Biomedical subjects

L E Bromberg

Publications and source records attributed to L E Bromberg.

7 recordsLinked to original sources

PubMed2001

Novel periodontal drug delivery system for treatment of periodontitis.

A conceptually novel periodontal drug delivery system (DDS) is described that is intended for treatment of microbial infections associated with periodontitis. The DDS is a composite wafer with surface layers possessing adhesive properties, while the bulk layer consists of antimicrobial agents, biodegradable polymers, and matrix polymers. The wafers contain poly(lactic-co-glycolic acid) as the main bioerodible component used in the bulk layer and ethyl cellulose applied as a matrix polymer enabling diffusion-controlled release. Starch and other polymers in combination with AgNO(3) serve as coatings adhesive to the teeth. In vitro experiments demonstrate that the wafers are capable of zero-order release of antimicrobial agents such as silver nitrate, benzylpenicillin, and tetracycline, for over 4 weeks.

Anti-Bacterial Agents↗

PubMed2001

Enhanced nasal retention of hydrophobically modified polyelectrolytes.

Hydrophobically modified polyelectrolytes (HMP) are polymers with a high content of ionizable groups bonded to hydrophobic groups. Copolymers of poly(acrylic acid) and Pluronic surfactants constitute a special class of HMP whereby poly(propylene oxide) segments act as hydrophobes. The poly(propylene oxide) segments possess temperature-dependent aqueous solubility and the solutions of the Pluronic-poly(acrylic acid) copolymers (MW > 3,000,000) undergo a sol-gel transition when kept at body temperature. Due to the presence of the poly(acrylic acid) segments, the Pluronic-poly(acrylic acid) copolymers are bioadhesive. We have examined the hypothesis that the in-situ gelling polymer formulations of Pluronic-poly(acrylic acid) copolymers may have an enhanced retention in the nasal cavity. The effects of putative bioadhesive (Carbomer 934P) and thermogelling (Pluronic F127) polymers on nasal clearance were compared with Pluronic-poly(acrylic acid) copolymers using a rat model. The enhancement of the residence time of fluorescent labels by the Pluronic-poly(acrylic acid) copolymers was shown to be 5-8-fold that of Carbomer, and 3-6-fold that of Pluronic F127. The results unequivocally demonstrate the superior retention of the HMP that combines bioadhesive and thermogelling capabilities over either a bioadhesive polyelectrolyte or a polymer of a low molecular weight that undergoes a sol-gel transition.

Acrylic Resins↗

PubMed2001

Interactions among proteins and hydrophobically modified polyelectrolytes.

A special class of hydrophobically modified polyelectrolytes was studied wherein poly(acrylic acid) (PAA) was conjugated with Pluronic F127 NF surfactant. The Pluronic-PAA copolymer solutions form gels at low concentrations when exposed to bodytemperature. Such gels possess enhanced retention in topical applications. Circular dichroism spectra indicate that tertiary structures of human insulin, haemoglobin, and albumin were stabilized in solutions of Pluronic-PAA. Aggregation of insulin in gelled solutions of Pluronic-PAA was impeded as demonstrated in shaking tests. The presence of Pluronic-PAA hindered the insulin degradation by alpha-chymotrypsin by at least 7-fold. Extraction of calcium ions from trypsin by Pluronic-PAA led to the dramatic changes in the tertiary structure and total loss of enzymatic activity, suggesting that Pluronic-PAA could inhibit tryptic degradation of proteins.

Acrylic Resins↗

PubMed2000

Sustained release of silver from periodontal wafers for treatment of periodontitis.

Periodontal wafers intended to treat the underlying infections in patients with periodontitis have been developed. The wafers consist of poly(lactic-co-glycolic acid) as a primary bioerodible polymeric component, poly(ethylene glycol) as a plasticizer and encapsulation aid, and silver nitrate as the antimicrobial agent. The wafers are capable of sustained in vitro release of bioactive silver for at least 4 weeks. The wafers exhibit silver release that follows erosion kinetics, confirming a bulk erosion/release mechanism. In clinical evaluation, sustained release of silver at bactericidal levels for at least 21 days is observed. Staining of hard and soft tissues due to the released silver is minimal and reversible.

Administration, Buccal↗

PubMed2000

Self-association of mucin.

Aggregation phenomena in aqueous solutions of purified human tracheobronchial mucin have been studied by rheological methods, steady-state fluorescence, quasielastic light scattering, and spin probe techniques. At temperatures below 30 degrees C and concentrations above 15 mg/mL and in the absence of chaotropic agents, mucin solutions are viscoelastic gels. A gel-sol transition is observed at temperatures above 30 degrees C that is manifested by the diminishing storage modulus and a loss tangent above unity throughout the studied frequency range of the oscillatory shear. No decline in the mucin molecular weight is observed by size-exclusion chromatography above 30 degrees C in the absence of redox agents or proteolytic enzymes. Aggregation of hydrophobic protein segments of the mucin chains at 37 degrees C is indicated by QELS experiments. The decreasing polarity of the microenvironment of pyrene solubilized into mucin solutions at temperatures above 30 degrees C, concomitant with the gel-sol transition, shows the hydrophobicity of the formed aggregates. ESR spectra of the fatty acid spin probe, 16-doxylstearic acid indicate that the aggregate-aqueous interface becomes more developed at elevated temperatures.

Bronchi↗

PubMed1995

Transport of proteins dissolved in organic solvents across biomimetic membranes.

Using lipid-impregnated porous cellulose membranes as biomimetic barriers, we tested the hypothesis that to afford effective transmembrane transfer of proteins and nucleic acids, the vehicle solvent should be able to dissolve both the biopolymers and the lipids. While the majority of solvents dissolve one or the other, ethanol and methanol were found to dissolve both, especially if the protein had been lyophilized from an aqueous solution of a pH remote from the protein's isoelectric point. A number of proteins, as well as RNA and DNA, dissolved in these alcohols readily crossed the lipidized membranes, whereas the same biopolymers placed in nondissolving solvents (e.g., hexane and ethyl acetate) or in those unable to dissolve lipids (e.g., water and dimethyl sulfoxide) exhibited little transmembrane transport. The solubility of biopolymers in ethanol and methanol was further enhanced by complexation with detergents and poly(ethylene glycol); significant protein and nucleic acid transport through the lipidized membranes was observed from these solvents but not from water.

Biological Transport↗

PubMed1994

Detergent-enabled transport of proteins and nucleic acids through hydrophobic solvents.

It is demonstrated that proteins and nucleic acids can be transported through hydrophobic organic solvents (liquid membranes) via nonspecific complex formation with detergents, whereas no macromolecule transport is observed without the latter. A protein (or a nucleic acid) first interacts with an oppositely charged detergent due to hydrophobic ion pairing in the aqueous feed phase. The resultant hydrophobic complex readily partitions into an organic solvent and then into the aqueous receiver phase, where it dissociates. Experiments with (i) different detergent/protein molar ratios, (ii) a range of unrelated organic solvents as liquid membranes, and (iii) homologous detergents with hydrophobic tails of varying lengths indicate that the protein flux through the membrane directly correlates with the partitioning of the protein-detergent complexes from the aqueous feed into the organic phase. Very little protein transport was detected at detergent concentrations above the critical micelle concentration, suggesting that individual detergent molecules, rather than micelles, play the key role. The rate of the detergent-enabled protein transport is not a function of the protein molecular weight, provided that enough detergent molecules bind to make the complex sufficiently hydrophobic; e.g., bovine serum albumin can be transported faster than insulin, which is less than 1/10th of its size.

Amino Acid Sequence↗