Quantum Dot Patent Infringement Lawsuit Resolved

Posted on July 27, 2009 by John C. Monica, Jr.

Readers may be interested in the recent resolution of a quantum dot patent infringement lawsuit between Nanosys and Nanoco/Sigma-Aldrich. 

In April 2009, Nanosys sued Nanoco and Sigma-Aldrich in Wisconsin federal court for allegedly infringing three quantum dot patents owned by MIT which were exclusively licensed to Nanosys.  Nanoco purportedly marketed and sold competing luminous quantum dot nanocrystals under its Lumnidot brand through its U.S. distributor Sigma-Aldrich.  The suit was brought in Wisconsin because that was where the products allegedly infringing the patents were sold.

In the complaint initiating the lawsuit, Nanosys explained that its "technology is covered by a portfolio of over 500 patents and patent applications, including patents in the quantum dot field, that is currently being applied to opportunities in multiple industries including energy, electronics, optoelectronics, life science, and defense. Current application areas of Nanosys technology include flat-panel displays, non-volatile memory, fuel cells, solid-state lighting, chemical analysis chips and medical devices."

The lawsuit was resolved prior to any substantive defense.  In June 2009, the parties told the Court that the case had been settled and that they were drafting the final settlement documentation.  In July 2009, Nanosys voluntarily dismissed the case with prejudice as to both defendants -- as to any prior act, or infringement by selling quantum dot nanocrystals having a CdSe/Zns core-shell structure.

According to a Nanoco press release, the parties settled the case without an admission of liability by Nanoco or Sigma-Aldrich. However, as part of the settlement, Nanoco agreed to terminate its U.S. business for heavy metal quantum dots. Nanoco's CEO explained the cost of defending the litigation was unwarranted by the amount of business generated by the product.  He further stated that the company would continue to market its quantum dot products based on heavy metal-free technology, differing from the technology involved in the lawsuit.

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Quantum Dot Skin Penetration Study

Posted on October 15, 2008 by John C. Monica, Jr.

A recent in vivo study published in NanoLetters focuses on the impact of ultraviolet radiation on the ability of Quantum Dots (QD) to penetrate skin.

L. Mortensen, et al., "In Vivo Skin Penetration of Quantum Dot Nanoparticles in the Murine Model: The Effect of UVR," NanoLetters, Vol. 8, No. 9, pp. 2779-2787 (August 2008).

The article begins by noting that "[n]anoparticles (NP) are commonly used in sunscreens and other cosmetics, and since consumer use of sunscreen is often applied to sun damaged skin, the effect of UVR on NP skin penetration is a concern due to potential toxicity;" and "[t]he question of whether or not NP can penetrate the healthy stratum corneum skin barrier in vivo remains largely unanswered."

The authors note that there are conflicting results from recent studies in this area, which they attribute to different researchers using different nanoscale materials with different sizes/diameters. The authors point out that the inconsistent results of prior studies "highlight the need for standardization of experimental techniques in ex vivo skin models are to be useful."

Despite the authors’ stated concern with possible dermal penetration of NP contained in cosmetics and sunscreens, they chose to test a nanoscale material which is not used in any cosmetic or sunscreen – Quantum Dots.

The authors explain:

We selected to investigate QD, as they posses ideal characteristics for in vivo experimentation including broad excitability, narrow emission bandwidth, high fluorescence quantum yield, photostability, and ease of surface functionalization. Moreover, QD are of a similar size to TiO2 NP used in sunscreen applications, they intrinsically generate ROS species, and the carboxyl terminated QD have a similar negative oxide surface chemistry to the TiO2 and ZnO raw materials often used in sunscreen applications.

There are no lack of manufacturers selling the very type of nanoscale zinc oxide and titanium oxide used in consumer cosmetics and sunscreens. Quantum dots are very remote cousins to these particles.  Why not test the substances themselves rather than a surrogate?

Regarding the animals used in the experiment, the researchers selected 6-7 week old SKH-1 hairless, albino mice.  The QD mouse application vehicle was a solution of 75% glycerol/25% carboxyl QD Stock Solution (pH=9.0 borate buffer, 8μm QD).  One half of the mice received an acute single UVR dose, which was administered by using UVA Sun 340 lamps (320-400 nm (UVA)) (290-320 nm (UVB)). 

The scientists found increased QD penetration for 8 hr and 24 hr treatment conditions after UVR exposure.  However, "[m]ost strikingly, under no circumstances is there evidence for massive QD penetration, even for UVR exposed mice 24 hr after QD application." "[N]one of the penetration observed was at a very high level."

The scientists conclude that "[t]hese studies demonstrate the importance of skin condition to effect the penetration of QD nanoparticles . . . in the . . . mouse model.  We have shown that QD work their way between corneocytes of the stratum corneum and penetrate deep in the epidermis and dermis of an in vivo model with UVR penetration exacerbation." "The minimal QD penetration observed in our study on barrier intact (non-UVR exposed) skin suggests the preponderance of current literature suggesting TiO2 and ZnO NP used in commercial sunscreens exhibit limited penetration in layers below the lower SC."
 

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