Unidirectional Lasing Emissions from CH₃NH₃PbBr₃ Perovskite Microdisks

Very recently, perovskite based microdisk lasers have attracted considerable research attention. However, most of the researches are focused on the lasing spectra in bottom-up synthesized microdisks with regular shapes. The directionality, which is also essential for practical applications, has not been explored. Here we demonstrate unidirectional lasing emissions from perovskite microdisks for the first time. We synthesized the rectangle-shaped microdisks connected with straight waveguides and studied the lasing characteristics, where unidirectional emissions along the waveguides have been observed. Numerical calculations reveal that the unidirectional emissions are formed by the breaking of total internal reflections at the joints between waveguides and microdisks. Since waveguides are compatible with other photonic elements, we believe that our finding will be essential for the applications of perovskite microdisks in integrated photonic circuits and networks

Heterodimeric BMP-2/7 Antagonizes the Inhibition of All-Trans Retinoic Acid and Promotes the Osteoblastogenesis

<div><p>Objectives</p><p>Hypervitaminosis A and alcoholism can result in a low mineral density and compromised regenerative capacity of bone, thus delaying implant osteointegration. The inhibitory effect of all-trans retinoic acid on osteoblastogenesis is considered to be one of the mechanisms. We hypothesized that heterodimeric bone morphogenetic protein-2/7 could antagonize all-trans retinoic acid and enhance osteoblastogenesis, with an aim to accelerate and enhance bone regeneration and implant osteointegration.</p><p>Materials and Methods</p><p>We applied 5 ng/ml or 50 ng/ml bone morphogenetic protein-2/7 to restore the osteoblastogenesis of pre-osteoblasts (MC3T3-E1 cell line) that was inhibited by 1 µM all-trans retinoic acid. We evaluated the efficacy by assessing cell numbers (proliferation), alkaline phosphatase activity (a marker for early differentiation), osteocalcin (a marker for late differentiation), calcium deposition (a marker for final mineralization) and the expression of osteoblastogenic genes (such as Runx2, Collagen Ia, alkaline phosphatase and osteocalcin) at different time points.</p><p>Results</p><p>All-trans retinoic acid significantly inhibited the expression of all the tested osteoblastogenic genes and proteins except alkaline phosphatase activity. In the presence of ATRA, 50 ng/ml bone morphogenetic protein-2/7 not only completely restored but also significantly enhanced all the osteoblastogenic genes and proteins. On the 28^th day, mineralization was completely inhibited by all-trans retinoic acid. In contrast, 50 ng/ml BMP-2/7 could antagonize ATRA and significantly enhance the mineralization about 2.5 folds in comparison with the control treatment (no ATRA, no BMP2/7).</p><p>Conclusions</p><p>Heterodimeric bone morphogenetic protein-2/7 bears a promising application potential to significantly promote bone regeneration and implant osteointegration for the patients with hypervitaminosis A and alcoholism.</p></div

The activity of alkaline phosphatase (ALP) of murine calvarial pre-osteoblasts (MC3T3-E1 cells) under the different treatments.

<p>1) no ATRA, no BMP-2/7; 2) 1 µM ATRA, no BMP-2/7; 3) 1 µM ATRA, 5 ng/ml BMP-2/7; 4) 1 µM ATRA, 50 ng/ml BMP-2/7; 5) no ATRA, 5 ng/ml BMP-2/7; 6) no ATRA, 50 ng/ml BMP-2/7 after for 4 day and 7 days. The ALP activity was normalized to total cellular protein content. All data are presented as mean values together with the standard deviation (SD). *: <i>p</i><0.05, **: <i>p</i><0.01, ***: <i>p</i><0.001.</p

The cell numbers of murine calvarial pre-osteoblasts (MC3T3-E1 cells) per well under the different treatments.

<p>1) no ATRA, no BMP-2/7; 2) 1 µM ATRA, no BMP-2/7; 3) 1 µM ATRA, 5 ng/ml BMP-2/7; 4) 1 µM ATRA, 50 ng/ml BMP-2/7; 5) no ATRA, 5 ng/ml BMP-2/7; 6) no ATRA, 50 ng/ml BMP-2/7 for 1 day and 4 days. All data are presented as mean values together with the standard deviation (SD). *: <i>p</i><0.05, **: <i>p</i><0.01, ***: <i>p</i><0.001.</p

The relative expression of four osteogenic genes under the different treatments.

<p>1) no ATRA, no BMP-2/7; 2) 1 µM ATRA, no BMP-2/7; 3) 1 µM ATRA, 5 ng/ml BMP-2/7; 4) 1 µM ATRA, 50 ng/ml BMP-2/7; 5) no ATRA, 5 ng/ml BMP-2/7; 6) no ATRA, 50 ng/ml BMP-2/7 for 1 day, 4 days and 7 days. (A) Runx2; (B) Collagen I; (C) Alkaline phosphatase; (D) Osteocalcin. The gene expression was first normalized to the corresponding β-actin gene expression for each sample. Then all the gene data were normalized to the gene data in control group on the 1^st day. All data are presented as mean values together with the standard deviation (SD). *: <i>p</i><0.05, **: <i>p</i><0.01, ***: <i>p</i><0.001.</p

The mineralization of murine calvarial pre-osteoblasts (MC3T3-E1 cells) under the different treatments.

<p>1) no ATRA, no BMP-2/7; 2) 1 µM ATRA, no BMP-2/7; 3) 1 µM ATRA, 5 ng/ml BMP-2/7; 4) 1 µM ATRA, 50 ng/ml BMP-2/7; 5) no ATRA, 5 ng/ml BMP-2/7; 6) no ATRA, 50 ng/ml BMP-2/7. (A) Light micrographs depicting the alizarin red staining on the 28^th day. (B) Graph depicting the calcification area on the 21^st day and the 28^th day. All data are presented as mean values together with the standard deviation (SD). *: <i>p</i><0.05, **: <i>p</i><0.01, ***: <i>p</i><0.001.</p

The expression of osteocalcin (OCN) of murine calvarial pre-osteoblasts (MC3T3-E1 cells) under the different treatments.

<p>1) no ATRA, no BMP-2/7; 2) 1 µM ATRA, no BMP-2/7; 3) 1 µM ATRA, 5 ng/ml BMP-2/7; 4) 1 µM ATRA, 50 ng/ml BMP-2/7; 5) no ATRA, 5 ng/ml BMP-2/7; 6) no ATRA, 50 ng/ml BMP-2/7 for 4 days and 7 days. All data are presented as mean values together with the standard deviation (SD). *: <i>p</i><0.05, **: <i>p</i><0.01, ***: <i>p</i><0.001.</p

Primer sequences for real-time quantitative polymerase chain reaction analysis of the expression of Runx2, collagen I, alkaline phosphatase (ALP) and osteocalcin (OCN) genes.

<p>Primer sequences for real-time quantitative polymerase chain reaction analysis of the expression of Runx2, collagen I, alkaline phosphatase (ALP) and osteocalcin (OCN) genes.</p

Miscellaneous Lasing Actions in Organo-Lead Halide Perovskite Films

Lasing actions in organo-lead halide perovskite films have been heavily studied in the past few years. However, due to the disordered nature of synthesized perovskite films, the lasing actions are usually understood as random lasers that are formed by multiple scattering. Herein, we demonstrate the miscellaneous lasing actions in organo-lead halide perovskite films. In addition to the random lasers, we show that a single or a few perovskite microparticles can generate laser emissions with their internal resonances instead of multiple scattering among them. We experimentally observed and numerically confirmed whispering gallery (WG)-like microlasers in polygon shaped and other deformed microparticles. Meanwhile, owing to the nature of total internal reflection and the novel shape of the nanoparticle, the size of the perovskite WG laser can be significantly decreased to a few hundred nanometers. Thus, wavelength-scale lead halide perovskite lasers were realized for the first time. All of these laser behaviors are complementary to typical random lasers in perovskite film and will help the understanding of lasing actions in complex lead halide perovskite systems

High-Density and Uniform Lead Halide Perovskite Nanolaser Array on Silicon

The realization of high density and highly uniform nanolaser arrays in lead halide perovskite is quite challenging, especially on silicon. Herein, we demonstrate a simple way to form lead halide nanolaser array on silicon chip with high density and uniform lasing wavelengths. By positioning a perovskite microwire onto a silicon grating, only the suspended parts can hold high quality (Q) resonances and generate laser emissions. As the perovskite microwire is periodically segmented by the silicon grating, the transverse lasers are divided into a periodic nanolaser array and the lasing wavelengths from different subunits are almost the same. The transverse laser has been observed in an air gap as narrow as 420 nm, increasing the density of nanolasers to about 1250 per millimeter (800 nm period in experiment). We believe this research shall shed light on the development of perovskite microlaser and nanolaser arrays on silicon and their applications