Shape Matters: Highly Selective Antimicrobial Bottle Brush Copolymers via a One-Pot RAFT Polymerization Approach

The one-pot synthesis of antimicrobial bottle brush copolymers is presented. Reversible addition-fragmentation chain-transfer (RAFT) polymerization is used for the production of the polymeric backbone, as well as for the grafts, which were installed using a grafting-from approach. A combination of N-isopropyl acrylamide and a Boc-protected primary amine-containing acrylamide was used in different compositions. After deprotection, polymers featuring different charge densities were obtained in both linear and bottle brush topologies. Antimicrobial activity was tested against three clinically relevant bacterial strains, and growth inhibition was significantly increased for bottle brush copolymers. Blood compatibility investigations revealed strong hemagglutination for linear copolymers and pronounced hemolysis for bottle brush copolymers. However, one bottle brush copolymer with a 50% charge density revealed strong antibacterial activity and negligible in vitro blood toxicity (regarding hemolysis and hemagglutination tests) resulting in selectivity values as high as 320. Membrane models were used to probe the mechanism of shown polymers that was found to be based on membrane disruption. The trends from bioassays are accurately reflected in model systems indicating that differences in lipid composition might be responsible for selectivity. However, bottle brush copolymers were found to possess increased cytotoxicity against human embryonic kidney (HEK) cells compared with linear analogues. The introduced synthetic platform enables screening of further, previously inaccessible parameters associated with the bottle brush topology, paving the way to further improve their activity profiles.

The difference between photo-iniferter and conventional RAFT polymerization: high livingness enables the straightforward synthesis of multiblock copolymers

Photo-iniferter (PI)-RAFT polymerization, the direct activation of chain transfer agents via light, is a fascinating polymerization technique, as it overcomes some restriction of conventional RAFT polymerization. As such, we elucidated...

Spontaneous trigger words associated with confirmed out-of-hospital cardiac arrest: a descriptive pilot study of emergency calls

BACKGROUND

According to the International Liaison Committee on Resuscitation (ILCOR), the trigger words used by callers that are associated with cardiac arrest constitute a scientific knowledge gap. This study was designed to find hypothetical trigger words in emergency calls in order to improve the specificity of out-of-hospital cardiac arrest recognition.

METHODS

In this descriptive pilot study conducted in a Finnish hospital district, linguistic contents of 80 emergency calls of dispatcher-suspected or EMS-encountered out-of-hospital cardiac arrests between January 1, 2017 and May 31, 2017 were analysed. Spontaneous trigger words used by callers were transcribed and grouped into 36 categories. The association between the spontaneous trigger words and confirmed true cardiac arrests was tested with logistic regression.

RESULTS

Of the suspected cardiac arrests, 51 (64%) were confirmed as true cardiac arrests when ambulance personnel met the patient. A total of 291 spontaneous trigger words were analysed. 'Is not breathing' (n = 9 [18%] in the true cardiac arrest group vs n = 1 [3%] in the non-cardiac arrest group, odds ratio [OR] 6.00, 95% confidence interval [CI] 0.72-50.0), 'the patient is blue' (n = 9 [18%] vs n = 1 [3%], OR 6.00, 95% CI 0.72-50.0), 'collapsed or fallen down' (n = 12 [24%] vs n = 2 [7%], OR 4.15, 95% CI 0.86-20.1) and 'is wheezing' (n = 17 [33%] vs n = 5 [17%], OR 2.40, 95% CI 0.78-7.40) were frequently used to describe true cardiac arrest. 'Is snoring' was associated with a false suspicion of cardiac arrest (n = 1 [2%] vs n = 6 [21%], OR 0.08, 95% CI 0.009-0.67).

CONCLUSIONS

In our pilot study, no trigger word was associated with confirmed cardiac arrest. 'Is wheezing' was a frequently used spontaneous trigger word among later confirmed cardiac arrest victims.

The effects of the brown ear-tick, Rhipicephalus appendiculatus, on milk production of Sanga cattle

Lactating Sanga cows of the Mashona breed from Zimbabwe, receiving either a low or high level of nutritional supplement, were exposed to two levels of infestation of adults of the brown ear-tick, Rhipicephalus appendiculatus in the highveld of Zimbabwe. The effect of the ticks on the milk yield was measured over an 11-week period during the rainy season from January to April 1986. A technique in which calves were weighed before and after suckling was used to estimate milk yield. There were significant treatment effects of ticks (P < 0.05) on milk production but no significant differences in liveweight gain between calves from tick-free and tick-infested dams. The loss in milk production was poorly related to the number of female ticks that engorged, being 9 g (SEM 4) per tick. A Friesian x Hereford (Bos taurus) reference group of cattle carried 50% more ticks than the Mashona cows, illustrating a difference in resistance between the breeds. Thirteen screw-worm (Chrysomya bezziana) strikes were recorded amongst the thirty-two Mashona cows compared with twenty-one amongst the ten Friesian x Hereford animals between January and the end of March.

The effect of the brown ear-tick Rhipicephalus appendiculatus on the growth of Sanga and European breed cattle

The effects of larvae, nymphs and adults of the brown ear-tick Rhipicephalus appendiculatus on the growth of Bos indicus X B. taurus (Sanga) steers and on B. taurus steers and heifers was measured by exposing groups, maintained in the same pastures, to different levels of tick challenge. Larvae and nymphs had no significant effect on liveweight gains, but adults had a large effect. Each engorging female tick counted was associated with a loss of 4 g. Their effect on the Sanga cattle was minimised by host resistance which severely limited the number of ticks feeding on them. The B. taurus animals were severely affected and suffered extensive ear damage. Both breeds were subjected to screw-worm fly (Chrysomya bezziana) strike in the lesions caused by heavy tick infestations, but the B. taurus animals were much more prone to attack. The results provide a basis for calculating losses in production caused by this species of tick which is widespread in Africa.

Planar waveguide refractive-index profiling using modal intensity distributions

The intensity distributions of optical modes in planar waveguides were examined using a conventional near-field scanning apparatus. A new method is given, where the mode penetration depths are used for refractive-index profiling. The method was experimentally tested using planar optical waveguides fabricated with silver-sodium ion exchange into soda-lime glass. The observation of the modal intensity distributions was also used to ease the propagation constant measurement and to examine the waveguide quality, including the scattering and modal cross-coupling properties.