A nucleic acid origami device comprising a scaffold strand and a plurality of staple strands, wherein: (i) one of the staple strands comprises either (a) an aptamer domain capable of binding to a glucokinase having a first configuration but incapable of binding to the glucokinase having a second configuration; or (b) an oligonucleotide comprising a nucleotide sequence of a glucose responsive regulatory element capable of binding a glucose response factor having a first configuration but incapable of binding to the glucose response factor having a second configuration; (ii) another of the staple strands comprises a latch domain linked to the glucokinase, and the aptamer of (a) is capable of binding to the glucokinase having the first configuration but incapable of binding to the glucokinase having the second configuration such that the latch domain is displaced from the aptamer of (a) when glucokinase transitions from the first to the second configuration; or another of the staple strands comprises a latch domain linked to the glucose response factor and the oligonucleotide of (b) is capable of binding to the glucose response factor, having the first configuration but incapable of binding to the glucose response factor having the second configuration such that the latch domain is displaced from the oligonucleotide of (b) when the glucose response factor transitions from the first to the second configuration; (iii) the aptamer domain of (a) or the oligonucleotide of (b), and the latch domain, when bound to one another, hold the device in a closed configuration; and the device transitions to an open configuration when said aptamer domain of (a) or oligonucleotide of (b), and the latch domain, are not hybridized or bound to one another; and (iv) a further staple strand comprises a handle domain bound to insulin, optionally via a linker, wherein said nucleic acid origami device is either alkylated, acylated or hydroxylated, or interacts with a compound capable of non-covalently binding to the major- or minor-groove of a double stranded nucleic acid, and therefore is resistant to nucleases, and/or said nucleic acid origami device lacks TLR9 recognition elements or the TLR9 recognition elements of said nucleic acid origami device are masked or modified and therefore said nucleic acid origami device is non-immunogenic. (i) one of the staple strands comprises either (a) an aptamer domain capable of binding to a glucokinase having a first configuration but incapable of binding to the glucokinase having a second configuration; or (b) an oligonucleotide comprising a nucleotide sequence of a glucose responsive regulatory element capable of binding a glucose response factor having a first configuration but incapable of binding to the glucose response factor having a second configuration; (ii) another of the staple strands comprises a latch domain linked to the glucokinase, and the aptamer of (a) is capable of binding to the glucokinase having the first configuration but incapable of binding to the glucokinase having the second configuration such that the latch domain is displaced from the aptamer of (a) when glucokinase transitions from the first to the second configuration; or another of the staple strands comprises a latch domain linked to the glucose response factor and the oligonucleotide of (b) is capable of binding to the glucose response factor, having the first configuration but incapable of binding to the glucose response factor having the second configuration such that the latch domain is displaced from the oligonucleotide of (b) when the glucose response factor transitions from the first to the second configuration; (iii) the aptamer domain of (a) or the oligonucleotide of (b), and the latch domain, when bound to one another, hold the device in a closed configuration; and the device transitions to an open configuration when said aptamer domain of (a) or oligonucleotide of (b), and the latch domain, are not hybridized or bound to one another; and (iv) a further staple strand comprises a handle domain bound to insulin, optionally via a linker, wherein