The measurement of the shear modulus of a porous polymer layer with two microphones

2009 ◽  
Vol 28 (5) ◽  
pp. 508-510 ◽  
Author(s):  
Vincent Gareton ◽  
Denis Lafarge ◽  
Sohbi Sahraoui
Keyword(s):  
Shear Modulus ◽  
Porous Polymer ◽  
Polymer Layer

scholarly journals Robocasting of Single and Multi-Functional Calcium Phosphate Scaffolds and Its Hybridization with Conventional Techniques: Design, Fabrication and Characterization

2020 ◽  
Vol 10 (23) ◽  
pp. 8677
Author(s):  
Mehdi Mohammadi ◽  
Patricia Pascaud-Mathieu ◽  
Valeria Allizond ◽  
Jean-Marc Tulliani ◽  
Bartolomeo Coppola ◽  
...  
Keyword(s):  
Surrounding Medium ◽  
Silver Ions ◽  
Octacalcium Phosphate ◽  
Hybrid Structure ◽  
Functionally Graded ◽  
Porous Polymer ◽  
Polymer Layer ◽  
Polymer Scaffolds ◽  
Salt Leaching ◽  
Porous Part

In this work, dense, porous, and, for the first time, functionally-graded bi-layer scaffolds with a cylindrical geometry were produced from a commercially available hydroxyapatite powder using the robocasting technique. The bi-layer scaffolds were made of a dense core part attached to a surrounding porous part. Subsequently, these bi-layer robocast scaffolds were joined with an outer shell of an antibacterial porous polymer layer fabricated by solvent casting/salt leaching techniques, leading to hybrid ceramic-polymer scaffolds. The antibacterial functionality was achieved through the addition of silver ions to the polymer layer. All the robocast samples, including the bi-layer ones, were first characterized through scanning electron microscopy observations, mechanical characterization in compression and preliminary bioactivity tests. Then, the hybrid bi-layer ceramic-polymer scaffolds were characterized through antimicrobial tests. After sintering at 1300 °C for 3 h, the compressive strengths of the structures were found to be equal to 29 ± 4 MPa for dense samples and 7 ± 4 MPa for lattice structures with a porosity of 34.1%. Bioactivity tests performed at 37 °C for 4 weeks showed that the precipitated layer on the robocast samples contained octacalcium phosphate. Finally, it was evidenced that the hybrid structure was effective in releasing antibacterial Ag+ ions to the surrounding medium showing its potential efficiency in limiting Staphylococcus aureus proliferation during surgery.

scholarly journals Smart Microneedles with Porous Polymer Coatings for pH-Responsive Drug Delivery

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1834 ◽  
Author(s):  
Ullah ◽  
Khan ◽  
Choi ◽  
Kim
Keyword(s):  
Drug Delivery ◽  
Controlled Release ◽  
Drug Release ◽  
Sodium Bicarbonate ◽  
Porous Polymer ◽  
Polymer Layer ◽  
Ph Responsive ◽  
Acidic Microenvironment ◽  
Model Drug

: This work demonstrates a simple approach for coating a porous polymer layer on stainless-steel (SS) microneedles characterized by a pH-responsive formulation for self-regulated drug delivery. For many drug-delivery applications, the release of therapeutic agents in an acidic microenvironment is desirable. Acid-sensitive polymers and hydrogels were extensively explored, but easily prepared polymeric microcarriers that combine acid sensitivity and biodegradability are rare. Here, we describe a simple and robust method of coating a porous polymer layer on SS microneedles (MNs) that release a model drug (lidocaine) in a pH-responsive fashion. It was constructed by packing the model drug and a pH-sensitive component (sodium bicarbonate) into the pores of the polymer layer. When this acid-sensitive formulation was exposed to the acidic microenvironment, the consequent reaction of protons (H+) with sodium bicarbonate (NaHCO3) yielded CO2. This effect generated pressure inside the pores of the coating and ruptured the thin polymer membrane, thereby releasing the encapsulated drug. Scanning electron micrographs showed that the pH-sensitive porous polymer-coated MNs exposed to phosphate-buffered saline (PBS) at pH 7.4 were characterized by closed pores. However, MNs exposed to PBS at pH 5.5 consisted of open pores and the thin membrane burst. The in vitro studies demonstrated the pH sensitivity of the drug release from porous polymer-coated MNs. Negligible release was observed for MNs in receiving media at pH 7.4. In contrast, significant release occurred when the MNs were exposed to acidic conditions (pH 5.5). Additionally, comparable results were obtained for drug release in vitro in porcine skin and in PBS. This revealed that our developed pH-responsive porous polymer-coated MNs could potentially be used for the controlled release of drug formulations in an acidic environment. Moreover, the stimuli-responsive drug carriers will enable on-demand controlled release profiles that may enhance therapeutic effectiveness and reduce systemic toxicity.

scholarly journals Porous polymer coatings on metal microneedles for enhanced drug delivery

2018 ◽  
Vol 5 (4) ◽  
pp. 171609 ◽  
Author(s):  
Asad Ullah ◽  
Chul Min Kim ◽  
Gyu Man Kim
Keyword(s):  
Drug Delivery ◽  
Rhodamine B ◽  
Skin Penetration ◽  
Dip Coating ◽  
Polymer Coatings ◽  
Porous Polymer ◽  
Polymer Layer ◽  
Simple Method ◽  
Modified Surface ◽  
Rhodamine B Dye

We present a simple method to coat microneedles (MNs) uniformly with a porous polymer (PLGA) that can deliver drugs at high rates. Stainless steel (SS) MNs of high mechanical strength were coated with a thin porous polymer layer to enhance their delivery rates. Additionally, to improve the interfacial adhesion between the polymer and MNs, the MN surface was modified by plasma treatment followed by dip coating with polyethyleneimine, a polymer with repeating amine units. The average failure load (the minimum force sufficient for detaching the polymer layer from the surface of SS) recorded for the modified surface coating was 25 N, whereas it was 2.2 N for the non-modified surface. Calcein dye was successfully delivered into porcine skin to a depth of 750 µm by the porous polymer-coated MNs, demonstrating that the developed MNs can pierce skin easily without deformation of MNs; additional skin penetration tests confirmed this finding. For visual comparison, rhodamine B dye was delivered using porous-coated and non-coated MNs in gelatin gel which showed that delivery with porous-coated MNs penetrate deeper when compared with non-coated MNs. Finally, lidocaine and rhodamine B dye were delivered in phosphate-buffered saline (PBS) medium by porous polymer-coated and non-coated MNs. For rhodamine B, drug delivery with the porous-coated MNs was five times higher than that with the non-coated MNs, whereas 25 times more lidocaine was delivered by the porous-coated MNs compared with the non-coated MNs.

scholarly journals Use of peak sharpening effects to improve the separation of chiral compounds with molecularly imprinted porous polymer layer open-tubular capillaries

2017 ◽  
Vol 38 (8) ◽  
pp. 1179-1187 ◽  
Author(s):  
Chadin Kulsing ◽  
Yuanzhong Yang ◽  
Jamil M. Chowdhury ◽  
Reinhard I. Boysen ◽  
Milton T. W. Hearn
Keyword(s):  
Porous Polymer ◽  
Polymer Layer ◽  
Molecularly Imprinted ◽  
Chiral Compounds

scholarly journals Smart Microneedles with Porous Polymer Layer for Glucose-Responsive Insulin Delivery

Pharmaceutics ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 606 ◽  
Author(s):  
Asad Ullah ◽  
Hye Jin Choi ◽  
Mijin Jang ◽  
Sanghyun An ◽  
Gyu Man Kim
Keyword(s):  
Diabetic Rats ◽  
Porous Polymer ◽  
Polymer Layer ◽  
Thin Polymer Film ◽  
Sem Images ◽  
Thin Polymer ◽  
Carbon Dioxide Co2

A closed-loop system imitating the function of pancreatic cells, connected to microneedles (MNs) that automatically “release” insulin in response to the blood glucose (BG) levels would be highly satisfactory for improving the quality of life and health for diabetes patients. This paper describes an easy, fast and simple technique of coating a porous polymer layer on stainless steel (SS) MNs that release insulin in a glucose-responsive fashion. It was fabricated by sealing insulin, sodium bicarbonate (a pH-sensitive element [NaHCO3]) and glucose oxidase (glucose-specific enzymes [GOx]) into the pores of a porous polymer coating. Glucose can passively diffuse into the pores and become oxidized to gluconic acid by GOx, thereby causing a decrease in local pH. The subsequent reaction of protons with NaHCO3 forms carbon dioxide (CO2) which creates pressure inside the pores, thereby rupturing the thin polymer film and releasing the encapsulated insulin. Field emission scanning electron microscopy (FE-SEM) images displayed that upon the exposure of MNs to glucose-free phosphate buffer saline (PBS) with pH 7.4, the pores of the porous MNs were closed, while in MNs exposed to a hyperglycemic glucose level, the pores were opened and the thin film burst. These MNs demonstrated both in vitro (in porcine skin and PBS) and in vivo (in diabetic rats) glucose-mediated insulin release under hyperglycemic conditions with rapid responsiveness. This study validated that the release of insulin from porous MNs was effectively correlated with glucose concentration.

Resorcinarene Cavitand Polymers for the Remediation of Halomethanes and 1,4-Dioxane

2019 ◽  
Author(s):  
Luke Skala ◽  
Anna Yang ◽  
Max Justin Klemes ◽  
Leilei Xiao ◽  
William Dichtel
Keyword(s):  
Drinking Water ◽  
Activated Carbon ◽  
High Capacity ◽  
The United States ◽  
Water Sources ◽  
Disinfection Byproducts ◽  
Porous Polymer ◽  
Organic Micropollutants ◽  
Executive Summary ◽  
Regulatory Limits

<p>Executive summary: Porous resorcinarene-containing polymers are used to remove halomethane disinfection byproducts and 1,4-dioxane from water.<br></p><p><br></p><p>Disinfection byproducts such as trihalomethanes are some of the most common micropollutants found in drinking water. Trihalomethanes are formed upon chlorination of natural organic matter (NOM) found in many drinking water sources. Municipalities that produce drinking water from surface water sources struggle to remain below regulatory limits for CHCl<sub>3</sub> and other trihalomethanes (80 mg L<sup>–1</sup> in the United States). Inspired by molecular CHCl<sub>3</sub>⊂cavitand host-guest complexes, we designed a porous polymer comprised of resorcinarene receptors. These materials show higher affinity for halomethanes than a specialty activated carbon used for trihalomethane removal. The cavitand polymers show similar removal kinetics as activated carbon and have high capacity (49 mg g<sup>–1</sup> of CHCl<sub>3</sub>). Furthermore, these materials maintain their performance in real drinking water and can be thermally regenerated under mild conditions. Cavitand polymers also outperform activated carbon in their adsorption of 1,4-dioxane, which is difficult to remove and contaminates many public water sources. These materials show promise for removing toxic organic micropollutants and further demonstrate the value of using supramolecular chemistry to design novel absorbents for water purification.<br></p>

ANISOTROPIC TRANSPORT THROUGH POLYMER LAYER AND POROUS ARTERIAL WALL WITH BINDING IN DRUG-ELUTING STENTS USING THE FEM

2018 ◽  
Author(s):  
fabiane aparecida dos santos frazzoli ◽  
Rachel Manhaes de Lucena ◽  
Norberto Mangiavacchi ◽  
José da Rocha Miranda Pontes ◽  
Gustavo Rabello dos Anjos ◽  
...  
Keyword(s):  
Arterial Wall ◽  
Polymer Layer ◽  
Drug Eluting Stents ◽  
Drug Eluting ◽  
Anisotropic Transport
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