Observation of electric current induced by optically injected spin current

A normally incident light of linear polarization injects a pure spin current in a strip of 2-dimensional electron gas with spin-orbit coupling. We report observation of an electric current with a butterfly-like pattern induced by such a light shed on the vicinity of a crossbar shaped InGaAs/InAlAs quantum well. Its light polarization dependence is the same as that of the spin current. We attribute the observed electric current to be converted from the optically injected spin current caused by scatterings near the crossing. Our observation provides a realistic technique to detect spin currents, and opens a new route to study the spin-related science and engineering in semiconductors.Comment: 15 pages, 4 figure

In situ coherent diffractive imaging

Coherent diffractive imaging (CDI) has been widely applied in the physical and biological sciences using synchrotron radiation, XFELs, high harmonic generation, electrons and optical lasers. One of CDI's important applications is to probe dynamic phenomena with high spatio-temporal resolution. Here, we report the development of a general in situ CDI method for real-time imaging of dynamic processes in solution. By introducing a time-invariant overlapping region as a real-space constraint, we show that in situ CDI can simultaneously reconstruct a time series of the complex exit wave of dynamic processes with robust and fast convergence. We validate this method using numerical simulations with coherent X-rays and performing experiments on a materials science and a biological specimen in solution with an optical laser. Our numerical simulations further indicate that in situ CDI can potentially reduce the radiation dose by more than an order of magnitude relative to conventional CDI. As coherent X-rays are under rapid development worldwide, we expect in situ CDI could be applied to probe dynamic phenomena ranging from electrochemistry, structural phase transitions, charge transfer, transport, crystal nucleation, melting and fluid dynamics to biological imaging.Comment: 19 pages, 5 figure

Brain-Mimetic Hydrogel Platform for Investigation of Glioblastoma Drug Resistance

Glioblastoma (GBM) is the most lethal and malignant cancer originating from the central nervous system. Even with intense treatment involving surgery and radio-chemotherapy, median survival after prognosis remains within 12 months, as GBM constantly develops resistance to common therapies. Many novel therapies developed for GBM have shown promising results in in-vitro studies, but unfortunately failed in actual clinical practices, partially because traditional model systems failed to recapitulate the microenvironment surrounding GBM tumors. Therefore, we posit that unique brain extracellular matrix (ECM) facilitates therapeutic resistance in GBM. To study this problem, we investigated ECM deposition in GBM patient samples and fabricated brain-mimetic, orthogonally tunable hydrogel system in which to culture patient-derived GBM cells in 3-dimensional manner. To validate our novel ex-vivo culture system, genomic sequencing and gene expression profiling were performed for comparison with traditional in-vitro culture and animal xenograft models. At the same time, cell viability, proliferation and markers for cancer stem cell were assessed. Our model system was used to study the therapeutic response of GBM cells to commonly used therapeutics and to investigate resistance mechanisms. We found GBM cells displayed drug response kinetics comparable to in-vivo xenograft models. We also found novel molecular mechanisms describing how unique brain matrix facilitates therapeutic resistance through corresponding receptors in our 3D culture models. By utilizing novel engineered platforms to study drug resistance, we are able to uncover mechanisms that could not be observed through traditional methods

Brain-Mimetic Hydrogel Platform for Investigation of Glioblastoma Drug Resistance

Glioblastoma (GBM) is the most lethal and malignant cancer originating from the central nervous system. Even with intense treatment involving surgery and radio-chemotherapy, median survival after prognosis remains within 12 months, as GBM constantly develops resistance to common therapies. Many novel therapies developed for GBM have shown promising results in in-vitro studies, but unfortunately failed in actual clinical practices, partially because traditional model systems failed to recapitulate the microenvironment surrounding GBM tumors. Therefore, we posit that unique brain extracellular matrix (ECM) facilitates therapeutic resistance in GBM. To study this problem, we investigated ECM deposition in GBM patient samples and fabricated brain-mimetic, orthogonally tunable hydrogel system in which to culture patient-derived GBM cells in 3-dimensional manner. To validate our novel ex-vivo culture system, genomic sequencing and gene expression profiling were performed for comparison with traditional in-vitro culture and animal xenograft models. At the same time, cell viability, proliferation and markers for cancer stem cell were assessed. Our model system was used to study the therapeutic response of GBM cells to commonly used therapeutics and to investigate resistance mechanisms. We found GBM cells displayed drug response kinetics comparable to in-vivo xenograft models. We also found novel molecular mechanisms describing how unique brain matrix facilitates therapeutic resistance through corresponding receptors in our 3D culture models. By utilizing novel engineered platforms to study drug resistance, we are able to uncover mechanisms that could not be observed through traditional methods

Integrating the glioblastoma microenvironment into engineered experimental models.

Glioblastoma (GBM) is the most lethal cancer originating in the brain. Its high mortality rate has been attributed to therapeutic resistance and rapid, diffuse invasion - both of which are strongly influenced by the unique microenvironment. Thus, there is a need to develop new models that mimic individual microenvironmental features and are able to provide clinically relevant data. Current understanding of the effects of the microenvironment on GBM progression, established experimental models of GBM and recent developments using bioengineered microenvironments as ex vivo experimental platforms that mimic the biochemical and physical properties of GBM tumors are discussed