Changes In Zeta Potential Research Articles

Gum tragacanth modified nano-hydroxyapatite: An angiogenic- osteogenic biomaterial for bone tissue engineering

Bone tissue engineering (BTE) is an evolving domain and provides encouraging solution to address the current demands in the orthopaedic healthcare system. However, even a well-exploited biomaterial such as synthetic hydroxyapatite (nHAp) fails to induce ideal bone regeneration in the complex in vivo conditions owing to its poor angiogenic potential. Hence, in addition to the osteogenic property, designing smart biomaterials with intrinsic angiogenic property is key for the success of bone tissue engineering implants. Recently, gum tragacanth (TG) has been testified to imbibe both angiogenic and osteogenic characteristics. In this context, TG functionalized nano-hydroxyapatite (TG-HAp) would be an ideal angiogenic-osteogenic material for BTE application. Here, we have reported the biofunctionalization of nHAp with TG through a silanized nHAp intermediate, and its osteogenic and angiogenic properties. X-ray diffraction (XRD) revealed the crystalline apatite phase of HAp. Biofunctionalization of nHAP with TG was confirmed both qualitatively and quantitatively by FTIR and TGA analysis respectively. TEM analysis confirmed the formation of needle shaped nanoparticles having size range (100–300 nm). Biofunctionalization lead to a change in zetapotential of nHAp from – 8.1 mV to 0.1 mV. The existence of multi-layered gum tragacanth on nHAp was confirmed by BET analysis. TG-HAp was found osteogenic when tested invitro using MG-63, (human osteoblast cells) and hMSCs, (human mesenchymal stem cells). Further, TG-HAp was found to increase the cellular VEGF expression in MG-63. Angiogenic property of TG-HAp was confirmed by in vitro tube formation of human umbilical vein endothelial cells (HUVECs). The study altogether indicates about the angiogenic and osteogenic potential of synthesized TG-HAp, which may be used as a new biomaterial in bone tissue engineering.

Cell Adaptations of Rhodococci to Pharmaceutical Pollutants

Against the background of atense environmental situation, the risk of drug pollution in the natural environment is steadily increasing. Pharmaceuticals entering open ecosystems can cause toxic effects in wildlife from molecular to population levels. The aim of this research was to examine the impact of pharmaceutical pollutants on rhodococci, which are typical representatives of soil actinobacteria and active biodegraders of these compounds. The pharmaceutical products used in this research werediclofenac sodium and ibuprofen, which are non-steroidal anti-inflammatory drugs (NSAIDs) that are widely used and frequently found in the environment. The most common cell adaptations of rhodococci to the effects of NSAIDs were changes in zeta potential, catalase activity, morphometric parameters and degree of hydrophobicity; elevated contents of total cellular lipids; and the formation of cell conglomerates. The findings demonstrated the adaptation mechanisms of rhodococci and their increased resistance to the toxic effects of the pharmaceutical pollutants.
 Keywords: pharmaceutical pollutants, NSAIDs, diclofenac, ibuprofen, cell responses, Rhodococcus

Viral vector purification with thermoresponsive-anionic mixed polymer brush modified beads-packed column

Viral vectors have attracted attention as a potential new therapeutic modality for gene therapy. In this study, we developed a temperature-modulated viral vector purification column using a mixed polymer brush composed of thermoresponsive and anionic polymers as packing material ligands. The mixed polymer brushes were modified on silica beads using a combination of reversible addition − fragmentation chain transfer (RAFT) polymerization of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and subsequent atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAAm). The temperature-modulated zeta potential change in the prepared mixed polymer brush was attributed to the PNIPAAm shrinking and exposing of PAMPS. The prepared mixed polymer brush modified beads were used as packing materials, and the elution behavior of the adeno associated virus type 2 (AAV2) vector was observed. The AAV2 vector was adsorbed on the mixed polymer brush by electrostatic and hydrophobic interactions at 40 °C. By reducing the temperature to 5 °C, adsorbed AAV2 vector on the mixed polymer brush was desorbed and eluted from the column due to lowering the electrostatic and hydrophobic interactions between the AAV2 vector and mixed polymer brush. The AAV2 vector was separated from bovine serum proteins as a contaminant using the column. The ability to infect cells was maintained by the recovered AAV2 vectors from the column. Thus, the developed column would be beneficial for the simple purification of viral vectors.

Synthesis and Characterization of TiO2-Water Nanofluids

Nanofluids made of TiO2 and multiwalled carbon nanotubes are the focus of our study. Using TiO2 and water as the basic fluids, nanofluids were created in 100 : 0, 75 : 25, and 50 : 50 proportions. Carbon nanotubes (CNTs) were disseminated into these base fluids of three types at 0.125, 0.25, and 0.5 percentages. Over the course of two months, the change of zeta potential is monitored to assess the stability of the dispersion. XRD analysis and SEM and TEM analysis are carried out for TiO2 nanofluids. Nanoparticles were analyzed using EDAX analysis to identify their composition. SEM examination was used to investigate the morphology for TiO2 nanoparticles. Particles of TiO2 produced in this manner seemed to have an average diameter of 27 nm. Nanofluids have a poor stability, which is the most important aspect of employing them, although most studies did not focus on this. When it comes to nanofluids, this study is unique in that it provides an in-depth look of surface modification approaches that have been employed by researchers to address these issues, as well as an evaluation of their stability over two months. Solubility is improved by acid treatment of CNTs, which results in functional groups on the surface of CNTs.

Tetracycline adsorption on magnetic sludge biochar: size effect of the Fe3O4 nanoparticles.

Activated sludge, which is difficult and expensive to treat and dispose of, is a key concern in wastewater treatment plants. In this study, magnetic sludge biochar containing activated sludge and different sizes (14.3, 40.2 and 90.5 nm) of Fe3O4 nanoparticles was investigated as an effective adsorbent for tetracycline (TC) adsorption. Magnetic sludge-based biochar was prepared by a facile cross-linking method and characterized by transmission electron microscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and zeta potential analysis. The adsorption performances of TC on three kinds of adsorbents were investigated. Although 14.3 nm Fe3O4 nanoparticles could be inclined to aggregate and partially filled with pores of biochar, it turned out that magnetic sludge biochar with 14.3 nm Fe3O4 nanoparticles exhibited optimum performance for TC removal with adsorption capacity up to 184.5 mg g−1, due to the larger amounts of functional groups and the change of zeta potential. Furthermore, the adsorption kinetics of TC on three kinds of adsorbents were studied, which implied that the pseudo-second-order kinetic model exhibited the better fit for the entire sorption process.

Influence of the sign of the zeta potential of nanodiamond particles on the morphology of graphene-detonation nanodiamond composites in the form of suspensions and aerogels

A new method of using the detonation nanodiamond with positive and negative zeta potential as a spacer for aerogels based on graphene oxide is presented. It is shown that the dosed addition of detonation nanodiamonds' particles to the suspension of graphene oxide hydrosol made it possible to triple the specific surface area of the resulting aerogel compared to graphene oxide aerogel, and this effect is more significant when nanodiamonds with a positive zeta potential are used. It was also shown that aerogels derived from graphene oxide and detonation nanodiamond with a positive zeta potential have a specific morphology with graphene oxide platelets being twisted. This effect is discussed in terms of the change in the average zeta potential of the initial mixtures. Keywords: two-component systems, carbon materials, colloid chemistry.

Charge balancing stabilized apatite enter into collagen fibers by osmotic pressure to induce the formation of intrafibrillar mineralization

Intrafibrillar mineralized collagen is the main form of natural mineralized collagen in bone matrix. However, the mechanism involved in the intrafibrillar mineralization is still unclear. Here, by measuring the changes of Zeta potential and adjusting the osmotic pressure of collagen fibers to study the mechanism of intrafibrillar mineralization. The changes in zeta potential and reduction in size during the formation of amorphous calcium phosphate (ACP) after adding negatively charged polyacrylic acid (PAA) and positively charged cationicpolyacrylamide (CPAM) indicate that the stabilization mechanism of ACP induced by polyelectrolyte compound is charge balance. Then, osmotic pressure pressures charge balancing stabilized ACP into collagen fibers to induce intrafibrillar mineralization. This discovery provides basis for further understanding the intrafibrillar mineralization, preparing new biomimetic mineralized materials and promoting the development of tissue engineering.

Impact of cocultivation on the aggregation and sedimentation trends of cyanobacteria with native and modified clay minerals

• Diazotrophic cyanobacteria were cocultivated with clays and clay composites. • Ca-Montmorillonite and kaolinite slightly hindered cyanobacteria growth. • Incubation with chitosan and iron oxide coated clay caused cell death. • Humic acid coated clay delayed sedimentation of cyanobacteria. • Chitosan- and iron-oxide clays were bactericidal and efficient flocculants. Removal and separation of cyanobacteria is of interest from both environmental and industrial standpoints. Flocculation and sedimentation using clay minerals can be advantageous, however, long-term effects such as resuspension of live bacteria or membrane damage, can be detrimental to these processes. In this respect, the effect of cocultivation of clays with cyanobacteria (CB) on aggregation trends and viability and consequently on separation processes is still largely unknown. In this study, Anabaena PCC 7120 was cultivated in the presence of relevant types of clays and clay composites, to observe their impact on growth, activity, and clay-CB complexation over time. Growth and activity of CB were monitored by looking at chlorophyll content and ammonia production. Clay-CB aggregation trends, extent, and morphology were assessed by measuring the decline of optical density over time, monitoring changes in zeta potential, and characterization using light and electron microscopy. The results revealed that CB grown in the presence of native Ca-montmorillonite and kaolinite suffer only a minor hindrance in growth rate and activity but undergo rapid sedimentation. Humic acid coated clay only slightly hindered growth yet inhibited sedimentation significantly. In contrast, chitosan and iron oxide coating caused damage to the cell membrane and CB death after several days. In terms of sedimentation, chitosan coated clays produced large flocs (up to 400 µm) and achieved high sedimentation rates of 46% after 3 min. Iron-oxide coated clays created the largest apparent aggregates (∼600 µm floc size) and exhibited the fastest sedimentation rates, 73% after 3 min and 87% after 30 min. The results stress the importance of looking at cocultivation with the different particles, since viability is not a priori hindered by aggregation, as in the case of native and humic-acid coated clays. On the other hand, chitosan and iron coated clays were both bactericidal and excellent flocculants. Thus, these findings can advance and improve the design of CB separation and removal strategies in natural and engineered systems.

Changes in the compound zeta potential of erythrocyte membranes in patients with arterial hypertension and obesity

The development of microcirculatory disorders is considered to be one of the earliest changes in the cardiovascular system with a combination of arterial hypertension (AH) and obesity. The rheological properties of blood play a significant role in the system of microcirculation. An important place in changing the rheological characteristics of blood is largely assigned to erythrocytes. Aggregation of erythrocytes is closely related to the magnitude of the surface-bound charge of their membranes or zeta potential of erythrocyte membranes. Purpose. To study the state of compound zeta potential of erythrocyte membranes in patients with hypertension and obesity. Material and methods. The study included 112 patients with AH and Index of Mass Corporal more than 30 kg/m2 (main group); the control group consisted of 25 people without AH and obesity. All patients of the main group received standard antihypertensive, lipid-lowering and hypoglycemic therapy to achieve the target levels of the indices under correction. Results. The level of compound zeta potential of erythrocyte membranes in patients with AH and obesity was significantly lower than in the control group and amounted to 1.57 ± 0.06 × 107 and 1.67 ± 0.03 × 107, respectively (p < 0.05). At the same time, in patients of the main group with an increase in AH, lower indices were noted. In patients with AH and obesity, a significant inverse correlation was found between the compound zeta potential of erythrocyte membranes and the degree of hypertension, which indicates a negative effect of hypertension on the rheological properties of blood at the microvasculature level. A correlation analysis was carried out to evaluate the association between Index of Mass Corporal and zeta potential of erythrocyte membranes in obese hypertensive patients. A negative direct correlation was revealed (r = 0.7, p < 0.05). Conclusion: a decrease in the total charge of erythrocytes can be considered as an early sign of microrheological disorders in patients with a controlled course of arterial hypertension and obesity.

Toward Sustainable Crop Protection: Aqueous Dispersions of Biodegradable Particles with Tunable Release and Rainfastness

AbstractFabrication of aqueous particulate dispersions of biodegradable cellulose esters (CEs) as efficient carriers of agrochemical active‐ingredients (AIs) for foliar applications, is reported. The use of different ester substituent groups on CE permits modulation of particle morphology and size, from irregular shapes (<350 nm) to spheres (≈1.1 µm diameter), while maintaining stability as supported by minimal change in zeta potential and particle size over one year. Rainfastness is tested by simulating >50 mm h−1 rainfall on coated banana and tomato leaves and silicon. Surface coverage loss as low as 9%, based on the nature of leaf and formulation, confirms the rainfastness of the formulations. Variation in the release kinetics of a model AI fluopyram from different CEs can be attributed to the particle morphology and the nature of binding between fluopyram and various CEs. Thermodynamic analysis demonstrates spontaneous binding between fluopyram and multiple sites of CEs, justifying its two‐step release from CE particles. System functionalities are corroborated via in‐vitro fungal inhibition assays demonstrating a 100% inhibition of the fungal growth. This “lab‐to‐leaf” approach of materials development involving fundamental insights and functional performance reveals CE dispersions are promising green agricultural formulations with the potential to impact a myriad of crops around the globe.

Nitrogen-Enriched Conjugated Polymer Enabled Metal-Free Carbon Nanozymes with Efficient Oxidase-Like Activity.

Metal-free carbon nanozymes could be promising with the unique features of intrinsic catalytic ability, structure diversity, and strong tolerance to acidic/alkaline media. However, to date, the study of metal-free carbon nanozymes fell far behind metal-based nanomaterials, in which, the majority reported much more peroxidase-like activity than other enzyme-mimicking behavior (e.g., oxidase). Thus, the exploit of high-performance carbon nanozymes is of importance but challenging. In this work, the nitrogen-rich conjugated polymer (Aza-CPs) with rigid network structure is utilized as precursor to yield N-doped carbon material QAU-Z1 in high yield via a direct pyrolysis method. Surprisingly, QAU-Z1 stood out in oxidase-like behavior, which significantly outperformed the control materials GNC-900 and QAU-Z2 with nucleobase or conjugated small molecule as precursor, respectively. More importantly, it is a crucial revelation that the catalytic performance is closely related to the change of zeta potential for carbon nanozyme during the substrate 3,3',5,5'-tetramethylbenzidine oxidation process, as well as its catalytical capacity to O2 , which could be insightful to understand the inherent mechanism. This work not only presents the potential of conjugated polymers in constructing highly efficient carbon nanozyme, but also reveals the vital role of interaction mode between the nanozyme and substrate in the catalytic performance.

Synthesis, Controlled Release, and Stability on Storage of Chitosan-Thyme Essential Oil Nanocapsules for Food Applications.

The nanoencapsulation of thyme essential oil has been greatly important in food science, given its remarkable antioxidant and antimicrobial capacity. However, its analysis in storage has not been established in terms of physical stability, antioxidant capacity, and release studies. In this paper, chitosan-thyme oil nanocapsules were prepared by the ionic gelation method. These were characterized for differential calorimetry, release kinetic, and infrared spectroscopy. The chitosan-thyme oil nanocapsules were stored at 4 and 25 °C for 5 weeks, the changes in particle size, zeta potential, stability (diffuse reflectance), and antioxidant capacity were analyzed and associated with nanocapsules’ functionality. The results show that the storage time and temperature significantly modify the particle size (keeping the nano-size throughout the storage), the release of the bioactive was Fickian with t0.193 according to Korsmery & Peppas and best described by Higuchi model associated with changes in the zeta potential from 8 mV to −11 mV at 4 °C. The differential scanning calorimetry and infrared spectroscopy results confirm the good integration of the components. The antioxidant capacity revealed a direct relationship with residual oil concentration with a decrease in the ABTS test of 15% at 4 °C and 37% at 25 °C. The residual bioactive content was 77% at 4 °C and 62% at 25 °C, confirming nanoencapsulation effectiveness. The present investigation provides helpful information so that these systems can be applied in food conservation.

Blood Compatibility of Amphiphilic Phosphorous Dendrons-Prospective Drug Nanocarriers.

Dendrons are branched synthetic polymers suitable for preparation of nanosized drug delivery systems. Their interactions with biological systems are mainly predetermined by their chemical structure, terminal groups, surface charge, and the number of branched layers (generation). Any new compound intended to be used, alone or in combination, for medical purposes in humans must be compatible with blood. This study combined results from in vitro experiments on human blood and from laboratory experiments designed to assess the effect of amphiphilic phosphorous dendrons on blood components and model membranes, and to examine the presence and nature of interactions leading to a potential safety concern. The changes in hematological and coagulation parameters upon the addition of dendrons in the concentration range of 2–10 µM were monitored. We found that only the combination of higher concentration and higher generation of the dendron affected the selected clinically relevant parameters: it significantly decreased platelet count and plateletcrit, shortened thrombin time, and increased activated partial thromboplastin time. At the same time, occasional small-sized platelet clumps in blood films under the light microscope were observed. We further investigated aggregation propensity of the positively charged dendrons in model conditions using zwitterionic and negatively charged liposomes. The observed changes in size and zeta potential indicated the electrostatic nature of the interaction. Overall, we proved that the low-generation amphiphilic phosphorous dendrons were compatible with blood within the studied concentration range. However, interactions between high-generation dendrons at bulk concentrations above 10 µM and platelets and/or clotting factors cannot be excluded.

Recycling of electrode materials from spent lithium-ion battery by pyrolysis-assisted flotation

In this study, the flotation technology is used for the separation and purification of cathode and anode material after removing organics by pyrolysis. Effects of surface microscopic properties on the flotation efficiency of spent electrode materials are investigated, and on this basis, surface analysis combined with flotation foundation tests are conducted to reveal pyrolysis-assisted surface modification mechanism. Residual electrolyte and organic binders decrease the difference in wettability of cathode and anode material, and hinder the interaction between electrode particles and collecting agent. Organics and their pyrolysis products can be adequately removed at the optimum pyrolysis temperature of 550 °C. After pyrolysis, the change of Zeta potential and surface free energy demonstrates that hydrophilic components of cathode material increase while the hydrophobic components of the anode material increase. The induction time of cathode material rises from 190 ms to 650 ms while the induction time of the anode material decrease from 145 ms to 37 ms. Collector adsorption capacity of anode material is obviously improved and anode material is easy to incorporate with bubbles and will be collected in the froth product. After one stage flotation, the recovery rate of cathode material is 83.75% with a high grade of 94.72%.

Interactions between zinc oxide nanoparticles and hexabromocyclododecane in simulated waters

The zinc oxide nanoparticles (ZnO-NPs) have been increasingly applied in industries and consumer products, causing release of these nanoparticles in environments. The behaviour of ZnO-NPs in the water systems is complicated due to the presence of different cations, anions, organic substances (e.g. humic acid HA) and other organic pollutants (e.g. commonly used brominated flame retardant, BFR). In particular, the aggregation and alteration of these nanoparticles can be influenced by co-existence contaminants. In this study, the interactions between hexabromocyclododecane (HBCD) and ZnO-NPs were investigated for the physicochemical properties and colloidal stability changes in various simulated waters. This is significant to understand the fate and behaviour of ZnO-NPs at environmental relevant conditions. The surface chemistry and particle size distribution (PSD) of ZnO-NPs with and without the existence of HBCD, HA and electrolytes (NaCl, CaCl 2 and MgCl 2 ) after different periods (1 and 3 weeks) were investigated at pH 7.00 ± 0.02. The size of the ZnO-NPs increased from nanometres to micrometres with the addition of numerous concentrations of HBCD, HA, and cations and their mixtures. The zeta potential of ZnO-NPs increased upon addition of HBCD, HA and electrolytes indicating a more stable agglomeration form while less agglomeration was observed in the ZnO-NPs and HA suspension after 3 weeks. Hydrophobic and electrostatic interactions, van der Waals forces, including hydrogen bonding and cation bridging could be potential interactive driving forces. The results indicated agglomeration of ZnO-NPs in the existence of organic substances, salts and contaminants, thus sedimentation and precipitation are promising under salty surface water/sea water. • Enhanced aggregation of ZnO-NPs after interactions with HBCD, HA and electrolytes. • Alterations in the surface charge of ZnO-NPs after the interactions. • Ageing influences the changes in size, shape and zeta potential of ZnO-NPs.

Stability Study of Super Saturable Catechin-Self Nano Emulsifying Drug Delivery System as Antidiabetic Therapy

Diabetes mellitus is a metabolic syndrome characterized by hyperglycemic and increased ROS production, which causes oxidative stress. Catechin isolated from the tea plant has oxidative stress inhibitor activity and anti-diabetic activity with low absorption in circulation systemic. Therefore, it is formulated in a super saturable catechin-self nano emulsifying drug delivery system (SSC-SNEDDS). Stability is one of the factors that affect the safety, quality, and efficacy of SSC-SNEDDS. This study aims to evaluate the stability of the formulated oil phase using oleic acid, croduret as a surfactant, and propylene glycol as a co-surfactant. Stability studies were carried out by several tests, namely heating-cooling cycle assay, freeze-thaw cycle assay, centrifugation, and endurance assay. Droplet characterization in the form of changes in diameter, zeta potential, and mobility in evaluating stability tests using dynamic light scattering-particle size analyzer (DLS-PSA). Real-time stability was also evaluated by observing changes in the infrared spectrum pattern using FTIR-ATR. After the stability test, the emulsion droplet size of SSC-SNEDDS was still below 100 nm and showed good stability. It can be concluded that the formula has a good stability profile.

Drinking water treatment residual as a ballast to sink Microcystis cyanobacteria and inactivate phosphorus in tropical lake water

The combination of a low dose of coagulant with a ballast that can inactive phosphorus (P) in lake sediment—a technique known as “flock and lock”—is one method for restoration of eutrophic lakes. The effectiveness of a drinking water treatment residual (DWTR) as a ballast in flock and lock was assessed using assays of eutrophic lake water from Thailand dominated by Microcystis aeruginosa cyanobacteria colonies by measuring changes in chlorophyll-a, pH, and zeta potential. P sorption isotherms were developed from long-term batch equilibrium experiments; desorption of nutrients and metals was assessed via leaching experiments; and morphological changes to cellular structure were assessed using scanning electron microscopy. Results showed that combining DWTR with a low dose of aluminum sulfate (0.6-4.0 mg Al/L) effectively sank 74-96% of Microcystis, with DWTR dose (50-400 mg/L), initial chlorophyll-a concentration (92-976 µg/L), pH (7.4-9.3), and alkalinity (99-108 ppm CaCO3) identified as factors significantly associated with sinking efficacy. P sorption capacity of the DWTR (7.12 mg/g) was significantly higher than a local soil (0.33 mg/g), enabling the DWTR to inactivate P in lake sediment. Desorption of Al, Fe, Ca and N from the DWTR was estimated to contribute to a marginal increase in concentrations of those compounds in the water column of a small shallow lake (1.2, 0.66, 53.4, and 0.07 µg/L, respectively) following a simulated application. Therefore, pre-treated DWTRs may be a viable alternative ballast in the flock and lock approach to lake restoration, supplementing or replacing modified local soils or lanthanum modified clays.

Polymeric Hydrogels for Controlled Release of Black Tea and Coffee Extracts for Topical Applications.

Tea and coffee are popular beverages. Both are also used in topical applications, such as ultraviolet (UV) protection, anti-aging, and wound healing. However, the impact of tea and coffee extract on skin cells is minimally explored. This study investigated the direct exposure of tea and coffee extract on skin cells using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. It was found that direct exposure of tea and coffee to skin cells can be toxic at a high dose on prolonged exposure (72 h). Therefore, it was hypothesized that a formulation providing a controlled release of tea and coffee could improve their skin compatibility. Thermally cross-linked poly(acrylic acid) hydrogels loaded with tea and coffee extracts (with and without milk) were formulated and optimized. The release profiles of these hydrogels were studied at varying loading efficiency. Milk addition with tea extract retarded the tea extract release from hydrogel while minimally affecting the coffee release. This effect was due to the molecular interaction of tea with milk components, showing changes in size, zeta potential, and polydispersity index. The release study best fitted the Korsmeyer–Peppas release model. Skin cells exposed to tea or coffee-loaded hydrogel showed normal skin cell morphology under fluorescence microscopic analysis. In conclusion, the hydrogels controlled the tea and coffee release and showed biocompatibility with skin cells. It can potentially be used for skin applications.

Poly(amidoamine) Dendrimers as Nanocarriers for 5-Fluorouracil: Effectiveness of Complex Formation and Cytotoxicity Studies.

Two generations of positively charged poly(amidoamine) dendrimers (PAMAMs) were selected for study as potential carriers for the anticancer drug 5-fluorouracil (5FU), a drug primarily used in the treatment of colorectal cancer. Analytical techniques, such as UV-Vis spectrophotometry, NMR Spectroscopy and Laser Doppler Velocimetry (LDV), have shown that the most critical factor determining the formation of a PAMAM–5FU complex is the starting components’ protonation degree. The tests confirmed the system’s ability to attach about 20 5FU molecules per one dendrimer molecule for the G4PAMAM dendrimer and about 25 molecules for the G6PAMAM dendrimer, which gives a system yield of 16% for the fourth generation and 5% for sixth generation dendrimers. Additionally, using the QCM-D method, the adsorption efficiency and the number of drug molecules immobilized in the dendrimer structure were determined. A new aspect in our study was the determination of the change in zeta potential (ζ) induced by the immobilization of 5FU molecules on the dendrimer’s outer shell and the importance of this effect in the direct contact of the carrier with cells. Cytotoxicity tests (resazurin reduction and MTS tests) showed no toxicity of dendrimers against mouse fibroblast cells (L929) and a significant decrease in cell viability in the case of four human malignant cell lines: malignant melanoma (A375), glioblastoma (SNB-19), prostate cancer (Du-145) and colon adenocarcinoma (HT-29) during incubation with PAMAM–5FU complexes. The purpose of our work was to investigate the correlation between the physicochemical properties of the carrier and active substance and the system efficiency and optimizing conditions for the formation of an efficient system based on PAMAM dendrimers as nanocarriers for 5-fluorouracil. An additional aspect was to identify potential application properties of the complexes, as demonstrated by cytotoxicity tests.

Formation of a colloidal band via pH-dependent electrokinetics.

Electroosmosis on nonuniformly charged surfaces often gives rise to intriguing flow behaviors, which can be utilized in applications such as mixing processes and designing micromotors. Here, we demonstrate nonuniform electroosmosis induced by electrochemical reactions. Water electrolysis creates pH gradients near the electrodes that cause a spatiotemporal change in the wall zeta potential, leading to nonuniform electroosmosis. Such nonuniform EOFs induce multiple vortices, which promote the continuous accumulation of particles that subsequently form a colloidal band. The band develops vertically into a "wall" of particles that spans from the bottom to the top surface of the chamber. Such a flow-driven colloidal band can be potentially used in colloidal self-assembly and separation processes irrespective of the particle surface properties. For instance, we demonstrate these vortices can promote rapid segregation of soft colloids such as oil droplets and fatglobules.