Search results for "Biomedical engineering"
showing 10 items of 2020 documents
Bone Scaffolds Based on Degradable Vaterite/PEG‐Composite Microgels
2019
Vaterite, a metastable modification of calcium carbonate, embedded in a flexible microgel packaging with adjustable mechanical properties, functionality, and biocompatibility, provides a powerful scaffolding for bone tissue regeneration, as it is easily convertible to bone-like hydroxyapatite (HA). In this study, the synthesis and physical analysis of a packaging material to encapsulate vaterite particles and osteoblast cells into monodisperse, sub-millimeter-sized microgels, is described whereby a systematic approach is used to tailor the microgel properties. The size and shape of the microgels is controlled via droplet-based microfluidics. Key requirements for the polymer system, such as …
Biocompatibility of alginates for grafting: impact of alginate molecular weight.
2003
Optimising microencapsulation technology towards the effective clinical transplantation has created the need for highly biocompatible alginates. Therefore, in this study the biocompatibility of different beads prepared from alginates with varying average molecular weight was examined. In some experiments the beads were covered with a multilayer membrane surrounded by an alginate layer. First of all, we found that beads made of a lower weight average alginate elicted a much stronger fibrotic response compared to beads made of a higher weight average alginate (LV-alginate > MV-alginate). The results were confirmed by the observation that the extent of tissue fibrosis was significantly increas…
Spectroscopic study of the loading of cationic porphyrins by carbon nanohorns as high capacity carriers of photoactive molecules to cells
2019
Carbon nanomaterials are attractive candidates for drug delivery due to their high surface area, ease of functionalisation and biocompatibility. This work describes the spectroscopic monitoring of the loading capacity of oxidised carbon nanohorns for two cationic porphyrins. Addition of the COOH functionalised carbon nanohorns to both meso-tetra(4-N-methylpyridyl) free base (H2TMPyP4) and platinum (PtTMPyP4) porphyrin in aqueous solution results in hypochromism of the Soret band and quenching of the porphyrin emission. These changes are used to monitor the non-covalent binding interactions with the nanohorn surface and determine the surface loading. The colloidal stability of the nanohorns …
[68Ga]Ga-THP-Pam: A Bisphosphonate PET Tracer with Facile Radiolabeling and Broad Calcium Mineral Affinity
2020
Calcium minerals such as hydroxyapatite (HAp) can be detected non-invasively in vivo using nuclear imaging agents such as [18F]NaF (available from cyclotrons), for positron emission tomography (PET) and 99mTc-radiolabelled bisphosphonates (BP; available from 99mTc generators for single photon emission computed tomography (SPECT) or scintigraphy). These two types of imaging agents allow detection of bone metastases (based on the presence of HAp) and vascular calcification lesions (that contain HAp and other calcium minerals). With the aim of developing a cyclotron-independent PET radiotracer for these lesions, with broad calcium mineral affinity and simple one-step radiolabelling, we develop…
Influence of Surface Charge and Polymer Coating on Internalization and Biodistribution of Polyethylene Glycol-Modified Iron Oxide Nanoparticles
2015
International audience; The aim of this study was to investigate the influence of the surface charge and coating of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) on their in vitro and in vivo behaviors. Neutral and negatively-charged PEG-based SPIONs were synthesized and compared to Resovist (R), a carboxydextran-based SPION currently used in clinics. Their cytotoxicity, cell internalization, and potential as contrast agents for magnetic resonance imaging were assessed. Neutral pegylated SPIONs were internalized less readily by the reticuloendothelial system and showed a lower uptake by the liver, compared to negatively-charged SPIONs (with carboxydextran and PEG). These results sugge…
Bisphosphonate-polyaspartamide conjugates as bone targeted drug delivery systems.
2015
Poly-hydroxy-aspartamide was used as a backbone to synthesize bisphosphonate derivatives thus achieving macromolecular carriers to be potentially used as targeting agents for bone drug delivery. Molecules bearing bisphosphonate groups, such as aminobisphosphonate (ABP) and neridronate (NRD), have been conjugated to polyaspartamide (α,β-poly(N-2-hydroxyethyl)-dl-aspartamide, PHEA), with or without a spacer (succinic acid or 6-aminocaproic acid) thus obtaining PHEA-succinate-ABP and PHEA-caproylcarbamate-ABP and PHEA-ABP and PHEA-NRD, respectively. Bisphosphonate-polymer conjugates were physico-chemically characterized using size exclusion chromatography and 1H-NMR; and their in vitro and e…
Aggregation Behavior of Polystyrene-Nanoparticles in Human Blood Serum and its Impact on the in vivo Distribution in Mice
2014
The interactions between nanoparticles (NPs) and proteins in complex biological application media such as blood serum are capable of inducing aggregate formation which can lead to subsequent changes in biological activity. Here, we correlate surface charge, aggregation-tendency, and surface serum protein adsorption with cellular uptake and biodistribution in mice. Polystyrene-based NPs (80 - 170 nm) with different surface functionalizations were synthesized and incubated with human serum. Interaction of NPs with serum proteins and aggregate formation were analyzed by mass spectrometryanalysis and dynamic light-scattering. Influence of surface functionalization on specific cellular uptake an…
In vivo biodistribution and lifetime analysis of cy5.5-conjugated rituximab in mice bearing lymphoid tumor xenograft using time-domain near-infrared …
2008
Rituximab is a chimeric monoclonal antibody directed against human CD20 antigen, which is expressed on B-cell lymphocytes and on the majority of B-cell lymphoid malignancies. Herein we report the conjugate of rituximab with the near-infrared (NIR) fluorophore Cy5.5 (RI-Cy5.5) as a tool for in vitro, in vivo, and ex vivo NIR time-domain (TD) optical imaging. In vitro, RI-Cy5.5 retained biologic activity and led to elevated cell-associated fluorescence on tumor cells. In vivo, TD optical imaging analysis of RI-Cy5.5 injected into lymphoma-bearing mice revealed a slow tumor uptake and a specific long-lasting persistence of the probe within the tumor. Biodistribution studies after intraperiton…
Highly Loaded Semipermeable Nanocapsules for Magnetic Resonance Imaging.
2017
Magnetic resonance imaging has become an essential tool in medicine for the investigation of physiological processes. The key issues related to contrast agents, i.e., substances that are injected in the body for imaging, are the efficient enhancement of contrast, their low toxicity, and their defined biodistribution. Polyurea nanocapsules containing the gadolinium complex Gadobutrol as a contrast agent in high local concentration and high relaxivity up to 40 s-1 mmol-1 L are described. A high concentration of the contrast agent inside the nanocapsules can be ensured by increasing the crystallinity in the shell of the nanocapsules. Nanocapsules from aliphatic polyurea are found to display hi…
PET: Theoretical Background and Practical Aspects
2012
Positron emission tomography (PET) is a nuclear medicine imaging tool utilized for investigation of physiological processes in vivo. PET uses the decay characteristics of positron-emitting radionuclides which are produced in a cyclotron and then used to label compounds involved in physiological processes. Usually, the labeled compound—the tracer—is administered intravenously and distributed in the tissue. The radionuclide decays and the emitted photons are detected by the PET scanner. PET then offers the possibility to compute three-dimensional images of the biodistribution and kinetics of the regional radioactivity concentration. There are several options to analyze reconstructed PET image…