BioCompatability of Metal Coated Spheres

For those scientists who are looking to use silver coated materials such as silver coated microspheres in biomedical applications, it is important to understand whether they are bio-compatable.  A selection of abstracts and article references related to the biocompatability of silver follow:

The Biocompatibility of Silver²

The experiments reported have referred to some of the characteristics of the biocompatibility of Ag. Silver has been shown to display interactions with albumin, as an example of a plasma protein, quite different from those of most metals. Such studies shed further light on the complex issue of protein adsorption on biomaterials. It has also been demonstrated that Ag at concentrations < 1 ppm exerts a considerable influence on the activity of lactate dehydrogenase, this effect being reversed in the presence of albumin. A significant but transient increase in blood levels of Ag following intramuscular implantation of the metal has been observed. This is not reflected in any raised urine level. It is proposed that the richly vascular tissue immediately surrounding the implant in the acute phase of the response gives rise to the transient increase, but a subsequent decrease in vascularity reduces this possibility. It appears that Ag released from implants following this initial period substantially remains in the local area.²

Lack of toxicologocial side-effects in silver-coated megaprostheses in humans¹

Deep infection of megaprostheses remains a serious complication in orthopedic tumor surgery. Furthermore, reinfection gets a raising problem in revision surgery of patients suffering from infections associated with primary endoprosthetic replacement of the knee and hip joint. These patients will need many revision surgeries and in some cases even an amputation is inevitable. Silver-coated medical devices proved their effectiveness on reducing infections, but toxic side-effects concerning some silver applications have been described as well. Our study reports about a silver-coated megaprosthesis for the first time and can exclude side-effects of silver-coated orthopedic implants in humans. The silver-levels in the blood did not exceed 56.4 parts per billion (ppb) and can be considered as non-toxic. Additionally we could exclude significant changes in liver and kidney functions measured by laboratory values. Histopathologic examination of the periprosthetic environment in two patients showed no signs of foreign body granulomas or chronic inflammation, despite distant effective silver concentrations up to 1626 ppb directly related to the prosthetic surface. In conclusion the silver-coated megaprosthesis allowed a release of silver without showing any local or systemic side-effects.¹

Specific Article References for the biocompatability of silver are below: See the References

High Index of Refraction Retroreflective Glass Microspheres

Barium Titanate Glass Microspheres are excellent for use as a functional retro reflective additive  to paints and coatings.  Spheres with sizes of about 50 micron (~0.002 inches) mean diameter provide a small enough size for most coatings while offering a large enough size to reflective a significant amount of light.  Barium Titanate Glass Spheres are offered in both partially aluminum coated retro-reflective version for addition into transparent coatings, or as uncoated glass spherical powder for uses in colored paints.

Barium Titanate Glass microbeads offers one of the highest indexes of refraction with an IR greater than 1.9 which provides high intensity retroreflectivity from these spheres.

For those applications calling for a high density filler, barium titanate glass spheres offer a density of 4.5g/cc, that is almost double that of the more common soda lime glass spheres.   In addition to a high density, barium titanate glass spheres have a hardness of about 55-65 on the Gardner scale and a crush strength of over 30,000 psi (207 Mpa) making these spheres very durable in high wear environments.

The spheres offered by Cospheric as product ID:  BTGMS (uncoated ) and P2453BTA (aluminized) are produced in the USA, and are Lead free.

Silica Microspheres – 6 micron mean Diameter

Properties

Silica is a chemically stable inorganic synthetic material.   It has the benefit of providing no irritation to human skin.  Silica is essentially transparent, colorless and promote a high degree of slip in products.  The skin feel is generally lubricious in nature.   Spherical silica imparts exceptional lubricity to loose and pressed powder products. The effect is increased ‘play time’ and a luxurious feel.  Spherical products with mean particle size between 3 to 10 micron will scatter light on the surface of its particle, ie which are transparent, but give natural coverage.

• Properties :
  - Hollow and porous spherical powder
  - Uniform size distribution
  - Excellent dispersibility
  - Good oil absorbancy
  - Good fluidity
• Applications :
  - Emulsion products
  - Makeup products
  - Anticaking agent
  - Additive carrier and perfume carrier
• Available with Optional Silicone Coating (Dimethylpolysiloxane)
  - Increases Hydrophobicity
  - Transparent
  - Resistant to acid, alkalis, UV and moisture

Silica Microspheres are available for purchase at Cospheric in R&D quantities or bulk.

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.

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)” »