Everything about Microspheres
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  • Microspheres Used as a Drug Delivery System

    There has been numerous studies done and articles published in scientific publications about the advantages of microspheres as a drug delivery system vs conventional approach to drug delivery.  Design, Development and Future Application of Microspheres by Divya Rawat , U.K> Singh and Faizi Muzaffar,  Kharvel Subharti College of Pharmacy, published in PharmaTutor discusses the types of microspheres that posses the properties needed for various drug delivery systems, their advantages and limitations.  The micropsheres best suitable to be used in biomedical applications, research and lab experiments are polystyrene.  According to the article: “Polystyrene microspheres are typically used in biomedical applications due to their ability to facilitate procedures such as cell sorting and immune precipitation. Proteins and ligands adsorb onto polystyrene readily and permanently, which makes polystyrene microspheres suitable for medical research and biological laboratory experiments. Polyethylene microspheres are commonly used as permanent or temporary filler. Lower melting temperature enables polyethylene microspheres to create porous structures in ceramics and other materials. High sphericity of polyethylene microspheres, as well as availability of colored and fluorescent microspheres, makes them highly desirable for flow visualization and fluid flow analysis, microscopy techniques, health sciences, process troubleshooting and numerous research applications.”

    Another research paper that discusses advantages and disadvantages of microspheres use for drug delivery, as well as techniques to prepare microsheres and principle behind drug delivery system is Microspheres as Drug Carriers for Controlled Drug Delivery: a Review by Nisha Sharma, Neha Purwar and Prakash Chandra Gupta, University Institute of Pharmacy, C.S.J.M. University, Kanpur, India published in International Journal of Pharmaceutical Sciences and Research.  Polymer microspheres were used for the experiment. The authors conclude that “microspheres are better choice of drug delivery system than many other types of drug delivery system. In future by combining various other strategies, microspheres will find the central and significant place in novel drug delivery, particularly in diseased cell sorting, diagnostics, gene & genetic materials, safe, targeted, specific and effective in-vitro delivery and supplements as miniature version of diseased organ and tissues in the body.”

  • 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

  • FDA-Approved Microspheres

    What makes a microsphere FDA-approved?

    In order to tell whether the microsphere can be used in cosmetics, food, or medical devices it is important to look at the raw materials that are incorporated into the microsphere during manufacturing process.  For example, unpigmented or clear polyethylene microspheres supplied by Cospheric in sizes from 10 micron to 1000 micron meet the quality requirements of the US FDA as specified in 21 CFR 172.888 and 21 CFR 178.3720.  Specific grade of polyethylene used in manufacturing of these microspheres is  FDA-approved for food applications in chewing gum base, on cheese and raw fruits and vegetables, and as a defoamer in food.

    Color additives are subject to a strict system of approval under U.S. law (FD&C Act), sec. 721; 21 U.S.C. 379e. Color additive violations are a common reason for detaining imported cosmetic products offered for entry into this country. If a product contains a color additive, by law [FD&C Act, Sec. 721; 21 U.S.C. 379e; 21 CFR Parts 70 and 80] you must adhere to requirements for:

    • Approval. All color additives used in cosmetics (or any other FDA-regulated product) must be approved by FDA. There must be a regulation specifically addressing a substance’s use as a color additive, specifications, and restrictions.
    • Certification. In addition to approval, a number of color additives must be batch certified by FDA if they are to be used in cosmetics (or any other FDA-regulated product) marketed in the U.S.
    • Identity and specifications. All color additives must meet the requirements for identity and specifications stated in the Code of Federal Regulations (CFR).
    • Use and restrictions. Color additives may be used only for the intended uses stated in the regulations that pertain to them. The regulations also specify other restrictions for certain colors, such as the maximum permissible concentration in the finished product.

    Continue reading “FDA-Approved Microspheres” »

  • Microspheres: Technologies and Global Markets

    An extensive market research report titled Microspheres: Technologies and Global Markets was recently published by BCC Research marketing firm. The microspheres report examines the spherical microparticles used as components in many advanced materials and composites, in the healthcare and personal care industries, and in many specialty research and development applications. The report estimates the size of the microsphere industry worldwide and makes predictions on a 5-year compound annual growth rate of the microsphere market.

    The global market for microspheres in 2010 is estimated to be $2 billion and growing at a 5–year compound annual growth rate (CAGR) of 11.6%, reaching global sales of $3.5 billion by 2015.

    The use of microspheres in medical technology is a relatively new and evolving industry that will see an estimated compound annual growth rate (CAGR) of 24.5% over the next 5 years. This sector is valued at $481 million in 2010 and is expected to reach $1.4 billion by 2015.

    BCC’s analysis suggests that microspheres will see significantly increased demand in the life–sciences markets, which include medicine and biotechnology. The life sciences sector is worth an estimated $203 million in 2010 and is expected to increase at a 9.3% compound annual growth rate (CAGR) to reach $317 million in 2015.

    The key objective of compiling a market research report on microspheres was to present a comprehensive analysis of the global market for microspheres, including analysis of  supply and demand for microspheres across various industries and geographic regions. The report also includes a technical description of a wide variety of types of microspheres available on the market, as well as relevant industries, technologies and applications.
    • Describes demand for microspheres in six major industries: composites; paints and coatings; oil and gas; cosmetics and personal care; biotechnology and life sciences; and medicine and medical devices.
    • Analyses the demand for 2009 and 2010 and forecasts sales over the next 5 years by industry, type of microspheres, and geographic location.
    • Describes different types of microspheres with respect to their chemical composition, including glass, ceramic, and polymer microspheres, and unique material properties that make them suitable for specific industries and applications.
    • Provides detailed descriptions of major players in the market and their product portfolios.
    • Identifies areas of the market that are expected to experience the highest growth in demand.
    • Discusses the history and structure of the industry, technologies, and factors influencing pricing, supply and demand.
    • Reviews price trends and the relationship between price, quality, end–use application and functionality in the microsphere industry.
    • Examines recent advances in technology, newly evolving markets and companies, as well other factors influencing supply.

    This report can be purchased from BCC Research.

    Report Code: AVM073A, Published: November 2010, Analyst: Yelena Lipovetskaya

  • Patent Review: Use of Adsorbent Carbon Microspheres for Treatment of Irritable Bowel Syndrome

    United States Patent 7,749,497 was recently issued to Ocera Therapeutics, Inc. (San Diego, CA) regarding the use of adsorbent carbon microspheres for the treatment of irritable bowel syndrome.

    The patent invention primarily describes the use of adsorbent carbon microspheres for the treatment of irritable bowel syndrome and symptoms associated with it.  Irritable bowel syndrome (IBS) is a gastrointestinal disorder characterized by altered bowel habits without the presence of detectable structural abnormalities. IBS is fairly common and makes up 20-50% of visits to gastroenterologists.  Most commonly, patients have abdominal pain associated with altered bowel habits that consist of constipation, diarrhea, or both. The other group consists of patients with painless diarrhea.

    One embodiment disclosed herein includes a method of treating one or more symptoms of irritable bowel syndrome by  administering to the subject adsorbent carbon microspheres with a particle size of 0.01mm to about 2 mm to reduce the abdominal discomfort or pain. In one embodiment, the amount of the adsorbent carbon microspheres is sufficient to achieve at least about a 50% reduction in the number of days the subject experiences abdominal pain or discomfort.

    In some of the embodiments, the adsorbent carbon microspheres have a particle size of about 0.05mm to about 0.8 mm. In some of the above embodiments, the adsorbent carbon microspheres have a specific surface area of about 700 m.sup.2/g or more as determined by a BET method. In some of the above embodiments, the adsorbent carbon microspheres have a specific surface area of about 700 m.sup.2/g to about 2500 m.sup.2/g as determined by a BET method.

    Microsphere Manufacturing Process:

    First, a dicyclic or tricyclic aromatic compound or a mixture thereof having a boiling point of 200.degree. C. or more is added as an additive to a pitch such as a petroleum pitch or a coal pitch. The whole is heated and mixed, and then shaped to obtain a shaped pitch. Thereafter, the shaped pitch is dispersed and granulated in hot water at 70 to 180.degree. C., with stirring, to obtain a microspherical shaped pitch. The aromatic additive is extracted and removed from the shaped pitch by a solvent having a low solubility to the pitch but a high solubility to the additive. The resulting porous pitch is oxidized by an oxidizing agent to obtain a porous pitch subject to heat infusibility. The resulting infusible porous pitch is treated at 800 to 1000.degree. C. in a gas flow such as steam or carbon dioxide gas reactive with carbon to obtain a porous carbonaceous substance.

    The resulting porous carbonaceous substance is then oxidized in a temperature range of 300 to 800.degree. C., preferably 320 to 600.degree. C., in an atmosphere containing 0.1 to 50% by volume, preferably 1 to 30% by volume, particularly preferably 3 to 20% by volume, of oxygen. The substance is thereafter reduced in a temperature range of 800 to 1200.degree. C., preferably 800 to 1000.degree. C., in an atmosphere of a non-oxidizable gas to obtain the final product. More details of suitable production processes and suitable products may be found in U.S. Pat. Nos. 4,681,764 and 6,830,753 and U.S. Application Publication No. 2005/0112114, filed May 26, 2005, all of which are incorporated herein by reference in their entirety. Suitable adsorbent carbon microspheres are commercially available from Kureha Corp., and is sold in Japan under the trade name KREMEZIN.RTM. (also known as AST-120).

    Administration of the Microspheres to the Patient:

    For use as described herein, adsorbent carbon microspheres may be administered to the gut of a subject by any suitable means. In one embodiment, the carbon is administered orally. Formulations for oral administration may include, but are not limited to, free flowing microspheres, granules, tablets, sugar-coated tablets, capsules, suspensions, sticks, divided packages, or emulsions. In the case of capsules, gelatin capsules, or if necessary, enteric capsules may be used. The oral dosage administered to a subject may be any amount suitable to achieve the desired therapeutic result. In some embodiments, the oral dosage in the case of a human is about 1 to 20 g of the adsorbent per day.