Rare-earth activated upconversion materials are receiving renewed attention for their potential applications in bioimaging and solar energy conversion. To enhance the upconversion efficiency, surface plasmon has been employed but the reported enhancements vary widely and the exact enhancement mechanisms are not clearly understood. In this study, we synthesized upconversion nanoparticles (UCNPs) coated with amphiphilic polymer which makes UCNPs water soluble and negatively charged. We then designed and fabricated a silver nanograting on which three monolayers of UCNPs were deposited by polyelectrolyte-mediated layer-by-layer deposition technique. The final structures exhibited surface plasmon resonance at the absorption wavelength of UCNP. The green and red photoluminescence intensity of UCNPs on nanograting was up to 16 and 39 times higher than the reference sample deposited on flat silver film, respectively. A thorough analysis of rate equations showed that the enhancement was due entirely to absorption enhancement in the strong excitation regime, while the enhancement of both absorption and Förster energy transfer contribute in the weak excitation regime. The Purcell factor was found to be small and unimportant because the fast nonradiative decay dominates the relaxation process. From the experimentally observed enhancements, we concluded 3.1× and 1.7× enhancements for absorption and Förster energy transfer, respectively. This study clearly shows the plasmon enhancement mechanism and its excitation power dependence. It provides the basis for comparison of the enhancements of various plasmonic UCNP systems in the literature. It also lays the foundation for rational design of optical plasmonic structures for upconversion enhancement.

Frequency conversion has always been an important topic in optics. Nonlinear optics has traditionally focused on frequency conversion based on nonlinear susceptibility but with the recent development of upconversion nanomaterials, luminescence upconversion has begun to receive renewed attention. While upconversion nanomaterials open doors to a wide range of new opportunities, they remain too inefficient for most applications. Incorporating plasmonic nanostructures provides a promising pathway to highly efficient upconversion. Naturally, a plethora of theoretical and experimental studies have been published in recent years, reporting enhancements up to several hundred. It is however difficult to make meaningful comparisons since the plasmonic fields are highly sensitive to the local geometry and excitation condition. Also, many luminescence upconversion processes involve multiple steps via different physical mechanisms and the overall output is often determined by a delicate interplay among them. This review is aimed at offering a comprehensive framework for plasmon enhanced luminescence upconversion. We first present quantum electrodynamics descriptions for all the processes involved in luminescence upconversion, which include absorption, emission, energy transfer and nonradiative transitions. We then present a bird's eye view of published works on plasmon enhanced upconversion, followed by more detailed discussion on comparable classes of nanostructures, the effects of spacer layers and local heating, and the dynamics of the plasmon enhanced upconversion process. Plasmon enhanced upconversion is a challenging and exciting field from the fundamental scientific perspective and also from technological standpoints. It offers an excellent system to study how optical processes are affected by the local photonic environment. This type of research is particularly timely as the plasmonics is placing heavier emphasis on nonlinearity. At the same time, efficient upconversion could make a significant impact on many applications including solar energy conversion and biomedical imaging. The marriage of luminescent materials research with nanophotonics currently being initiated with plasmon enhanced upconversion research explores a new frontier in photonics that could potentially spawn many exciting new fields.

IntroductionAnti-estrogen therapy has been shown to reduce mammographic breast density (MD). We hypothesized that a short-term change in breast density may be a surrogate biomarker predicting response to adjuvant endocrine therapy (ET) in breast cancer.MethodsWe analyzed data for 1,065 estrogen receptor (ER)-positive breast cancer patients who underwent surgery between 2003 and 2006 and received at least 2 years of ET, including tamoxifen and aromatase inhibitors. MD was measured using Cumulus software 4.0 and expressed as a percentage. MD reduction (MDR) was defined as the absolute difference in MD of mammograms taken preoperatively and 8-20 months after the start of ET.ResultsAt a median follow-up of 68.8 months, the overall breast cancer recurrence rate was 7.5% (80/1065). Mean MDR was 5.9% (range, -17.2% to 36.9%). Logistic regression analysis showed that age < 50 years, high preoperative MD, and long interval between start of ET to follow-up mammogram were significantly associated with larger MDR (p < 0.05). In a survival analysis, tumor size, lymph node positivity, high Ki-67 (≥ 10%), and low MDR were independent factors significantly associated with recurrence-free survival (p < 0.05). Compared with the group showing the greatest MDR (≥ 10%), the hazard ratios for MDRs of 5-10%, 0-5%, and < 0% were 1.33, 1.92, and 2.26, respectively.ConclusionsMD change during short-term use of adjuvant ET was a significant predictor of long-term recurrence in women with ER-positive breast cancer. Effective treatment strategies are urgently needed in patients with low MDR despite about 1 year of ET.

Upstaging was associated with lesions that were large, palpable or high grade. It was also associated with use of the 14-gauge needle method. Our scoring system might be helpful to identify patients who do not require sentinel lymph node biopsy.

Although BCL2 has occasionally been suggested as a candidate prognostic factor for breast cancer, it is still not accepted as a prognostic factor. We attempted to validate the role of BCL2 as a prognostic factor of breast cancer. Data on 7,230 primary breast cancer patients from the Seoul National University Hospital Breast Care Center were analyzed. Three current prognostic models, including the St. Gallen model, the Nottingham prognostic index (NPI) model and the TNM model, were used for analysis of the prognostic influence of BCL2. The positive BCL2 group showed more favorable features with regard to clinicopathologic parameters than the BCL2 negative group and a strong correlation was observed between BCL2 and the hormonal receptor. The positive BCL2 group showed better prognosis in overall survival and disease free survival (log-rank test, both p < 0.001), even in all subgroups, than the BCL2 negative group. BCL2 was a significant prognostic factor in both univariate (hazard ratio [HR], 0.361; 95% confidence interval (CI), 0.306-0.426; p < 0.001) and multivariate analyses (HR, 0.417; 95% CI, 0.417-0.705; p < 0.001). BCL2 had a strong influence on the established prognostic models, including the St. Gallen model, the NPI model and the TNM model. BCL2 was a powerful independent prognostic factor for breast cancer and had a strong influence on the current prognostic models. Favorable clinicopathologic features and a strong correlation with the hormonal receptor are suggested as the causes of superior survival in patients with BCL2 positive breast cancer.BCL2 has occasionally been suggested as a candidate prognostic factor for breast cancer; however, in general, it is still not accepted as a prognostic factor.1 Although most previously reported papers have suggested the possibility of BCL2 as a prognostic factor for breast cancer, the results were not consistent, but conflicting. Some papers have reported that by multivariate analysis BCL2 was found to be a statistically significant independent factor 2-6 ; however, other papers have reported that by survival analysis BCL2 was not found to be a statistically significant prognostic factor. 7-9 Furthermore, other papers have reported that BCL2 was significant by univariate analysis but not by multivariate analysis.10 Two papers reported that by meta-analysis BCL2 was found to be a statistically significant independent factor in breast cancer prognostication. 11,12The general acceptance of BCL2 as a prognostic factor has in part been impeded by a lack of robustness of the original research findings. A small number of papers could not provide sufficient evidence, and, due to small numbers of enrolled patients, statistical powers were too weak to show independence of influences in multivariate analyses. Furthermore, many prognostic factors are correlated and small studies have limited statistical power, especially in subgroup analyses. For these reasons, large scaled clinical studies are needed to validate the possibilities of BCL2 as a prognosticator for breast can...