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Psychorheology is a term that is familar to the food industry, having been used for many years. Its use in other areas, such as consumer products, is slowly starting to make its way into the common lexicon. Psychorheology is the relationship between instrumental data and sensory data. Sensory data may include 'mouth-feel', warmness, and richness. Consumer products companies often conduct panel studies on their developmental products. An assembled panel of consumers will test different formulations of hand creams, and then will fill out forms ranking the creams in terms of smoothness, thickness, slimyness, stringiness, warmth, and a variety of other sensory perceptions. While these rankings are very important to marketing and development people, it would be beneficial to R&D staff to be able to assign these characteristics to new formulations without the time and cost of assembling the panels. By assembling a database of quantitative, instrument-based numbers that are associated with the panels' more qualitative perceptions, the researcher can a priori tell how their new formulation will be perceived.

One single test is usually insufficient for this type of analysis. Rheology, or the study of fluid motion, is most commonly employed, as it provides information on viscosity, elasticity, and other properties that scale with sensory perception. However, other tests are employed. For example, smoothness or slimyness is usually associated with coefficient of friction, with slimyness also associated with the rheological properties of the material. Stickiness is a property associated with both tack and extensional flow properties, whereas stringiness is more associated with extensional flow properties alone. The gel-like behavior associated with high quality shampoos is related to the yield stress properties of the material; the material will retain its form under gravitational conditions, but will flow when sheared between the hand and scalp.

Cambridge Polymer Group assists clients with designing a testing suite to characterize the psychorheological characteristics of their materials, with the intent of finding testing conditions that distinctly separate formulations that have shown a sensory separation in field testing. With these suites, we then characterize the client's formulations, forming a database of properties, from which R&D staff from many divisions within the company can select components to achieve a specific sensory experience.

Throughout our history, we have worked on a variety of interesting projects for our clients and our own internal research. Projects have included cleaning systems for ships, hydrogels for biomedical applications, psychorheology of food products, and synthetic tissue models. We have posted case studies on our web site for prospective clients to see the range of projects on which we have worked. Click here to go to our case studies.

On June 9-8, 2011, the FDA hosted a workshop to discuss issues involved in the re-processing of re-usable medical devices, such as endoscopes and orthoscopic shavers. The purpose of the workshop was to establish what guidance documents should be established to ensure that reusable devices are being properly cleaned and disinfected/sterilized to ensure patient safety. Representatives from hospitals, regulatory, reprocessors, OEMs, and testing labs discussed the state of instructions for use, cleaning testing and validation, and the risks associated with poor cleaning.

Cambridge Polymer Group presented the most recent work performed at ASTM on standards targeted towards improving medical device cleanliness, and participated in a panel discussion of what future standards will be required.

The archived webcast of the conference can be found on the FDA website. A summary of the discussion can be found here.

CPG presentation on ASTM activities in Medical Device Reprocessing

Researchers at the University of Nebraska Medical center recently published their results of a study in which they developed an optical imaging agent to detect inflammation due to wear debris generated from implants. In this study, a N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-based optical imaging contrast agent (P-IRDye) was developed and used for the detection of wear particle-induced inflammation employing a murine calvaria osteolysis model. The particle-induced osteolysis of calvaria was evaluated by H&E, tartrate-resistant acid phosphatase (TRAP) staining and μ-CT after necropsy. One-day post particle implantation, P-IRDye was administrated to the mice via tail vein injection. Live imaging of the animals 6 days after implantation revealed the preferential distribution and sustained retention of the macromolecular contrast agent at the site of particle implantation. Immunohistochemical staining and FACS analyses of the calvaria-associated soft tissue revealed extensive uptake of the HPMA copolymer by F4/80, Ly-6G (Gr1) and CD11c positive cells, which accounts for the retention of the macromolecular probes at the inflammatory sites.

The FDA has issued a mandate to manufacturers of re-usable medical devices to design with re-cleaning of the these devices in mind. This mandate is in response to an on-going effort to reduce the risk of infection, contamination, or disease transmission due to improperly cleaned devices. Device design should include smooth interior surface, avoidance of sharp corners and blind spots, as well as easy disassembly for cleaning. Material choice should be selected with reprocessing in mind.

More information can be found on the FDA's web site.

The on-going discussion of patient response to metal-on-metal hip implants has recently increased. For the past few years, papers presented at ORS and AAOS have discussed concerns about tissue response to metal ions and debris liberated from wear in metal-on-metal hip implants. These articles allege that the metal ions can result in pseudo-tumors in some patients. The FDA has recently requested that all orthopedic manufacturers who produce a metal-on-metal (MOM) implant conduct clinical studies on patients who have received a MOM implant. A NY Times article discusses the nature of this request. A recent NPR story also talks about issues with MOM, and Depuy's recent recall of their ASR system.