Visible-Light-Activated High-Density Materials for Controlled in Vivo Insulin Release

Abstract

In this work we describe the synthesis, characterization and ultimate in-vivo assessment of second generation insulin photoactivated depot (PAD) materials. These are the first to use visible light to stimulate insulin release, and have in-vivo performance that is twenty eight fold improved relative to first generation materials. This improvement is due to two major factors linked to the utilized chemistry: 1) We have incorporated the coumarin photocleavable group, which increases the photo-release wavelength into the visible range, enhancing tissue penetration of the light and 2) Photo-toggling of insulin solubility is produced by linking three insulin molecules to a central bridge via light cleaved groups, and not by bonding to a large polymer. The resulting trimer is therefore highly dense (87% insulin dry w/w) but retains the insolubility required of the approach. Only after irradiation with visible light is native, soluble insulin released from the dermal depot. This high density increases the amount and ease of insulin release, as the density of photolytic groups is 10-20 fold higher than in polymer based first generation materials. We have synthesized new azide-terminated coumarin linkers that we react with the amine groups of insulin. Using mass spectrometry methods we identify the sites of reaction and purify individual isomers, which we demonstrate have in-vitro photolysis rates that are within a factor of two of each other. We then reacted these terminal azide groups with a tri-dentate strained alkyne linker. We show that the resulting insulin trimer is highly insoluble, but can be milled into injectable particles that release insulin only in response to light from a 406nm light source. Finally, we demonstrate that these materials have significantly improved in-vivo performance, releasing twenty eight fold more insulin on a per energy basis than first generation materials.

pH-Responsive Cellulose-Based Microspheres Designed as an Effective Oral Delivery System for Insulin

“…Insulin is a hormone, which regulates blood sugar, advised to diabetic patients, and it also undergoes degradation in the presence of gastric enzymes and acids due to destruction of disulfide bonds. − pH-responsive carriers offer excellent potential as oral therapeutic systems by enhancing the stability of insulin delivery in stomach and achieving controlled release in intestines. This motivates the development of an oral insulin transport carrier to improve its bioavailability, and various studies have been reported. − Considering the advantages of natural materials, researchers are looking for nontoxic, biocompatible, biorenewable, and low-cost natural materials to replace synthetics.…”

A Light Activated Glucagon Trimer with Resistance to Fibrillation

“…These species include polymers, nonpolar small molecules, and isoelectric point shifting moieties. − The resultant conjugates have minimal solubility, but upon irradiation release native active insulin which can ultimately be absorbed into systemic circulation from the depot site. We have demonstrated the efficacy of this approach both in vitro and in vivo. , The aim of such materials is to allow for the continuously variable release of insulin using light in response to continuously varying blood glucose signals. The combination of continuously variable insulin release and continuous blood glucose information (provided by a continuous blood glucose monitor or CGM) are the central elements of an artificial pancreas (AP). − Currently, AP systems exclusively use insulin pumps for delivery.…”

“…We have demonstrated the efficacy of this approach both in vitro and in vivo. 6,7 The aim of such materials is to allow for the continuously variable release of insulin using light in response to continuously varying blood glucose signals.…”

Direct Photorelease of Alcohols from Boron-Alkylated BODIPY Photocages

“…Photocages are useful in studies that require the spatial and temporal control that can be provided by pulsed light irradiation. These include biological investigations of short-lived species, small molecules, and signaling agents; 1, 2 targeted phototherapeutics; 3,4 and microarray synthesis. [5][6][7][8] Visible light absorbing photocages have been an exciting new development as they allow for less toxic visible light irradiation in biological studies.…”

“…[5][6][7][8] Visible light absorbing photocages have been an exciting new development as they allow for less toxic visible light irradiation in biological studies. 1,4,[9][10][11] In particular, our group along with others have developed BODIPY photocages which can release leaving groups from the meso position after activation with single photons of green to near IR light. [12][13][14][15][16][17][18] Many biological targets (e.g.…”