Plasmonic nanoparticles embedded in single crystals synthesized by gold ion implantation for enhanced optical nonlinearity and efficient Q-switched lasing.

We report on the synthesis of embedded gold (Au) nanoparticles (NPs) in Nd:YAG single crystals using ion implantation and subsequent thermal annealing. Both linear and nonlinear absorption of the Nd:YAG crystals have been enhanced significantly due to the embedded Au NPs, which is induced by the surface plasmon resonance (SPR) effect in the visible light wavelength band. Particularly, through a typical Z-scan system excited by a femtosecond laser at 515 nm within the SPR band, the nonlinear absorption coefficients of crystals with Au NPs have been observed to be nearly 5 orders of magnitude larger than that without Au NPs. This giant enhancement of nonlinear absorption properties is correlated with the saturable absorption (SA) effect, which is the basis of passive Q-switching or mode-locking for pulsed laser generation. In addition, the linear and nonlinear absorption enhancement could be tailored by varying the fluence of implanted Au+ ions, corresponding to the NP size and concentration modulation. Finally, the Nd:YAG wafer with embedded Au NPs has been applied as a saturable absorber in a Pr:LuLiF4 crystal laser cavity, and efficient pulsed laser generation at 639 nm has been realized, which presents superior performance to the MoS2 saturable absorber based system. This work opens an avenue to enhance and modulate the nonlinearities of dielectrics by embedding plasmonic Au NPs for efficient pulsed laser operation.

Combinations of retinoic acid with either sodium butyrate, dimethyl sulfoxide, or hexamethylene bisacetamide synergistically induce differentiation of the human myeloid leukemia cell line HL60.

All-trans-retinoic acid (RA), sodium n-butyrate (NaB), hexamethylene bisacetamide (HMBA), and dimethyl sulfoxide (DMSO) induce differentiation of the human acute myeloid leukemia cell line HL60. In the clinic, RA, NaB, or HMBA induce complete or partial remissions. However, the achievement and maintenance of effective plasma concentrations and toxicity have been problems. These difficulties led us to study the interaction of RA with these inducers. We found that combinations of RA with either NaB, HMBA, or DMSO synergistically induced terminal differentiation of HL60. A measure of the effectiveness of these combinations was that the doses of NaB, HMBA, and DMSO required alone to induce half-maximal differentiation were decreased about 4-fold in combination with normal plasma concentrations of about 30 nM RA. RA or NaB alone did not enhance the growth of HL60 cells. In contrast, HMBA or DMSO alone increased growth of HL60 cells even at concentrations that did not induce differentiation. The addition of RA reduced the promotion of growth and increased the extent of terminal differentiation seen with HMBA and DMSO alone. These data suggest that treatment of some malignancies with combinations of RA with HMBA or NaB may maintain differentiation-inducing effects and decrease the problems associated with the achievement and maintenance of effective plasma concentrations as single agents.

Retinoic acid inhibits sodium butyrate-induced monocytic differentiation of HL60 cells while synergistically inducing granulocytoid differentiation.

The human myeloid leukemia cell line HL60 is an in vitro model to study myeloid differentiation. HL60 cells differentiate along different cell type lineages in response to a variety of compounds. The direction of differentiation is usually inducer-specific. However, the response of HL60 cells to sodium n-butyrate (NaB) is pleiotropic. NaB induces HL60 along the monocytic, neutrophilic, eosinophilic, and basophilic pathways. In this study we saw that physiologic concentrations of all-trans-retinoic acid (RA) switched the direction of NaB-induced differentiation from monocytic to granulocytic. We showed previously (Breitman & He, Cancer Res 1990: 50: 6268-6273) that combinations of RA and NaB synergistically induce HL60 to cells that reduce nitroblue tetrazolium. The present study shows that this synergy was even greater if the parameter measured was mature granulocytes. Our results raise the possibility that the endogenous RA in the serum used to grow cells in culture may affect the direction of differentiation of HL60 cells induced by NaB. Furthermore, our results may provide additional rationale for the use of combinations of RA and NaB in the treatment of some leukemias.