Bacterial sepsis is a serious clinical condition that can lead to multiple organ dysfunction and death despite timely treatment with antibiotics and fluid resuscitation. We have developed an approach to clearing bacteria and endotoxin from the bloodstream, using magnetic nanoparticles (MNPs) modified with bis-Zn-DPA, a synthetic ligand that binds to both Gram-positive and Gram-negative bacteria. Magnetic microfluidic devices were used to remove MNPs bound to Escherichia coli , a Gram-negative bacterium commonly implicated in bacterial sepsis, from bovine whole blood at flows as high as 60 mL/h, resulting in almost 100% clearance. Such devices could be adapted to clear bacteria from septicemic patients.

Pain management would be greatly enhanced by a formulation that would provide local anesthesia at the time desired by patients and with the desired intensity and duration. To this end, we have developed near-infrared (NIR) light-triggered liposomes to provide on-demand adjustable local anesthesia. The liposomes contained tetrodotoxin (TTX), which has ultrapotent local anesthetic properties. They were made photo-labile by encapsulation of a NIR-triggerable photosensitizer; irradiation at 730 nm led to peroxidation of liposomal lipids, allowing drug release. In vitro, 5.6% of TTX was released upon NIR irradiation, which could be repeated a second time. The formulations were not cytotoxic in cell culture. In vivo, injection of liposomes containing TTX and the photosensitizer caused an initial nerve block lasting 13.5 ± 3.1 h. Additional periods of nerve block could be induced by irradiation at 730 nm. The timing, intensity, and duration of nerve blockade could be controlled by adjusting the timing, irradiance, and duration of irradiation. Tissue reaction to this formulation and the associated irradiation was benign.pain | site 1 sodium-channel blocker | photosensitizer | light | near infrared

Two structurally related fluorescent imaging probes allow optical imaging of bacterial leg infection models in living athymic and immunocompetent mice. Structurally, the probes are comprised of a deep-red fluorescent squaraine rotaxane scaffold with two appended bis(zinc(II)-dicolylamine) (bis(Zn-DPA)) targeting ligands. The bis(Zn-DPA) ligands have high affinity for the anionic phospholipids and related biomolecules that reside within the bacterial envelope, and they are known to selectively target bacterial cells over the nearly uncharged membrane surfaces of healthy mammalian cells. Planar, whole-animal optical imaging studies showed that intravenous dosing of either probe (10 nmol) allowed imaging of localized infections of Grampositive Staphylococcus aureus and Gram-negative Salmonella enterica serovar typhimurium. High selectivity for the infected target leg (T) over the contralateral non-target leg (NT) was reflected by T/NT ratios up to six. The infection imaging signal was independent of mouse humoral immune status, and there was essentially no targeting at a site of sterile inflammation induced by injection of λ-carrageenan. Furthermore, the fluorescent probe imaging signal colocalized with the bioluminescence signal from a genetically engineered strain of S. enterica serovar typhimurium. Although not highly sensitive (the localized infection must contain at least 10 6 colony forming units for fluorescence visualization) the probes are remarkably selective for bacterial cells considering their low molecular weight (<1.5 kDa) and simple structural design. The more hydrophilic of the two probes produced a higher T/NT ratio in the early stages of the imaging experiment and washed out more rapidly from the blood clearance organs (liver, kidney). Therefore, it is best suited for longitudinal studies that require repeated dosing and imaging of the same animal. The results indicate that fluorescent probes based on squaraine rotaxanes should be broadly useful for in vivo animal imaging studies, and they further validate the ability of imaging probes with bis(Zn-DPA) ligands to selectively target bacterial infections in living animals.

Injectable materials often have shortcomings in mechanical and drug-eluting properties that are attributable to their high water contents. A water-free, liquid four-armed PEG modified with dopamine end groups is described which changed from liquid to elastic solid by reaction with a small volume of Fe3+ solution. The elastic modulus and degradation times increased with increasing Fe3+ concentrations. Both the free base and the water-soluble form of lidocaine could be dissolved in the PEG4-dopamine and released in a sustained manner from the cross-linked matrix. PEG4-dopamine was retained in the subcutaneous space in vivo for up to 3 weeks with minimal inflammation. This material’s tailorable mechanical properties, biocompatibility, ability to incorporate hydrophilic and hydrophobic drugs and release them slowly are desirable traits for drug delivery and other biomedical applications.

We describe a new antifouling surface coating, based on aggregation of a short amphiphilic four-armed PEG-dopamine polymer into particles, and on surface binding by catechol chemistry. An unbroken and smooth polymeric coating layer with an average thickness of approximately 4 microns was formed on top of titanium oxide surfaces by a single step reaction. Coatings conferred excellent resistance to protein adhesion. Cell attachment was completely prevented for at least eight weeks, although the membranes themselves did not appear to be intrinsically cytotoxic. When linear PEG or four-armed PEG of higher molecular weight were used, the resulting coatings were inferior in thickness and in preventing protein adhesion. This coating method has potential applicability for biomedical devices susceptible to fouling after implantation.

A simple macrocyclic amine is alkylated by methylene chloride to give a quaternary ammonium chloride salt. When methylene chloride is the solvent, the reaction exhibits pseudo-first-order kinetics, and the reaction half-life at 25.0 degrees C is 2.0 min. The reaction half-life for a structurally related, acyclic amine is approximately 50 000 times longer. Detailed calculations favor a mechanism where the methylene chloride associates with the macrocycle to form an activated prereaction complex. The macrocyclic nitrogen subsequently attacks the methylene chloride with a classic SN2 trajectory, and although the carbon-chlorine bond breaks, the chloride leaving group does not separate from the newly formed cationic macrocycle, such that the product is a tightly associated ion-pair. X-ray crystal structures of the starting amine and the product salt, as well as kinetic data, support this mechanism.

Polystyrene nanoparticles stained with squaraine catenane endoperoxide exhibit remarkably high chemiluminescence and enable optical imaging of biodistribution in living mice. Whole-body chemiluminescence imaging was much more effective than fluorescence at identifying lung accumulation of the nanoparticles.

Compared to structurally related linear trialkylamines, a simple macrocyclic amine with an anion-binding cavity exhibits very large rate enhancements (>10(5)) for stoichiometric N-alkylation with primary alkyl, allyl, and benzyl halides in the weakly polar solvent CDCl3. There is also a major distortion of the halide leaving-group order. For example, with benzyl halides the relative leaving-group order with a control amine is Cl (1) < Br (71) < I (160), whereas the leaving-group order with the macrocyclic amine is I (0.4) < Cl (1) < Br (8.5). Reaction with the macrocyclic amine is inhibited by the addition of DMSO, which is unusual because the Menschutkin reaction is normally enhanced by the presence of a polar aprotic solvent. Competitive inhibition studies indicate that the reaction proceeds through a prereaction complex. Effective molarities for the subsequent unimolecular N-alkylation step with 4-t-butylbenzyl halides are 4-t-BuBnCl (62,000 M) > 4-t-BuBnBr (2200 M) > 4-t-BuBnI (35 M); thus, the free energy of activation is selectively decreased for organohalides having smaller and more charge dense leaving groups. Likely reasons for this selective enhancement effect are: (a) increased transition-state stabilization due to hydrogen bonding in the macrocyclic pocket and (b) reduced entropic penalty in the transition state due to an increased fraction of prereaction complexes that are oriented in a near attack conformation. The study suggests that it should be possible to develop highly reactive macrocyclic amines that selectively sense or scavenge carcinogenic haloalkanes from the atmosphere.