Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the present study solid dispersions of Raloxifene HCl were prepared by melt mixing. As drug carriers, biodegradable/biocompatible aliphatic polyesters were used. These formulations were compared to those based on extensively used drug carriers such as PEG and Gelucire 50/13. The used aliphatic polyesters namely poly(propylene succinate) (PPSu) and poly(propylene adipate) (PPAd) were prepared by melt polycondensation. The polyesters have melting points close to human body temperature and were used for first time as drug carries. Polymer cytocompatibility based on HUVEC cells viability in the presence of increasing concentrations of polymer was investigated and it was found that PPSu and PPAd exhibit comparable cytocompatibility with poly(dl-lactide). The physical state of solid dispersions was evaluated by FTIR, SEM and XRD techniques. In all cases the interactions between drug and carriers are limited and thus the dispersed drug was mainly in the crystalline state. SEM revealed that the particles size of the dispersed drug increases with increasing the drug amount. The release behavior of the drug is affected from both the drug amount and the kind of the used carrier. The drug is released almost immediately from PEG formulations while Gelucire results in sustained release. In formulations that polyesters were used as drug carriers the release is slower.
 ...
PMID:Effectiveness of various drug carriers in controlled release formulations of raloxifene HCl prepared by melt mixing. 1975 Dec 1

In this study, we synthesized a biodegradable triblock copolymer poly(ethylene glycol)-poly(epsilon-caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE) by ring-opening copolymerization, and nanohydroxyapatite (n-HA) powder was prepared by a hydrothermal precipitation method. The obtained n-HA was incorporated into the PECE matrix to prepare injectable thermosensitive hydrogel nanocomposites. (1)H NMR, FT-IR, XRD, DSC, and TEM were used to investigate the properties of PECE copolymer and n-HA/PECE nanocomposites. The rheological measurements for n-HA/PECE nanocomposites revealed that the gelation temperature was approximately 36 degrees C. The sol-gel-sol transition behavior and phase transition diagrams were recorded through a test tube inverting method. The results showed that n-HA/PECE nanocomposites still had thermoresponsivity like that of PECE thermosensitive hydrogel. The morphology of the nanocomposites was observed by SEM; the results showed that the nanocomposites had a 3D network structure. In addition, the effects of n-HA contents on the properties of n-HA/PECE nanocomposites are also discussed in the paper. From the results, n-HA/PECE hydrogel is believed to be promising for injectable orthopedic tissue engineering due to its good thermosensitivity and injectability.
 ...
PMID:Injectable biodegradable thermosensitive hydrogel composite for orthopedic tissue engineering. 1. Preparation and characterization of nanohydroxyapatite/poly(ethylene glycol)-poly(epsilon-caprolactone)-poly(ethylene glycol) hydrogel nanocomposites. 1994 37

The ability to predict the in vivo performance of multiblock-copolymer-based biomaterials is crucial for their applicability in the biomedical field. In this work, XPS analysis of PCL-PEG copolymers was carried out, as well as morphological and wettability evaluations by SEM and CA measurements, respectively. XPS analysis on films equilibrated in PBS demonstrated a further enrichment in the PEG component on the surface. Copolymer films obtained by casting using different solvents showed a dependence in segregation according to the solvent employed. Cell adhesion tests demonstrated the importance of copolymer segregation and rearrangement in a wet environment, with a dependence of these phenomena on the copolymer molecular weight.
 ...
PMID:Surface segregation assessment in poly(epsilon-caprolactone)-poly(ethylene glycol) multiblock copolymer films. 1995 86

In the present study, a series of praziquantel (PZQ) loaded implants based on PEG/PCL blends are fabricated by a combination of twin-screw mixing and hot-melt extrusion. In vitro drug release from these implants and the performance of the implants after implantation in rats are evaluated. XRD and DSC analysis results exhibit each component in the implants is mainly in its crystalline state. Dissolution test shows that the higher PEG content there is in the implants, the faster the drug will be released. Interestingly, PEG release from all implants is far faster than PZQ release, and complete PEG release occurs in 72 h. SEM result displays that after the in vitro drug release test, the cross-sections of implants with low PEG contents (0-5%) primarily consist of discrete pores; while those of implants with high PEG contents (10-30%) consist of interconnected pores or channels. The fitting results of drug release data with kinetic models reveal that PZQ release is governed by diffusion. After implantation, drug release becomes more moderate compared with in vitro drug release, and it tends to follow zero-order in the later stage. These results suggest that changing the composition of the PEG/PCL blends is an effective tool to adjust in vitro/in vivo drug release from the implants.
 ...
PMID:In vitro and in vivo evaluation of praziquantel loaded implants based on PEG/PCL blends. 2000 28

Most of the floating systems have an inherent drawback of high variability in the GI transit time, invariably affecting the bioavailability of drug. An attempt has been made to develop floating drug delivery system for improving the drug bioavailability by prolongation of gastric residence time of famotidine in stomach. The floating microballoons were prepared using polymer Eudragit L-100 by solvent evaporation and diffusion technique. The prepared famotidine loaded microspheres were characterised for drug loading, entrapment, encapsulation efficiency, particle size distribution, surface morphology, differential scanning calorimetry, test for buoyancy, in-vitro release and in-vivo antiulcer studies. The results showed an increased drug loading, encapsulation and entrapment efficiency. The thermogram of the DSC showed that the drug was encapsulated in amorphous form and SEM studies revealed the discrete, spherical shaped spheres with rough surface and presence of holes on floating microspheres due high entrapment of PEG which are responsible for drug release and floating ability. The sizes of spheres were found between 20-120 microm which exhibited prolonged release (In-vitro > 8 h) and remained buoyant for > 10 h. The mean particle size increased and the drug release rate decreased at higher Eudragit L-100 polymer concentration. The in-vivo results showed significant antiulcer property of famotidine loaded microspheres when compared to control and standard group of rats by using pyloric ligation method. The mean volume of gastric secretion, mean pH and mean total acid for formulation treated group was calculated as 3.45+/-0.88 ml, 5.65+/-0.74, and 114.15+/-1.80 mEq/L respectively.
 ...
PMID:Floating controlled drug delivery system of famotidine loaded hollow microspheres (microballoons) in the stomach. 2004 7

Poly[monomethylnona(ethylene glycol) 1-methylene-3-(4-methylphenyl)-1H-indene-2-carboxylate] (poly-1b) a new polymer based on a PEG-functionalized benzofulvene macromonomer have been investigated as hydrogel-based material for complexation and release of immunoglobulin (IgG) at physiological mimicking conditions. The polymer ability to complex human IgG has been studied by preparing copolymer/protein complexes obtained by spontaneous protein interactions onto polymer hydrogel aggregates, and the protein release rate has been evaluated at physiological conditions. SEM analysis was used to visualize the copolymer/IgG aggregates and its microstructured deposition. Moreover, rheological studies performed at 37 degrees C allowed determining hydrogel mechanical properties. On the basis of these information and NMR transverse relaxation measurements, the estimation of hydrogel mesh size distribution was possible. Finally, biological studies performed with poly-1b aqueous dispersions showed no cytotoxic effect on MCF-7 cell line, suggesting potential biocompatibility features for this polymer and making this new polymer a good potential candidate for the production of drug delivery systems.
 ...
PMID:PEG-benzofulvene copolymer hydrogels for antibody delivery. 2015 13

(PEG)(3)-PLA copolymer has been explored for the formation of polymersomes. For this, three chains of methoxy-PEG(1100) were directly attached to citric acid by esterification. (Methoxy-PEG(1100))(3)-citrate was then reacted at its hydroxyl terminal with different moles of d,l-lactide by ring-opening polymerization to obtain polymers with five different PEG-to-PLA ratios ranging from 10:90 to 90:10. Polymers were characterized by GPC, FTIR, (1)H NMR, and DSC, films were characterized for hydrophilicity by contact angle, and surface topography was observed by SEM and AFM. All five polymers were evaluated for the formation of polymersomes. Among these, polymers with PEG content of 10-30% were able to self-assemble into polymersomes. To affirm their self-arrangement and drug carrier properties, hydrophilic and hydrophobic dyes were simultaneously encapsulated in these structures. SEM and TEM analysis of the blank polymersomes confirmed the vesicular nature of the polymersomes, whereas CLSM analysis of dye-loaded polymersomes demonstrated the presence of two separate regions viz. hydrophilic core and hydrophobic wall. Hydrophobic dye, fluorescein was released relatively faster from the wall of polymersomes, whereas hydrophilic dye, propidium iodide, was released in controlled fashion up to 18 days. It is expected that these systems may serve as a suitable carrier for simultaneous or separate delivery of drug molecules with varying physicochemical properties.
 ...
PMID:Self assembly of amphiphilic (PEG)(3)-PLA copolymer as polymersomes: preparation, characterization, and their evaluation as drug carrier. 2017 78

In this paper, a new kind of polymeric nanocomposite materials based on nano-hydroxyapatite (n-HA) and PCL-Pluronic-PCL (PCFC) copolymer were prepared by in situ combination method. Firstly, the PCFC copolymer was synthesized by ring-opening polymerization of epsilon-caprolactone initiated by Pluronic (PEG-PPG-PEG); Secondly, n-HA powder were combined with PCFC to form polymeric composites in the presence of hexamethylene diisocyanate (HDI). The obtained composites were characterized by 1H-NMR, FTIR, XRD, TEM, SEM, DTA/TGA, and tensile testing. The results revealed that n-HA could be dispersed into polymer matrix uniformly, and the n-HA/PCFC composite showed great mechanical properties when the content of n-HA was 10 wt%. The microstructure and thermal properties of the composites were discussed in the paper too. The experimental results suggested that this polymeric nanocomposite might have great potential application in the field of tissue engineering.
 ...
PMID:Preparation and characterization of n-hydroxyapatite/PCL-pluronic-PCL nanocomposites for tissue engineering. 2035 8

Polymer nano-composite membranes, based on aliphatic biodegradable polyurethane (PU) elastomers and nano-hydroxyapatite (n-HA), were prepared by solvent casting and freeze-drying. The PU matrix was synthesized from 4,4'-dicyclohexylmethane diisocyanate (H(12) MDI), poly(ethylene glycol) (PEG), castor oil (CO) and 1,4-butandiol (BDO). The n-HA/PU membranes were characterized by SEM, XRD, IR, TG, mechanical test and in vitro biocompatibility. The results revealed that incorporation of 30 wt% n-HA into the PU matrix increased the tensile strength nearly by 186% and the elongation-at-break by 107% compared to pure PU. The addition of n-HA had the slight positive effect on the thermal stability of PU. Cell culture and MTT assays showed that the incorporation of n-HA into the PU matrix provided a favourable environment for initial cell adhesion, maintained cell viability and cell proliferation. These results suggested that the n-HA/PU composite membrane might be a prospective biodegradable guided bone regeneration (GBR) membrane for future applications.
 ...
PMID:Physicochemical and biological properties of nano-hydroxyapatite-reinforced aliphatic polyurethanes membranes. 2053 45

Two vinyl sulfone functionalized crosslinkers were developed for the purpose of preparing degradable poly(ethylene glycol) (PEG) hydrogels (EMXL and GABA-EMXL hydrogels). A self-elimination degradation mechanism in which an N-terminal residue of a glutamine is converted to pyroglutamic acid with subsequent release of diamino PEG (DAP) is proposed. The hydrogels were formed via Michael addition by mixing degradable or nondegradable crosslinkers and copolymer {4% w/v; poly[PEG-alt-poly(mercapto-succinic acid)]} at room temperature in phosphate buffer (PB, pH = 7.4). Hydrogel degradation was characterized by assessing diamino PEG release and examining morphological changes as well as the swelling and weight loss ratio under physiological conditions (37 degrees C). Degradation of EMXL and GABA-EMXL hydrogels occurred by surface erosion (confirmed by SEM). GABA-EMXL degradation was significantly faster (approximately 3-fold) than EMXL; however, the degradation of both hydrogels in mouse plasma was 12-times slower than in PBS. The slower degradation rate in plasma as compared to buffer is consistent with the presence of gamma-glutamyltransferase, gamma-glutamylcyclotransferase and/or glutaminyl cyclase (QC), which have been shown to suppress pyroglutamic acid formation. The current studies suggest that EMXL and GABA-EMXL hydrogels may have biomedical applications where 1-2 week degradation timeframes are optimal.
 ...
PMID:Biodegradable poly(ethylene glycol) hydrogels based on a self-elimination degradation mechanism. 2056 80


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>