimidine- and Triazine-Substituted Chlorsulfuron Derivatives.

Chlrosulfuron, a classical sulfonylurea herbicide that exhibits good safety for wheat but causes a certain degree of damage to subsequent corn in a wheat–corn rotation mode, has been suspended field application in China since 2014. Our previous study found that diethylamino-substituted chlorsulfuron derivatives accelerated the degradation rate in soil. In order to obtain sulfonylurea herbicides with good crop safety for both wheat and corn, while maintaining high herbicidal activities, a series of pyrimidine- and triazine-based diethylamino-substituted chlorsulfuron derivatives (W102–W111) were systematically evaluated. The structures of the synthesized compounds were confirmed with 1H NMR, 13C NMR, and HRMS. The preliminary biological assay results indicate that the 4,6-disubstituted pyrimidine and triazine derivatives could maintain high herbicidal activity. It was found that the synthesized compounds could accelerate degradation rates, both in acidic and alkaline soil. Especially, in alkaline soil, the degradation rate of the target compounds accelerated more than 22-fold compared to chlorsulfuron. Moreover, most chlorsulfuron analogs exhibited good crop safety for both wheat and corn at high dosages. This study provided a reference for the further design of new sulfonylurea herbicides with high herbicidal activity, fast degradation rates, and high crop safety.

Severe plastic deformation (SPD) of biodegradable magnesium alloys and composites: A review of developments and prospects

The use of magnesium in orthopedic and cardiovascular applications has been widely attracted by diminishing the risk of abnormal interaction of the implant with the body tissue and eliminating the second surgery to remove it from the body. Nevertheless, the fast degradation rate and generally inhomogeneous corrosion subsequently caused a decline in the mechanical strength of Mg during the healing period. Numerous researches have been conducted on the influences of various severe plastic deformation (SPD) processes on magnesium bio-alloys and biocomposites. This paper strives to summarize the various SPD techniques used to achieve magnesium with an ultrafine-grained (UFG) structure. Moreover, the effects of various severe plastic deformation methods on magnesium microstructure, mechanical properties, and corrosion behavior have been discussed. Overall, this review intends to clarify the different potentials of applying SPD processes to the magnesium alloys and composites to augment their usage in biomedical applications.

Effect of glutaraldehyde and calcium chloride as different crosslinking agents on the characteristics of chitosan/cellulose nanocrystals scaffold

The effect of glutaraldehyde and calcium cations as covalent and ionic crosslinkers was investigated on the main characteristics of scaffolds based on chitosan and cellulose nanocrystals. Therefore, four different scaffolds based on chitosan/cellulose nanocrystals with different crosslinking methods were fabricated using the freeze-drying method for potential use in bone tissue engineering. The structural and chemical features of prepared scaffolds were studied by the FTIR technique. FESEM images revealed that all scaffold samples are porous three-dimensional networks in which the pores are connected. TGA analysis showed that the thermal stability of scaffolds based on chitosan/cellulose nanocrystals has not been changed significantly by using different crosslinking methods. The chitosan/cellulose nanocrystals scaffold crosslinked by glutaraldehyde represented the highest compressive strength and the uncrosslinked scaffold showed the highest swelling ratio in comparison to the other scaffolds. The fastest degradation rate belonged to the scaffold crosslinked by calcium cations. FESEM images and EDX analysis confirmed that fabricated scaffolds have good biomineralization ability. The cell viability and cell attachment results indicated that all four scaffolds support cell proliferation and cell adhesion. However, the viability of NIH3T3 fibroblast cells in the presence of glutaraldehyde-containing scaffolds was lower than that of other scaffolds.

Remaining Service Life (RSL ) Assessment of Engine Oil in Rock Excavators

The quality of lubricant oil plays a central role in the performance of machineries. Aggressive working environment of industry, particularly in mining industry, remains a dominant point in faster rate of degradation. The colossal consumption of oil is a factor to an inflated maintenance cost which can be averted by optimizing the lubricant oil consumption using scientific and methodical approaches. At present the schedule drain-off interval is accomplished at a regular interval of operation hour recommended by manufacturers. This is a conservative approach and results in loss of useful life. This work aims to determine the Remaining Service life (RSL) of the engine oil in Excavators. The oil properties are measured at regular intervals. Kinematic Viscosity, Viscosity Index (VI), Total Acid Number (TAN) and Total Base Number (TBN) are measured. The measured values suggest the degradation level of oil before filling fresh oil. The remaining service life (RSL) is determined by juxtaposing Parameter Profile Approach (PPA), Analytical Hierarchy Process (AHP) and Vector Projection Approach (VPA). The approach will be a precursor to the excavator maintenance personnel to drain-off the oil at right time despite of manufacturer’s recommendation.

Synthesis and Characterization of Sn-Doped CeO2-Fe2O3 Nanocomposite and Application in Photocatalytic Degradation of Sudan I

Photocatalysis is a promising technique to treat organic dyes as pollutants over traditional technologies. The application of organic dyes has increased lately for industries such as textile, medicines, plastics, etc. Thus, in this report, we prepared a Tin-doped CeO2-Fe2O3 photocatalyst via the thermal decomposition method to effectively degrade Sudan I under sunlight. The synthesized catalyst was explored by different studies such as powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET), UV-vis diffuse reflectance (UV-vis DRS). The catalyst was found to have a particle size of 1-2 µm with a high surface area. The bandgap energy of the catalyst was changed to 2.2 eV due to the Sn doping. The effect of Sn4+ doping into the CeO2 lattice was observed as the modification in the Fermi levels of the catalyst, which resulted in enhanced photocatalytic activity. The catalyst was found to have a fast degradation rate towards Sudan I under the sunlight and showed complete degradation. The result of COD removal confirmed the removal of dye from the dye solution. Further, scavenger tests confirmed the role of the active species, hydroxyl (•OH) and superoxide (O2•) radicals, in the degradation of Sudan I by photocatalyst. High-performance liquid chromatography (HPLC) was used to confirm the complete degradation of the dye. A possible mechanism is put forward to describe the degradation process and charge transfer during the degradation.

Targeted Printing of Cells: Evaluation of ADA-PEG Bioinks for Drop on Demand Approaches.

A novel approach, in the context of bioprinting, is the targeted printing of a defined number of cells at desired positions in predefined locations, which thereby opens up new perspectives for life science engineering. One major challenge in this application is to realize the targeted printing of cells onto a gel substrate with high cell survival rates in advanced bioinks. For this purpose, different alginate-dialdehyde—polyethylene glycol (ADA-PEG) inks with different PEG modifications and chain lengths (1–8 kDa) were characterized to evaluate their application as bioinks for drop on demand (DoD) printing. The biochemical properties of the inks, printing process, NIH/3T3 fibroblast cell distribution within a droplet and shear forces during printing were analyzed. Finally, different hydrogels were evaluated as a printing substrate. By analysing different PEG chain lengths with covalently crosslinked and non-crosslinked ADA-PEG inks, it was shown that the influence of Schiff’s bases on the viscosity of the corresponding materials is very low. Furthermore, it was shown that longer polymer chains resulted in less stable hydrogels, leading to fast degradation rates. Several bioinks highly exhibit biocompatibility, while the calculated nozzle shear stress increased from approx. 1.3 and 2.3 kPa. Moreover, we determined the number of cells for printed droplets depending on the initial cell concentration, which is crucially needed for targeted cell printing approaches.

Photodegradation of Congo Red by Modified P25-Titanium Dioxide with Cobalt-Carbon Supported on SiO2 Matrix, DFT Studies of Chemical Reactivity

Congo red is a hazardous material in the environment. The present work describes the synthesis of TiO2/CoC@SiO2-bipy (1) and TiO2/CoC@SiO2-phen (2) nanocomposites for the photodegradation of azo-dye Congo red (CR) dye in aqueous solution, by combining pure TiO2 with CoC@SiO2-bipy (s1) and CoC@SiO2-phen (s2) nanoparticles. The prepared nanocomposites were evaluated in term of photocatalytic activity rates in aqueous solution using CR. The nanocomposites TiO2/CoC@SiO2-bipy (1) and TiO2/CoC@SiO2-phen (2) were prepared from TiO2 (75%) and CoC@SiO2-bipy (s1) or CoC@SiO2-phen (s2) (25%) (weight ratio). Ultra-sonication and milling were used to prepare the heterogeneous nano catalysts. The pH, initial dye concentration, and catalyst dosage appeared to have a significant impact on the photocatalytic degradation performance. Molecular oxygen and other active species played a significant role in the photocatalyst degradation of CR with sunlight energy (UV-index 5.0). The chemical reactions were accelerated depending upon electrophilicity (ω) and energy gap (Eg) of azo dye species CR-N=N, CR-N=NH and CR=N-NH species which were calculated by density function theory (DFT). It can be concluded that the rate of electron–hole recombination of the TiO2 catalyst, when adding CoC@SiO2-bipy (s1) or CoC@SiO2-phen (s2), not only enhances the degradation but also effectively removes toxic dye molecules and their by-products. The newly prepared TiO2/CoC@SiO2-bipy (1) nanocomposites showed increased photocatalytic efficiency at low catalyst dose and faster rate of degradation of Congo red compared to TiO2/CoC@SiO2-phen (2) and TiO2 catalysts. The novel catalysts (1) and (2) can be easily separated by centrifugation and filtration, from the reaction mixture compared to TiO2.

Optimizing the bio-degradability and biocompatibility of a biogenic collagen membrane through cross-linking and zinc-doped hydroxyapatite

Biogenic collagen membranes have been widely used as soft tissue barriers in guided bone regeneration (GBR) and guided tissue regeneration (GTR). Nevertheless, their clinical performance remains unsatisfactory because of their low mechanical strength and fast degradation rate in vivo. Although cross-linking with chemical agents is effective and reliable for prolonging the degradation time of collagen membranes, some adverse effects including potential cytotoxicity and undesirable tissue integration have been observed during this process. As a fundamental nutritional trace element, zinc plays an active role in promoting the growth of cells and regulating the degradation of the collagen matrix. Herein, a biogenic collagen membrane was cross-linked with glutaraldehyde-alendronate to prolong its degradation time. The physiochemical and biological properties were enhanced by the incorporation of zinc-doped nanohydroxyapatite (nZnHA), with the native structure of collagen preserved. Specifically, the cross-linking combined with the incorporation of 1% and 2% nZnHA seemed to endow the membrane with the most appropriate biocompatibility and tissue integration capability among the cross-linked membranes, as well as offering a degradation period of six weeks in a rat subcutaneous model. Thus, improving the clinical performance of biogenic collagen membranes by cross-linking together with the incorporation of nZnHA is a promising strategy for the improvement of biogenic collagen membranes. Statement of significanceThe significance of this research includes:•We fabricated a cross-linked collagen membrane with enhanced mechanical properties, prolonged degradation time and uncompromised biocompatibility by GA-alendronate cross-linking and nZnHA doping.•Tuning the incorporation concentration of zinc ions can effectively manipulate the biocompatibility and degradation process of the membrane fabricated.•We proposed a promising strategy to improve the clinical performance of biogenic collagen membranes by cross-linking together with the incorporation of nZnHA.