Antimicrobial loading into and release from poly(ethylene glycol)/poly(acrylic acid) semi‐interpenetrating hydrogels

Electrostatic interactions within a semi‐interpenetrating network (semi‐IPN) gel can control the postsynthesis loading, long‐term retention, and subsequent release of small‐molecule cationic antibiotics. Here, electrostatic charge is introduced into an otherwise neutral gel [poly(ethylene glycol) (PEG)] by physically entrapping high‐molecular‐weight poly(acrylic acid) (PAA). The network structure is characterized by small‐angle neutron scattering. PEG/PAA semi‐IPN gels absorb over 40 times more antibiotic than PAA‐free PEG gels. Subsequent soaking in physiological buffer (pH 7.4; 0.15 M NaCl) releases the loaded antibiotics for periods as long as 30 days. The loaded gels elute antibiotics with diffusivities of 4.46 × 10^?8 cm²/s (amikacin) and 2.08 × 10^?8 cm²/s (colistin), which are two orders of magnitude less than those in pure PEG gels where diffusion is controlled purely by gel tortuosity. The release and hindered diffusion can be understood based on the partial shielding of the charged groups within the loaded gel, and they have a significant effect on the antimicrobial properties of these gels. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 64–72     

Characterization of the network properties of poly(ethylene glycol)–acrylate hydrogels prepared by variations in the ethanol–water solvent composition during crosslinking copolymerization

The characteristics of poly(ethylene glycol) (PEG)–acrylate hydrogel networks were investigated as a function of the ethanol–water solvent composition during free‐radical crosslinking copolymerization. Macromonomer (88% ω‐methoxy‐PEG–acrylate and 10% ω‐phenoxy‐PEG–acrylate) and crosslinker (2% PEG–diacrylate) concentrations were kept constant. As the copolymerization progressed, the polymer solution in 100% ethanol became increasingly turbid, indicating the development of a heterogeneous network structure. In 100% water, however, the initially turbid polymer solution became increasingly transparent as the crosslinking copolymerization progressed. All the gels were optically clear upon equilibration in water. Kinetic studies, with attenuated total reflectance‐infrared, showed a long induction period, along with a lowered reaction rate, in 100% ethanol, and a decrease in conversion with an increase in ethanol content. These results agree with the UV analysis of the sol fractions, which indicated an increase in the amounts of unreacted PEG–acrylates with an increase in the ethanol content. The gels which were formed with a high ethanol concentration exhibited lower Young's modulus and higher swelling ability, suggesting that the network structure was significantly affected by the solvent composition during free‐radical crosslinking copolymerization. From the stress–strain and swelling experiments, the Flory–Huggins interaction parameter was evaluated. The creep characteristics of the hydrogels were modeled with two Kelvin elements. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2677–2684, 2002     

Ionic and pH effects on the osmotic properties and structure of polyelectrolyte gels

We investigate the effects of salt concentration and pH on neutralized poly(acrylic acid) (PAA) gels in near physiological salt solutions. Either adding calcium ions or decreasing the pH is found to induce reversible volume transitions but the nature of these transitions seems to be different. For example, the osmotic pressure exhibits a simple power law dependence on the concentration as the transition is approached in both systems, but the power law exponent n is substantially different in the two cases. On decreasing the pH the value of n gradually increases from 2.1 (at pH = 7) to 3.2 (at pH = 1). By contrast, n decreases with increasing calcium ion concentration from 2.1 (in 100 mM NaCl solution) to 1.6 (0.8 mM CaCl₂ in 100 mM NaCl solution). In both systems, a strong increase of the small-angle neutron scattering intensity (SANS) is observed near the volume transition. The SANS results reveal that calcium ions favor the formation of linearly aligned regions in PAA gels. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2803–2810, 2008     

Biological UV dosimeters in quality control of tanning tubes

Although according to the International Radiological Protection Association-International Non-Ionizing Radiation Committee recommendation (1991) the use of sunbeds for cosmetic purposes is not recommended, tanning devices are used widely. Ten different types of commercially available sunbed tubes have been studied using a uracil biological UV dosimeter, and three of them were analyzed in detail. Dimerization effectiveness of the tubes was measured directly, whereas efficiency of erythema induction was calculated weighting the emission spectra by the Commission Internationale de l'Eclairage erythema action spectrum. The data obtained demonstrate that quality control of sunbed tubes has to include not only the determination of the UV doses administered but also the assessment of the health risk due to the UVB and UVA components of the lamp. A method of quality control using the uracil biological dosimeter was elaborated, and the estimation of the "acceptable" exposure time was checked/controlled on 15 volunteers by assessing individually the erythema induction threshold. A correct classification of the sunbed tubes is proposed by characterizing the erythema induction versus DNA-damaging effectiveness of tubes.     

Scaling equations for a biopolymer in salt solution

The effect of the simultaneous presence of monovalent and divalent cations on the thermodynamics of polyelectrolyte solutions is an incompletely solved problem. In physiological conditions, combinations of these ions affect structure formation in biopolymer systems. Dynamic light scattering measurements of the collective diffusion coefficient D and the osmotic compressibility of semidilute hyaluronan solutions containing different ratios of sodium and calcium ions are compared with simple polyelectrolyte models. Scaling relationships are proposed in terms of polymer concentration and ionic strength J of the added salt. Differences in the effects of sodium and calcium ions are found to be expressed only through J.     

Über die Reproduzierbarkeit der turbidimetrischen Bestimmung von Phosphorspuren mit Strychninmolybdostickstoff(V)säure

Microchimica Acta - Mit der turbidimetrischen Strychninnitrat-Methode für Phosphorspurenbestimmung nach der Version von Hegedüs und Dvorszky kann man nur dann ausgezeichnete...     

Anomalous small angle x-ray scattering determination of ion distribution around a polyelectrolyte biopolymer in salt solution

The distribution of counterions in solutions of high molecular mass hyaluronic acid, in near-physiological conditions where mono- and divalent ions are simultaneously present, is studied by small angle neutron scattering and anomalous small angle x-ray scattering. The solutions contain either sodium or rubidium chloride together with varying concentrations of calcium or strontium chloride. The effects of monovalent-divalent ion exchange dominate the amplitude and the form of the counterion cloud. In the absence of divalent ions, the shape of the anomalous scattering signal from the monovalent ions is consistent with the distribution calculated from the Poisson-Boltzmann equation, as found by other workers. In mixtures of monovalent and divalent ions, however, as the divalent ion concentration increases, both the diameter and the amplitude of the monovalent ion cloud decrease. The divalent counterions always occupy the immediate neighborhood of the charged polyanion. Above a given concentration their anomalous scattering signal saturates. Even in a large excess of divalent ions, ion exchange is incomplete.     

Toward a Constitutive Law of Cartilage: A Polymer Physics Perspective

To describe load bearing and lubrication of cartilage requires treating its collagen network and proteoglycan (PG) phases separately in a constitutive law of the tissue. We propose a framework for developing such an empirical constitutive law that treats the cartilage extracellular matrix (ECM) as a composite medium, with a PG phase that exerts a swelling pressure, and a collagen network phase that restrains it. We compare and contrast this model to a biomechanical constitutive law that aggregates the collagen and PG phases into a single “solid-like” elastic tissue matrix, and show that aggregation obscures essential differences in the physical-chemical properties of the collagen and PG constituents as well as their distinct biological roles within cartilage's ECM. We also relate moduli in the aggregate constitutive model to quantities measured in an osmotic stress titration experiment.     

Zur emissionsspektralanalytischen Bestimmung von Cu-, Fe- und Pb-Spuren in ZnS-Leuchtstoffen

Zusammenfassung Eine emissionsspektralanalytische Methode wird beschrieben, mit deren Hilfe 3 · 10^–7 bis 3 · 10^–5 g Fe, 2 · 10^–6 bis 3,2 · 10^–6 g Pb und 3 · 10^–8 bis 1 · 10^–5 g Cu pro g ZnS bestimmt werden können.

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Summary An emission spectral analytical method is described by which 3 · 10^–7 to 3 · 10^–5 g iron, 2 · 10^–6 3.2 · 10^–5 g lead, and 3 · 10^–8–1 · 10^–5 g copper per g ZnS can be determined.

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Résumé On décrit une méthode d'analyse spectrale par émission permettant de doser 3 · 10^–7–3 · 10^–5 g Fe, 2 · 10^–6–3,2 · 10^–5 g Pb et 3 · 10^–8–1 · 10^–5g Cu par g ZnS.

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Herrn Prof. Dr.A. A. Benedetti-Pichler zum 70. Geburtstag gewidmet. Vorgetragen am XI. Colloquium Spectroacopicum Internationale, Beograd, 1963.

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Wir danken auch an dieser Stelle HerrnP. Endröi für die Zubereitung der Standards mit Cu- und Fe-Zusatz und Herrn DirektorF. Kömüves für die Erlaubnis zur Publikation dieser Arbeit.