Manipulation of up-conversion emission in NaYF4 core@shell nanoparticles doped by Er3+, Tm3+, or Yb3+ ions by excitation wavelength-three ions-plenty of possibilities

Nanoparticles (NPs) based on host compound NaYF₄ with core@shell structures were synthesised by the precipitation reaction in high-boiling point octadecene/oleic acid solvent. Four laser wavelengths were used (808, 975, 1208, or 1532 nm) for excitation of the obtained NPs. The resulting emission and mechanisms responsible for spectroscopic properties were studied in detail. Depending on NP compositions, i.e. type of doping ion (Er³⁺, Tm³⁺, or Yb³⁺) or presence of dopants in the same or different phases, adjustable up-conversion (UC) could be obtained with emission peaks covering the visible to near-infrared range (475 to 1625 nm). The presented results demonstrated multifunctionality of the prepared NPs. NaYF₄:2%Tm³⁺@NaYF₄ NPs exhibited emission at 700 and 1450 nm under 808 nm laser excitation or 800 and 1625 nm emission under 1208 nm laser radiation, as a result of ground- and excited-state absorption processes (GSA and ESA, respectively). However, NaYF₄:5%Er³⁺,2%Tm³⁺@NaYF₄ NPs showed the most interesting properties, as they can convert all studied laser wavelengths due to the absorption of Tm³⁺ (808, 1208 nm) or Er³⁺ ions (808, 975, 1532 nm), revealing a photon avalanche process under 1208 nm laser excitation, as well as GSA and ESA at other excitation wavelengths. The NaYF₄:2%Tm³⁺@NaYF₄:5%Er³⁺ NPs revealed the resultant emission properties, as the dopant ions were separated within core and shell phases. The NaYF₄:18%Yb³⁺,2%Tm³⁺@NaYF₄ and NaYF₄:18%Yb³⁺,2%Tm³⁺@NaYF₄:5%Er³⁺ samples showed the brightest emission, around 800 nm, under 975 nm excitation, though other laser wavelengths allowed for observation of luminescence, as well, especially in NPs with Er³⁺ in the outer shell, capable of UC under 1532 nm. The presented results highlight the unique and universal properties of lanthanide ions for designing luminescent NPs for a variety of potential applications, such as confocal microscopy.

Photodynamic effect of glycochlorin conjugates in human cancer epithelial cells

The effect of glycochlorins in HeLa cells shows that the galactose conjugate is the most efficient photosensitizer.

Gold nanorod assisted intracellular optical manipulation of silica microspheres

We report on the improvement of the infrared optical trapping efficiency of dielectric microspheres by the controlled adhesion of gold nanorods to their surface. When trapping wavelength was equal to the surface plasmon resonance wavelength of the gold nanorods (808 nm), a 7 times improvement in the optical force acting on the microspheres was obtained. Such a gold nanorod assisted enhancement of the optical trapping efficiency enabled the intracellular manipulation of the decorated dielectric microsphere by using a low power (22 mW) infrared optical trap.

A secretion of the mollusc Cryptomphalus aspersa promotes proliferation, migration and survival of keratinocytes and dermal fibroblasts in vitro

Regenerative properties of skin decrease with age, and thus, the search for substances that minimize cutaneous ageing has increased in the last few years. The secretion of the mollusc Cryptomphalus Aspersa (SCA) is a natural product that bears regenerative properties when applied topically. The purpose of this work is to study the in vitro effects of SCA on cell proliferation and migration, as well as on cell-cell (E-cadherin and β-catenin) and cell-substrate (vinculin and β1-integrin) adhesion proteins expression, using a human keratinocyte cell line (HaCaT cells) and primary dermal fibroblasts (HF). We tested the effects of SCA on cell proliferation using a colorimetric assay. In addition, SCA-induced changes on cell migration were studied by wound-healing assays. Besides, Western blot and immunofluorescence microscopy were carried out to test the expression of different cell adhesion proteins. We found that SCA promotes proliferation and migration of HaCaT cells in a time- and dose-dependent manner. Moreover, treatment with SCA increases the migratory behaviour and the expression of adhesion molecules in both HaCaT and HF. Finally, SCA also improves cell survival and promotes phosphorylation of FAK and nuclear localization of β-catenin. These results shed light on the molecular mechanisms underlying the regenerative properties of SCA, based on its promoting effect on skin cell migration, proliferation and survival. Moreover, these results support future clinical uses of SCA in the regeneration of wounded tissues.

VLA-4-dependent myeloma cell adhesion

In multiple myeloma, the malignant plasma cells in the bone marrow attach to stromal elements using several adhesion receptors. The integrin VLA-4 plays a major role in mediating myeloma cell adhesion to the stroma, by interacting with its ligands VCAM-1 and fibronectin. VLA-4, as well as other integrins, can be expressed in different states of activation, which convey different levels of adhesion. Modulation of VLA-4 adhesive activity by external stimuli has been demonstrated for hematopoietic progenitor cells and lymphocytes, and can represent a potential mechanism contributing to the localization of myeloma cells in the bone marrow. In this review we have summarized data on the characterization of VLA-4-mediated myeloma cell adhesion, and we present potential mechanisms of modulation of VLA-4 activity. In addition, we also speculate on the signalling generated upon interaction of myeloma VLA-4 with its ligands on the survival of these cells in the bone marrow.

Chemokine stromal cell-derived factor-1alpha modulates VLA-4 integrin-dependent adhesion to fibronectin and VCAM-1 on bone marrow hematopoietic progenitor cells

Stromal cell-derived factor-1alpha (SDF-1alpha) is a potent chemoattractant for hematopoietic progenitor cells (HPC), suggesting that it could play an important role during their migration within or to the bone marrow (BM). The integrin VLA-4 mediates HPC adhesion to BM stroma by interacting with CS-1/fibronectin and VCAM-1. It is required during hematopoiesis and homing of HPC to the BM. As HPC migration in response to SDF-1alpha might require dynamic regulation of integrin function, we investigated if SDF-1alpha could modulate VLA-4 function on BM CD34(hi) cells.CD34(hi) BM cells and hematopoietic cell lines were tested for the effect of SDF-1alpha on VLA-4-dependent adhesion to CS-1/fibronectin and VCAM-1, as well as to BM stroma. CD34(hi) BM cells that adhered to VLA-4 ligands after SDF-1alpha treatment were characterized in colony-forming and long-term culture-initiating cell (LTC-IC) assays.SDF-1alpha rapidly (1 minute) and transiently upregulated the adhesion of CD34(hi) BM cells and hematopoietic cell lines to both CS-1/fibronectin and VCAM-1, and to BM stromal cells. The upregulation of VLA-4-dependent cell adhesion by SDF-1alpha targeted primitive LTC-IC as well as committed CD34(hi) cells. SDF-1alpha-triggered enhancement in VLA-4 function was inhibited by pertussis toxin (PTx) and cytochalasin D, indicating the involvement of G(i) protein downstream signaling and an intact cytoskeleton. Instead, activation of p44/42 MAP kinases by SDF-1alpha did not functionally correlate with enhancement of VLA-4-dependent cell adhesion. Modulation of VLA-4-mediated CD34(hi) BM cell adhesion by SDF-1alpha could play a key role in their migration within and to the BM and therefore influence their proliferation and differentiation.

Chemokine stromal cell-derived factor-1alpha modulates VLA-4 integrin-mediated multiple myeloma cell adhesion to CS-1/fibronectin and VCAM-1

The chemokine stromal cell-derived factor-1alpha (SDF-1alpha) and its G-protein-linked receptor CXCR4 are involved in hematopoietic progenitor cell and lymphocyte migration. The integrin VLA-4 is a cell adhesion receptor for CS-1/fibronectin and VCAM-1 and constitutes one of the main adhesion receptors mediating myeloma cell adhesion to bone marrow (BM) stroma in multiple myeloma (MM). It is shown here that MM CD38(hi)CD45RA(-) BM cells and myeloma-derived cell lines expressed CXCR4 and displayed a moderate chemotactic response to SDF-1alpha. Because cell migration in response to SDF-1alpha might require a dynamic regulation of integrin function, it was investigated whether SDF-1alpha can modulate VLA-4 function on myeloma cells. SDF-1alpha rapidly and transiently up-regulated VLA-4-mediated myeloma cell adhesion to both CS-1/fibronectin and VCAM-1, which was inhibited by pertussis toxin and cytochalasin D, indicating the involvement of G(i) protein downstream signaling and an intact cytoskeleton. Modulation of VLA-4-dependent myeloma cell adhesion by SDF-1alpha could contribute to the trafficking and localization of these cells in the BM microenvironment.

Maturation-dependent expression and function of the CD49d integrin on monocyte-derived human dendritic cells

Dendritic cells (DC) are highly specialized APC that are critical for the initiation of T cell-dependent immune responses. DC exert a sentinel function while immature and, after activation by inflammatory stimuli or infectious agents, mature and migrate into lymphoid organs to prime T cells. We have analyzed integrin expression on monocyte-derived DC (MDDC) and found that expression of CD49d integrins (CD49d/CD29 and CD49d/beta7) was induced/up-regulated during TNF-alpha- or LPS-initiated MDDC maturation, reflecting the induction/up-regulation of CD49d and beta7 mRNA. CD49d mRNA steady-state level increased more than 10 times during maturation, with the highest levels observed 24 h after TNF-alpha treatment. CD49d integrin expression conferred mature MDDC with an elevated capacity to adhere to the CS-1 fragment of fibronectin, and also mediated transendothelial migration of mature MDDC. Up-regulation of CD49d integrin expression closely paralleled that of the mature DC marker CD83. CD49d integrin expression was dependent on cell maturation, as its induction was abrogated by N:-acetylcysteine, which inhibits NF-kappaB activation and the functional and phenotypic maturation of MDDC. Moreover, CD49d integrin up-regulation and MDDC maturation were prevented by SB203580, a specific inhibitor of p38 mitogen-activated protein kinase, but were almost unaffected by the mitogen-activated protein/extracellular signal-related kinase kinase 1/2 inhibitor PD98059. Our results support the existence of a link between functional and phenotypic maturation of MDDC and CD49d integrin expression, thus establishing CD49d as a maturation marker for MDDC. The differential expression of CD49d on immature and mature MDDC might contribute to their distinct motility capabilities and mediate mature DC migration into lymphoid organs.

Characterization of VLA-4-dependent myeloma cell adhesion to fibronectin and VCAM-1

The integrin VLA-4 mediates attachment of myeloma cells to multiple myeloma (MM) bone marrow stroma. The alternatively-spliced CS-1 region of fibronectin (FN) and VCAM-1 are main ligands for VLA-4 and are both expressed on MM stroma. The H1 region is present in all FN isoforms and represents an additional binding site for VLA-4. We employed FN fragments FN-H89 and FN-H0, that contain either the CS-1 and H1, or only the H1 sites, respectively, as well as soluble VCAM-1 (sVCAM-1), to characterize VLA-4-mediated adhesion pathways used by myeloma cells to attach to MM stroma. CD38highCD45RA- cells from MM bone marrow, and the myeloma-derived cell lines NCI-H929, IM-9 and RPMI 8226, specifically adhered, by different degrees, to FN-H89, FN-H0 and sVCAM-1, and their VLA-4-dependent adhesion was substantially up-regulated by the anti-beta1 antibody TS2/16, which increases the affinity of VLA-beta1 integrins. Furthermore, VLA-4 function on NCI-H929 cells was enhanced by TS2/16 during adhesion to MM stroma. The alpha4beta7 integrin mediated a small portion of myeloma cell line adhesion to FN-H89, mainly upon integrin activation with Mn2+. These results indicate that myeloma cells use VLA-4 to interact with CS-1/FN, H1/FN and VCAM-1 on MM stroma, and that its function can be potentially up-regulated, enabling higher degrees of cell adhesion to these VLA-4 ligands, which might influence myeloma cell localization in the bone marrow.