The treatment of alkaline burns of the skin by neutralization

Literature reports dating as far back as 1927 have lured clinicians into the belief that alkaline skin burns are best treated by water dilution and that neutralization attempts should be avoided. Although this belief has never been substantiated, neutralization of an alkaline burn of the skin with acid was thought to increase tissue damage secondary to the exothermic nature of acid-base reactions. The authors proposed that topical treatment of alkaline burns with a weak acid such as 5% acetic acid (i.e., household vinegar) would result in rapid tissue neutralization and reduction of injury in comparison to water irrigation alone. In a rat skin burn model, animals were exposed to an alkaline injury when filter paper (2 cm in diameter) saturated with 2N sodium hydroxide was placed over the volar aspect of the animal for a period of 1 minute. Treatment was initiated 1 minute after injury and included either neutralization with a 5% acetic acid solution (n = 8) or irrigation (n = 8) with water. Skin temperature and pH were monitored using subdermal needle probes until the pH of the skin returned to physiologic values. Punch-biopsy specimens were obtained from the wound edges 24 hours after injury to assess burn depth and leukocyte infiltration, and biopsies were repeated 10 days later to assess wound healing. The authors proposed that neutralization of an alkaline substance with household vinegar (i.e., 5% acetic acid solution) would result in rapid neutralization and thus reduce extent of tissue injury. Animals treated with acetic acid demonstrated a more rapid return to physiologic pH (14.69 +/- 4.06 minutes versus 31.62 +/- 2.83 minutes; p < 0.001), increased depth of dermal retention (0.412 +/- 0.136 mm versus 0.214 +/- 0.044 mm; p = 0.015), decreased leukocyte infiltrate (31.0 +/- 5.1 cells/high-power field versus 51.8 +/- 6.8 cells/high-power field; p < 0.001), and improved epithelial regeneration (4.0 +/- 0.6 cell layers versus 1.7 +/- 0.5 cell layers; p < 0.001) when compared with animals treated with water irrigation. No difference was detected in peak pH (10.35 +/- 0.28 pH versus 10.36 +/- 0.25 pH; p = 0.47) nor in rise of skin temperature (maximum temperature, 32.8 degrees C versus 32.9 degrees C; p = 0.33) between acetic acid-neutralized and water-irrigated burn wounds. The observed benefits of treating alkaline burns with 5% acetic acid in the rat model are significant and require clinical testing.     

Structural characterization and solution properties of a galacturonate polysaccharide derived from Aloe vera capable of in situ gelation

A series of highly purified galacturonate polysaccharides have been extracted from the Aloe vera plant and analyzed in terms of chemical composition and molecular weight. This Aloe vera polysaccharide (AvP) has been found to exist as a high molecular weight species and possess a unique chemical composition, including a high galacturonic acid (GalA) content and low degree of methyl ester substitution. These factors facilitate gel formation upon exposure to low concentrations of calcium ions, leading to potential application in formulations designed for in situ nasal or subcutaneous protein delivery. Thorough examination of classic dilute solution properties, the [eta]-M(w), and R(g)-M(w) relationships, persistence length (L(p)), and inherent chain stiffness (B parameter), indicate an expanded random coil in aqueous salt solutions. The critical concentration for transition from dilute to concentrated solution, C(e), was determined by measuring both the zero shear viscosity (eta(o)) and fluorescence emission of the probe molecule 1,8-anilino-1-naphthalene sulfonic acid (1,8-ANS) as a function of polymer concentration. Examination of zeta potential and C(e) as a function of ionic strength indicates that the shift in C(e) from 0.60 to 0.30 wt % is related to an increased occurrence of intermolecular interactions at high salt concentrations. Additionally, dynamic rheology data are presented highlighting the ability of AvP to form gels at low polymer and calcium ion concentrations, exemplifying the technological potential of this polysaccharide for in situ drug delivery.     

Chitosan gelation induced by the in situ formation of gold nanoparticles and its processing into macroporous scaffolds

This work describes a simple synthetic route to induce chitosan (CHI) gelation by the in situ formation of gold nanoparticles (AuNPs). AuNPs were obtained by thermal treatment (e.g., 40 and 80 °C) of CHI aqueous solutions containing HAuCl(4) and in the absence of further reducing agents. The CHI hydrogels resulting after AuNP formation were submitted to unidirectional freezing and subsequent freeze-drying via ISISA (ice-segregation-induced self-assembly) process for the preparation of CHI scaffolds. The study of AuNP-CHI scaffolds by SEM and confocal fluorescence microscopy revealed a morphological structure characteristic of the hydrogel nature of the samples subjected to the ISISA process. Interestingly, not only the morphology but also the dissolution and swelling degree of the resulting CHI scaffolds were strongly influenced by the strength of the hydrogels obtained by the in situ formation of AuNP. We have also studied the catalytic activity AuNP-CHI scaffolds in the reduction of p-nitrophenol. The negligible dissolution and low swelling degree obtained in certain AuNP-CHI scaffolds allowed them to be used for more than four cycles with full preservation of the reaction kinetics.     

Design of an injectable in situ gelation biomaterials for vitreous substitute

To adapt the physical properties of living materials to their biological function, nature developed various types of polymers with outstanding physical behavior. One example is the vitreous body, which is important intraocular elements not only because of its optical and mechanical performances, but also due to its important role in the pathogenesis and treatment of conditions affecting adjacent tissues and eventually the whole eye. Here, we report a novel biocompatible material for injectable vitreous substitute, composed of thermosensitive amphiphilic polymer, which is capable of forming a transparent gel in the vitreous cavity. It is nontoxic, provides adequate support for the retina, and allows light to reach the sensory elements at the back of the eye. The amphiphilic polymer exhibits mechanical stability by assembling to form highly interconnected hydrophobic domains, which leads to the constitution of a network structure.     

Scleroglucan and oxalic acid formation by Sclerotium glucanicum in sucrose supplemented fermentations

Summary Strategies for adding sucrose to stationary phase cultures of Sclerotium glucanicum to improve scleroglucan production were examined. Particular attention was paid to the effect of sucrose supplementation on the formation of the toxic by-product, oxalic acid. The rate of addition of sucrose was found to markedly influence the outcome of the process, with addition at a rate of 0.084 gl^–1h^–1 giving a 50% improvement in broth biopolymer concentration. Additions at higher rates seemed to cause inhibition of the culture. However, greatly increased oxalic acid concentrations in the sucrose supplemented fermentations, and the impact of unfavourable changes in productivity and specific productivity call into question the utility of this proposed method of process improvement for this microorganism.     

Rheometric study of the gelation of chitosan in aqueous solution without cross-linking agent

A new process of formation of chitosan physical hydrogels in aqueous solution, without any organic solvent or cross-linking additive, was studied. The three conditions required for the physical gelation were an initial polymer concentration over C*, a critical value of the balance between hydrophilic and hydrophobic interactions, and a physicochemical perturbation responsible for a bidimensional percolating mechanism. The time necessary to reach the gel point was determined by rheometry, and gelations were compared according to different initial conditions. Thus, we investigated the influence of the polymer concentration and the degree of acetylation (DA) of chitosan on gelation. The number of junctions per unit volume at the gel point varied with the initial polymer concentration, i.e., the initial number of chain entanglements per unit volume or the number of gel precursors. The time to reach the gel point decreased with both higher DAs and concentrations. For a chitosan of DA = 36.7%, a second critical initial concentration close to 1.8% (w/w) was observed. Above this concentration, the decrease of the time to reach the gel point was higher and fewer additional junctions had to be formed to induce gelation. To optimize these physical hydrogels, to be used for cartilage regeneration, their final rheological properties were studied as a function of their degree of acetylation and their polymer concentration. Our results allowed us to define the most appropriate gel for the targeted application corresponding to a final concentration of chitosan in the gel of near 1.5% (w/w) and a DA close to 40%.     

Unique gelation behavior of cellulose in NaOH/urea aqueous solution

A transparent cellulose solution was prepared by mixing 7 wt % NaOH with 12 wt % urea aqueous solution which was precooled to below -10 degrees C and which was able to rapidly dissolve cellulose at ambient temperature. The rheological properties and behavior of the gel-formed cellulose solution were investigated by using dynamic viscoelastic measurement. The effects of temperature, time, cellulose molecular weight, and concentrations on both the shear storage modulus (G') and the loss modulus (G") were analyzed. The cellulose solution having a viscosity-average molecular weight (M(eta)) of 11.4 x 10(4) had its sol-gel transition temperature decreased from 60.3 to 30.5 degrees C with an increase of its concentration from 3 to 5 wt %. The gelation temperature of a 4 wt % cellulose solution dropped from 59.4 to 30.5 degrees C as the M(eta) value was increased from 4.5 x 10(4) to 11.4 x 10(4). Interestingly, at either higher temperature (above 30 degrees C), or lower temperature (below -3 degrees C), or for longer gelation time, gels could form in the cellulose solutions. However, the cellulose solution remains a liquid state for a long time at the temperature range from 0 to 5 degrees C. For the first time, we revealed an irreversible gelation in the cellulose solution system. The gel having been formed did not dissolve even when cooled to the temperature of -10 degrees C, at which it was dissolved previously. Therefore, this indicates that either heating or cooling treatment could not break such stable gels. A high apparent activation energy (E(a)) of the cellulose solution below 0 degrees C was obtained and was used to explain the gel formation under the cooling process.     

Activation of nylon by alkaline glutaraldehyde solution for enzyme immobilisation

Summary Nylon tube was directly activated by alkaline glutaraldehyde solution. PEI was utilised as a spacer molecule. Glucose oxidase was immobilised to the nylon tube after reactivating the spacer molecules with glutaraldehyde. On immobilising glucose oxidase there was more protein binding and higher immobilised enzyme activity when compared to immobilised enzyme tube activated by triethyloxonium salt. The optimal condition for direct glutaraldehyde activation of nylon was incubation with 18.5% (w/v) glutaraldehyde in 0.12M borate pH 9.0 for 15 min at 90 °.     

Identification of non-specific alkaline phosphatases in hyphal cells of the fungus Neurospora crassa by in situ histochemistry

The present study was designed to identify alkaline phosphatases in non-permeabilized hyphal cells of the fungus Neurospora crassa by staining these enzymatic activities with a modified azo dye coupling method. Our strategy allowed the identification of three non-specific alkaline phosphatase activities, one of them possibly being a novel putative enzyme, which is not responsive to either Mg(2+) or EDTA. Another alkaline phosphatase activity, whose location in the hyphal cell is regulated by phosphate, is stimulated by Mg(2+), inhibited by EDTA, and somehow dependent on the expression of the pho-2(+) -encoded Pi-repressible alkaline phosphatase.     

Conformational transitions of schizophyllan in aqueous alkaline solution

The conformational transitions of schizophyllan were studied in aqueous alkaline solutions by high-sensitivity differential scanning calorimetry (DSC) and optical rotation measurements. The temperature of half completion for reversible intramolecular conformational transition determined by DSC, centered at 7.4°C in water, increases to 37.2°C at 0.01M KOH with increasing alkaline concentration. The transition enthalpy per mole of the polysaccharide repeating unit is 2.62 ± 0.23 kJ mol⁻¹ independent of the alkaline concentration. The cooperative unit size for the transition decreases with increasing alkaline concentration. Optical rotation was measured as a function of pH at 25 and 60°C. A sharp decrease in optical rotation was observed at pH = 13, which is ascribed to the triple helix-coil transition. From data obtained by DSC and optical rotation measurements, in combination with results reported previously, a phase diagram for the conformation of schizophyllan as a function of temperature and pH is proposed. The irreversibility of the triple helix to single coil transition, induced by strong alkali, was investigated as a function of polymer concentration by gel permeation chromatography and electron microscopy. The renatured samples at polymer concentrations < 1.0 mg/mL, which are prepared by dissolution in 0.25M KOH followed by neutralization with HCl, are observed as a mixture of globular, linear, and circular structures, and larger aggregates with less-defined morphology by electron microscopy. Higher concentrations lead to increased proportions of multichain clusters (aggregates). Subsequent annealing of the renatured samples at 115–120°C increases the proportion of circular species. The change in molecular weight distribution of samples that accompanies the renaturation and annealing mentioned above can be well interpreted in terms of the proportion of species having different morphology as observed by electron microscopy. © 1996 John Wiley & Sons, Inc.     

The conformation of amylose in alkaline salt solution

The conformation of amylose in various solvents is discussed. It is shown that the changes in molecular volume of the polysaccharide (measured by viscosity) as potassium chloride is added to a solution of amylose at pH 12 are similar to those obtained on adding butan-1-ol to the solution. The viscosity number in both cases decreases to values less than that observed for amylose in water, in which Flory theta-conditions are approximated. The minimum value of the viscosity number, in fact, is identical to that observed on the addition of butan-1-ol and iodine to neutral aqueous solution of amylose—conditions known to result in a helical complex. It is concluded that amylose undergoes a coil-to-helix transition as potassium chloride is dadde to solutions of the polysaccharide at pH 12.     

Catalytic dehydrogenation of reducing sugars in alkaline solution

Aldoses in alkaline medium under the catalytic action of platinum or rhodium are converted into aldonic acids with high selectivity and with concomitant evolution of hydrogen gas. The dehydrogenation reaction has been studied for 25 different mono- and di-saccharides, and is generally applicable for reducing sugars. The influence of several reaction variables has been studied, leading to an adsorption model in which both the negatively charged O-1 and the close contact of H-1 with the catalyst surface are considered to be driving forces for the transfer of hydride from C-1 of the sugar to the catalyst.     

Kinetics of the tuberculocidal response by alkaline glutaraldehyde in solution and on an inert surface

Single cell suspensions of BCG and Mycobacterium tuberculosis were exposed to 2% alkaline glutaraldehyde solution (pH 8·0) and the rate of kill measured at intervals up to 30 min. Residual glutaraldehyde was neutralized with freshly prepared 1% sodium bisulphite. The rate of kill was directly proportional to the temperature and independent of the inoculum size whether the organism was tested in suspension or attached to an inert surface. Glutaraldehyde was slightly more bactericidal for the virulent M. tuberculosis than for the attenuated BCG. A substantial proportion of the mycobacterial population on an inert surface floated off during its exposure to the glutaraldehyde solution but the 'floaters'were killed at an equivalent rate to the attached bacilli. Complete sterility of a standardized suspension of M. tuberculosis could not be achieved within the 10 min period specified by the tuberculocidal assay, although it was usually attained within 20 min.     

Kinetics of the tuberculocidal response by alkaline glutaraldehyde in solution and on an inert surface

Single cell suspensions of BCG and Mycobacterium tuberculosis were exposed to 2% alkaline glutaraldehyde solution (pH 8.0) and the rate of kill measured at intervals up to 30 min. Residual glutaraldehyde was neutralized with freshly prepared 1% sodium bisulphite. The rate of kill was directly proportional to the temperature and independent of the inoculum size whether the organism was tested in suspension or attached to an inert surface. Glutaraldehyde was slightly more bactericidal for the virulent M. tuberculosis than for the attenuated BCG. A substantial proportion of the mycobacterial population on an inert surface floated off during its exposure to the glutaraldehyde solution but the 'floaters' were killed at an equivalent rate to the attached bacilli. Complete sterility of a standardized suspension of M. tuberculosis could not be achieved within the 10 min period specified by the tuberculocidal assay, although it was usually attained within 20 min.     

In situ biochemical studies of intestinal alkaline phosphatase in normal and phosphate-depleted rats by microdensitometry

A quantitative microdensitometric study has been designed to characterize in situ intestinal brush border-bound alkaline phosphatase of rat duodenal villosities. Intestinal slices were incubated with beta-glycerophosphate as substrate. Free phosphate liberated was precipitated in presence of a lead reagent as lead sulfide. The precipitate was quantified in situ by scanning and integrating microdensitometry. Kinetic parameters of the reaction were determined at 37 degrees C, pH 8.8, in the middle part of the villosities. Apparent Michaelis constant (Km) for beta-glycerophosphate was found to be 8.16 +/- 0.56 mM (mean +/- S.E.). Maximal enzyme activation was obtained at pH 8.5. Maximal inhibition of enzyme activity was observed in the presence of L-phenylalanine (30 mM) or theophylline (5 mM). Along the villosity axis, enzyme activity rose from the crypt up to the midportion of the villosity and finally decreased at the tip region. In phosphate-depleted rats, enzyme activity was increased in all portions of the villosity, with conservation of the same activity gradient. In this situation, kinetic analysis showed a marked decrease of Km, i.e. 4.56 +/- 0.39 mM (mean +/- S.E.) as compared to normal rats.     

A study on a cell wall-bound factor which causes the gelation of pectin solution

By extracting the cell wall fraction obtained from hypocotyls of soybean seedlings with 1 M NaCl solution, a factor which caused the gelation of the pectin solution was released. Mixed with the extract, the pectin solution increased in viscosity and eventually solidified. The pectin-gelatinizing factor (PGF) was of protein nature and seemed to modify pectin molecules to make them coagulate. The physiological significance of the PGF action was discussed. PGF seemed to be widely distributed among seed plants and to be cell wall-boundin situ.     

Near-infrared chemiluminescence from the oxidation of ammonia in aqueous alkaline solution.

The chemiluminescent oxidation of ammonia with hypobromite in aqueous alkaline solution evokes a broadly distributed emission in the near-infrared region, with intensity maxima at 1055 nm and 1270 nm.