Improved Buffering Capacity Research Articles

New insights on waste mixing for enhanced fermentative hydrogen production

Co-fermentation can differently impact H2 production, with positive or negative interactions observed. Positive interactions were usually attributed to a balanced composition and improved buffer capacity. However, the impact of co-fermentation on microbial communities (H2-producing and H2-consuming bacteria) remains unexplored. This work aimed to deepen the interaction mechanisms observed in co-fermentation targeting microbial communities with an innovative focus on H2-consuming bacteria (homoacetogens). The H2 production of seven mixtures (food waste fractions and rye silage) and individual performances were compared by Biochemical Hydrogen Potential (BHP). Final microbial communities were characterized by sequencing and qPCR. A positive correlation between H2 yield and Soluble and Easily Extractible Sugars (SEES) content was observed for all the substrates (R² = 0.79), confirming this correlation not only for individual substrates but also mixtures. Positive interactions were observed for most of the mixtures, with a H2 yield significantly higher (16–37 %) than expected. The faster H2 production observed in mixtures (2.6 times faster) was correlated to the selection of Clostridiaceae_1 family (final relative abundance of 90–98 %) and decline of homoacetogens. It is therefore essential to further understand the microbial communities’ dynamics in co-fermentation to develop efficient fermentation systems.

Evaluation of Capping Materials to Reduce Zinc Flux from Sediments in a Former Mining Pit Lake.

Wilson Mine is a former vanadium mine site located in the Ouachita Mountains near Hot Springs, Arkansas. The site, which drains via two streams to Lake Catherine, has undergone extensive reclamation to significantly reduce groundwater and surface water contact with mine spoils. One of the streams passes through a former mine pit forming East Wilson Pond, and flux from pit lake sediments can result in elevated metal, that is, zinc (Zn), concentrations in overlying water. To mitigate potential risks, an investigation was conducted to evaluate the efficacy of capping materials for partitioning Zn-contaminated sediments from overlying water in East Wilson Pond. A 28-day laboratory study compared the effectiveness of capping materials including combinations of limestone, bentonite clay, and gravel for mitigating Zn flux, including under reasonable worst-case conditions (pH 5.5) encountered in the hypolimnion. Dissolved Zn was monitored over time in overlying water and in sediment porewaters within untreated controls and within the capping layer of treated systems. The use of limestone and/or bentonite clay improved buffering capacity compared to the noncapped control, and pH declined gradually but only modestly in the overlying water and porewater of all treated systems. Concentrations of Zn in overlying water of the noncapped control increased from approximately 30 to 100 µg/L during the study period, while concentrations in the overlying water and porewater of systems containing capping materials remained low (10-30 µg/L). The results demonstrated the effectiveness of the capping materials for neutralizing pH and reducing Zn flux, and a three-layer cap consisting of limestone (top) + bentonite clay (middle) + gravel (bottom) was determined to be most effective. These results were used to inform the selection of materials for the application of a cap to reduce Zn flux from the pit lake sediments. Environ Toxicol Chem 2022;41:193-200. © 2021 SETAC.

THE EFFECTIVENESS OF HIGH INTENSITY INTERVAL TRAINING WITH BLOOD FLOW RESTRICTION TRAINING ON ANAEROBIC THRESHOLD IN RUNNERS

The performance of runners is related to the anaerobic threshold level. Anaerobic threshold plays an important role in runner’s endurance. Anaerobic threshold value is also closely related to the level of runner’s fatigue when doing physical exercise or when competing for a long time. If the body’s endurance level cannot withstand the activities carried out, it will give a negative effect on their performance. There are exercises that aim to increase the anaerobic threshold value, namely high intensity interval training and blood flow restriction training. High intensity interval training can increase the anaerobic value through the mechanism of provide a high stimulus to anaerobic glycolytic and carbonic anhydrase reaction with formation (H+) that improved buffering capacity. Addition of blood flood restriction training by using limb occlusion pressure causes local hypoxia, so it will increase muscle metabolic demand. It will induce metabolic acidosis with increased hydrogen ions and lactate production.
 Key Words: High Intesity Interval Training; Blood Flow Restriction; Anaerobic Threshold; Anaerobic Capacity; Runners

Bioethanol production from pretreated whole slurry rice straw by thermophilic co-culture

In this study, an innovative approach is proposed for the valorization of all sugars (cellulosic and hemicellulosic) contained in a lignocellulosic feedstock, as is rice straw biomass (RSB), for the production of second-generation bioethanol. For this purpose, the whole slurry obtained after dilute sulfuric acid pretreatment at a biomass loading of 5% (w/v) was subjected to consolidated bioprocessing without previous solid-liquid separation and/or detoxification and the concentrated solution of carbohydrates recovered was fermented to bioethanol by a co-culture of thermophilic anaerobic bacteria. To bypass the inhibitory effect of undetoxified whole slurry on the lower fermentability of the co-culture, the concentration of different additives was optimized for improved buffering capacity, enhanced substrate-microbe interaction, and by-product elimination. The individual supplementation of 3 selected additives at optimum concentration; 20 mM calcium carbonate, 0.4% (v/v) polyethylene glycol, and 1% (w/v) sodium acetate resulted in enhanced ethanol yield of 130.83 mM, 106.37 mM, and 99.10 mM, respectively, compared to 75.03 mM ethanol yield in control. The combined effect of optimal dosage of these additives was able to improve the ethanol concentration and yield to 142 mM and 48% of the theoretical maximum respectively, suggesting about 88.58% increase compared to control medium without additives supplementation. The combined supplementation of additives proved to be an advantageous strategy for bioethanol production using undetoxified whole slurry biomass.

Chronic Ingestion of Bicarbonate-Rich Water Improves Anaerobic Performance in Hypohydrated Elite Judo Athletes: A Pilot Study.

In combat sports, anaerobic power and anaerobic capacity determine sport performance and the dominant metabolic pathways. The decline in performance during exercise that is attributed to the cumulative effects of fatigue, including excessive accumulation of metabolites, depletion of energy substrates, and water and electrolyte disturbances, seems to be of greatest significance. In our experiment, we evaluated the effectiveness of three weeks of bicarbonate-rich water ingestion on anaerobic performance in a state of hydration and dehydration in elite judo athletes. Eight male, elite judo athletes participated in two single-blind, repeated-measures trials. They were assigned to two hydration protocols, ingesting low mineralized table water and bicarbonate-rich water. Anaerobic performance was evaluated by two 30 s Wingate tests for lower and upper limbs, respectively, under conditions of hydration as well as exercise-induced dehydration. Resting, post-ingestion, and post-exercise concentrations of bicarbonate (HCO3), urine osmolality (UOSM), urine specific gravity (UGRAV), and lactate (La) were measured. The current investigation assessed two related factors that impair anaerobic performance—hypohydration and buffering capacity. High-bicarbonate water ingestion improved buffering capacity, and we demonstrated the potential role of this mechanism and its phenomenon in masking the adverse effects of dehydration in the context of repeated high-intensity anaerobic exercise (HIAE).

Alleviation of ammonia inhibition via nano-bubble water supplementation during anaerobic digestion of ammonia-rich swine manure: Buffering capacity promotion and methane production enhancement

Anaerobic digestion (AD) of ammonia-rich swine manure (SM) with nano-bubble water (NBW) supplementation was studied in this work with the expectation of ammonia inhibition alleviation, buffering capacity promotion, and methane production enhancement. Results indicated that cumulative methane yield was elevated by 12.3–38.7% in NBW groups. Besides, the reduced methane production rate and elongated lag phase under ammonia inhibition were increased and shortened by NBW supplementation, respectively. The rapid increase of total alkalinity (TA) and partial alkalinity (PA) could be observed with NBW supplementation, as well as the rapid decline of VFA/TA, thus improved buffering capacity and alleviated ammonia inhibition. Moreover, higher level of extracellular hydrolases and coenzyme F420 could be detected in NBW groups. In conclusion, NBW with higher mobility and zeta potential (absolute value) could be a promising strategy for the alleviation of ammonia suppression during the AD of SM.

Unreduced Male Gamete Formation in Cymbidium and Its Use for Developing Sexual Polyploid Cultivars.

Polyploidy plays an important role in crop improvement. Polyploid plants, particularly those produced through unreduced gametes (2n gametes), show increased organ size, improved buffering capacity for deleterious mutations, and enhanced heterozygosity and heterosis. Induced polyploidy has been widely used for improving floriculture crops, however, there are few reported sexual polyploid plants in the floriculture industry. This study evaluated nine cultivars of Cymbidium Swartz and discovered that 2n male gametes occurred in this important orchid. Depending on cultivars, 2n male gamete formation frequencies varied from 0.15 to 4.03%. Interspecific hybrids generally produced more 2n male gametes than traditional cultivars. To generate sexual polyploid plants, seven pairs of crosses were made, which produced five triploid and two tetraploid hybrids. Two triploid hybrids were evaluated for in vitro regeneration and growth characteristics. Compared to the diploid parents, the triploids were more easily regenerated through rhizomes or protocorms, and regenerated plants had improved survival rates after transplanting to the greenhouse. Furthermore, the sexual polyploid plants had more compact growth style, produced fragrant flowers, and demonstrated heterosis in plant growth. Through this study, a reliable protocol for selection of appropriate parents for 2n gamete production, ploidy level evaluation, in vitro culture of polyploid progenies, and development of new polyploid cultivars was established. Our study with Cymbidium suggests that the use of 2n gametes is a viable approach for improving floriculture crops.

Effect of Cl– and $${\text{SO}}_{4}^{{2 - }}$$ Ions on Electrodeposition of Cobalt from Acidic Gluconate Solutions

A role of anions in potentiostatic electrodeposition of cobalt from acidic gluconate solutions was investigated. Equilibrium distribution of soluble species in the solutions was calculated and compared with absorption spectra. Cyclic voltammetry and potentiostatic measurements confirmed that cathodic process was inhibited mainly by free sulfate ions. Improved buffer capacity of gluconate baths by addition of sulfate ions protected against contamination of metal deposits by products of cobalt salt hydrolysis. Mathematical models of metal nucleation were tested indicating progressive mode responsible for the formation of the metal phase. Diffusion coefficients of cobalt species were also calculated using various approaches. Thickness, morphology and structure of cobalt deposits as well as cathodic current efficiency were also discussed.

Improved Buffering Capacity and Methane Production by Anaerobic Co-Digestion of Corn Stalk and Straw Depolymerization Wastewater

A new method has been developed to improve the buffer capacity and methane production of the anaerobic digestion of Corn Stalk (CS), in which both an anaerobic co-digestion of CS with Straw Depolymerization Wastewater (SDW) and a mono-digestion of CS at different substrate concentrations (25.9, 36.2 and 45.3 mg/L) were investigated. Batch assays were conducted under thermophilic conditions for 70 days, which showed that an anaerobic co-digestion significantly increased the buffering capacity and methane production of the digestion process. The lag time for methane generation resulting from an anaerobic co-digestion of CS with SDW was 10 days, while the lag time for a mono-digestion of CS was 23 days. A maximum methane production of 214.81 mL/g-VS was obtained for the anaerobic co-digestion of CS with SDW when the substrate concentration was 36.2 g/L, which was around 13.54% higher than for mono-digestion of CS of 189.20 mL/g-VS. The removal rate for sulfate increased from 10.43% to 58.40% when the substrate concentration was increased from 25.9 to 45.3 mg/L for the anaerobic co-digestion of CS with SDW. Microbial communities were analyzed using 16S rDNA sequencing technology which showed that anaerobic co-digestion of CS and SDW promotes the growth of methanogens. The relative abundance of these methanogens (Euryarchaeota) for the anaerobic co-digestion of CS with SDW was increased significantly, being approximately 8.25% higher than that of a mono-digestion of CS, which was at a substrate concentration of 36.2 g/L. This means that the anaerobic co-digestion of CS and SDW is beneficial for improving buffer capacity and methane production from the digestion of CS, with higher organic matter and sulfate removal rates also being obtained.

Improved root zone temperature buffer capacity enhancing sweet pepper yield via soil-ridged substrate-embedded cultivation in solar greenhouse

A novel soilless cultivation method, called as soil-ridged substrate-embedded cultivation (SSC) was invented, and an experiment was designed to investigate root zone temperature and production efficiency of sweet pepper cultivated by two SSC patterns, i.e., SSC-P (polyethylene groove inserted) and SSC-W (wire-mesh groove inserted), and also other two cultivation methods, i.e., soil ridge (SR) and naked polyethylene groove (PG). Results showed that PG, SSC-P and SSC-W increased the average minimal root zone temperature by 1.01°C, 0.75°C, and 1.16°C compared to SR (16.33°C) during March 16-20, 2015. During June 1-5, SSC-P and SSC-W decreased the average maximal root zone temperature by 1.28°C and 1.29°C compared to SR (34.99°C), while PG increased it by 1.44°C. PG, SSC-P, and SSC-W decreased the differences of average daytime and night time temperatures by 1.34°C, 2.13°C, and 2.88°C compared to SR (4.56°C) during early stage. However, SSC-P and SSC-W decreased temperature differences of average daytime and night time by 0.9°C and 1.07°C compared to SR (0.95°C) during later stage, but PG improved by 2.85°C. Temperature difference of daytime and night time of SSC-W was minimal, and the temperature difference between the diurnal highest and the lowest temperature of SSC-W was also minimal. The buffer capacity of SSC-W was slightly better than that of SSC-P. SSC-W significantly improved the growth of sweet pepper compared to SR. Similarly, fruit yield per square meter of sweet pepper cultivated on SSC-P and SSC-W improved by 21.24% and 50.33%, respectively compared to SR (3.06 kg/m2), while PG lowered the yield by 13.72%. SSC-W was a better SSC pattern compared with SSC-P in terms of production efficiency. Keywords: soil cultivation, SSC, substrate cultivation, solar greenhouse, diurnal temperature difference, root zone temperature DOI: 10.25165/j.ijabe.20181102.2679 Citation: Fu G H, Li Z G, Liu W K, Yang Q C. Improved root zone temperature buffer capacity enhancing sweet pepper yield via soil-ridged substrate-embedded cultivation in solar greenhouse. Int J Agric & Biol Eng, 2018; 11(2): 41–47.

Qualitative and quantitative measurement of cannabinoids in cannabis using modified HPLC/DAD method

This study presents an accurate and high throughput method for the quantitative determination of various cannabinoids in cannabis plant material using high pressure liquid chromatography (HPLC) with a diode array detector (DAD). Sample extraction and chromatographic analysis conditions for the measurement of cannabinoids in the complex cannabis plant material matrix were optimized. The Agilent Poroshell 120 SB-C18 column provided high resolution for all target analytes with a short run time (10minutes) given the core shell technology. The aqueous buffer mobile phase was optimized with ammonium acetate at pH 4.75. The change in the mobile phase and the new column ensured a separation between cannabidiol (CBD and cannabigerol (CBG) along with cannabigerol and tetrahydrocannabinolic acid (THCA), which were not well separated by previous publications, improved buffering capacity, and provided analytical performance stability. Moreover, baseline drifting was significantly minimized by the use of a low concentration buffer solution (25mM ammonium acetate). In addition, evaporation and reconstitution of the sample residue with a methanol-organic pure (OP) water solution (65:35) significantly reduced the matrix interference. The modified extraction produced good recoveries (>91%) for each of the eight cannabinoids.The optimized method was validated for specificity, linearity, sensitivity, precision, accuracy, and stability. The combined relative standard deviation (%RSD) for intra-day and inter-day precision for all eight analytes varied from 2.5% to 5.2% and 0.28% to 5.5%, respectively. The %RSD for the repeatability study varied from 1.1% to 5.5%. The recoveries from spiked cannabis matrix samples were greater than 90% for all analytes, except delta-8-tetrahydrocannabinol (Δ8-THC), which was 80%. The recoveries varied from 81% to 107% with a precision of 0.7-8.1%RSD. Delta-9-tetrahydrocannabinol (Δ9-THC) in all of the cannabis samples (n=635) was less than 10%, which is in compliance with the NJ Medicinal Marijuana regulation. Analysis of samples from two cultivars, which included ten individual samples, four composite samples, seven calibration standards, and four quality control standards, can be performed within 24hours by this high throughput method.

Ethanol prefermentation of food waste in sequencing batch methane fermentation for improved buffering capacity and microbial community analysis

This study investigates the effects of ethanol prefermentation (EP) on methane fermentation. Yeast was added to the substrate for EP in the sequencing batch methane fermentation of food waste. An Illumina MiSeq high-throughput sequencing system was used to analyze changes in the microbial community. Methane production in the EP group (254mL/g VS) was higher than in the control group (35mL/g VS) because EP not only increased the buffering capacity of the system, but also increased hydrolytic acidification. More carbon source was converted to ethanol in the EP group than in the control group, and neutral ethanol could be converted continuously to acetic acid, which promoted the growth of Methanobacterium and Methanosarcina. As a result, the relative abundance of methane-producing bacteria was significantly higher than that of the control group. Kinetic modeling indicated that the EP group had a higher hydrolysis efficiency and shorter lag phase.

Enhancement of anaerobic co-digestion in acidogenic (ACIDO-DR) and methanogenic (METHA-DR) digester system

Abstract Acidogenic (ACIDO-DR) and methanogenic (METHA-DR) digesters were synchronously operated under the semi-continuous modes of mono-digestion (control) and co-digestion (mixture). The CH4 gas production rate was enhanced by 19.8% in co-digestion at an optimum ratio of 7:3 (food waste to sewage sludge). At this ratio, the maximum BMP of 620 ± 18 mL CH4 g−1 VS was attained in co-digestion but control showed lower BMP of 440 ± 14 mL CH4 g−1 VS. Co-digestion of food waste and sewage sludge was enhanced due to the adequate adjustment of C/N ratio for feed waste, improved buffer capacity and the necessary amounts of trace elements. Additionally, this system provided better buffering potential to high OLR than the one-phased system. As a result, the two-phased anaerobic co-digestion system suggested the alternatives for many struggling wastewater treatment plants, without any major remodeling of facilities, to enhance sustainable energy production that could be beneficial to public use.

The effects of pre-aeration and inoculation on solid-state anaerobic digestion of rice straw

Pre-aeration was investigated for enhancing biodegradation of recalcitrant lignocellulosic structure of rice straw under various low temperatures regimes (25, 35 and 45°C) and aeration durations (0, 2, 4, 6 and 8days). It was demonstrated aerated rice straw for 2days at 35°C resulted in highest hydrolytic efficiency and biochemical methane potential (BMP) (355.3±18.7mlCH4/gVS). Furthermore, both methane yields and initiation speeds of the solid-state anaerobic digestion (SS-AD) were inversely proportional to substrate-to-inoculum ratios due to the accumulation of volatile fatty acids (VFAs) and poor mass transfer. The highest methane yield achieved under SS-AD was 234mlCH4/gVS at TS of 16% which 72% of the BMP. Inoculum dilution with recycled water improved buffering capacity and mitigated accumulation of VFAs, resulting in an improved SS-AD performance. The combined pre-aeration and SS-AD was therefore established as a viable option to accelerate methane production for lignocellulosic biomass.

Facile fabrication of poly(acrylic acid) coated chitosan nanoparticles with improved stability in biological environments

Chitosan is one of the most important and commonly used natural polysaccharides in drug delivery for its biocompatible and biodegradable properties. However, poor blood circulation of the chitosan nanoparticles due to their cationic nature is one of the major bottlenecks of chitosan-based drug delivery systems. To address this problem, a versatile platform based on poly(acrylic acid) (PAA) coated ionically cross-linked chitosan/tripolyphosphate nanoparticles (CTS/TPP-PAA NPs), is reported. The zeta potentials of CTS/TPP and CTS/TPP-PAA NPs are approximately 33mV and −25mV, respectively. CTS/TPP NPs quickly aggregate in PBS (phosphate buffered saline) and DMEM (Dulbecco’s modified Eagle’s medium). Conversely, CTS/TPP-PAA NPs exhibit excellent colloidal stability in plasma solution for more than 24h. The PAA coating also endows CTS/TPP-PAA NPs with decreased protein adsorption capacity and improved buffering capacity. More importantly, the residual carboxyl and amino groups on CTS/TPP-PAA NPs provide abundant reactive sites for further functional modifications. Therefore, the CTS/TPP-PAA NPs reported here may be useful as an alternative drug delivery system.

Co-digestión anaerobia de vinaza y gallinaza de jaula: alternativa para el manejo de residuos agrícolas colombianos

La digestión anaerobia es una tecnología atractiva para el manejo de residuos al producir energía en forma de biogás y estabilizar la materia orgánica. En este estudio, se evaluó el proceso de co-digestión de vinaza y gallinaza de jaula como una alternativa de manejo y estabilización de residuos generados por la agroindustria colombiana. Se llevaron a cabo, ensayos de biometanización en relaciones de mezcla vinaza y gallinaza de 1:0, 3:1, 1:3 y 0:1 en base a VS. La relación de 3:1 de vinaza y gallinaza permitió aumentar la producción específica de metano en un 55% respecto a la producción específica ponderada de 0.65 m3 CH4/kg VS. Las mezclas entre los sustratos presentaron un efecto sinérgico positivo. La gallinaza de jaula mejoró la capacidad de amortiguación de la mezcla, disminuyendo el riesgo de acidificación por cambio drástico en el pH durante la digestión de la vinaza. Por otra parte, la vinaza permitió diluir la concentración total de nitrógeno amoniacal evitando la inhibición de amoniaco. Dado el aumento de la producción de metano, el co-tratamiento de vinaza y gallinaza mejora la recuperación de energía y la viabilidad económica de la instalación de la planta de biogás como parte de la cadena de producción de etanol.Palabras clave: digestión anaerobia, vinaza, gallinaza de jaula, prueba de potencial de biometanización, efecto sinérgico

Mesophilic anaerobic co-digestion of cattle manure and corn stover with biological and chemical pretreatment

Biological and chemical pretreatment methods using liquid fraction of digestate (LFD), ammonia solution (AS), and NaOH were compared in the process of mesophilic anaerobic co-digestion of cattle manure and corn stover. The results showed that LFD pretreatment could achieve the same effect as the chemical pretreatment (AS, NaOH) at the performance of anaerobic digestion (AD). Compared with the untreated corn stover, the cumulative biomethane production (CBP) and the volatile solid (VS) removal rate of three pretreatment methods were increased by 25.40–30.12% and 14.48–16.84%, respectively, in the co-digestion of cattle manure and corn stover. T80 was 20–37.14% shorter than that of the control test (35±1days). LFD pretreatment not only achieved the same effect as chemical pretreatment, but also reduced T80 and improved buffer capacity of anaerobic digestion system. Therefore, this study provides meaningful insight for exploring efficient pretreatment strategy to stabilize and enhance AD performance for practical application.

Effect of gluconate ions on electroreduction phenomena during manganese deposition on glassy carbon in acidic chloride and sulfate solutions

Cathodic processes occurring during manganese deposition from acidic baths (pH 3.5) were investigated using glassy carbon rotating disk electrode. Cyclic voltammetry, linear sweep voltammetry and anodic sweep voltammetry were applied. Speciation and buffer capacities of chloride, chloride-gluconate, sulfate and sulfate-gluconate solutions were determined. Two ranges of the potentials (vs. Ag/AgCl) were considered: from −0.8V to −1.56V and below (up to −1.8V) corresponding to hydrogen evolution and manganese deposition, respectively. In the chloride bath, strong adsorption of MnCl+ on the cathode inhibited hydrogen evolution, favored fast metal nucleation and deposition of fine grained coatings, but low buffering action of the bath enhanced self-dissolution of manganese. Addition of gluconate improved buffer capacity of the bath, inhibited metal nucleation and hindered somewhat secondary metal dissolution, but the presence of chloride ions and low ammonium ions concentration resulted in the formation of hydroxide species as a secondary product of metal oxidation. Sulfate bath prevented manganese dissolution, but buffer effect of the solution was too small to stabilize pH at the cathode surface. The best buffering action of the sulfate-gluconate system originated from the cooperative action of gluconate and ammonium species made possible to obtain metallic layer protected from the dissolution by the electrolyte. Weak adsorption of MnSO4 on the cathode in sulfate baths lead to the hydrogen evolution under limiting current in the potential range preceding manganese deposition. Independently on the bath composition, manganese started to deposit at approx. −1.56±0.01V (vs. Ag/AgCl) according to the instantaneous model of 3D nucleation. Average diffusion coefficients of the manganese species of order 10−6cm2/s were found.

Synthesis and evaluation of tetramethylguanidinium-polyethylenimine polymers as efficient gene delivery vectors.

Previously, we demonstrated that 6-(N,N,N′,N′-tetramethylguanidinium chloride)-hexanoyl-polyethylenimine (THP) polymers exhibited significantly enhanced transfection efficiency and cell viability. Here, in the present study, we have synthesized a series of N,N,N′,N′-tetramethylguanidinium-polyethylenimine (TP1-TP5) polymers via a single-step reaction involving peripheral primary amines of bPEI and varying amounts of 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU). These polymers were found to interact efficiently with negatively charged pDNA and formed stable complexes in the size range of ~240–450 nm. Acid-base titration profiles revealed improved buffering capacity of TP polymers as compared to bPEI. Transfection and cytotoxicity assays performed with TP/pDNA complexes on HEK293, CHO, and HeLa cells showed significantly higher transfection efficiency and cell viability with one of the complexes, TP2/pDNA complex, exhibited the highest transfection efficiency (~1.4–2.3-fold) outcompeting native bPEI and the commercially available transfection reagent, Lipofectamine 2000. Compared to previously reported THP polymers, the transfection efficiency of TP/pDNA complexes was found to be lower, as examined by flow cytometry. These results highlight the importance of the hydrophobic C-6 linker in THP polymers in forming compact nanostructures with pDNA, which might lead to efficient uptake and internalization of the complexes; however, the projected TP polymers offer an advantage of their rapid and economical one-step synthesis.

Cell line dependent uptake and transfection efficiencies of PEI–anionic glycopolymer systems

Branched Poly(ethylenimine) (bPEI) is a commercially available cationic polymer, which is well-studied due to its superior gene transfection efficacies. However, its toxicity is a major concern for its use in clinical applications. Therefore, bPEI is modified with various non-ionic, non-toxic moieties in an effort to reduce its toxicity. Ternary complexes of PEI with anionic polymers have also been used to decrease its toxicity. In this report, we have prepared pH-sensitive glycopolymers of linear and hyperbranched architecture via reversible addition-fragmentation chain transfer polymerization (RAFT). These anionic glycopolymers were complexed with bPEI at varying weight by weight (w/w) ratios to reduce the toxicity of PEI in vitro. In addition, these PEI-anionic glycopolymer complexes showed improved buffering capacity, as compared to PEI alone. The interactions of anionic glycopolymers with Hep G2 and HEK 293T cells were then studied as a function of time. The cellular uptake and gene expression of PEI polyplexes in the presence of anionic glycopolymers was directly related to the interactions of anionic glycopolymers with Hep G2 and HEK 293T cells.