Monodisperse gelatin microspheres as a drug delivery vehicle: release profile and effect of crosslinking density

Uniform gelatin microspheres (GMS) of a wet size of 100 microm in diameter were fabricated by the electric field assisted precision particle fabrication (E-PPF) method and crosslinked with different glutaraldehyde (GA) concentrations to study the effect of the crosslinking density on drug release. The drug release profiles of the crosslinked GMS were studied along with the intraparticle drug distribution and the particle degradation characteristics. Due to the concentration gradient of GA along the diffusion path into the GMS, the crosslinking density is higher on the GMS surface, making it less susceptible to degradation. As a result, the GMS with higher GA concentrations (0.375-0.875%) exhibited a highly resistant surface toward enzymatic degradation. On the other hand, the amount of drug complexation at the surface decreases as the GA concentration increases, which can be attributed to the lowered basicity of gelatin caused by the increased crosslinking density. These factors collectively affect the drug release kinetics and give rise to similar release profiles for GMS above a GA concentration of 0.375%.     

Biodegradable Inorganic Nanovector: Passive versus Active Tumor Targeting in siRNA Transportation

The biodegradable inorganic nanovector based on a layered double hydroxide (LDH) holds great promise for gene and drug delivery systems. However, in vivo targeted delivery of genes through LDH still remains a key challenge in the development of RNA interference therapeutics. Here, we describe in vivo and in vitro delivery system for Survivin siRNA (siSurvivin) assembled with passive LDH with a particle size of 100 nm or active LDH conjugated with a cancer overexpressing receptor targeting ligand, folic acid (LDHFA), conferring them an ability to target the tumor by either EPR‐based clathrin‐mediated or folate receptor‐mediated endocytosis. When not only transfected into KB cells but also injected into xenograft mice, LDHFA/siSurvivin induced potent gene silencing at mRNA and protein levels in vitro, and consequently achieved a 3.0‐fold higher suppression of tumor volume than LDH/siSurvivin in vivo. This anti‐tumor effect was attributed to a selectively 1.2‐fold higher accumulation of siSurvivin in tumor tissue compared with other organs. Targeting to the tumor with inorganic nanovector can guide and accelerate an evolution of next‐generation theranosis system.     

Transition metal oxides as hole-transporting materials in organic semiconductor and hybrid perovskite based solar cells

Organic polymer solar cells (OSCs) and organic-inorganic hybrid perovskite solar cells (PSCs) have achieved notable progress over the past several years. A central topic in these fields is exploring electronically efficient, stable and effective hole-transporting layer (HTL) materials. The goal is to enhance hole-collection ability, reduce charge recombination, increase built-in voltage, and hence improve the performance as well as the device stability. Transition metal oxides (TMOs) semiconductors such as NiO _x , CuO _x , CrO _x , MoO _x , WO₃, and V₂O₅, have been widely used as HTLs in OSCs. These TMOs are naturally adopted into PSC as HTLs and shows their importance. There are similarities, and also differences in applying TMOs in these two types of main solution processed solar cells. This concise review is on the recent developments of transition metal oxide HTL in OSCs and PSCs. The paper starts from the discussion of the cation valence and electronic structure of the transition metal oxide materials, followed by analyzing the structure-property relationships of these HTLs, which we attempt to give a systematic introduction about the influences of their cation valence, electronic structure, work function and film property on device performance.     

Preparation of Polyester Polyol from Epoxidized Palm Olein

In this work, polyester polyols with high weight average molecular weight (M_w) (M_w?10000–15000) were prepared from epoxidized palm olein (EPO_o) and a series of dicarboxylic acids (C₆–C₁₂) at elevated temperature under non‐catalyzed condition. The optimal reaction conditions were determined as 180°C for 4 h. Longer carbon chain length of dicarboxylic acids was more reactive when reacted with EPO_o. The physical appearance of the product was observed as liquid at room temperature. This palm oil‐based polyester polyol is proposed as starting material for flexible polyurethane. For reaction monitoring purposes, FTIR was used while ¹H NMR analysis was carried out to characterize the important functional groups of the products. The effects of reaction time and temperature on the M_w of the reaction mixture were also studied by GPC.     

Palladium-catalyzed direct and regioselective C-H bond functionalization/oxidative acetoxylation of indoles

The first general examples of palladium-catalyzed direct and selective oxidative C3-acetoxylation of indoles are presented. The mild reaction conditions (70 °C and with weak base, KOAc) in this indole C-H-acetoxylation are notable.     

Synthesis of large ring 3,4-alkylenedioxythiophenes (ADOT) derivatives via Mitsunobu reaction

Poly(3,4-ethylenedioxythiophene) (PEDOT) stands out for its optimized conductivity, stability, and high degree of transparency which has led to its successful commercialization. These excellent properties of PEDOT are mostly ascribed to the alkylenedioxy bridge across the 3- and 4-positions, and thus much effort has been dedicated to synthesizing 3,4-ethylenedioxythiophene (EDOT) analogs. However, only few homologous compounds were successfully synthesized, such as 3,4-propylenedioxythiophene (PrDOT) or 3,4-(1,4-butylenedioxy)thiophene (BuDOT). In this Letter, we use Mitsunobu reaction to synthesize a series of 3,4-alkylenedioxythiophenes (ADOTs) derivatives with 8- to 16-membered rings. The eight-membered compounds were obtained in high or excellent yield. We also found that the 9- to 16-membered EDOT analogs were obtained in relatively low yield because of the competitive reaction to make dimers. Our method provides an easy way to modify ethylenedioxythiophenes (EDOTs), and these obtained ADOTs compounds are promising building blocks for the synthesis of functional π-conjugated systems used in material chemistry.     

Charge dynamics in solar cells with a blend of π-conjugated polymer-fullerene studied by transient photo-generated voltage

The biphasic feature of transient photo-generated voltage (TPV) is investigated in organic solar cells (OSCs) with a blend active layer of poly(3-hexylthiophene) (P3HT) and phenyl C61 butyric acid methyl ester (PCBM). The positive and negative components in biphasic TPV are explained through PCBM only and P3HT only devices. The negative and positive components are ascribed to the dipole formation at the buried interface of P3HT/indium tin oxide (ITO) and PCBM/ITO respectively. Based on these findings, two fundamental phenomena are revealed as follows: (1) interfacial modification on the buried interface inverts the negative component in biphasic TPV to a positive component, which prevents the leakage current channel in the conventional OSC structure; and (2) the solvent chosen transforms the positive component in biphasic TPV into a negative signal, which blocks the leakage current channel in the inverted OSC structure. Consequently, the study of TPV polarity provides the justification of the interaction at the buried interface. Besides, the decay of TPV is found to be bi-exponential, which can be used as a tool to estimate the degree of charge balance in OSCs.     

Broadband enhancement of spontaneous emission in a photonic-plasmonic structure

We demonstrate that a broadband enhancement of spontaneous emission can be achieved within a photonic-plasmonic structure. The structure can strongly modify the spontaneous emission by exciting plasmonic modes. Because of the excited plasmonic modes, an enhancement up to 30 times is observed, leading to a 4 times broader emission spectrum. The reflectance measurement and the finite-difference time-domain simulation are carried out to support these results.     

Inorganic Metal Hydroxide Nanoparticles for Targeted Cellular Uptake Through Clathrin‐Mediated Endocytosis

Layered double hydroxides (LDHs) are biocompatible materials which can be used as drug‐delivery nanovehicles. In order to define the optimum size of LDH nanoparticles for efficient cellular uptake and drug‐delivery pathway, we prepared different sized LDH nanoparticles with narrow size distribution by modulating the crystal growth rate, and labelled each LDH particle with a fluorophore using a silane coupling reaction. The cellular uptake rate of LDHs was found to be highly dependent on particle size (50>200≥100>350 nm), whose range of 50 to 200 nm was selectively internalized into cells through clathrin‐mediated endocytosis with enhanced permeability and retention. Our study clearly shows that not only the particle size plays an important role in the endocytic pathway and processing, but also the size control of LDH nanoparticles results in their targeted uptake to site‐specific clathrin‐mediated endocytosis. This result provides a new perspective for the design of LDH nanoparticles with maximum ability towards targeted drug delivery.     

Generation of Pseudocontact Shifts in Proteins with Lanthanides Using Small “Clickable” Nitrilotriacetic Acid and Iminodiacetic Acid Tags

Pseudocontact shifts (PCS) induced by paramagnetic lanthanide ions provide unique long‐range structural information in nuclear magnetic resonance (NMR) spectra, but the site‐specific attachment of lanthanide tags to proteins remains a challenge. Here we incorporated p‐azido‐phenylalanine (AzF) site‐specifically into the proteins ubiquitin and GB1, and ligated the AzF residue with alkyne derivatives of small nitrilotriacetic acid and iminodiacetic acid tags using the Cu^I‐catalysed “click” reaction. These tags form lanthanide complexes with no or only a small net charge and produced sizeable PCSs with paramagnetic lanthanide ions in all mutants tested. The PCSs were readily fitted by single magnetic susceptibility anisotropy tensors. Protein precipitation during the click reaction was greatly alleviated by the presence of 150 mM NaCl.