Everything about Microspheres
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  • Microspheres for Coatings Applications (Opaque Polyethylene)

    Microspheres are well known in the coatings industry for their use as low-surface-area fillers that offer benefits in viscosity and density control, solids content, application and flow characteristics.

    Hemispherically Coated Spheres

    Cospheric LLC, a Santa Barbara-based microtechnology company, recently launched a line of opaque polyethylene microspheres that act as a superior opacifying agent and provide maximum hiding power with just one monolayer of microspheres as small as 40 microns in diameter. Microspheres are manufactured in any color imaginable and even in combinations of two differently colored hemispheres. Continue reading “Microspheres for Coatings Applications (Opaque Polyethylene)” »

  • Chitosan microspheres prepared by spray drying

    Spray drying has been used in the production of fine powders from emulsions for many years, but it is not a process in which most people associate the production of microspheres.  This journal article shows how the authors were able to produce highly spherical microspheres in the 2-10um range by controlling the levels of Chitosan and crosslinking agents used.

    Chitosan MicrospheresThe key items I found of interest in this article were:

    The quality of the microspheres that were produced, as seen the the attached SEM micrograph.

    How the process variables did not affect the zeta potential of the microspheres produced (Table 4 below), and how the size can be varied by varying the concentrations of Chitosan or the Molecular weight (MW). Continue reading “Chitosan microspheres prepared by spray drying” »

  • Fluorescent Microspheres – Properties and Applications

    Fluorescent microspheres are round spherical particles that emit bright colors when illuminated by UV light. Ability to emit intense color under UV (black light) illumination provides contrast and visibility of microspheres relative to background materials. In addition to the benefits of conventional high quality microspheres, such as sphericity, smoothness and spreadability among others, fluorescent spheres offer extra sensitivity and detectability for analytical methods. For example, fluorescent microbeads are often used as traces to simulate spread of viruses in medical research.

    Typical applications of fluorescent spheres include: testing of filtration media and systems, vial and container cleaning studies, flow tracing, flow visualization, and fluid mechanics studies, medical imaging and flow cytometry, fluorescence microscopy and photography, as well as biomedical technology research, qualification and validation of medical devices, biomedical diagnostics, process troubleshooting and process flow among others. Specifically fluorescent microspheres are often used for water- and air-flow testing and bead-based diagnostic applications. New unique applications of fluorescent spheres are being discovered daily.

    75-90um Dual Response - Daylight & 365nm UV  20um-1000umFluorescent spheres have a unique ability to appear translucent (clear) and practically invisible under ordinary light, and emit intense visible color when energized by ultraviolet (UV) light. This effect allows scientists and engineers to design blind tests and controlled experiments (e.g. simulate spread of viruses) where the microspheres are invisible to the operator doing the procedure until after the fact, therefore, eliminating any operator bias and uncertainty in the validity of experiment. This unique feature of fluorescent microspheres has numerous applications in biomedical research and process troubleshooting. Continue reading “Fluorescent Microspheres – Properties and Applications” »

  • Chitosan Coated PLGA-Microspheres – A Modular System for Targeted Drug Delivery

    During some research on PLGA microspheres we found this interesting article published in European Cells and Materials Vol 7 Suppl 2. 2004 (pages 11-12).   They were able to achieve a significant change in the zeta potential of their microspheres just by increasing the dosage of Chitosan.   The authors conclusions and a graph of their data follow.

    Discussion and Conclusions by the authors:

    The increase in zeta potential from –70.8 mV (chitosan-free PLGA particles) to +20.5 mV with increasing chitosan concentrations in the W2-phase used for particle preparation strongly suggests that the polycationic chitosan was firmly adsorbed to the particle surface. This finding was confirmed by X-ray photoelectron spectroscopy (data not shown). The coupling of biotin via a NHS-PEGlinker showed that the amino groups of  chitosan represent suitable sites for covalent bioconjugation of different ligands. The process allows the production of particles with a mean diameter between 1 and 10 um, a useful size range for the phagocytosis by  phagocytes like dendritic cells or macrophages. Continue reading “Chitosan Coated PLGA-Microspheres – A Modular System for Targeted Drug Delivery” »

  • Biodegradable microspheres for vitreoretinal drug delivery

    One of the microsphere topics that seems to be growing these days is biodegradability.  For those of you who are unfamiliar with the topic an excellent introductory article can be found in: Advance Drug Delivery Reviews 52 (2001) 5-16, called “Biodegradable microspheres for vitreoretinal drug delivery.”  The article does a good job describing the advantages of the various polymers available, such as poly(lactic acid) [PLA], poly(glycolic acid) [PGA], and its copolymer poly(lactic-coglycolic) acid [PLGA].

    The article also recommends the prefered sterlization method for drug delivery (the authors recommend irradiation). Continue reading “Biodegradable microspheres for vitreoretinal drug delivery” »