Fluorescence turn-on detection of Sn2+ in live eukaryotic and prokaryotic cells.

Sn(2+) is usually added to toothpaste to prevent dental plaque and oral disease. However, studies of its physiological role and bacteriostatic mechanism are restricted by the lack of versatile Sn(2+) detection methods applicable to live cells, including Streptococcus mutans. Here we report two Sn(2+) fluorescent probes containing a rhodamine B derivative as a fluorophore, linked via the amide moiety to N,N-bis(2-hydroxyethyl)ethylenediamine (R1) and tert-butyl carbazate group (R2), respectively. These probes can selectively chelate Sn(2+) and show marked fluorescence enhancement due to the ring open reaction of rhodamine induced by Sn(2+) chelation. The probes have high sensitivity and selectivity for Sn(2+) in the presence of various relevant metal ions. Particularly, both R1 and R2 can target lysosomes, and R2 can probe Sn concentrations in lysosomes with rather acidic microenvironment. Furthermore, these two probes have low toxicity and can be used as imaging probes for monitoring Sn(2+) not only in live KB cells (eukaryotic) but also in Streptococcus mutans cells (prokaryotic), which is a useful tool to study the physiological function of Sn(2+) in biological systems.

In Situ Regulation of Macrophage Polarization to Enhance Osseointegration Under Diabetic Conditions Using Injectable Silk/Sitagliptin Gel Scaffolds.

As a chronic inflammatory disease, diabetes mellitus creates a proinflammatory microenvironment around implants, resulting in a high rate of implant loosening or failure in osteological therapies. In this study, macroporous silk gel scaffolds are injected at the bone-implant interface for in situ release of sitagliptin that can regulate macrophage response to create a prohealing microenvironment in diabetes mellitus disease. Notably, it is discovered that sitagliptin induces macrophage polarization to the M2 phenotype and alleviates the impaired behaviors of osteoblasts on titanium (Ti) implants under diabetic conditions in a dose-dependent manner. The silk gel scaffolds loaded with sitagliptin elicite a stronger recruitment of M2 macrophages to the sites of Ti implants and a significant promotion of osteointegration, as compared to oral sitagliptin administration. The results suggest that injectable silk/sitagliptin gel scaffolds can be utilized to modulate the immune responses at the bone-implant interface, thus enhancing bone regeneration required for successful implantation of orthopedic and dental devices in diabetic patients.

A rewritable optical storage medium of silk proteins using near-field nano-optics.

Nanoscale lithography and information storage in biocompatible materials offer possibilities for applications such as bioelectronics and degradable electronics for which traditional semiconductor fabrication techniques cannot be used. Silk fibroin, a natural protein renowned for its strength and biocompatibility, has been widely studied in this context. Here, we present the use of silk film as a biofunctional medium for nanolithography and data storage. Using tip-enhanced near-field infrared nanolithography, we demonstrate versatile manipulation and characterize the topography and conformation of the silk in situ. In particular, we fabricate greyscale and dual-tone nanopatterns with full-width at half-maximum resolutions of ~35 nm, creating an erasable 'silk drive' that digital data can be written to or read from. As an optical storage medium, the silk drive can store digital and biological information with a capacity of ~64 GB inch-2 and exhibits long-term stability under various harsh conditions. As a proof-of-principle demonstration, we show that this silk drive can be biofunctionalized to exhibit chromogenic reactions, resistance to bacterial infection and heat-triggered, enzyme-assisted decomposition.

Amidinate aluminium complexes: synthesis, characterization and ring-opening polymerization of rac-lactide.

A series of aluminium alkyl complexes {PhC(NR')(NR'')}AlR(2) (4a-n, R' = 2,6-(i)Pr(2)C(6)H(3), 2,6-Me(2)C(6)H(3); R'' = aryl groups with various ortho-, para- or meta-substituents, tert-butyl; R = methyl, ethyl) bearing non-symmetrically N-substituted benzamidinate ligands were synthesized via the reaction of trialkylaluminium and the corresponding benzamidine proligands. Complex 5 bearing symmetric amidinate ligand was also obtained for comparison purposes. The X-ray diffraction studies of complexes 4b, 4c and 5 show in each case a distorted tetrahedral geometry around the aluminium center. All the amidinate aluminium complexes were found to catalyze the ring-opening polymerization (ROP) of rac-lactide with moderate activities. The steric and electronic characteristics of the ancillary ligands have a significant influence on the polymerization performance of the corresponding aluminium complexes. The introduction of electron-withdrawing substituents at the ortho-positions of N-phenyl ring of the ligands resulted in an obvious increase in catalytic activity. Complex 4b showed the highest activity among the investigated aluminium complexes due to the high electrophilicity of the metal center induced by the ortho-chloro substituents on the phenyl ring. The existence of ortho-substituents of small steric bulkiness is also beneficial for the increase of activity of these catalysts. However, further increase of steric hindrance of the ligands by introducing bulky ortho-substituents onto the phenyl moieties resulted in a decrease of activity and an increase in the isotactic bias of the obtained polylactides. The broad molecular weight distributions (PDI = 1.13-2.02) of the polymer samples indicated that the ROP of rac-lactide initiated by these complexes was not well-controlled.