Targeting the guanylate cyclase c receptor with an agonist peptide from enterotoxegenic Y. Enterocolitica [abstract]

Heat-stable enterotoxin peptides (ST's) are expressed by enterotoxigenic strains of bacteria in order to co-opt an endogenous ligand-receptor system that regulates fluid homeostasis within the gut. Bacteria such as E. coli, V. Cholerae, and Y. enterocolitica have evolved ST's which mimic native guanylin/uroguanylin peptides by activating guanylate cyclase C (GC-C), yet possess increased resistance to heat/enzymatic degradation as well as superagonist activity by virtue of a third disulfide bond. We have previously utilized ST peptides derived from an E. coli isolate, as well as analogs of the endogenous peptide hormone uroguanylin, as imaging and therapeutic agents for GC-C-expressing colorectal cancers. In this work, we have compared the ability of these peptides to target GC-C and engender production of cGMP with that of an ST analog derived from Yersinia enterocolitica.Previous results had suggested that the Y. enterocolitica sequence may elicit higher cyclase activity than other peptides in this class. We have generated the peptide GENDWDWCCELCCNPACFGC both with and without an N-terminal DOTA chelating moiety and characterized its receptor binding affinity and ability to stimulate cGMP production in comparison to other peptides in this class. Our findings indicate that the Yersinia peptide possesses receptor binding affinity and cyclase stimulating activity intermediate between known E. coli ST analogs and human uroguanylin. However, in vivo biodistribution results obtained using the 64Cu-labeled DOTA-peptide demonstrated normal tissue distributions substantially different from E. coli-derived peptides, and more akin to those obtained with radiolabeled uroguanylin peptides

Evaluation of a tranfected HEK293 cell line overexpressing the gc-c receptor [abstract]

Guanylate cyclase C (GC-C) is typically highly expressed in the brush border of the intestinal epithelium and in human colorectal adenocarcinomas, but is minimally expressed in extraintestinal tissues. Many studies have demonstrated that GC-C is a useful target for imaging and treatment of colorectal cancers using GC-C ligands. In this study, we have established a transfected Hek293 cell line overexpressing the human GC-C receptor and tested its ligand binding, proliferation, biodistribution and imaging properties. A pcDNA3.1(+)/GC-C plasmid was constructed and used to stably transfect Hek293 cells. A Hek293/GC-C cell line was successfully selected and confirmed by receptor binding studies, western blot and RT-PCR. Transfection did not significantly influence the in vitro cell growth rate compared with Hek293/control. Scatchard assay, immunoblot, and RT-PCR analyses all demonstrated significant overexpression of GC-C in the transfected cell line, and the functionality of the expressed protein was demonstrated by a > 150-fold increase in generation of cGMP upon ligand stimulation relative to the control cell line. Further, treatment of Hek293/GC-C with GC-C ligands resulted in decreased cell proliferation measured by MTT assay, as has been previously observed for other GC-C- expressing colorectal cancer cell lines. Biodistribution and in vivo imaging studies carried out in nude mice bearing Hek293/GC-C xenografts also demonstrated high specific uptake of an Indium-111-labeled GC-C agonist. The Hek293/GC-C cell line described here will provide a useful model for the development of GC-C agonists as diagnostic and therapeutic agents for colorectal cancer

Adhesive, multifunctional, and wearable electronics based on MXene-coated textile for personal heating systems, electromagnetic interference shielding, and pressure sensing

Adhesion between flexible devices and skin surface facilitates portability of devices and reliable signal acquisition from human body, which is essential for medical therapy devices or monitoring systems. Here, we utilize a simple, cost-effective, and scalable layer-by-layer dip-coating method to fabricate a skin-adhesive multifunctional textile-based device, consisting of three parts: low-cost and easily available airlaid paper (AP) substrate, conductive MXene sensitive layer, and adhesive polydimethylsiloxane (PDMS). The adhesive layer of lightly cross-linked PDMS enables the device to form conformal contact with skin even during human joint bending. The smart textile device exhibits excellent electro-thermal and photo-thermal conversion performance with good cycling stability and tunability. Furthermore, the textile electronics show good electromagnetic interference (EMI) shielding properties due to the good electrical conductivity, as well as sensitive and stable pressure sensing properties for human motion detection. Consequently, this efficient strategy provides a possible way to design multifunctional and wearable electronic textiles for medical applications

Dosimetry of [²¹²Pb]VMT01, a MC1R-Targeted Alpha Therapeutic Compound, and Effect of Free ²⁰⁸Tl on Tissue Absorbed Doses

[212Pb]VMT01 is a melanocortin 1 receptor (MC1R) targeted theranostic ligand in clinical development for alpha particle therapy for melanoma. 212Pb has an elementally matched gamma-emitting isotope 203Pb; thus, [203Pb]VMT01 can be used as an imaging surrogate for [212Pb]VMT01. [212Pb]VMT01 human serum stability studies have demonstrated retention of the 212Bi daughter within the chelator following beta emission of parent 212Pb. However, the subsequent alpha emission from the decay of 212Bi into 208Tl results in the generation of free 208Tl. Due to the 10.64-hour half-life of 212Pb, accumulation of free 208Tl in the injectate will occur. The goal of this work is to estimate the human dosimetry for [212Pb]VMT01 and the impact of free 208Tl in the injectate on human tissue absorbed doses. Human [212Pb]VMT01 tissue absorbed doses were estimated from murine [203Pb]VMT01 biodistribution data, and human biodistribution values for 201Tl chloride (a cardiac imaging agent) from published data were used to estimate the dosimetry of free 208Tl. Results indicate that the dose-limiting tissues for [212Pb]VMT01 are the red marrow and the kidneys, with estimated absorbed doses of 1.06 and 8.27 mGyRBE = 5/MBq. The estimated percent increase in absorbed doses from free 208Tl in the injectate is 0.03% and 0.09% to the red marrow and the kidneys, respectively. Absorbed doses from free 208Tl result in a percent increase of no more than 1.2% over [212Pb]VMT01 in any organ or tissue. This latter finding indicates that free 208Tl in the [212Pb]VMT01 injectate will not substantially impact estimated tissue absorbed doses in humans

Preclinical Evaluation of a Lead Specific Chelator (PSC) Conjugated to Radiopeptides for 203Pb and 212Pb-Based Theranostics

203Pb and 212Pb have emerged as promising theranostic isotopes for image-guided α-particle radionuclide therapy for cancers. Here, we report a cyclen-based Pb specific chelator (PSC) that is conjugated to tyr3-octreotide via a PEG2 linker (PSC-PEG-T) targeting somatostatin receptor subtype 2 (SSTR2). PSC-PEG-T could be labeled efficiently to purified 212Pb at 25 °C and also to 212Bi at 80 °C. Efficient radiolabeling of mixed 212Pb and 212Bi in PSC-PEG-T was also observed at 80 °C. Post radiolabeling, stable Pb(II) and Bi(III) radiometal complexes in saline were observed after incubating [203Pb]Pb-PSC-PEG-T for 72 h and [212Bi]Bi-PSC-PEG-T for 5 h. Stable [212Pb]Pb-PSC-PEG-T and progeny [212Bi]Bi-PSC-PEG-T were identified after storage in saline for 24 h. In serum, stable radiometal/radiopeptide were observed after incubating [203Pb]Pb-PSC-PEG-T for 55 h and [212Pb]Pb-PSC-PEG-T for 24 h. In vivo biodistribution of [212Pb]Pb-PSC-PEG-T in tumor-free CD-1 Elite mice and athymic mice bearing AR42J xenografts revealed rapid tumor accumulation, excellent tumor retention and fast renal clearance of both 212Pb and 212Bi, with no in vivo redistribution of progeny 212Bi. Single-photon emission computed tomography (SPECT) imaging of [203Pb]Pb-PSC-PEG-T and [212Pb]Pb-PSC-PEG-T in mice also demonstrated comparable accumulation in AR42J xenografts and renal clearance, confirming the theranostic potential of the elementally identical 203Pb/212Pb radionuclide pair

Preclinical Evaluation of a Lead Specific Chelator (PSC) Conjugated to Radiopeptides for ²⁰³Pb and ²¹²Pb-Based Theranostics

203Pb and 212Pb have emerged as promising theranostic isotopes for image-guided α-particle radionuclide therapy for cancers. Here, we report a cyclen-based Pb specific chelator (PSC) that is conjugated to tyr3-octreotide via a PEG2 linker (PSC-PEG-T) targeting somatostatin receptor subtype 2 (SSTR2). PSC-PEG-T could be labeled efficiently to purified 212Pb at 25 °C and also to 212Bi at 80 °C. Efficient radiolabeling of mixed 212Pb and 212Bi in PSC-PEG-T was also observed at 80 °C. Post radiolabeling, stable Pb(II) and Bi(III) radiometal complexes in saline were observed after incubating [203Pb]Pb-PSC-PEG-T for 72 h and [212Bi]Bi-PSC-PEG-T for 5 h. Stable [212Pb]Pb-PSC-PEG-T and progeny [212Bi]Bi-PSC-PEG-T were identified after storage in saline for 24 h. In serum, stable radiometal/radiopeptide were observed after incubating [203Pb]Pb-PSC-PEG-T for 55 h and [212Pb]Pb-PSC-PEG-T for 24 h. In vivo biodistribution of [212Pb]Pb-PSC-PEG-T in tumor-free CD-1 Elite mice and athymic mice bearing AR42J xenografts revealed rapid tumor accumulation, excellent tumor retention and fast renal clearance of both 212Pb and 212Bi, with no in vivo redistribution of progeny 212Bi. Single-photon emission computed tomography (SPECT) imaging of [203Pb]Pb-PSC-PEG-T and [212Pb]Pb-PSC-PEG-T in mice also demonstrated comparable accumulation in AR42J xenografts and renal clearance, confirming the theranostic potential of the elementally identical 203Pb/212Pb radionuclide pair