n (i) (ii) n HIGHLIGHTS 3 Scheme 2


to mechanical grinding, produce fluorescent blue (cyan) powder which, intriguingly, reverts to the green emission after 24 hours. (S. Bhattacharyya, S. Sobczak, A. Pjłrolniczak, S. Roy, D. Samanta, A. Katrusiak, T. K. Maji; Chem. Eur. J., 2019, 25, 6092).


Energy from the grinding process


changes the relative molecular orientations within the solid state structure, leading to a kinetic product, which gradually reverts to the more


O N 4 Figure 1 Advanced materials


ARNO KRAFT Heriot-Watt University, Edinburgh, UK


Oral delivery system for insulin The regular subcutaneous injection of insulin is crucial in the treatment of type 1 diabetes. Oral delivery has long been considered as being not feasible since insulin would be readily hydrolysed in the gastrointestinal tract and, even if this could be prevented, absorption of the protein from either the stomach or the intestine would still be difficult. Abramson et al have proposed a


small device called a self-orienting millimetre-size applicator, or SOMA, that could make the oral delivery of insulin possible (Science, 2019, 363, 611).


The SOMA not only mimicked the shape but also the ability of a tortoise or a weeble-wobble toy of always landing on its feet. The tortoise shape and its centre of gravity in the lower ‘body’ ensured it had a preferred orientation perpendicular to the lining of the stomach (Scheme 1). The SOMA consisted of a


biodegradable polycaprolactone shell and a stainless steel bottom, which shifted the centre of gravity towards the lower part. Inside the protective shell was placed a tip consisting of a compressed mixture of insulin and poly(ethylene oxide), another biodegradable polymer. The amount of insulin used (0.5mg) was comparable to a dose required after


a light lunch. A spring at the end of the tip helped to fire the needle- shaped tip several millimetres deep into the lining of the stomach. From there, the insulin was readily absorbed. The ‘injections’ did not cause any perforation of the stomach. Moreover, gastric tissue is known to regenerate and heal quickly. Initial tests were carried out on


swine with human insulin. Monitoring of blood glucose and insulin levels revealed that insulin release was almost constant and followed near zero-order kinetics for 30 hours. It also confirmed that insulin remained stable during the high-pressure manufacturing process, thus opening the way for an alternative way for delivering insulin or other biomacromolecules.


Bottlebrush polymers for antifouling coatings


Lubricin is a glycoprotein found in the synovial fluid that, due to its


extremely low friction coefficient, helps to protect joints in the body from wear and tear. The protein owes its excellent lubricating properties to a ‘bottlebrush’ structure where highly charged end domains promote adhesion to surfaces and a large number of negative charges in the brush part favours the formation of a strongly bound hydrated layer that resists adsorption of proteins and bacteria alike. R. Su, K. Matyjaszewski, X. Banquy


Scheme 1 Like a weeble-wobble toy, the SOMA orients itself perpendicular to the wall of the stomach, then injects insulin into the lining of the stomach


Polycaprolactone shell Steel bottom


and co-workers have come up with an ABA-type block copolymer, which has been inspired by the bottlebrush architecture of lubricin (Angew. Chem. Int. Ed., 2019, 58, 1308). The two end blocks consisted of polymethacrylates with a positively charged side chain at statistical positions (Scheme 2). Throughout the central block polyzwitterionic branches, composed of poly(ethyl phosphorylcholine methacrylate) chains, were grafted onto the


Insulin tip Spring N O


Figure 1 The cross- shaped molecule (4) crystallises with eclipsed stacks of pentyl and pyridine arms that alternate in an ABAB/BABA fashion.


stable thermodynamic form. The initial crystalline material has been examined in detail by X-ray crystallography and also by applying mechanical pressure in a more controlled way using a diamond anvil cell. When compressed slowly, a phase transition noticeably lengthens the crystals in one direction and shortens them in another. In contrast, strong rapid compression distorts the crystal faces and caused amorphisation.


STOMACH LINING


06 | 2019 43


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