H2O2-Responsive Vesicles Integrated with Transcutaneous Patches for Glucose-Mediated Insulin Delivery

Abstract

A self-regulated "smart" insulin administration system would be highly desirable for diabetes management. Here, a glucose-responsive insulin delivery device, which integrates H₂O₂-responsive polymeric vesicles (PVs) with a transcutaneous microneedle-array patch was prepared to achieve a fast response, excellent biocompatibility, and painless administration. The PVs are self-assembled from block copolymer incorporated with polyethylene glycol (PEG) and phenylboronic ester (PBE)-conjugated polyserine (designated mPEG-b-P(Ser-PBE)) and loaded with glucose oxidase (GOx) and insulin. The polymeric vesicles function as both moieties of the glucose sensing element (GOx) and the insulin release actuator to provide basal insulin release as well as promote insulin release in response to hyperglycemic states. In the current study, insulin release responds quickly to elevated glucose and its kinetics can be modulated by adjusting the concentration of GOx loaded into the microneedles. In vivo testing indicates that a single patch can regulate glucose levels effectively with reduced risk of hypoglycemia.

Keywords: diabetes; drug delivery; glucose-responsive; insulin; polymersome; vesicles.

Figure 1

Schematic of the H₂O₂-responsive vesicles for glucose-mediated insulin delivery: (A) chemical structure of mPEG-b-P(Ser-PBE) and its degradation products; (B) self-assembly of block copolymer mPEG-b-P(Ser-PBE) into vesicles loaded with insulin and GOx. The vesicles are dissociated to release insulin in the presence of a hyperglycemic state; (C) PVs were further integrated into the hyaluronic acid (HA)-based microneedle-array patches for smart insulin delivery in a mouse model of type 1 diabetes.

Figure 2

Characterization of glucose-responsive polymer vesicles (PVs). (A) TEM images of (left) blank polymeric vesicles (PVs) and (right) vesicles encapsulated with GOx enzyme and insulin (PVs(E+I)), scale bar is 200 nm; (B) size distribution of PV and PV(E+I). (C) (Top) 2.5D fluorescence images of PV(E+I) solution pre- and postincubation in 400 mg/dL glucose solution for 1 and 2 h at 37 °C, respectively. (Bottom) Distribution of the fluorescence intensity along the indicated white dash line in arbitrary unit (a.u.); (D, E) TEM images (D) and size distribution (E) of PV(E+I) postincubation in 400 mg/dL glucose solution for 1(D, left) and 2 (D, right) h at 37 °C, respectively. Scale bar is 200 nm.

Figure 3

In vitro glucose-responsive release of insulin from PVs. (A) In vitro released insulin concentration from PVs(E+I) at several glucose concentrations at 37 °C; (B) The release rate (line slope) of insulin as a function of glucose concentration in the release media for PV(E+I) and [PV(/₂E+I) (containing one-half amount of GOx compared to PV(E+I)]; (C) Pulsatile release profile of insulin from PV(E+I) when the glucose concentration changed between 100 and 400 mg/dL alternatively for 10 min each; (D) CD spectra of native insulin solution and insulin released from the PVs incubated with 400 mg/mL glucose. Error bars indicate SD (n = 3).

Figure 4

Characterization and in vivo studies the MN-array patch for type 1 diabetes treatment. (A)(a) Fluorescence microscopy image of MN loaded with PVs containing FITC-labeled insulin. (Inset is zoomed-in image of MN). Scale bar is 200 μm. (b) SEM image of an MN patch. Scale bar is 200 μm. (c) Trypan blue staining of mouse skin transcutaneously treated with an MN-array patch for 1 h. (B) Blood glucose levels in STZ-induced diabetic mice after treatment with MN[HA], MN[I], MN[PV(E+I)], and MN[PV(I)]. *P < 0.05 for administration with MN[PV(E+I)] compared with MN[I]. (C) Plasma human insulin concentrations in STZ-induced diabetic mice after treatment with MN[PV(E+I)] and MN[PV(I)]. *P < 0.05 for administration with MN[PV(E+I)] compared with MN[PV(I)]. (D) In vivo glucose tolerance test toward diabetic mice 1 h post-administration of MN[PV(E+I)] or MN[I] in comparison to the healthy mice. *P < 0.05 for administration with MN[PV(E+I)] compared with MN[I]. (E) Responsiveness was calculated based on the area under the curve (AUV) in 150 min, with the baseline set at the 0 min blood glucose reading. *P < 0.05 for administration with MN[I] compared with healthy mice. (F) Blood glucose changes of healthy mice treated with MN patch over time. *P < 0.05 for administration with MN[PV(E+I)] compared with MN[I]. (G) Quantification of the hypoglycemia index, which was calculated as the difference between the initial and nadir blood glucose readings divided by the time at which the nadir was reached. *P < 0.05 for administration with MN[PV(E+I)] compared with MN[PV(I)]. Error bars indicate SD (n = 5).