Computational Study of Complex Formation between Hyaluronan Polymers and Polyarginine Peptides at Various Ratios

Hyaluronic acid, a naturally occurring carbohydrate biopolymer in human tissues, finds wide application in cosmetics, medicine, and material science. Its anionic properties play a crucial role in its interaction with positively charged macromolecules and ions. Among these macromolecules, positively charged arginine molecules or polyarginine peptides demonstrate potential in drug delivery when complexed with hyaluronan. This study aimed to compare and elucidate the results of both experimental and computational investigations on the interactions between hyaluronic acid polymers and polyarginine peptides. Experimental findings revealed that by varying the length of polyarginine peptides and the molar ratio, it is possible to modulate the size, solubility, and stability of hyaluronan-arginine particles. To further explore these interactions, molecular dynamics simulations were conducted to model the complexes formed between hyaluronic acid polymers and arginine peptides. The simulations are considered in different molar ratios and lengths of polyarginine peptides. By analysis of the data, we successfully determined the shape and size of the resulting complexes. Additionally, we identified the primary driving forces behind complex formation and explained the observed variations in peptide interactions with hyaluronan.

Functional Hydrogels for Agricultural Application

Ten different hydrogels were prepared and analyzed from the point of view of their use in soil. FT-IR spectra, morphology, swelling ability, and rheological properties were determined for their characterization and appraisal of their stability. The aim was to characterize prepared materials containing different amounts of NPK as mineral fertilizer, lignohumate as a source of organic carbon, and its combination. This study of stability was focused on utility properties in their application in soil-repeated drying/re-swelling cycles and possible freezing in winter. Lignohumate supported the water absorbency, while the addition of NPK caused a negative effect. Pore sizes decreased with NPK addition. Lignohumate incorporated into polymers resulted in a much miscellaneous structure, rich in different pores and voids of with a wide range of sizes. NPK fertilizer supported the elastic character of prepared materials, while the addition of lignohumate shifted their rheological behavior to more liquid. Both dynamic moduli decreased in time. The most stable samples appeared to contain only one fertilizer constituent (NPK or lignohumate). Repeated re-swelling resulted in an increase in elastic character, which was connected with the gradual release of fertilizers. A similar effect was observed with samples that were frozen and defrosted, except samples containing a higher amount of NPK without lignohumate. A positive effect of acrylamide on superabsorbent properties was not confirmed.

Incarcerated metastasis as the first manifestation of a rare sarcoma

Desmoplastic small round cell tumor belongs to a group of soft tissue sarcomas. It is a rare disease, since its discovery in 1989, only hundreds of cases have been described in the literature. Due to the rare incidence of the tumor, this disease remains unknown in common medical practice. It occurs most often in men at young age. Its prognosis is serious and the average survival of patients ranges from 1.5 to 2.5 years. Treatment options include surgical resection, chemo-, radio- and targeted therapy. Our work presents a case report of a 40 year-old patient sufferred from this sarcoma. The first manifestation of the disease was an incarcerated epigastric hernia with omentum and sarcoma metastasis. A resection of the incarcerated part of the omentum was performed with a biopsy from another intra-abdominal lesion. Biopsy specimens were sent for histopathological evaluation. For the generalization of the disease, further surgery was not indicated and systemic palliative chemotherapy in the VDC-IE regimen was chosen. At the time of submitting the manuscript, the patient has survived 6 months since the surgical procedure.

Reaction-Diffusion Systems: Self-Balancing Diffusion and the Use of the Extent of Reaction as a Descriptor of Reaction Kinetics

Self-balancing diffusion is a theoretical concept that restricts the introduction of extents of reactions. This concept is analyzed in detail for general mass- and molar-based balances of reaction-diffusion mixtures, in relation to non-self-balancing cases, and with respect to its practical consequences. Self-balancing is a mathematical restriction on the divergences of diffusion fluxes. Fulfilling this condition enables the proper introduction of the extents of (independent) reactions that reduce the number of independent variables in thermodynamic descriptions. A note on a recent generalization of the concept of reaction and diffusion extents is also included. Even in the case of self-balancing diffusion, such extents do not directly replace reaction rates. Concentration changes caused by reactions (not by diffusion) are properly described by rates of independent reactions, which are instantaneous descriptors. If an overall descriptor is needed, the traditional extents of reactions can be used, bearing in mind that they include diffusion-caused changes. On the other hand, rates of independent reactions integrated with respect to time provide another overall, but reaction-only-related descriptor.

Hyaluronan interactions with cationic surfactants - Insights from fluorescence resonance energy transfer and anisotropy techniques

Interactions of hyaluronan with micelles formed by cationic surfactants were studied by the time-resolved measurement of fluorescence resonance energy transfer (FRET) using perylene and fluorescein as probes. Two surfactants were studied - Cetyltrimethylammonium bromide (CTAB) and Septonex. In pure micellar solutions, the same values of FRET efficiency were found for both surfactants, but values for the binding of the probe pair were lower for Septonex micelles than in the case of CTAB. This was attributed to steric effects of the carbethoxy group in the Septonex polar head. Upon the addition of hyaluronan, decreased FRET efficiency and increased binding were detected in comparison with pure surfactants. To resolve the structure of the formed aggregates, steady state and time-resolved fluorescence anisotropy was employed as an additional technique. All results indicated that cationic micelles bind to hyaluronan forming a pearl necklace structure with micelles of smaller size compared to pure surfactant. Besides theoretical interest, the studied polyelectrolyte-surfactant system may be interesting for the formulation of drug delivery systems.

Diffusion of dyes in polyelectrolyte-surfactant hydrogels

In this work, hydrogels formed by interaction of biopolymeric electrolytes and oppositely charged surfactants are studied from the point of view of their ability to incorporate model hydrophobic dyes in their micelle-like structure. Two types of hydrogels were investigated. The first type was based on cationized dextran cross-linked by sodium dodecylsulphate. The second type was prepared by interactions of hyaluronan with carbethoxypendecinium bromide (septonex). Nile red and Atto488 were used as model dyes for the diffusion experiments. The dyes were dissolved in two different media: surfactant and physiological saline. The diffusion of dyes into hydrogel was monitored over time. Effective diffusion coefficients were determined. It was found that their values are strongly influenced by the hydrogel character, the types of dye used and the solvent. The obtained effective coefficients were higher in comparison with the values determined for the diffusion in the opposite direction (release from the hydrogel). The dyes are presented as free in physiological saline and in the form of micelles or micelle aggregates in surfactants. During diffusion into the hydrogel, they can be gradually incorporated in a "pearl necklace structure" which suppresses their mobility. In contrast, this partial immobilization of dyes can increase the concentration gradient which is a driving force of diffusion. Also, the gradual incorporation of dyes into hydrogel structures influences the values of the effective diffusion coefficients.

Partial jejunal diversion (PJD) with jejunocolic anastomosis preliminary results of a pilot study

INTRODUCTION

Bariatric-metabolic surgery is an effective tool in the treatment of severe obesity and related diseases. Its importance has increased even more in the era of the type II diabetes mellitus and COVID 19 pandemics. The aim of our study is to present the initial results of a new operation that minimizes surgical trauma.

METHODS

In the prospective study, laparoscopic side-to-side anisoperistaltic jejunocolic anastomosis was constructed in order to derive part of the chyme by the anastomosis. Patients were operated in the period of IV/2018VII/2019; their mean age was 48.43±10.36 years, mean weight 112.3±16.6 kg and mean BMI 41.9±5.2. Patients were examined one month before surgery and then followed at 3, 6 and 12 months after surgery. We evaluated weight loss and changes in carbohydrate metabolism.

RESULTS

We did not record any perioperative or postoperative surgical complications. There was a statistically significant weight loss during the study period. There was a significant decrease in absolute weight in kilograms (p.

CT evaluated sarcopenia signals: Shorter survival for small cell lung cancer patients

Sarcopenia is an independent risk factor for morbidity and mortality in patients suffering from small cell lung cancer (SCLC), however, a universal indicator of sarcopenia usable in clinical practice is still missing. A novel indicator for describing the severity of cancer could be helpful in tailoring the anti-tumor therapy. The aim of this study was to evaluate the computed tomography (CT) scans of total muscle area and radiation attenuation in patients suffering from small cell lung cancer. We used staging CT scans performed at the time of diagnosis to measure total muscle area (TMA) and average psoas density (PD) at level of the 3rd lumbar vertebra. TMA and PD were statistically evaluated in association with overall survival and disease staging. We used Mann-Whitney test and Spearman´s correlation coefficient for statistical testing and p-value under 0.05 was considered statistically significant. Retrospectively we examined 47 patients suffering from SCLC (mean age 65.05+/-7.3 years, BMI 23.97+/-4.4 kg/m2, BSA 1.77+/-0.2 m2, 30-day mortality was 4.3 % with 10 months median survival). As sarcopenia was pointed TMA under 55 and 39 cm2/m2 for men and women respectively. The sarcopenic patients had significantly shorter median survival (7 vs. 11 months, p=0.05). We observed a significant relationship between survival and performance status (Spearman´s correlation, R=-0.39, p=0.05). The patients were divided into two groups according to the extensive (ED, n=34) or limited (LD, n=13) form of the disease. We observed significant difference in PD (42.49+/-6.1 vs. 47.67+/-4.5 HU, p=0.006) between ED vs. LD groups.

Interactions between Cationic Ion Pair Amphiphile Vesicles and Hyaluronan-A Physicochemical Study

High-resolution ultrasound spectroscopy (HR-US), size and ζ-potential titrations, and isothermal titration calorimetry (ITC) were used to characterize the interactions between hyaluronan and catanionic ion pair amphiphile vesicles composed of hexadecyltrimethylammonium-dodecylsulphate (HTMA-DS), dioctadecyldimethylammonium chloride (DODAC), and cholesterol. In addition to these methods, visual observations were performed with the selected molecular weight of hyaluronan. A very good correlation was obtained between data from size titration, HR-US, and visual observation, which indicated in lower charge ratios the formation of hyaluronan-coated vesicles. On the contrary, at higher charge ratios, coated vesicles disintegrated to a size of around 2000 nm. The intensity of these interactions and the disaggregation were dependent on the molecular weight of hyaluronan. All interactions studied by ITC showed strong exothermic behavior, and these interactions between vesicles and hyaluronan were confirmed from the first addition, independently of the molecular weight of hyaluronan.

Cholesterol Effect on Membrane Properties of Cationic Ion Pair Amphiphile Vesicles at Different Temperatures

This work is focused on the study of the effect of cholesterol on the properties of vesicular membranes of ionic amphiphilic pairs at different temperatures. The hexadecyltrimethylammonium-dodecyl sulfate ionic amphiphilic pair system with the addition of 10 mol % dioctadecyldimethylammonium chloride was chosen for a detailed study of vesicle properties. A large range of cholesterol concentrations (0-73 mol %) in the temperature range 10-80 °C was studied. Under these conditions, the size distribution, the membrane fluidity, and the surface layer were monitored together with the change in the mobility of water in the surface layer. Obtained quantities were correlated with each other and combined into appropriate graphs. It was found that in stable systems that meet the condition of unimodal size distribution with a PDI value lower than 0.3, temperature has virtually no effect on the size of vesicular systems. On the contrary, when studying the hydration and fluidity of the membrane, significant changes in these parameters were found, which, however, do not affect the short-term stability of these vesicular systems. The presented results thus indicate the possibility of adjusting the composition of the vesicular system in terms of fluidity and membrane hydration while maintaining short-term stability and size distribution.

Hyaluronan-Arginine Interactions-An Ultrasound and ITC Study

High-resolution ultrasound spectroscopy and isothermal titration calorimetry were used to characterize interactions between hyaluronan and arginine oligomers. The molecular weight of arginine oligomer plays an important role in interactions with hyaluronan. Interactions were observable for arginine oligomers with eight monomer units and longer chains. The effect of the ionic strength and molecular weight of hyaluronan on interactions was tested. In an environment with increased ionic strength, the length of the arginine oligomer was crucial. Generally, sufficiently high ionic strength suppresses interactions between hyaluronan and arginine oligomers, which demonstrated interactions in water. From the point of view of the molecular weight of hyaluronan, the transition between the rod conformation and the random coil conformation appeared to be important.

Fluorescence Study of Aggregation Behaviour of Cationic Surfactant Carbethopendecinium Bromide and its Comparison with Cetyltrimethylammonium Bromide

The aggregation behaviour of the cationic surfactant carbethopendecinium bromide (Septonex) and cetyltrimethylammonium bromide (CTAB) in aqueous solution was investigated by steady-state and time-resolved fluorescence experiments. Values of critical micelle concentration were obtained from the pyrene emission polarity index. The micellar aggregation numbers for four different concentrations of both surfactants were determined by steady-state and time-resolved fluorescence quenching methods, using pyrene as a probe and cetylpyridinium chloride as a quencher. The results obtained for Septonex were compared with the aggregation parameters of CTAB. Generally, Septonex micelles were formed by a smaller number of surfactant monomers than in the case of CTAB and the critical micelle concentration of Septonex is lower than that of CTAB. Also, the concentration dependence of the micelle aggregation number was found.

Compositional and Temperature Effects on the Rheological Properties of Polyelectrolyte-Surfactant Hydrogels

The rheological properties of hydrogels prepared by physical interactions between oppositely charged polyelectrolyte and surfactant in micellar form were studied. Specifically, hyaluronan was employed as a negatively charged polyelectrolyte and Septonex (carbethopendecinium bromide) as a cationic surfactant. Amino-modified dextran was used as a positively charged polyelectrolyte interacting with sodium dodecylsulphate as an anionic surfactant. The effects of the preparation method, surfactant concentration, ionic strength (the concentration of NaCl background electrolyte), pH (buffers), multivalent cations, and elevated temperature on the properties were investigated. The formation of gels required an optimum ionic strength (set by the NaCl solution), ranging from 0.15–0.3 M regardless of the type of hydrogel system and surfactant concentration. The other compositional effects and the effect of temperature were dependent on the polyelectrolyte type or its molecular weight. General differences between the behaviour of hyaluronan-based and cationized dextran-based materials were attributed to differences in the chain conformations of the two biopolymers and in the accessibility of their charged groups.

DEAE-dextran hydrochloride behaviour in aqueous solution-The effect of ionic strength and concentration

DEAE-dextran hydrochloride is a positively charged biocompatible polyelectrolyte. Its behaviour in aqueous solutions - the changes in its colloidal characteristics and resulting conformation changes - were investigated using a combination of light scattering, densitometry and ultrasound spectrometry. The results indicated the formation of a voluminous, hydrated and coiled conformation of chains having average particle sizes in the range of units of microns at low ionic strength. This phenomenon was supported by an increase in DEAE-dextran hydrochloride concentration in the solution. The increase in ionic strength caused the shielding of DEAE-dextran hydrochloride charges on its chain, resulting in the destabilization of the conformation arrangement of the polyelectrolyte and the formation of denser, more compact and stiffer structures having smaller particle sizes. The proposed model of DEAE-dextran hydrochloride density in the studied environments (distilled water, NaCl solutions) showed the possibility of using a single equation model to calculate the overall density of the system.

Thermodynamics and foundations of mass-action kinetics

A critical overview is given of phenomenological thermodynamic approaches to reaction rate equations of the type based on the law of mass-action. The review covers treatments based on classical equilibrium and irreversible (linear) thermodynamics, extended irreversible, rational and continuum thermodynamics. Special attention is devoted to affinity, the applications of activities in chemical kinetics and the importance of chemical potential. The review shows that chemical kinetics survives as the touchstone of these various thermody-namic theories. The traditional mass-action law is neither demonstrated nor proved and very often is only introduced post hoc into the framework of a particular thermodynamic theory, except for the case of rational thermodynamics. Most published “thermodynamic'’ kinetic equations are too complicated to find application in practical kinetics and have merely theoretical value. Solely rational thermodynamics can provide, in the specific case of a fluid reacting mixture, tractable rate equations which directly propose a possible reaction mechanism consistent with mass conservation and thermodynamics. It further shows that affinity alone cannot determine the reaction rate and should be supplemented by a quantity provisionally called constitutive affinity. Future research should focus on reaction rates in non-isotropic or non-homogeneous mixtures, the applicability of traditional (equilibrium) expressions relating chemical potential to activity in non-equilibrium states, and on using activities and activity coefficients determined under equilibrium in non-equilibrium states.

Ultrasonic study of hyaluronan interactions with Septonex-A pharmaceutical cationic surfactant

Interactions between hyaluronan and the cationic surfactant Septonex were studied using high resolution ultrasound spectroscopy. Four different interaction regions were identified in aqueous solution in a narrow interval of surfactant concentrations. In contrast, in 0.15 mol/L NaCl solution, essentially only two principal regions were observed. Hyaluronan-Septonex aggregates were generally less compressible than Septonex monomers or micelles and their formation in water was not appreciably affected by hyaluronan molecular weight. In the presence of NaCl, the effect of hyaluronan molecular weight was more profound, which can be ascribed to its conformational sensitivity to ionic strength combined with its role as a surfactant counterion. Hyaluronan-Septonex interactions were closer to interactions with CTAB than with TTAB. Differences in structure or Krafft temperature (solubility) between Septonex and CTAB were thus not significantly reflected in these interactions. The basic characteristics of Septonex surfactant were also determined.

Buccal adhesive films with moisturizer- the next level for dry mouth syndrome?

This study was undertaken to prepare films by solvent evaporation method comprising well-known polymers in order to investigate their potential for buccal suitability. Mucoadhesive films were manufactured using different polymers such as ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methylcellulose as well as carboxymethyl cellulose. Buccal films were evaluated in regards of mucoadhesiveness, swelling and physico-chemical properties. Furthermore rheological measurement and adhesion study were carried out on the buccal porcine mucosa. Moreover, allantoin as humectant was incorporated and trans-mucosal water loss was determined. The results showed that physico-chemical, buccal adhesive and swelling properties varied depending on the composition of the polymers. The findings indicated films containing allantoin to be suitable for buccal application. In completion, adhesive films are appropriate and promising formulations in the treatment of various disease in the intraoral cavity.

Non-invasive assessment of vascular system function and damage induced by anthracycline treatment in the pediatric cancer survivors

Anthracyclines represent one of the important classes of anti-cancer drugs; however, their major disadvantage is their profound cardiovascular toxicity. This study aimed to evaluate influence of anthracyclines on cardiovascular stiffness parameters estimated from pulse wave (PW). PW was measured in 59 cancer survivors treated with anthracyclines in childhood and in 248 healthy age-matched controls. Both patients and controls were divided into three age groups (13 - 15, 16 - 18 and 19 - 24 years). Central PW augmentation index (C-AI75) and augmentation pressure (C-AP75), both normalized to heart rate 75 bpm, were calculated as parameters of arterial wall stiffness. Central Buckberg sub-endocardial viability ratio (SEVR) was calculated as a parameter of diastolic function. Patients and controls were compared in each age group. C-AI75 and C-AP75 were significantly increased in patients in age groups 16 - 18 and 19 - 24 years. SEVR was decreased in patients in the oldest age group. Our results suggest that although toxic influence of anthracyclines to arterial wall and heart are developing during childhood and puberty, they can be detected rather in the adulthood. These changes are yet subclinical; however, their presence indicates potentially increased cardiovascular risk in childhood cancer survivors treated with anthracyclines during childhood.

Rates of Reactions as a Mathematical Consequence of the Permanence of Atoms and the Role of Independent Reactions in the Description of Reaction Kinetics

Linear algebra treatment of the permanence of atoms (mass conservation) naturally leads to the transformation of formation or destruction rates of components of a reaction mixture into rates of reaction steps, which are sufficient to describe the transformations mathematically. These steps form a scheme of independent reactions that can provide a rational basis for elucidating the reaction mechanism (network) while reducing both the component and parametric dimensionality of the description of kinetics. Several particular reaction examples are used to explain the method and show that rates of additional, dependent reactions cannot be unambiguously related to measured component rates. They also illustrate how the rates of dependent reactions can be correctly expressed in terms of the rates of independent reactions. The method starts only with a knowledge of the components of a reaction mixture. It is argued that the design of consistent reaction networks or mechanisms should take into account not only chemistry but also mathematics.

Thermodynamic Analysis of Chemically Reacting Mixtures-Comparison of First and Second Order Models

Recently, a method based on non-equilibrium continuum thermodynamics which derives thermodynamically consistent reaction rate models together with thermodynamic constraints on their parameters was analyzed using a triangular reaction scheme. The scheme was kinetically of the first order. Here, the analysis is further developed for several first and second order schemes to gain a deeper insight into the thermodynamic consistency of rate equations and relationships between chemical thermodynamic and kinetics. It is shown that the thermodynamic constraints on the so-called proper rate coefficient are usually simple sign restrictions consistent with the supposed reaction directions. Constraints on the so-called coupling rate coefficients are more complex and weaker. This means more freedom in kinetic coupling between reaction steps in a scheme, i.e., in the kinetic effects of other reactions on the rate of some reaction in a reacting system. When compared with traditional mass-action rate equations, the method allows a reduction in the number of traditional rate constants to be evaluated from data, i.e., a reduction in the dimensionality of the parameter estimation problem. This is due to identifying relationships between mass-action rate constants (relationships which also include thermodynamic equilibrium constants) which have so far been unknown.

Fluorescence study of freeze-drying as a method for support the interactions between hyaluronan and hydrophobic species

A freeze-drying method enabling solubilization of hydrophobic species in aqueous solutions of native hyaluronan is described. The method is based on opening the access to supposed hydrophobic patches on hyaluronan by disturbing its massive hydration shell. Hydrophobic and/or polarity-sensitive fluorescence probes were used as hydrophobic models or indicators of interactions with hydrophobic patches. Fluorescence parameters specific to individual probes confirmed the efficiency of the freeze-drying method. This work is the first step in developing biocompatible and biodegradable carriers for hydrophobic drugs with targeted distribution of the active compound from native, chemically non-modified hyaluronan.

Thermodynamic Analysis of Chemically Reacting Mixtures and Their Kinetics: Example of a Mixture of Three Isomers

Thermodynamics provides consequences of and restrictions on chemically reacting mixtures, particularly their kinetics, which have not been fully explored. Herein, a comprehensive thermodynamic analysis is illustrated for a reacting mixture of three isomers. The rate equation is first derived on the basis of the results of nonequilibrium continuum thermodynamics of linear fluids, and is then subjected to the requirement of consistency with entropic inequality (the second law). This consistency test involves the correct representation of the reaction rate as a function of affinities. It is shown that entropic inequality restricts the signs or values of coefficients in the constitutive equations for reaction rates/rate constants. The use of reverse rate constants and the identification of thermodynamic and kinetic equilibrium constants are not necessary in this approach. Although the presented thermodynamic analysis works only for independent reactions, the rates of dependent reactions are not excluded from having effects on kinetics. It is shown that the rates of dependent reactions are combined from the rates of independent reactions differently than dependent reactions are combined from independent reactions. The results are compared to the classical mass-action rate equations, and new restrictions on the values of the classical rate constants are derived.

[Lumbar sympathectomy literature review over the past 15 years]

INTRODUCTION

Lumbar sympathectomy (LS) irreversibly damages a part of the sympathetic trunk and adjacent ganglia between L1 and L5, typically between L2 and L4. The first LS was performed in 1923. Initially, it used to be performed very often; however, with the progress of vascular and endovascular surgery its importance gradually continues to decline. The aim of the paper is to present literature review focusing on LS over the past 15 years.

METHOD

Literature review of 113 academic articles found in academic journal databases.

PATHOPHYSIOLOGY

Irreversible interruption of the efferent innervation leads to relative vasodilation of small vessels in lower extremities (α1-receptors blockade), and it reduces the volume of sweat due to inactivation of eccrine glands and nociception from lower limbs.

INDICATION

Raynaud´s phenomenon, thromboangitis obliterans, non-revascularizable peripheral arterial disease (PAD) (Fontain grade III-IV), hyperhidrosis, persistent pain in lower extremities, chronic pain of amputation stump, frostbites, chilblains.Effect: The three largest studies showed a positive effect in 63.6-93.4% cases of PAD and in 97%100% cases of hyperhidrosis. The positive effect was defined as warmer lower extremities, increased blood flow, acceleration of chronic defects healing, sweating disappearance and pain reduction.

CONCLUSION

Lumbar sympathectomy still remains a useful method in the treatment of above mentioned diseases if properly indicated.

KEY WORDS

lumbar sympathectomy - Raynaud´s phenomenon - thromboangitis obliterans -peripheral arterial disease - hyperhidrosis.

The change in excited-state proton transfer kinetics of 1-naphthol i micelles upon the binding of polymers: The influence of hyaluronan hydration

The fast deprotonation of 1-naphthol was studied in aqueous solution and in polymer-cetyltrimethylammonium bromide (CTAB) mixtures using picosecond fluorescence spectroscopy to study the influence of hyaluronan hydration in polymer-surfactant interactions. The aqueous micelle solution showed the expected change of proton transfer rate around the reported critical micelle concentration (∼1 mM). The proton transfer rate dependence on CTAB concentration in the hyaluronan-CTAB and polystyrenesulfonate-CTAB systems differed significantly from that in the aqueous micelle solution. The dynamic study of excited state proton transfer (ESPT) revealed the significant influence of hyaluronan hydration in CTAB micelles. When hyaluronan-CTAB aggregates were formed at the CTAB concentration of 0.5mM, a tenfold decrease in the rate of deprotonation was observed when compared to polystyrenesulfonate-CTAB aggregates due to hyaluronan hydration. In 2mM CTAB-hyaluronan aggregates, the rate of deprotonation was found to be almost two times faster than in the 2mM CTAB or polystyrenesulfonate-CTAB system. Furthermore, the study of excited-state proton transfer of 1-naphthol confirmed that hyaluronan hydration layer penetrates into the micelle and changes the emission characteristics of 1-naphthol.

A simple microviscometric approach based on Brownian motion tracking

Viscosity-an integral property of a liquid-is traditionally determined by mechanical instruments. The most pronounced disadvantage of such an approach is the requirement of a large sample volume, which poses a serious obstacle, particularly in biology and biophysics when working with limited samples. Scaling down the required volume by means of microviscometry based on tracking the Brownian motion of particles can provide a reasonable alternative. In this paper, we report a simple microviscometric approach which can be conducted with common laboratory equipment. The core of this approach consists in a freely available standalone script to process particle trajectory data based on a Newtonian model. In our study, this setup allowed the sample to be scaled down to 10 μl. The utility of the approach was demonstrated using model solutions of glycerine, hyaluronate, and mouse blood plasma. Therefore, this microviscometric approach based on a newly developed freely available script can be suggested for determination of the viscosity of small biological samples (e.g., body fluids).

High-resolution ultrasonic spectroscopy study of interactions between hyaluronan and cationic surfactants

Interactions in a cationic surfactant-hyaluronan system in water and in sodium chloride solution were investigated by high-resolution ultrasonic spectroscopy at 25 °C. Two alkyltrimethylammonium bromide surfactants of different chain lengths (tetradecyl and hexadecyl) were used; hyaluronan molecular weight ranged from 10 to 1750 kDa. Two main parameters-ultrasonic velocity and attenuation-were measured in the titration regime. Up to six different regions could be identified in the velocity titration profiles in water in a narrow interval of surfactant concentration. These regions differed primarily in the compressibility of structures formed in the system. The number of detected transitions was higher for the tetradecyl surfactant; therefore, the increased length of the hydrophobic chain simplified the details of the structure-forming behavior. The measurement of attenuation was much less sensitive and detected only the formation of microheterogeneous structures or visible phase separates. The richness of the titration profiles was depressed in salt solution, where essentially only two principal regions were observed. On the other hand, the effect of hyaluronan molecular weight on the positions of boundaries between regions was more significant in the presence of salt. Besides electrostatic interactions, hydrophobic interactions are also relevant for determining the behavior of hyaluronan-surfactant systems and the properties of formed complexes (aggregates).

Formation and dissociation of the acridine orange dimer as a tool for studying polyelectrolyte-surfactant interactions

Steady-state and time-resolved fluorescence and UV-vis techniques were used to study the formation and dissociation of acridine orange dimer in order to investigate hyaluronan-acridine orange, hyaluronan-CTAB (cetyltrimethylammonium bromide), polystyrenesulfonate-acridine orange, and polystyrenesulfonate-CTAB interactions in aqueous solution. Steady-state and time-resolved fluorescence and the dimer:monomer absorbance ratio of acridine orange (AO) were used to determine dimer formation on polymer chains of polyelectrolytes. Acridine orange clearly formed dimers on polystyrensulfonate chains as well as on hyaluronan, but we show that the electrostatic interaction is much weaker in the case of hyaluronan. After the addition of surfactant, we observed an enhancement of fluorescence intensity, indicating the dissociation of AO dimers into monomers and the replacement of acridine orange on polymer chains by surfactant molecules. Importantly, we show that surfactant molecules bind to polymer chains before the critical micelle concentration is reached and form the so-called "bottle-brush" structure.