Search results for "Plastics"
showing 10 items of 2724 documents
Synthesis and In Vitro Evaluation of Defined HPMA Folate Conjugates: Influence of Aggregation on Folate Receptor (FR) Mediated Cellular Uptake
2010
In this article we report the synthesis and in vitro evaluation of well-defined, folate functionalized and fluorescently labeled polymers based on the clinically approved N-(2-hydroxypropyl)-methacrylamide (HPMA). The polymers were prepared applying the RAFT polymerization method as well as the reactive ester approach. The molecular weights of the polymers synthesized were around 15 and 30 kDa. The total content of conjugated folate varied from 0, 5, and 10 mol %. The cellular uptake of these polymers was investigated in the folate receptor (FR)-positive human nasopharyngeal epidermal carcinoma (KB-3-1) and FR-negative human lung epithelial carcinoma (A549) cancer cell lines. In FR-positive…
Biodegradable Protein Nanocontainers
2015
The application of synthetic polymers for drug delivery often requires tremendous efforts to ensure biocompatibility and -degradation. To use the body's own substances can help to overcome these problems. Herein, we present the first synthesis of nanocontainers entirely composed of albumin proteins. These protein nanocontainers (PNCs) were loaded with hydrophilic compounds and release of the payload is triggered through natural lysis in vitro in human monocyte-derived dendritic cells (moDCs). No aggregation of PNCs in human blood plasma was observed, indicating stability for blood circulation. As the PNCs were readily taken up by moDCs, they are considered as a promising delivery platform f…
Assessing incentives to increase digital payment acceptance and usage: A machine learning approach.
2022
An important step to achieve greater financial inclusion is to increase the acceptance and usage of digital payments. Although consumer adoption of digital payments has improved dramatically globally, the acceptance and usage of digital payments for micro, small, and medium-sized retailers (MSMRs) remain challenging. Using random forest estimation, we identify 14 key predictors out of 190 variables with the largest predictive power for MSMR adoption and usage of digital payments. Using conditional inference trees, we study the importance of sequencing and interactions of various factors such as public policy initiatives, technological advancements, and private sector incentives. We find tha…
Effect of in vivo stimulation of mice on the secretion of factor B of the alternative complement pathway by peritoneal macrophages
1977
After in vivo treatment of mice with thioglycollate medium, the amount of native factor B which could be detected in vitro in culture supernatants of peritoneal macrophages was much lower than that found in supernatants of macrophages taken from untreated mice. However, when the macrophages from thioglycollate medium-treated mice were cultured on a plastic surface covered with glutardialdehyde-linked bovine serum albumin, the culture supernatants contained larger quantities of native factor B than culture supernatants of macrophages from untreated mice under the same conditions. Thus, the effect of in vivo thioglycollate medium treatment on the in vitro secretion of factor B by peritoneal m…
Fluoropolymer Based on a Polyaspartamide containing 1,2,4-Oxadiazole Units: A Potential Artificial Oxygen (O2) Carrier
2007
Abstract In this preliminary work we have prepared a fluorinated polymer capable of solubilizing an appreciable amount of O(2) and, at the same time, maintaining a higher water solubility than perfluoroalkanes investigated as injectable O(2) carriers. In particular, we describe the synthesis and characterization of a new macromolecular conjugate obtained by derivatization of alpha,beta-poly(N-2-hydroxyethyl)-DL-aspartamide (PHEA) with 5-pentafluorophenyl-3-perfluoroheptyl-1,2,4-oxadiazole, called PHEA-F. This new water soluble fluoropolymer was prepared in high yield using a simple procedure. It was characterized by FT-IR and UV-vis spectrophotometry, (19)F-NMR and SEC measurements. O(2) so…
Galactosylated micelles for a ribavirin prodrug targeting to hepatocytes.
2013
Polymeric micelles potentially able to carry to hepatocytes a ribavirin (RBV) prodrug, exploiting the presence of carbohydrate receptors, that is, ASGPR, were prepared starting from a galactosylated polylactide-polyaminoacid conjugate. This latter was obtained by chemical reaction of α,β-poly(N-2-hydroxyethyl) (2-aminoethylcarbamate)-dl-aspartamide (PHEA-EDA) with polylactic acid (PLA), and subsequent reaction with lactose, obtaining PHEA-EDA-PLA-GAL copolymer. To enhance the entrapment into obtained nanostructures, a hydrophobic RBV prodrug, that is, RBV tripalmitate, was synthesized and its capability to release RBV in the presence of an adequate enzymatic activity was demonstrated. Liver…
How Low Can You Go? Low Densities of Poly(ethylene glycol) Surfactants Attract Stealth Proteins.
2018
It is now well-established that the surface chemistry and “stealth” surface functionalities such as poly(ethylene glycol) (PEG) chains of nanocarriers play an important role to decrease unspecific protein adsorption of opsonizing proteins, to increase the enrichment of specific stealth proteins, and to prolong the circulation times of the nanocarriers. At the same time, PEG chains are used to provide colloidal stability for the nanoparticles. However, it is not clear how the chain length and density influence the unspecific and specific protein adsorption keeping at the same time the stability of the nanoparticles in a biological environment. Therefore, this study aims at characterizing the…
Pegylated nanoparticles based on a polyaspartamide. Preparation, physico-chemical characterization and intracellular uptake
2006
Nanoparticles with different surface PEGylation degree were prepared by using as starting material alpha,beta-poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA). PHEA was functionalized with a PEG amino-derivative for obtaining PHEA-PEG(2000) copolymer. Both PHEA and PHEA-PEG(2000) were derivatized with methacrylic anhydride (MA) for obtaining poly(hydroxyethylaspartamide methacrylated) (PHM) and poly(hydroxyethylaspartamide methacrylated)-PEGylated (PHM-PEG(2000)), respectively. Nanoparticles were obtained by UV irradiation of an inverse microemulsion, using as internal phase an aqueous solution of PHM alone or of the PHM/PHM-PEG(2000) mixture at different weight ratio and as external phase a m…
HPMA-LMA copolymer drug carriers in oncology: an in vivo PET study to assess the tumor line-specific polymer uptake and body distribution.
2013
Polymeric drug carriers aim to selectively target tumors in combination with protecting normal tissue. In this regard polymer structure and molecular weight are key factors considering organ distribution and tumor accumulation of the polymeric drug delivery system. Four different HPMA based copolymer structures (random as well as block copolymers with lauryl methacrylate as hydrophobic block) varying in molecular weight, size and resulting architecture were analyzed in two different tumor models (AT1 prostate carcinoma and Walker-256 mammary carcinoma) in vivo. Polymers were labeled with (18)F and organ/tumor uptake was followed by μPET imaging and ex vivo biodistribution. Vascular permeabi…
Fate of Linear and Branched Polyether-Lipids In Vivo in Comparison to Their Liposomal Formulations by 18F-Radiolabeling and Positron Emission Tomogra…
2015
In this study, linear poly(ethylene glycol) (PEG) and novel linear-hyperbranched, amphiphilic polyglycerol (hbPG) polymers with cholesterol (Ch) as a lipid anchor moiety were radiolabeled with fluorine-18 via copper-catalyzed click chemistry. In vivo investigations via positron emission tomography (PET) and ex vivo biodistribution in mice were conducted. A systematic comparison to the liposomal formulations with and without the polymers with respect to their initial pharmacokinetic properties during the first hour was carried out, revealing remarkable differences. Additionally, cholesterol was directly labeled with fluorine-18 and examined likewise. Both polymers, Ch-PEG27-CH2-triazole-TEG-…