scholarly journals Unstirred Water Layer Effects on Biodegradable Microspheres

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Susan D’Souza ◽  
Jabar A. Faraj ◽  
Patrick P. DeLuca
Keyword(s):  
Drug Release ◽  
Mass Loss ◽  
Polymer Degradation ◽  
Water Layer ◽  
Biodegradable Microspheres ◽  
Release Process ◽  
Unstirred Water Layer ◽  
Fourfold Increase ◽  
Static Conditions

This study explores the mechanistic aspects of in vitro release from biodegradable microspheres with the objective of understanding the effect of the unstirred water layer on polymer degradation and drug release. In vitro drug release experiments on Leuprolide PLGA microspheres were performed under “static” and “continuous” agitation conditions using the “sample and separate” method. At specified time intervals, polymer degradation, mass loss, and drug release were assessed. While molecular weight and molecular number profiles for “static” and “continuous” samples were indistinct, mass loss occurred at a faster rate in “continuous” samples than under “static” conditions. In vitro results describe a fourfold difference in drug release rates between the “continuous” and “static” samples, ascribed to the acceleration of various processes governing release, including elimination of the boundary layer. The findings were confirmed by the fourfold increase in drug release rate when “static” samples were subjected to “continuous” agitation after 11 days. A schema was proposed to describe the complex in vitro release process from biodegradable polymer-drug dosage forms. These experiments highlight the manner in which the unstirred water layer influences drug release from biodegradable microspheres and stress the importance of selecting appropriate conditions for agitation during an in vitro release study.

scholarly journals Biological Properties of Ti-Nb-Zr-O Nanostructures Grown on Ti35Nb5Zr Alloy

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Zhaohui Li ◽  
Congqin Ning ◽  
Dongyan Ding ◽  
Hegang Liu ◽  
Lin Huang
Keyword(s):  
Stem Cell ◽  
Drug Release ◽  
Drug Loading ◽  
Biological Properties ◽  
Prolonged Release ◽  
Apatite Formation ◽  
Release Process ◽  
Oxide Nanostructures ◽  
Implant Alloys

Surface modification of low modulus implant alloys with oxide nanostructures is one of the important ways to achieve favorable biological behaviors. In the present work, amorphous Ti-Nb-Zr-O nanostructures were grown on a peak-aged Ti35Nb5Zr alloy through anodization. Biological properties of the Ti-Nb-Zr-O nanostructures were investigated throughin vitrobioactivity testings, stem cell interactions, and drug release experiments. The Ti-Nb-Zr-O nanostructures demonstrated a good capability of inducing apatite formation after immersion in simulated body fluids (SBFs). Drug delivery experiment based on gentamicin and the Ti-Nb-Zr-O nanostructures indicated that a high drug loading content could result in a prolonged release process and a higher quantity of drug residues in the oxide nanostructures after drug release. Quick stem cell adhesion and spreading, as well as fast formation of extracellular matrix materials on the surfaces of the Ti-Nb-Zr-O nanostructures, were found. These findings make it possible to further explore the biomedical applications of the Ti-Nb-Zr-O nanostructure modified alloys especially clinical operation of orthopaedics by utilizing the nanostructures-based drug-release system.

scholarly journals Studies on drug absorption from oral cavity. II Influence of the unstirred water layer on absorption from hamster cheek pouch in vitro and in vivo.

1987 ◽  
Vol 10 (4) ◽  
pp. 180-187 ◽  
Author(s):  
YUJI KUROSAKI ◽  
SHINICHI HISAICHI ◽  
CHIEKO HAMADA ◽  
TAIJI NAKAYAMA ◽  
TOSHIKIRO KIMURA
Keyword(s):  
Oral Cavity ◽  
Drug Absorption ◽  
Water Layer ◽  
Cheek Pouch ◽  
Hamster Cheek Pouch ◽  
Unstirred Water Layer

Jejunal uptake of sugars, cholesterol, fatty acids, and fatty alcohols in vivo in diabetic rats

1985 ◽  
Vol 63 (11) ◽  
pp. 1356-1361
Author(s):  
C. Hotke ◽  
Y. McIntyre ◽  
A. B. R. Thomson
Keyword(s):  
Fatty Acids ◽  
Lauric Acid ◽  
Water Layer ◽  
Diabetic Rats ◽  
The Body ◽  
Unstirred Layer ◽  
Unstirred Water Layer ◽  
Uptake Of Nutrients

Previous in vitro studies have demonstrated enhanced active and passive intestinal uptake of nutrients in streptozotocin-diabetic rats, but the effect of diabetes on the in vivo absorption of glucose and amino acids remains controversial, and the effect of diabetes on the in vivo uptake of lipids has not been reported. Accordingly, an in vivo perfusion technique was used in rats to examine the uptake of nutrients from the intestinal lumen, their transfer to the body, their mucosal and submucosal content, and the percentage of uptake transferred. Diabetes was associated with reduced uptake of fatty alcohols, indicating that the effective resistance of the unstirred water layer in vivo is higher in diabetic than in nondiabetic control rats. The mucosal and submucosal content of dodecanol was lower in diabetic than in control rats, but the percentage of the dodecanol uptake transferred to the body was higher. Although the uptake of varying concentrations of D-galactose was similar in diabetic and in control animals, kinetic analysis corrected for unstirred layer effects demonstrated lower mean values of the passive permeability coefficients (Pd) for galactose in diabetic than in control animals, with lower values of the Michaelis constant (Km) and higher values of the maximal transport rate [Formula: see text]. The uptake of lauric acid was reduced in diabetic rats, whereas the uptake of deconoic acid and of cholesterol was unchanged. With correction for unstirred layer effects, it was apparent that the jejunum of diabetic rats was in fact more permeable to decanoic and lauric acid as well as to cholesterol. The results suggest that (i) in diabetic rats the effective resistance of the unstirred water layer between the jejunal lumen and the brush border membrane is lower; (ii) the differences in unstirred layer resistance between the diabetic and control animals obscure the changes in the kinetic constants (Pd, Km, [Formula: see text]) describing the uptake of galactose, medium chain length fatty acids and cholesterol; and (iii) the kinetic changes in nutrient uptake observed in vitro may be confirmed in vivo once the effect of intestinal unstirred layers has been taken into account.

scholarly journals Intestinal absorption of linoleic acid in experimental renal failure

1991 ◽  
Vol 66 (3) ◽  
pp. 467-477
Author(s):  
M. V. Pahl ◽  
A. Barbari ◽  
N. D. Vaziri ◽  
D. Hollander ◽  
M. Yazdani ◽  
...  
Keyword(s):  
Renal Failure ◽  
Linoleic Acid ◽  
Water Layer ◽  
Short Term ◽  
Unstirred Water Layer ◽  
Wide Range ◽  
Significant Difference

Linoleic acid (LA) transport in rats with experimental short-term and long-term renal failure (RF) was compared with that of sham-operated normal animals on liberal food intake and pair-fed animals. The perfusions in vivo and incubations in vitro were conducted using a micellar solution containing a wide range of LA concentrations. Both absorption in vivo and uptake in vitro of LA were significantly reduced in animals with short-term RF. Lipid extraction and separation by thin-layer chromatography revealed a marked LA trapping as trilinolein (TL) in the perfused intestinal tissue in the short-term RF group. The esterification process, as defined by the rate of LA incorporation into TL, was moderately reduced in short-term RF animals. The thickness of the unstirred water layer showed no significant difference among the groups studied. In contrast, animals with long-term RF exhibited normal absorption of LA in vivo at all concentrations tested. In conclusion, LA absorption is reduced in short-term RF and restored in long-term RF. Several steps including LA transport into and TL transport out of the enterocyte and the esterification process were impaired in short-term RF. These changes are not due to alteration in the unstirred water layer, anorexia, weight loss or a rapid effect of uraemic chemical environment or circulatory factors.

Sign in / Sign up

Export Citation Format

Share Document