Mechanical Strain Regulates Osteoblast Proliferation Through Ca^(2+)-CaMK-CREB Signal Pathway

Objective To investigate the effects of mechanical strain on Ca^(2+)-calmodulin dependent kinase(CaMK)-cA MP response element binding protein(CREB) signal pathway and proliferation of osteoblasts. Methods Using a four-point bending device, MC3T3-E1 cells were exposed to mechanical tensile strains of 2500 μs and 5000 μs at 0.5 Hz respectively. The intracellular free Ca^(2+)([Ca^(2+)]i) concentration and calmodulin activity were assayed by fluorospectrophotometry, CaMK II β, CREB, and phosphorylated(activated) CREB(p-CREB) were assessed by Western blot, and cells proliferation was assayed with MTT. Pretreatment with verapamil was carried out to block Ca^(2+) channel, and inhibitor U73122 was used to inhibit phospholipase C(PLC). Results Mechanical strains of 2500 μs and 5000 μs for 1 to 10 minutes both increased [Ca^(2+)]i level of the cells. The 2500 μs strain, a periodicity of 1 h/d for 3 days, activated calmodulin, elevated protein levels of CaMK II β and p-CREB, and promoted cells proliferation, which were attenuated by pretreatment of verapamil or U73122. The effects of 5000 μs strain on calmodulin, CaMK II β, p-CREB and proliferation were contrary to 2500 μs strain. Conclusion The mechanical strain regulates osteoblasts proliferation through Ca^(2+)-Ca MK-CREB signal pathway via Ca^(2+) channel and PLC/IP_3 transduction cascades.

Liquid Crystal Biosensor Based on Cd²⁺Inducing the Bending of PS-Oligo for the Detection of Cadmium

In this study, a novel liquid crystal (LC) biosensor was developed for the highly sensitive and selective detection of Cd2+ based on Cd2+ inducing the bending of PS-oligo. This strategy makes use of the DNA conformational change to enhance the disruption of orientation of LC leading to an amplified optical signal. DNA containing-SH was bound on the glass slide of the LC cell modified with the DMOAP/APTES. The DMOAP can effectively induce the homeotropic alignment of LC. In the presence of Cd2+, Cd2+ can induce DNA to bend and become a 2 nm spherical structure, which can greatly disrupt the orientational arrangement of LC, resulting in the correspond changes of the optical image of LC cell birefringent under the polarizing microscope. When the Cd2+ concentration is low to 0.1 nM, the optical signal of LC biosensor has an obvious change. But in the absence of Cd2+, there is no orientational response of LC and the optical image under the polarizing microscope is still a uniform dark background. Thus, this LC sensing method has a sensitive and clear distinction between positive and negative results and offers a highly sensitive detection of Cd2+ with a low detection limit down to 0.1 nM.

Colorimetric Detection of Lead Ion Based on Gold Nanoparticles and Lead-Stabilized G-Quartet Formation

In this report, we present a method for the detection of Pb2+ based on the different adsorption capacity on the surface of gold nanoparticles (AuNPs) between ssDNA (single-stranded DNA) and G-quartet. In the absence of Pb2+, the DNA oligonucleotides probe, which is guanine-rich ssDNA, can be adsorbed on the surface of AuNPs protecting them from aggregation. After adding Pb2+, the DNA oligonucleotides probe can specifically form compact G-quartet, which can induce the aggregation of unmodified AuNPs, especially after adding NaCl aqueous solution. Consequently, the color turns from red to blue. Pb2+ can be detected by colorimetric response of AuNPs;its detection limit can reach 5 μM only observed by naked eyes. Most metal ions have no interferences, and the interference of Cu2+ can be effectively eliminated by adding cysteine. It provides a simple and effective colorimetric sensor for on-site and real time detection of Pb2+.