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Among different materials for bone engineering, calcium phosphates (CaPs) attract special attention because the main inorganic component of bones is poorly crystalline, non-stoichiometric, calcium deficient, Na-, Mg- and carbonate hydroxyapatite [1]. Despite their excellent bioactivity and osteoconductivity, CaPs" applications are limited to nonstress bearing applications due to their poor mechanical properties [2]. In recent years, the addition of inorganic nanomaterials (NMs) in CaPs based ceramics, cements and coatings is proposed as a solution to this problem [2]. TiO2 nanomaterials (TiNMs) attract attention due to their favorable properties for biomedical applications [3], and the possibility to prepare TiNMs of different morphologies, structure and composition. In order to rationalize the design of CaP/TiNM composites, the influence of TiNMs" surface structure and charge density on CaPs formation should be investigated. Until now, most of the studies were performed with TiO2 (TiNPs) nanoparticles and arrays of nanotubes (TiNTs) in simulated body fluid [6, 7]. In order to contribute to the understanding of CaPs formation on TiNMs of different dimensionality, in this research the formation of CaPs in the presence of TiNPs and TiNTs was investigated in two sets of experiments [8]. The ability of TiNMs to induce CaPs formation was tested in corrected simulated body fluid, while the influence of TiNMs on the kinetics of formation and properties of formed CaPs was investigated in the spontaneously precipitating system. The influence of TiNMs on CaPs precipitation has been investigated by potentiometric measurements, powder X-ray diffraction (PXRD), electron paramagnetic resonance spectroscopy (EPR), scanning (SEM) and transmission (TEM) electron microscopy, dynamic (DLS) and electrophoretic light scattering (ELS). Both TiNMs showed poor ability to promote CaPs formation in c-SBF which can be attributed to their low absolute zeta-potential value. However, during spontaneous precipitation, they exhibited unusual dual influence on precipitation kinetics, i.e. inhibition of initially formed amorphous calcium phosphate (ACP) transformation at lower and promotion at higher concentrations. After 1 hour reaction time, in presence of both TiNMs, calcium deficient hydroxyapatite was formed (CaDHA). Morphology of the CaDHA depended on the type and concentration of TiNMs. However, PXRD and EPR characterization confirmed that there is no significant difference between CaDHA formed in the presence of different TiNMs. Obtained results confirm the importance of surface structure and charge in CaPs – TiNMs interactions and point to a versatile method for biomimetic synthesis of novel biocomposites.

Composite materials based on calcium phosphates (CaPs) and TiO2 nanomaterials have recently attracted attention as new and innovative implant materials for bone regeneration.1 In addition, they can be prepared by the biomimetic method, considered to be a green synthesis route. In vivo, implant performance is affected by surface adsorption of soluble proteins from blood and interstitial fluids. Among them, albumin is the most abundant. However, its role in the formation of CaPs on titanium implants is still not clarified. In order to fill this void, the influence of albumin on biomimetic formation CaPs on TiO2 nanowires (TiNW) has been investigated. The TiNWs were prepared using a hydrothermal method. CaPs/TiNW composites were prepared by precipitating CaPs in the presence of TiNW. Precipitation systems were prepared by fast mixing of equal volumes of CaCl2 and Na2HPO4 solutions in the double-walled glass vessel. TiNW and/or BSA were added in Na2HPO4 solution. The progress of the reaction was followed by monitoring the changes of pH in the precipitation systems. Formed precipitates were filtered after 60 minutes of reaction time and characterized by Fourier – transform infrared spectroscopy, Raman spectroscopy, X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. It was shown that TiNWs act as promotors while BSA acts as an inhibitor of CaP formation. None of the additives influenced the composition and the morphology of the formed precipitate. The obtained results point to a biomimetic preparation route of multifunctional CaP based biominerals.

Streaming current measurements were used to study the interaction of polyoxometalates (POMs) and nanoparticles (NPs) with flat surfaces as an alternative, innovative approach to infer POM and NP properties of potential sparse material in terms of charge and magnitude. With respect to POMs, the approach was able to reveal subtle details of charging properties of +7 vs. +8 charge at very low POM concentrations. For NPs, the sign of charge and even the zeta-potential curve was retrieved. Concerning NPs, mutual interaction between TiO2 and SiO2 surfaces was studied in some detail via macroscopic measurements. Post-mortem analysis of samples from electrokinetic studies and separate investigations via AFM and HRTEM verified the interactions between TiO2 NPs and SiO2 collector surfaces. The interactions in the SiO2/TiO2 system depend to some extent on NP morphology, but in all our systems, irreversible interactions were observed, which would make the studied types of NPs immobile in natural environments. Overall, we conclude that the measurement of streaming currents at flat surfaces is valuable (i) to study NP and POM collector surface interactions and (ii) to simultaneously collect NPs or POM (or other small mobile clusters) for further (structural, morphological or release) investigations., publishedVersion

Among largest health issues in modern society increased frequency of hard tissue chronical diseases takes special place [1]. These diseases could be a consequence of physical trauma, birth defects, other diseases (cancer), etc. In response to this problem, World health organization has appointed years 2000-2010 a Bone and Joint Decade [2]. Often the only treatment of such diseases is implantation with the aim to regenerate damaged or diseased tissue. However, only in the USA, approximately 10% of implants fail prematurely [3]. In addition, due to the continuous population ageing, many patients are outliving their implants [4]. These problems clearly urge the need to develop new, innovative implant materials. The solution of such problems is sought in development of multifunctional materials, which in addition to replacing missing tissue or enabling its regeneration, as well as having improved mechanical properties, will act as local drug delivery system [4-6]. New hard tissue regeneration biomaterials emerging in recent years are composite materials based on calcium phosphates (CaPs) and different inorganic nanomaterials as they offer possible ways of preparing multifunctional materials because inorganic nanomaterials embedded within CaP can increase their mechanical strength [7] and can be used as drug delivery systems, like TiO2 nanotubes (TiNTs). Nowadays it is possible to produce arrays of TiNTs with precisely controlled diameter, length, wall thickness and phase [8]. In vitro cells response to nanotubular surface is better compared to not treated surfaces and can be modulated by changing the diameter of TiNTs [9]. TiNTs also offer a possibility to covalently immobilize bioactive molecules, and in that way act as drug delivery system [10]. Modifying TiNTs arrays with CaP can be achieved by different techniques, biomimetic, electrochemical and magnetron sputtering being mostly used [11]. However, to the best of our knowledge TiNTs are not used as fiber reinforcements of CaP ceramics and cements. In this research we have investigated the impact of TiO2 nanotubes (TiNT) on properties of formed CaP solid phase at conditions closed to physiological in the presence of bovine serum albumine (BSA). BSA is the most abudant protein in human plasma and is one of first macromolecules that will interact with synthesised nanocomposites in human body. It is one of three soluble proteins which are immediately adsorbed on the surface of the implant, influencing its in vivo performance [12]. However, its role in mineralization of titanium implants is still controversial [13]. All experiment systems were preformed in a thermostated double-walled glass vessel with a 50 mL capacity at 25 °C. Precipitation systems were not additionaly stirred. Control precipitation system (CS) was prepared by fast mixing of equal volumes (20 mL) of equimolar CaCl2 and Na2HPO4 reactant solutions (c = 4 mmol dm—3), so-called anionic and cationic solution. The pH of anionic solution was adjusted to 7.4 with HCl. Precipitation systems containing TiNT and/or BSA were prepared by adding TiNT suspension or BSA solution to the anionic reactant solution. Before mixing the reactant solutions the pH was readjusted when necessary. The progress of reaction was followed by measuring the pH of the precipitation systems. Based on pH curves induction time (tind), the time passed from initiation of precipitation process untill the begining of amorphous CaP (ACP) transforms into more stable crystalline phase was calculated. Prepared precipitates were filtered after 60 minutes of reaction time. The influence of TiNT and BSA on structure and morphology of precipitated CaP phase was investigated by Fourier – Transform Infrared spectroscopy (FTIR), Raman spectroscopy, Poxwder Diffaction (XRD), Scanning Electron microscopy (SEM), Transmission Electron Microscopy (TEM). Representative pH vs time curves are shown in Fig. 1. Curves obtained in all investigated systems showed typical sigmoidal shape reflecting three stages of the precipitation process: i) initial slight pH decrease associated with the formation of ACP, during which the changes in pH and calcium concentrations are small or absent, ii) an abrupt decrease in pH associated with the secondary precipitation of crystalline phase upon ACP, iii) final slight pH change associated with solution-mediated growth and phase transformation [14, 15]. Induction times were obtained from intersection of the tangents drawn on the second and third section of pH vs. time curve (Table 1.). In the presence of TiNTs a significant reduction of induction time was observed, indicating promotion of ACP transformation, which was not concentration dependent in the investigate concentration region. Contrary to TiNTs, in the presence of BSA transformation is inhibited and the influence is concentration dependent. In the precipitatuion systems containing both TiNTs and BSA the transformation was faster at higher TiNTs concentrations. PXRD patterns and FTIR spectra showed that presence of either TiNTs or BSA, or both of them does not influence the composition of the formed precipitate. In all systems calcium deficient hydroxyapatite (CaDHA, Ca10−x(HPO4)x(PO4)6−x(OH)2−x, 0 < x < 2) was formed. CaDHA is considered to be a promising material for manufacturing biomaterials for hard tissue regeneration as biological apatite, the main inorganic part of animal hard tissues, is in fact ion-substituted CaDHA [16]. Althought TiNTs do not influence the morphology, SEM investigation have shown that CaDHA grows on TiNT surface in linear layout. The obtained results point to a biomimetic preparation route of multifunctional CaP based biomaterials.

Prezentirani su rezultati istraživanja istovremenog i pojedinačnog utjecaja albumina iz goveđeg seruma te TiO2 nanocjevčica na taloženje kalcijevih fosfata pri uvjetima sličnim fiziološkim.

Nanoselenium regulated growth and lipid production of Dunaliella tertiolecta- increasing microalgal potential for biofuel production was investigated.

Selenium (Se) is a natural trace element which has large positive and negative environmental impacts that may alternate from an essential micronutrient to a toxic compound within a narrow concentration level. Investigation of selenium nanoparticles (SeNPs) as a possible source of selenium has just recently begun. They have received a lot of attention due to their lower toxicity when compared to sodium selenite (Na2SeO3). Although higher doses of SeNPs may have a negative impact on different processes in algae, lower doses can increase algal biomass without any toxic cellular effect. The objective of this study was to investigate the effects of different SeNPs concentrations on marine microalgae Dunaliella tertiolecta. Algae were cultured under a wide range of different SeNPs concentrations up to 14 days, followed by determination of chlorophyll a, total lipid and protein content, as well as composition of fatty and amino acids. The results have shown that lower concentrations caused a significant increase of biomass concentration and chlorophyll a content, contrary to results obtained in samples with higher SeNPs concentrations. Total protein content and productivity were similar at all tested SeNPs concentrations. Fatty acids, determined by using gas chromatography (GC), had higher content of unsaturated fatty acids in all tested samples. These results provide a better understanding of the effect of SeNPs on green microalgae, which may help in the development of new biotechnological applications considering that nanotechnology becomes a promising tool in many fields of research.

Selenium nanoparticles represent promising candidates in nanomedicine due to their biocidal and atioxidant activity, biocompatibility and biodegradability. In this study different selenium nanoparticles were designed using polyacrylic acid (PAA), polyvinylpyrrolidone (PVP) and poly-L-lysine (PLL) as surface modifiers. Physio-chemical characterization was performed regarding particle size, size distribution and surface charge using dynamic light scattering. Visualization was carried out with transmission electron microscopy. Prior to in vitro testing, evaluation of SeNP stability in cell culture media was determined by means of agglomeration and dissolution behavior.

Nanocomposites of calcium phosphate (CaP) and TiO 2 nanomaterials (TiNM) recently have attracted significant attention due to their potential application as implant materials. TiNM can improve mechanical properties of CaP and can be used as drug delivery systems, as is the case with titanium nanotubes (TiNT). The aim of this research was to determine the influence of TiNM on spontaneous CaP formation with the purpose to develop biomimetic routes of synthesis of CaP/TiNM nanocomposites. The influence of TiO 2 nanoparticles (TiNP) and nanotubes (TiNT) on kinetics of precipitation, composition, structure and morphology of formed CaP phase was determined by potentiometric measurements, FTIR spectroscopy, powder X-ray diffraction, scanning and transmission electron microscopy. Both TiNM exhibited dual influence on precipitation kinetics, i.e. inhibition at lower concentrations and promotion at higher concentrations. No significant differences in composition and morphology of formed precipitates were observed.

One of the largest health issue in modern society is increased frequency of hard tissues chronic diseases. Often the only treatment of such diseases is implementation with the aim to regenerate damaged or diseased tissue. Considering that the main inorganic component of hard tissue is biological apatite, form of calcium phosphate (CaP), composite materials based on calcium phosphate and different inorganic nanomaterials attracts attentions as possible new and innovative implant materials. Among different nanomaterials, TiO2 nanomaterials stand out because they can improve mechanical properties of CaP. Albumine is one of three soluble proteins which adsorbs on the surface of implant materialsright after its implantation and affect their behavior in vivo. But, its role in formation of calcium phosphates on titanium implants is still not clarified. Therefore, the aim of this study is to investigate the adsorption of bovine serum albumin (BSA) on nanocomposites of calcium phosphate (CaP) and TiO2 nanoparticles (CaP/TiNP) or nanotubes (CaP/TiNT). In order to do that, the kinetics of BSA adsorption kinetics of BSA adsorption on TiO2 nanoparticles (TiNP), titanate nanotubes (TiNT), calcium deficient hydoxiapatite (CaDHA) obtained in control system, CaP/TiNP and CaP/TiNT was measured in situ on UV/VIS scanning spectrophotomer. Samples obtained after adsorption were filtered and given for further analysis which included Fourier- transform infrared apectroscopy (FTIR), powder x-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of kinetics measurements were modeled using kinetics models of pseudo-first, pseudo-second rate and interparticle diffusion model. From the results of various kinetic models, the adsorption kinetics were found to follow pseudo-second- order rate kinetic model for CaP/TiNT nanocomposites, respectively pseudo-second- order rate and interparticle diffusion model for CaP/TiNP nanocomposites. Results obtained from FTIR, XRD and SEM analysis showed that albumin did not influence the composition and solid phase morphology

Introduction of nanoparticles (NPs) to biological environments results in the formation of the so-called biomolecular corona a layer of adsorbed biomolecules on the surface of NPs. The composition and nature of corona and its impact on pharmacodynamics and pharmacokinetics of thusly-modi ed NPs is a major question in nanomedicine. In this study, we employed nuclear magnetic resonance (NMR) to evaluate interaction of silver NPs with glutathione (GSH), an important biothiol. The selected silver NPs were functionalized with three distinct coatings - non-ionic polyvinylpyrrolidone (PVP), positively charged poly-Llysine (PLL), and negatively charged sodium bis(2- ethylhexyl)sulfosuccinate (AOT). The experiments involved exposing diferent silver NPs to GSH, analysis of size and surface charge by light scattering technique and tracking the change in NMR spectra of GSH.

Biomineralization is formation of hard tissues in organisms. From physical-chemical point of view it can be considered as a precipitation/crystallization process of inorganic minerals within the organic matrix and/or confined environments. The liposomes closed lipid bilayers, are typical experimental model of confined environment in which biomineralization can occur. The influence of lipid molecules’ structure or their chemical composition and charge (anionic, cationic, zwitterion), on biomineralization is still not fully understand. The aim of this study is to investigate the influence of three lipids (dimyristoylphosphatidylcholine, DMPC, dimyristoylphosphatidylserine, DMPS and phosphatidylcholine, EPC) with different charge of their polar heads, on CaP precipitation. Two precipitation strategies were investigated: fusion of liposomes loaded with constitutive ions (Ca2+ and HPO42–) and spontaneous precipitation of CaP in the presence of liposomes. DMPS exhibited the strongest influence on the precipitation and transformation of the CaP, in both precipitation systems. The obtained results may contribute to the understanding of the general mechanism of inorganic–organic interactions underlying the biomineralization processes, as well as for materials science.

Skin protection is important element in reducing the level of sunburns (erythema), and cancer risk from the ultraviolet radiation exposure. Titanium dioxide nanoparticles (TiO2NPs) are commonly used in sunlight protective products in spite of knowledge gaps on the safety issues concerning their use in medicine and cosmetics. This study aimed to examine the effects of differently shaped TiO2NPs (wire-, plate- and tube-shaped) on immortalized human keratinocytes (HaCaT cell line) before and after UVB exposure. Stability and morphology of TiO2NPs, as well as their biological effects on HaCaT cells, were determined.

Biomineralization, formation of hard tissues in organisms, continues to inspire the scientist to discover novel synthetic routes for advanced materials synthesis. From physical-chemical point of view it can be considered as a precipitation/crystallization process of inorganic minerals within the organic matrix and/or confined environments. The liposomes are typical experimental model of confined environment in which biomineralization can occur. However, the influence of lipid molecules’ structure or their chemical composition (anionic, cationic, zwitterion), on biomineralization is still not understand. The aim of this study is to investigate the influence of three lipids (dimyristoylphosphatidylcholine, DMPC, dimyristoylphosphatidylserine, DMPS and phosphatidylcholine, EPC) with different charge of their polar heads, on CaP precipitation. Two precipitation strategies were investigated: i) fusion of liposomes loaded with constitutive ions (Ca2+ and HPO42–) and ii) spontaneous precipitation of CaP in the presence of liposomes. It was shown that DMPS has the strongest influence on the precipitation and transformation of the CaP, in both precipitation systems. The obtained results may contribute to the understanding of the general mechanism of inorganic–organic interactions underlying the biomineralization processes, as well as for materials science.

Selenium (Se), essential natural trace element for various organisms recently attracts attention due to its potential beneficial effects in various fields, i.e. biomedicine, electronics and some other industrial applications. However, depending on the dose, it can exhibit adverse effects. Current opinion is that possible Se toxicity could be reduced if Se is applied in the form of nanoparticles. Despite this, little is known about possible negative impact of SeNPs on different organisms. In general, when addressing nanotoxicity, aquatic organisms are of major interest, since majority of engineered nanoparticles are released through waters into environment. In aquatic ecosystem microalgae acts as a major vector of Se transport from water to filter-feeders and other consumers. With the aim to determine safety of their use in cosmetic, food and pharmaceutical industry the influence of SeNPs on growth of freshwater microalgae Chlorella vulgaris and marine microalgae Dunaliella tertiolecta was compared to the influence of sodium selenite (NaSe2O3), inorganic Se source. SeNPs were synthesized by solution phase synthesis and characterized using powder X-ray diffraction. The hydrodynamic diameter and zeta potential of SeNPs were determined by dynamic and electrophoretic light scattering. Obtained results may contribute to the understanding of SeNPs toxicity and their biotechnological potential.

Selenium (Se) is a micronutrient metabolically required by a variety of organisms, including microalgae and bacteria. Chlorophyta (green algae) is a large group of aquatic photosynthetic organisms and about half of the global microalgal production corresponds to green microalgae (Chlorella and Dunaliella) species. The range of Se concentrations within Se uptake goes from insufficient to toxic is very narrow. Se toxicity depends on its chemical structure and concentration and it is species- and dose- dependent in the case of microalgae. Recently, instead of sodium selenite (inorganic Se form), selenium nanoparticles (SeNPs) have obtained the attention as a possible Se source because of its lower toxicity. With the aim to determine safety of their use in cosmetic, food and pharmaceutical industry, the influence of SeNPs on growth and chlorophyll a content of freshwater microalgae Chlorella vulgaris and marine microalgae Dunaliella tertiolecta was compared with the influence of sodium selenite. Within this study, SeNPs were synthesized by solution phase synthesis and characterized using powder X-ray diffraction to examine SeNPs composition and phase. The hydrodynamic diameter and zeta potential of SeNPs were determined by dynamic and electrophoretic light scattering. These results provide a better understanding of the effect of SeNPs on green microalgae and their biotechnological potential, which may help in the development of new technological applications considering that nanotechnology becomes a promising tool in many fields of research such as pharmacy, environmental, information technology and engineering, chemical industries, and others.

Titanium dioxide nanomaterials (TiO2NMs) are often a part of sunlight skin protection products within the concentration of 1-150 μg/ml. The controversy on their use concerning safety issues still remains, with the lack of reliable data on their cell penetration, cytotoxicity, oxidative stress and DNA damage especially in combination with UV radiation mostly in the range of UVB that can cause erythema in the superficial epidermis, mostly consisted from keratinocytes. We studied the impact of newly synthesized TiO2NMs in the shape of nanowires, nanotubes and nanoplates in concentration 10-100 μg/ml on the level of DNA damage ( alkaline comet assay) immediately and 24 hour after the treatment of immortalized human keratinocytes (HaCaT) cell line together with UVB medial erythemal dose (2 kJ/m2 , 312 nm) with plastic cover. Although some type of particles showed protective effect after 24 hours, but nor immediately, they did not demonstrate significantly protective effect. Further studies should be done without the plastic cover and on the level of lipid peroxidation and cellular reactive oxidative species level to further clarify the impact of TiO2NMs together with the effect of cellular uptake and subcellular localization.

Excellent biological properties of amorphous calcium phosphate (ACP), precursor of crystalline calcium phosphates (CaPs), as well as its major role in the normal and pathological biomineralization of vertebrates continues to motivate interest in elucidating its formation. Crucial part of ACP formation mechanism is aggregation at different scales, i.e. calcium and phosphate ions associate forming prenucleation clusters, which aggregate to spherical ACP nanosized particles, which in turn aggregate to chain-like aggregates. The aim of this study was to apply dynamic light scattering and laser diffraction, two widely used techniques for particle size’s determination, in order to follow aggregation kinetics of ACP particles at nano to micron scale at two different supersaturations. Precipitation of ACP was initiated by fast mixing of equimolar reactant solutions. Induction time for nucleation of crystalline phase, i.e. time needed for the commencement of ACP transformation, was determined from potentiometric measurements. Furthermore, formed ACP was characterized by FT-IR spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM). During induction time spherical particles and their chain like aggregates characteristic for ACP were formed, as confirmed by FTIR, AFM and TEM. The initial formation rates, as well as the size of the particles, depended on the initial supersaturation. Although the precipitation conditions differed in DLS and laser diffraction studies (mode of mixing, reaction volume), a general conclusion that aggregation of ACP particles is a process which simultaneously takes place at different length scales leading to highly polydisperse precipitate, can be drawn. This points to a possible way of controlling ACP formation by controlling aggregation on chosen scale.

There exist different micro-rheological techniques for studying the structural and dynamical properties of complex fluids at a supramolecular level. Among these we find the lightscattering techniques: Dynamic Light Scattering (DLS and Diffusing Wave Spectroscopy (DWS). Both of them work as a complementary technique of the other one, in this case because we can get a wider landscape of the viscoelastic spectrum of the studied systems. These light scattering techniques take advantage of the Brownian motion of probe particles embedded into the fluid, which scatter the incident light in all directions. Retrieving the scattered light, it is possible to estimate the mean square displacement of the particles (MSD) by means of the correlation function generated by the photons that reach the detector. It is important to note that the fluid medium to be analyzed should be transparent to the incident light, but using a resent technique developed by Prahl for medical applications and studied and applied by Sarmiento-Gómez et al., it is possible to extent the DWS technique to light absorbent fluids. This technique also allows the possibility of extent in time the MSD response, becoming a complementary technique when backscattering DWS is difficult to set up. In this work we show some preliminary microrheological results of a system of worm- like micelles made by the self-assembly of 1, 4 poly (1, 3-butadiene)-polyethylene oxide diblock copolymer in water solution and preliminary rheological results of a system of single wall carbon nanotubes (SWNT) dispersed in Poly(acrylic acid) as a function of a variation of its pH.

We are interested in the study of structure, equilibrium behavior, and rheology of fluids with embedded long linear and flexible or nonflexible threadlike supramolecular structures. Trapping and manipulation of single particles and molecules studies have gained insight into the behavior of biomolecules, as well as isolated polymers in simple flows. Hydrodynamic trapping is a useful tool based on the hydrodynamic forces that capture particles or cells using the fluid flow at stagnation points generated in microfluidic devices. In this way, we intend to develop a microfluidic device for achieving an elongational flow to be imposed to the fluid embedded with tubular micelles. This would allow observation of marked tubular polymer micelles with a fluorescent dye using a confocal microscopy. The other systems of our interest are carbon nanotubes that also represent threadlike supermolecular structure. The aim of this work is to obtain stable dispersions of single carbon nanotubes using polyacrylic acid that has viscoelastic properties. The organization within these supramolecular structures will depend on a complex interplay of molecular geometry, amphiphilic character, and charge of all the involved molecules in the supramolecular structures. Many factors can modify this interplay as polyelectrolyte concentration, pH, temperature, and ionic strength of the media. We intend to investigate the effect of pH and ionic strength on the microstructure of the carbon nanotubes stabilized with polyacrylic acid.