DBS Concentration Research Articles

Dried blood spot analysis for elements of nutritional concern as demonstrated in studies of Galápagos land iguanas (Conolophus species)

BackgroundDried blood spot (DBS) technology is valuable in providing simple means of storing blood samples from wildlife with small blood volumes. Methods designed for heavy metal analysis on DBS become more useful if extended to elements of nutritional significance. Purpose(1) Development of procedures for measuring Mn, Fe, Co, Cu, Zn, Se and Mo in DBS; (2) use the designed methods in health assessments of Galápagos land iguanas (Conolophus species). ProceduresElements were measured by inductively coupled plasma/mass spectrometry (ICP-MS) following acid digestion of whole blood or DBS from the same animal for direct comparison. Study animals comprised free-ranging iguanas from separate islands in the Galápagos archipelago. Main FindingsDBS spikes (Mn, Fe, Co, Cu, Zn, Se and Mo) demonstrated accuracy to ∼100 ppb; reporting limits were set there except for Fe and Zn which were set at 1000 ppb. Plasma samples – generally preferable for nutritional element diagnostics – were submitted from Galápagos land iguanas along with DBS as part of a large-scale health assessment. In plasma versus DBS concentration comparisons, Fe, Cu, Se and Mn correlated well with R^2 values of 0.799, 0.818, 0.896 and 0.899, respectively, and slopes ranging 0.88 – 1.3. Co and Zn showed greater scatter. Mo had insufficient points above its reporting limit and offered advantages for toxicity assessments. Bland-Altman diagrams showed flat scatter between 2x standard deviation boundaries with no undue trends except for Mn which had few points above its reporting limit. Bias, defined as the average difference [DBS – plasma] divided by the average value, was relatively low throughout, with values of − 19.3 % (Fe), − 48.7 % (Co), − 19.6 % (Cu), − 6.9 % (Zn), − 21.4 % (Se) and + 40.7 % (Mn). Normal distribution assessment of iguana Cu, Zn, Se and Fe plasma values showed unanticipated divergences between two species. ConclusionsThe DBS approach for nutritional element analysis offers a suitable methodology for determining crucial elements Mn, Fe, Co, Cu, Zn, Se, and Mo in veterinary samples. Analyses of samples from Conolophus species revealed interesting divergences particularly for Cu, Zn, Se and Fe, elements generally associated with defense against oxidative stress.

Influence of high pH state of dodecylbenzenesulfonate and dissolved organic matter complex solution on the ultraviolet spectrometry of dodecylbenzenesulfonate

AbstractDodecylbenzenesulfonate (DBS) is an anionic surfactant that is the most commonly used ingredient in modern cleaning agents. Globally, billions of liters of untreated DBS are released daily into natural water bodies, which may lead to fatal consequences in micro and macro living entities, and destroy the natural ecosystem. Therefore, a simple, precise, rapid, and inexpensive method for measuring DBS is crucial for developing countries. The conventional ultraviolet (UV) spectrophotometric method cannot accurately estimate the DBS concentration in a solution containing a considerable quantity of dissolved organic matter (DOM). Recently, a new spectrometric method was developed using the 222.5 nm UV and 400 nm UV–visible (UV–vis) spectra to precisely estimate DBS concentration in the DBS–DOM complex solution. However, this newly developed method is yet to be validated under higher pH conditions. The accuracy of DBS measurements from the DBS–DOM complex solution under lower pH (5.5 and 6.5) and higher pH (12.5) conditions was compared in this study using the previously developed method. With the higher pH, the influence of the electrolyte increased the absorbance under the 222.5 nm UV spectrum. However, such influence decreased with the increase in DBS and DOM concentration. The UV–vis absorbance at 400 nm decreased under higher pH values when the DOM concentration increased, owing to the conformational change in DOM. Despite the contrasting trends of the absorbances in the two spectra, the studied method was proven to be equally applicable and efficient, even under higher pH conditions.

Hematocrit and standardization in DBS analysis: A practical approach for hormones mainly present in the plasma fraction

Background and aimDried blood spot (DBS) sampling has many advantages over conventionally used blood samples, but is thought to suffer from hematocrit related issues. The aim of our research was to investigate whether reliable results can be obtained without bothering about hematocrit effects in DBS analysis of analytes that are mainly present in the plasma compartment. Materials and MethodsVenous blood samples with variation in hematocrit and spotted volume were prepared. Spot diameter and 25-OH Vitamin D3 and testosterone concentrations were measured. Moreover, DBS and plasma concentrations of 25-OH Vitamin D3, testosterone and hematocrit were determined in random patient samples. ResultsDBS spot size was linearly related to hematocrit. Measured DBS concentrations of 25-OH Vitamin D3 and testosterone were independent of hematocrit and spotted volume. Determining the relation between plasma and DBS concentration resulted in a factor that can be used to convert DBS concentrations to standardized plasma concentrations. ConclusionAddressing the hematocrit issue is not necessary for hormones that are mainly present in the plasma compartment. The relation between plasma and DBS concentration can be used to convert DBS concentrations to standardized plasma concentrations which makes interpretation of DBS concentrations easier.

Effects of self-assembled sorbitol-derived compounds on the structures and properties of biodegradable poly(L-lactic acid) prepared by melt blending

The microstructures and characteristics of biodegradable poly(L-lactic acid) (PLLA) with 1,3:2,4-dibenzylidene-D-sorbitol (DBS) prepared by melt blending were investigated in this study. DBS was added as a diluent to PLLA in the melted state, leading to the disentanglement of PLLA chains and the enhancement of PLLA mobility. Upon cooling from the melt, the formation of self-assembled DBS nanofibrils enhanced the hardness and stiffness of PLLA. DBS nanofibrils were measured with diameters of 40–50 nm, as observed using scanning electron microscopy (SEM). In addition, the thermal and crystallization behaviors of PLLA were significantly influenced by the addition of DBS. The ordered and regular α-crystals of PLLA were favored when DBS was added. The crystallization rates of PLLA are tunable by varying the isothermal crystallization temperatures of PLLA and the amounts of DBS. The presence of DBS interfered with the crystallization rates of PLLA. However, at higher crystallization temperatures of PLLA, DBS facilitated the formation of nuclei, leading to an increase in the crystallization rates of PLLA. Furthermore, the hydrophilicity of PLLA was significantly improved by a further increase in DBS concentration.

A case study of aggregation behaviors of titanium dioxide nanoparticles in the presence of dodecylbenzene sulfonate in natural water

The present work aims to ascertain the mechanisms of surfactant (dodecylbenzene sulfonate; DBS) effects on the aggregation behaviors of TiO2 nanoparticles (TiO2-NPs) in natural water samples. Aggregation experiments were conducted at a TiO2-NPs concentration of 10mg/L in deionized water and in natural water samples via dynamic light scattering and Zeta potential determination. Average attachment efficiency was calculated to compare the aggregation behaviors of nanoparticles in the two aqueous media. Results showed that the effects of DBS on aggregation could be interpreted by both Derjaguin–Landau–Verwey–Overbeek (DLVO) and non-DLVO mechanisms. In natural water samples, aggregation did not occur rapidly and was able to develop slowly under all conditions, and the roles of DBS were obvious at high DBS concentration owing to the impacts of inherent components of natural water samples, such as colloids and natural organic compounds. Future aggregation studies should concentrate on multi-factor, multi-colloidal and dynamic aspects under similar environmental conditions.

Crystallization and microporous membrane properties of ultrahigh molecular weight polyethylene with dibenzylidene sorbitol

ABSTRACTDibenzylidene sorbitol (DBS) was chosen as an in situ forming nucleating agent to study ultrahigh molecular weight polyethylene (UHMWPE) crystallization and microporous membrane. The experimental results indicated that DBS self‐assembled into fibrils first and the solution became a physical gel before UHMWPE crystallization during thermally induced phase separation (TIPS) of UHMWPE/liquid paraffin (LP)/DBS solution, and the temperature of DBS self‐assembly shows a strong dependence of DBS concentration. With decreasing temperature further, DBS fibrils as heterogeneous nucleating agent accelerated UHMWPE crystallization, which was showed more clearly in UHMWPE/LP/DBS phase diagram. UHMWPE microporous membranes were prepared through TIPS method with the control of DBS concentration. It was found that UHMWPE microporous membranes in the presence of DBS fibrils show small porous size and low water permeability, but relatively larger mechanical strength. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40706.

TiO2 microspheres with variable morphology, size and density synthesized by a facile emulsion-mediated hydrothermal process

A series of titanium dioxide (TiO2) microspheres with different morphology, size and density were facilely prepared by hydrothermally treating the emulsion which were prepared using tetrabutyl titanate complex as the disperse phase and water as the continuous phase. The Scanning electron microscope (SEM) observation indicates that spherical and quasi-spherical particles were obtained from the emulsion with and without dodecylbenzenesulfonic acid (DBS), respectively. It was found that the average diameter of the microspheres was influenced by the DBS concentration. Nitrogen adsorption–desorption isotherms show that the as-prepared TiO2 microspheres are mesoporous material, and the density decreases with the increasing of DBS.

Novel poly(ethylene glycol) gel electrolytes prepared using self-assembled 1,3:2,4-dibenzylidene-d-sorbitol

Gel electrolytes have usually been prepared by adding gelators or polymers to the liquid organic solvent-based electrolytes. In this study, we proposed a method to prepare gel electrolytes using gelators in liquid (low molecular weight) polymer-based electrolytes. Inexpensive 1,3:2,4-dibenzylidene-D-sorbitol (DBS) was chosen as a gelator for poly(ethylene glycol) (PEG)-based electrolytes at relatively low DBS concentrations. A series of gel electrolytes was produced by varying the DBS amounts, PEG molecular weights and PEG end groups. First, we found that DBS molecules self-assembled into 3-D networks consisting of nanofibrils that were approximately 10 nm in diameter, as measured by transmission electron microscopy; they exhibited spherulite-like morphologies under polarizing optical microscopy. Second, the dynamic rheological measurements demonstrated that the elastic modulus and the dissolution temperature of DBS-PEG gels increased with the increasing DBS content. The thermal degradation temperature of these gels also increased when the DBS concentration increased, as determined by thermogravimetric analysis. In addition, adding DBS may help to facilitate the dissolution of iodide and iodine in PEG due to its ether groups. Furthermore, the conductivity of the prepared DBS-PEG gel electrolytes was similar to that of the liquid PEG electrolytes (without DBS). When used in dye-sensitized solar cells (DSSC), the PEG-based electrolytes having inactive methyl end groups achieved the highest energy conversion efficiency among the tested cells. The efficiency of DSSC filled with our gel electrolytes remained basically the same over a one-month period, implying that the materials were relatively stable.

NMR Characterization of the Formation Kinetics and Structure of Di-O-Benzylidene Sorbitol Gels Self-Assembled in Organic Solvents

The molecule 1,3:2,4-di-O-benzylidene sorbitol (DBS) is a common "gelator" that forms thermally reversible gels in diverse organic solvents. Solid-state (13)C and (1)H NMR techniques, along with electron microscopy, are utilized in an exploratory study of DBS in the gelled state where we consider both in situ and dried gels. The gels were formed in either acetone or benzene, with the former being a better solvent for DBS. We find the in situ or dried DBS gels to be composed of rigid twisted nanofibrils (∼15 to 21 nm in diameter). The fibrils show local molecular ordering, but not crystalline order, and they contain no trapped solvent. The molecular mobility at the fibril surface is modestly enhanced, and all the free hydroxyl groups of the sorbitol moiety are involved in strong hydrogen bonding. We also attempted to find a truly crystalline form of DBS whose structure, as judged by the similarity of (13)C spectra, is close to that of the fibrils. We partially succeeded in this quest, employing melt crystallization followed by slow cooling. However, this sample was a mixed crystal having small domains, where only one type of domain was structurally similar to the fibrils. We also investigated the long-time evolution of the in situ DBS gel network. Specifically, high-resolution NMR kinetic studies were performed over periods of days where the residual concentration of DBS in acetone solution was monitored during and after gel formation. The DBS concentration on these long timescales evolved slowly, and we introduce a simple mathematical model and equation to describe this phenomenon.

Studies on the self‐assembly of neat DBS and DBS/PPG organogels

AbstractThe self‐assembly behavior of neat 1,3:2,4‐dibenzylidene‐D‐sorbitol (DBS) and DBS/poly(propylene glycol) (PPG) organogels has been investigated by scanning electron microscopy, polarizing optical microscopy, and rheological measurements. DBS molecules are capable of self‐organizing into fibrils and exhibit the birefringent spherulitic textures during cooling from the melt. On the other hand, DBS can self‐assemble into a fibrillar network in PPG to produce organogels. DBS/PPG organogels also reveal a spherulite‐like morphology. When a small amount of DBS is dispersed into a PPG matrix, we find that the spherulite sizes are much smaller than those of neat DBS. This is because the dilution of DBS causes DBS to self‐assemble in PPG at a lower temperature. Therefore, more nucleation sites and smaller spherulite sizes are found in the DBS/PPG organogel system. The rheological measurements demonstrate that the elastic modulus (G′) in DBS/PPG organogels increases as the DBS concentration increases. However, the increase in G′ is less obvious, as the DBS content exceeds 3 wt %. suggesting that the DBS networks become saturated. Also, it is found that these organogels require a certain period of time to reach thermodynamic equilibrium, depending on DBS concentrations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Energy‐Modulated Heterostructures Made with Conjugated Polymers for Directional Energy Transfer and Carrier Confinement

AbstractIn this paper we demonstrate that multilayer structures with modulated bandgaps can be used for efficient energy transfer and carrier confinement inside a nanostructured film of a light‐emitting polymer. The films were produced with the layer‐by‐layer technique (LbL) with a poly(p‐phenylene vinylene) (PPV) precursor and a long chain dodecylbenzenesulfonate ion (DBS). DBS is incorporated selectively into the precursor chain, and with a rapid, low temperature conversion process (100 °C) superstructures with variable HOMO–LUMO gap could be formed along the deposition direction by changing the DBS concentration. Structures with different stair‐type energy modulations were produced, which are thermally stable and reproducible, as demonstrated by UV‐VIS. absorption measurements. Energy differences of up to 0.5 eV between the lowest and highest conjugated layers inside the stair structure could be achieved, which was sufficient to guide the excitation over long distances to the lower bandgap layer.

Physical organogels composed of amphiphilic block copolymers and 1,3:2,4-dibenzylidene-D-sorbitol

The 1,3:2,4-dibenzylidene-D-sorbitol (DBS) molecule is capable of self-organizing into nanoscale fibrils through intermolecular forces such as hydrogen bonding and π interactions. At sufficiently high concentrations (typically less than ∼2 wt%), the nanofibrils can form a network that promotes physical gelation of the matrix medium. Previous studies have investigated the mechanism of DBS-induced gelation and the features of DBS-containing gels in poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG). In this work, we examine the effect of adding DBS to a series of amphiphilic PPG- b-PEG- b-PPG triblock copolymers differing in composition and molecular weight. Dynamic rheological measurements reveal that the resultant gels are thermoreversible (i.e., they exhibit comparable mechanical properties before dissolution and after reformation under quiescent conditions), exhibiting a maximum in the elastic modulus ( G′) at temperatures near the gel dissolution ( T d ) and formation ( T f ) temperatures. Both T d and T f tend to increase with increasing DBS concentration and PPG content, and their difference decreases with increasing PPG fraction in the copolymer. The magnitude of G′ is sensitive to copolymer composition and polymer identity at low DBS concentrations, but becomes polymer-independent as the DBS network saturates at concentrations in excess of ∼1 wt%.

Morphological Characteristics of 1,3:2,4-Dibenzylidene Sorbitol/Poly(propylene glycol) Organogels

The organic gelator 1,3:2,4-dibenzylidene sorbitol (DBS) self-organizes to form a 3-D network stabilized by hydrogen bonds at relatively low concentrations in a variety of nonpolar organic solvents and polymers. The resultant network consists of nanofibrils and is responsible for the physical gelation of the matrix component. In this work, the morphological characteristics of organogels composed of DBS and poly(propylene glycol) (PPG) are investigated as functions of DBS concentration, PPG molecular weight, and temperature through the use of polarized light microscopy, transmission electron microscopy, X-ray diffractometry, and spectrophotometry. Polarized light microscopy reveals thermally reversible features that become increasingly more pronounced with increasing DBS concentration. Electron microscopy verifies that these features arise due to the presence of a DBS nanofibrillar network, with nanofibrils measuring ca. 10 nm in diameter. Comparison of X-ray diffraction patterns of pure DBS crystals and DBS networks from which PPG is removed by supercritical fluid extraction reveals that the DBS nanofibrils are crystalline, differing slightly from the structure of pure DBS. Spectrophotometry is used to probe the temperature-dependent development of the molecular network in DBS/PPG organogels.

Dynamic rheological behavior of DBS-induced poly(propylene glycol) physical gels

Physical gelation can be induced in various organic and silicone-based liquids, as well as in polymeric melts, upon addition of 1,3:2,4-dibenzylidene sorbitol (DBS). Such gels are stabilized by the formation of a percolated DBS network composed of highly interconnected nanofibrils. In this study, we explore several factors affecting the rheological properties of poly(propylene glycol) (PPG) gelled by DBS. To ascertain the effect of PPG molecular weight (MPPG) on gel formation and rheology, we have investigated three series of DBS-induced PPG gels in which MPPG varies from 425 g/mol to 4000 g/mol. Dynamic stress measurements reveal that the DBS concentration identifying the onset of PPG gelation decreases with increasing MPPG. Since the solubility parameter (δs) of PPG decreases sharply as MPPG increases over this MPPG range, this observation suggests that DBS gelation is sensitive to δs of the matrix liquid, in agreement with previously reported data collected from DBS-gelled solvents. Moreover, the elastic modulus and yield stress are found to increase with increasing (i) DBS concentration for the three series of PPG/DBS gels examined here and (ii) recovery time after cessation of an introductory shear.

Effect of molecular architecture on DBS‐induced block copolymer gels: A rheological study

AbstractDibenzylidene sorbitol (DBS) is capable of gelling a variety of organic solvents and polymeric materials by forming a rigid, 3‐D hydrogen‐bonded network. In this work, two poly(siloxane)/poly(propylene oxide) segmented copolymers of equal composition and molecular weight, but different architectures (endblocked vs. pendant), as well as a pure poly(propylene oxide), have been gelled with DBS. We have investigated the dynamic rheological properties of these gels to ascertain the effect of copolymer architecture, PDMS comonomer and DBS concentration on network formation.

Micellar shape investigations of DBS aqueous solutions

The size of spherical micelles at low concentrations of DBS was determined and a transition from spherical to cylindrical micelles at a DBS concentration above 2% was found.

Adsorption and diffusion of sodium p-dodecylbenzene sulfonate of tetramer type in cellulose

The adsorption and diffusion of sodium p-dodecylbenzene sulfonate of a tetramer type (DBS) in cellulose from the wide concentration range of DBS solution were investigated by the method of the cylindrical film role at temperature between 10 and 50°C. The surface concentration of DBS in cellulose at first increased gradually with increase in the concentration of DBS in solution, then increased abruptly in the vicinity of the critical micelle concentration (CMC), reached a maximum, and finally decreased gradually. The diffusion profile of DBS in cellulose near and above the CMC showed the existence of two kinds of adsorbed species, the monomer and dimer of DBS. The adsorption of dimer corresponded to the adsorption maximum in the adsorption isotherm. The adsorption of monomer DBS ion on cellulose showed a Langmuir-type adsorption isotherm. The diffusion behavior of DBS in cellulose also supported these findings. With an increase in the DBS concentration above the CMC, larger micelles of DBS, which were not adsorbed by cellulose, were also formed and the adsorption of dimer gradually decreased due to the fact that the concentration of dimer in solution decreased as the micelle formation proceeded. Thus, a so-called adsorption maximum was observed in the adsorption isotherm. The adsorption of monomer DBS ions on cellulose was enhanced by the addition of sodium chloride. The diffusion coefficient of DBS in cellulose increased with increase in the concentration of DBS and/or NaCl added to the DBS solution.