Optimization of long-period grating-based refractive index sensor by bent-fiber interference.

In this paper, we propose and demonstrate a novel approach to enhance the refractive index (RI) sensitivity and eliminate the temperature cross-sensitivity of a long-period grating (LPG) -based refractive index sensor by bent-fiber interference. The approach is based on a hybrid structure composed of an LPG and a bent-fiber intermodal interferometer. The bent-fiber intermodal interferometer has a simple structure, which consists of a bare fiber semi-circular bending region with a 5 mm bending radius. As the RI increases, the resonance wavelength of the LPG moves toward a shorter wavelength, while the resonance wavelength of the bent-fiber intermodal interferometer shifts to a longer wavelength. The separation of two resonance dips increases with the RI; using two resonance dips allows us to measure an RI with a higher sensitivity than if we had only used one resonance dip. However, as the temperature increases, the separation of the two resonance dips is constant. This approach can effectively enhance the RI sensitivity and eliminate temperature cross-sensitivity.

Extraordinary optical properties in the subwavelength metallodielectric free-standing grating.

In this paper, we present a free-standing metallodielectric grating structure that can achieve multiple transmission dips and peaks at normal incidence over the visible spectrum. The amount of dips and peaks can be adjusted by the thickness of dielectric film. In our proposed structure, there are three types of resonance modes supported: Surface plasmon polarition (SPP) at horizontal metal/dielectric interface, vertical cavity mode in the metal slits, and guide mode in the dielectric film. Physically the coupling and resonant interactions among these modes lead to the generation of dips and peaks in the transmission spectrum. The transmission peaks is further interpreted by using Fano resonance. More surprisingly, the simultaneous excitation of three types of resonance modes can enhance the field distribution, which results in unexpected nearly perfect absorption in such simple structure. Moreover, compared to other absorption peaks, this high absorption peak originates from that guide mode resonance in the dielectric film inhibits transmission induced by cavity mode resonance in the metal slits. These results can be used in the design of many photonics components.

Layer-by-layer films with bioreducible and nonbioreducible polycations for sequential DNA release.

Layer-by-layer (LbL) films containing cationic polyelectrolytes and anionic bioactive molecules such as DNA are promising biomaterials for controlled and localized gene delivery for a number of biomedical applications including cancer DNA vaccine delivery. Bioreducible LbL films made of disulfide-containing poly(amido amine)s (PAAs) and plasmid DNA can be degraded by redox-active membrane proteins through the thiol-disulfide exchange reaction to release DNA exclusively into the extracellular microenvironment adjacent to the film. In order to better understand the film degradation mechanism and nature of the released species, the bioreducible film degradation is studied by atomic force microscopy, fluorescence, and dynamic light scattering in solutions containing a reducing agent. The PAA/DNA LbL film undergoes fast bulk degradation with micrometer-sized pieces breaking off from the substrate. This bulk degradation behavior is arrested by periodic insertions of a nonbioreducible poly(ethylenimine) (PEI) layer. The LbL films containing PAA/DNA and PEI/DNA bilayers display sequential film disassembly and are capable of continuously releasing DNA nanoparticles over a prolonged time. Insertion of the PEI layer enables the bioreducible LbL films to transfect human embryonic kidney 293 cells. The data conclude that the PEI layer is effective as a barrier layer against interlayer diffusion during LbL film assembly and more importantly during film disassembly. Without the barrier layer, the high mobility of cleaved PAA fragments is responsible for bulk degradation of bioreducible LbL films, which may prevent their ultimate gene-delivery applications. This work establishes a direct link among film internal structure, disassembly mechanism, and transfection efficiency. It provides a simple method to design bioreducible LbL films for sequential and long-time DNA release.

The mechanisms of rectification in Au|molecule|Au devices based on Langmuir-Blodgett monolayers of iron(III) and copper(II) surfactants.

Langmuir-Blodgett films of metallosurfactants were used in Au|molecule|Au devices to investigate the mechanisms of current rectification.

A Long-Acting Curcumin Nanoparticle/In Situ Hydrogel Composite for the Treatment of Uveal Melanoma.

Uveal melanoma (UM) is the most common primary intraocular tumor in adults with high mortality. In order to improve prognosis and survival of UM patients, it is critical to inhibit tumor progression and metastasis as early as possible after the initial presentation/diagnosis of the disease. Sustained local delivery of antitumor therapeutics in the posterior region can potentially achieve long-term UM inhibition, improve target therapeutic delivery to the posterior segments, as well as reduce injection frequency and hence improved patient compliance. To address the highly unmet medical need in UM therapy, a bioinspired in situ gelling hydrogel system composed of naturally occurring biopolymers collagen and hyaluronic acid was developed in the present research. Curcumin with anti-cancer progression, anti-metastasis effects, and good ocular safety was chosen as the model therapeutic. The developed in situ gelling delivery system gelled at 37 °C within two minutes and demonstrated excellent biocompatibility and slow degradation. The curcumin-loaded nanoparticle/hydrogel composite was able to sustain release payload for up to four weeks. The optimized nanoparticle/hydrogel composite showed effective inhibition of human UM cell proliferation. This novel nanoparticle/in situ hydrogel composite demonstrated a great potential for the treatment of the rare and devastating intraocular cancer.

Efficient inhibition of uveal melanoma via ternary siRNA complexes.

Uveal melanoma (UM) is rare yet the most common and malignant primary intraocular tumor in adults. Due to the lack of effective treatment, the mortality rate of UM has remained high over the past few decades. In the present study, hyaluronic acid (HA) coated chitosan (Chi)/siRNA ternary complexes have been developed and characterized as a novel therapeutic strategy molecularly targeting hypoxia-inducible factor 1α (HIF-1α) pathway for the treatment of UM. The cytotoxicity, cellular uptake, and siRNA silencing effect of the developed siRNA complexes were evaluated. In addition, whether the developed ternary complexes can inhibit UM migration and invasion was investigated. Results showed that the developed ternary siRNA complexes were negatively charged and with a particle size below 190 nm. The ternary siRNA complexes showed excellent cellular uptake and lysosome escape ability with low cytotoxicity. In addition, the ternary complexes were able to downregulate both HIF-1α and VEGF expression in UM cells, and successfully inhibit UM migration and invasion. These results demonstrated that the biocompatible ternary siRNA complexes are promising for local treatment of UM in the posterior segment with future clinical application potential.

A tunable extruded 3D printing platform using thermo-sensitive pastes.

Extruded 3D printing is emerging as an attractive fabrication technology in the field of personalized oral medicines. The objective of this study was to develop a tunable extruded 3D printing platform based on thermo-sensitive gelatin pastes to meet the needs of achieving different drug release characteristics with flexible dosing and design. The printability and mechanisms of extrusion and deposition of the gelatin pastes were systematically studied. Ibuprofen and diclofenac sodium were used as model drugs for immediate- and sustained-release formulations, respectively. Following the optimization of formulation and process parameters, ibuprofen immediate-release formulations with different designs, and reservoir-type diclofenac sodium sustained-release formulations were printed. Target drug release patterns were successfully obtained for both model drugs. Rheological studies revealed that additives such as microcrystalline cellulose and hydroxypropyl methylcellulose can act as both thickeners and proppants of gelatin matrix. Furthermore, computational fluid dynamics simulation was used to visualize the printing process, and quantitatively analyze the influence of material viscosity, inlet velocity and nozzle diameter on the pressure and velocity of extrusion flow field. The present study demonstrated the great potential of extruded 3D printing technology using the thermo-sensitive gelatin paste platform for personalized oral medicines.

Layer-By-Layer Film Engineering for Sequential Gene Delivery.

Layer-by-layer (LbL) films are assembled with poly(amido amine)s (PAAs), a type of polycations containing bioreducible disulfide bond, and DNA plasmids to enable LbL film degradation in physiologic conditions by reacting with glutathione or redox-active membrane proteins. The interior layer structure of the LbL films during assembly and disassembly is studied by atomic force microscopy (AFM), ellipsometry, dynamic light scattering (DLS), and fluorescence spectroscopy. Insertion of barrier layers in bioreducible LbL films is necessary to stabilize the interior layer structure and slow down the film degradation rate to achieve sequential gene delivery. Localized gene delivery from the LbL films is demonstrated using human embryonic kidney 293 (HEK 293) cells.

In Situ AFM Analysis Investigating Disassembly of DNA Nanoparticles and Nanofilms.

Synthetic vector-based gene delivery continues to gain strength as viable alternatives to viral vectors due to safety and other concerns. DNA release dynamics is key to the understanding and control of gene delivery from nanosystems. Here we describe atomic force microscope (AFM) application to the understanding of DNA release dynamics from bioreducible polycation-based nanosystems. The two nanosystems are polyplex nanoparticles and layer-by-layer (LbL) films.

Layer-by-layer DNA films incorporating highly transfecting bioreducible poly(amido amine) and polyethylenimine for sequential gene delivery.

BACKGROUND: The layer-by-layer (LbL) assembly method offers a molecular level control of the amount and spatial distribution of bioactive molecules. However, successful clinical translation of LbL film technology will most certainly require a better understanding and control of not only the film assembly process, but also film disassembly kinetics in physiologic conditions. PURPOSE: This work focuses on the understanding and control of degradation properties of LbL films for localized gene delivery. METHODS: Bioreducible poly(amido amine)s (PAAs) containing cystaminebisacrylamide (CBA), methylenebisacrylamide, and 5-amino-1-pentanol (APOL) were synthesized by Michael addition polymerization for the construction of bioreducible LbL films capable of sequential gene delivery. RESULTS: The synthesized PAAs were screened for desirable buffering capacity, cell transfection, and cytotoxicity characteristics together with 25 kDa branched polyethylenimine (PEI) and cross-linked 800 Da PEI. By screening the various polycations we were able to identify a copolymer of CBA and APOL for the subsequent construction of the LbL films. By incorporating a highly transfecting polycation and a nondiffusing polycation we were able to improve the overall transfection of HEK293 and MC3T3 cells from the bioreducible LbL films. We also demonstrated the dual-stage release and transfection of two different DNAs from the LbL films. CONCLUSION: The results indicate that LbL films consisting of bioreducible PAAs and non-diffusing polyelectrolytes have excellent degradation properties for the development of LbL coating technology for localized gene delivery applications.

Observation of current rectification by the new bimetallic iron(iii) hydrophobe [Fe(LN4O6)] on Au|LB-molecule|Au devices.

Targeting the development of stimulus-responsive molecular materials with electronic functionality, we have synthesized and studied the redox and electronic properties of a new bimetallic iron hydrophobe [FeIII2(LN4O6)] (1). The new H6LN4O6 ligand displays bicompartmental topology capable of accomodating two five-coordinate HSFeIII ions bridged by tetraaminobenzene at a close distance of ca. 8 Å. We show that the metal-based reduction processes in (1) proceed sequentially, as observed for electronically coupled metal centers. This species forms a well-defined Pockels-Langmuir film at the air-water interface, with collapse pressure of 32 mN m-1. Langmuir-Blodgett monolayers were deposited on gold substrates and used to investigate current-voltage (I-V) measurements. This unprecedented bimetallic hydrophobe [FeIII2(LN4O6)] (1) shows unquestionable molecular rectification and displays a rectification ratio RR between 2 and 15.

Hyaluronic acid-conjugated polyamidoamine dendrimers for targeted delivery of 3,4-difluorobenzylidene curcumin to CD44 overexpressing pancreatic cancer cells.

The current study was aimed to develop a targeted dendrimer formulation of 3, 4-difluorobenzylidene curcumin (CDF) and evaluate its potential in CD44 targeted therapy for pancreatic cancer. Using amine terminated fourth generation poly(amidoamine) (PAMAM) dendrimer nanocarrier and hyaluronic acid (HA) as a targeting ligand, we engineered a CD44-targeted PAMAM dendrimer (HA-PAMAM) formulation of CDF. The resulting dendrimer nanosystem (HA-PAMAM-CDF) had a particle size and surface charge of 9.3 ± 1.5 nm and -7.02 ± 9.53 mV, respectively. When CD44 receptor overexpressing MiaPaCa-2 and AsPC-1 human pancreatic cancer cells were treated with HA-PAMAM-CDF, a dose-dependent cytotoxicity was observed. Furthermore, blocking the CD44 receptors present on the MiaPaCa-2 cells using free excess soluble HA prior to treatment with HA-PAMAM-CDF nano-formulation resulted in 1.71 fold increase in the IC50 value compared to non-targeted formulation (PAMAM-CDF), confirming target specificity of HA-PAMAM-CDF. Additionally, HA-PAMAM-CDF formulation when compared to PAMAM-CDF, displayed higher cellular uptake in MiaPaCa-2 cancer cell lines as shown by fluorescence studies. In summary, the novel CD44 targeted dendrimer based nanocarriers appear to be proficient in mediating site-specific delivery of CDF via CD44 receptors, with an improved therapeutic margin and safety.