Nitric oxide-releasing semi-crystalline thermoplastic polymers: preparation, characterization and application to devise anti-inflammatory and bactericidal implants.

Semi-crystalline thermoplastics are an important class of biomaterials with applications in creating extracorporeal and implantable medical devices. In situ release of nitric oxide (NO) from medical devices can enhance their performance via NO's potent anti-thrombotic, bactericidal, anti-inflammatory, and angiogenic activity. However, NO-releasing semi-crystalline thermoplastic systems are limited and the relationship between polymer crystallinity and NO release profile is unknown. In this paper, the functionalization of poly(ether-block-amide) (PEBA), Nylon 12, and polyurethane tubes, as examples of semi-crystalline polymers, with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) within, is demonstrated via a polymer swelling method. The degree of crystallinity of the polymer plays a crucial role in both SNAP impregnation and NO release. Nylon 12, which has a relatively high degree of crystallinity, exhibits an unprecedented NO release duration of over 5 months at a low NO level, while PEBA tubing exhibits NO release over days to weeks. As a new biomedical application of NO, the NO-releasing PEBA tubing is examined as a cannula for continuous subcutaneous insulin infusion. The released NO is shown to enhance insulin absorption into the bloodstream probably by suppressing the tissue inflammatory response, and thereby could benefit insulin pump therapy for diabetes management.

Detection and Quantification of Polyquaterniums via Polyion-Sensitive Ion-Selective Optodes Inkjet Printed on Cellulose Paper.

A universal method for the detection, quantification, and characterization of polyquaterniums (PQs) in a simple background electrolyte solution and in more complex recreational swimming pool water samples is presented. This method involves the application of polycation-sensitive ion-selective optodes (ISOs) prepared by inkjet printing dinonylnaphthalenesulfonic acid (H+DNNS-) and chromoionophore I directly onto WhatmanTM qualitative filter paper. No plasticizer or added polymer matrix is required for the fabrication of the sensing layer which is coated on the cellulose fibers of the filter paper. PQ-6, PQ-2, PQ-10, and poly(2-methacryloxyethyltrimethylammonium) chloride (PMETAC) are used as model PQ species for direct optical detection at ppm levels. We further demonstrate that PQ-6 can be detected in recreational swimming pool water samples using this new type of sensor, and that detection of polyanions is also possible using an indirect detection method. Lastly, to circumvent the challenge of polyion-sensitive ISOs exhibiting a pH dependence, the sensors were soaked in buffer and dried to provide local buffering for applied liquid samples and an optical signal independent of sample pH.

Inkjet-Printed Paper-Based Colorimetric Polyion Sensor Using a Smartphone as a Detector.

The first paper-based polyion-sensitive optodes are reported. Dinonylnaphthalene sulfonic acid (a cation exchanger) and chromoionophore I (a lipophilic optical pH indicator) are printed on filter paper in the absence of any plasticizer and/or additional hydrophobic polymeric phase. The resulting optodes exhibit sensitive colorimetric response to polycations such as protamine but not to small inorganic cations because only polycations are able to form cooperative ion pairs with dinonylnaphthalenesulfonate adsorbed to the cellulose paper. The color change of the optode is recorded via an iPhone camera and analyzed by an iPhone App. The protamine-sensing optode platform is used to indirectly detect protease activity (trypsin) based on proteolytic digestion of protamine, and polyanions (pentosan polysulfate and heparin) based on the strong binding reaction of polyanions with protamine. The indirect sensing system is further simplified on a multilayer membrane device that consists of an optode paper site modified with buffer to prevent optode dependence on sample pH, and an underlying cellulose acetate filter membrane coated with protamine to eliminate addition of the indicator polycation into the sample. The detection of pentosan polysulfate concentrations in an undiluted urine sample is successfully demonstrated via this approach. Lastly, it is shown that plasticizer-free polyanion-sensitive optodes based on an adsorbed layer of quaternary ammonium type anion exchanger and a phenolic azo type proton chromoionophore can also be fabricated directly on cellulose paper strips.

An Ionophore-Based Anion-Selective Optode Printed on Cellulose Paper.

A general anion-sensing platform is reported based on a portable and cost-effective ion-selective optode and a smartphone detector equipped with a color analysis app. In contrast to traditional anion-selective optodes using a hydrophobic polymer and/or plasticizer to dissolve hydrophobic sensing elements, the new optode relies on hydrophilic cellulose paper. The anion ionophore and a lipophilic pH indicator are inkjet-printed and adsorbed on paper and form a "dry" hydrophobic sensing layer. Porous cellulose sheets also allow the sensing site to be modified with dried buffer that prevents any sample pH dependence of the observed color change. A highly selective fluoride optode using an AlIII -porphyrin ionophore is examined as an initial example of this new anion sensing platform for measurements of fluoride levels in drinking water samples. Apart from Lewis acid-base recognition, hydrogen bonding recognition is also compatible with this sensing platform.