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The response of mesenchymal stem cell (MSCs) to elaborate microarchitectured topographies in three-dimensional environment and the underlying molecular mechanism remain poorly understood. Here, with hierarchical mesoporous bioactive glass (MBG) scaffolds as substrate model, we show the effects of specific, elaborate microtextured topographies (micrograiny, microporous and hybrid micrograiny/microporous surface) on MSCs osteogenesis and the molecular mechanism involved. With a similar size and density, the microporous surface was more favorable for the MSC osteogenesis, and the hybrid micrograiny/microporous surface exhibited a synergetic effect. All the microscaled topographies facilitated expression of integrin subunits, focal adhesion complexes, and up-regulated FAK/MAPK and ILK/β-catenin signaling pathways. Separately blocking FAK/MAPK and ILK/β-catenin cascade dramatically attenuated the heightened β-catenin signaling, and the phosphorylation of ERK1/2 and P38, respectively, indicating a typical crosstalk between FAK/MAPK and ILK/β-catenin signalings was involved. Correlating the MSCs response with the specific topographical cues, it can be inferred that the micrograiny/microporous topographies induced FAs assembly and homeostasis, and thus FAK/MAPK and ILK/β-catenin signalings played critical role in regulating MSCs osteogenic differentiation. The findings, therefore, have significant implications in better understanding of the MSCs fate in a 3D environment and provided guidance of the development of novel biomaterial for bone regeneration.

The ability to detect nanoscale objects is particular crucial for a wide range of applications, such as environmental protection, early-stage disease diagnosis and drug discovery. Photonic crystal nanobeam cavity (PCNC) sensors have attracted great attention due to high-quality factors and small-mode volumes (Q/V) and good on-chip integrability with optical waveguides/circuits. In this review, we focus on nanoscale optical sensing based on PCNC sensors, including ultrahigh figure of merit (FOM) sensing, single nanoparticle trapping, label-free molecule detection and an integrated sensor array for multiplexed sensing. We believe that the PCNC sensors featuring ultracompact footprint, high monolithic integration capability, fast response and ultrahigh sensitivity sensing ability, etc., will provide a promising platform for further developing lab-on-a-chip devices for biosensing and other functionalities.Micromachines 2020, 11, 72 2 of 20 microcavities confine the light in a small volume, leading to significant enhancement of light-matter interaction, resulting in ultra-high sensitivity (S) and a low detection limit. When subject to slight environmental changes, the spectral properties change can be obtained, e.g., resonator wavelength shift [20][21][22] and mode broadening [23].The main types of optical microcavities include whispering gallery mode (WGM) cavities, Fabry-Perot (F-P) cavities and photonic crystal (PhC) cavities [24]. Among these, PhC cavities have been investigated as advantageous platforms due to their ultra-high Q/V enabling the enhancement of lightmatter interactions. Particularly, compared with two-dimensional (2D) PhC cavities, one-dimensional photonic crystal nanobeam cavities (1D-PCNCs) attract great attention for their ultra-sensitive optical sensing and lab-on-a-chip applications, owing to their ultra-compact size, ultra-small mode volume, high integrability with bus-waveguide and excellent complementary metal-oxide-semiconductor (CMOS) compatible properties [25][26][27][28][29][30][31][32][33].In this review, we will focus on nanoscale optical sensing based on 1D-PCNCs. The structure of the review is organized as follows. A comprehensive overview about basic properties and sensing mechanisms of 1D-PCNCs sensors is discussed in Section 2. In Section 3, firstly, we introduce the efforts to pursue ultra-high figure of merit (FOM) in refractive index (RI) sensing based on 1D-PCNCs. Secondly, we outline the applications of 1D-PCNC sensors on single nanoparticle and label-free molecule (viruses, proteins and DNAs) detection. Thirdly, a monolithic integrated 1D-PCNC sensor array for multiplexed sensing is introduced explicitly. In addition, we present other sensing applications of 1D-PCNC sensors such as temperature sensing and optomechanical sensing, etc. Next, we review the nanofabrication and coupling techniques in the development of 1D-PCNC sensors in Section 4. Finally, we draw a brief conclusion. Figure 2. (a) Schematic of photonic circuits. The green lines, red boxes and black boxes represe...

Optical microcavities have become an attractive platform for precision measurement with merits of ultrahigh sensitivity, miniature footprint and fast response. Despite the achievements of ultrasensitive detection, optical microcavities still face significant challenges in the measurement of biochemical and physical processes with complex dynamics, especially when multiple effects are present. Here we demonstrate operando monitoring of the transition dynamics of a phase-change material via a self-referencing optofluidic microcavity. We use a pair of cavity modes to precisely decouple the refractive index and temperature information of the analyte during the phase-transition process. Through real-time measurements, we reveal the detailed hysteresis behaviors of refractive index during the irreversible phase transitions between hydrophilic and hydrophobic states. We further extract the phase-transition threshold by analyzing the steady-state refractive index change at various power levels. Our technology could be further extended to other materials and provide great opportunities for exploring on-demand dynamic biochemical processes.