Imaging assessment of photosensitizer emission induced by radionuclide-derived Cherenkov radiation using charge-coupled device optical imaging and long-pass filters

BACKGROUND Radionuclides produce Cherenkov radiation(CR),which can potentially activate photosensitizers(PSs)in phototherapy.Several groups have studied Cherenkov energy transfer to PSs using optical imaging;however,cost-effectively identifying whether PSs are excited by radionuclide-derived CR and detecting fluorescence emission from excited PSs remain a challenge.Many laboratories face the need for expensive dedicated equipment.AIM To cost-effectively confirm whether PSs are excited by radionuclide-derived CR and distinguish fluorescence emission from excited PSs.METHODS The absorbance and fluorescence spectra of PSs were measured using a microplate reader and fluorescence spectrometer to examine the photo-physical properties of PSs.To mitigate the need for expensive dedicated equipment and achieve the aim of the study,we developed a method that utilizes a chargecoupled device optical imaging system and appropriate long-pass filters of different wavelengths(manual sequential application of long-pass filters of 515,580,645,700,750,and 800 nm).Tetrakis(4-carboxyphenyl)porphyrin(TCPP)was utilized as a model PS.Different doses of copper-64(^(64)CuCl_(2))(4,2,and 1 mCi)were used as CR-producing radionuclides.Imaging and data acquisition were performed 0.5 h after sample preparation.Differential image analysis was conducted by using ImageJ software(National Institutes of Health)to visually evaluate TCPP fluorescence.RESULTS The maximum absorbance of TCPP was at 390-430 nm,and the emission peak was at 670 nm.The CR and CRinduced TCPP emissions were observed using the optical imaging system and the high-transmittance long-pass filters described above.The emission spectra of TCPP with a peak in the 645-700 nm window were obtained by calculation and subtraction based on the serial signal intensity(total flux)difference between^(64)CuCl_(2)+TCPP and^(64)CuCl_(2).Moreover,the differential fluorescence images of TCPP were obtained by subtracting the^(64)CuCl_(2)image from the^(64)CuCl_(2)+TCPP image.The experimental results considering different^(64)CuCl_(2)doses showed a dosedependent trend.These results demonstrate that a bioluminescence imaging device coupled with different longpass filters and subtraction image processing can confirm the emission spectra and differential fluorescence images of CR-induced TCPP.CONCLUSION This simple method identifies the PS fluorescence emission generated by radionuclide-derived CR and can contribute to accelerating the development of Cherenkov energy transfer imaging and the discovery of new PSs.

Whole-body PET tracking of a D-dodecapeptide and its radiotheranostic potential for PD-L1 overexpressing tumors

Peptides that are composed of dextrorotary(D)-amino acids have gained increasing attention as a potential therapeutic class.However,our understanding of the in vivo fate of D-peptides is limited.This highlights the need for whole-body,quantitative tracking of D-peptides to better understand how they interact with the living body.Here,we used mouse models to track the movement of a programmed death-ligand 1(PD-L1)-targeting D-dodecapeptide antagonist(DPA)using positron emission tomography(PET).More specifically,we profiled the metabolic routes of[^(64)Cu]DPA and investigated the tumor engagement of[^(64)Cu/^(68)Ga]DPA in mouse models.Our results revealed that intact[^(64)Cu/^(68)Ga]DPA was primarily eliminated by the kidneys and had a notable accumulation in tumors.Moreover,a single dose of[^(64)Cu]DPA effectively delayed tumor growth and improved the survival of mice.Collectively,these results not only deepen our knowledge of the in vivo fate of D-peptides,but also underscore the utility of D-peptides as radiopharmaceuticals.

PET imaging on neurofunctional changes after optogenetic stimulation in a rat model of panic disorder

Panic disorder (PD) is an acute paroxysmal anxiety disorder with poorly understood pathophysiology. The dorsal periaqueductal gray (dPAG) is involved in the genesis of PD. However, the downstream neurofunctional changes of the dPAG during panic attacks have yet to be evaluated in vivo. In this study, optogenetic stimulation to the dPAG was performed to induce panic-like behaviors, and in vivo positron emission tomography (PET) imaging with ,8F-flurodeoxyglucose (18F-FDG) was conducted to evaluate neurofunctional changes before and after the optogenetic stimulation. Compared with the baseline, post-optogenetic stimulation PET imaging demonstrated that the glucose metabolism significantly increased (P < 0.001) in dPAG, the cuneiform nucleus, the cerebellar lobule, the cingulate cortex, the alveus of the hippocampus, the primary visual cortex, the septohypothalamic nucleus, and the retrosplenial granular cortex but significantly decreased (P < 0.001) in the basal ganglia, the frontal cortex, the forceps minor corpus callosum, the primary somatosensory cortex, the primary motor cortex, the secondary visual cortex, and the dorsal lateral geniculate nucleus. Taken together, these data indicated that in vivo PET imaging can successfully detect downstream neurofunctional changes involved in the panic attacks after optogenetic stimulation to the dPAG.

Development of a highly-specific ^(18)F-labeled irreversible positron emission tomography tracer for monoacylglycerol lipase mapping

As a serine hydrolase,monoacylglycerol lipase(MAGL) is principally responsible for the metabolism of 2-arachidonoylglycerol(2-AG) in the central nervous system(CNS),leading to the formation of arachidonic acid(AA).Dysfunction of MAGL has been associated with multiple CNS disorders and symptoms,including neuroinflammation,cognitive impairment,epileptogenesis,nociception and neurodegenerative diseases.Inhibition of MAGL provides a promising therapeutic direction for the treatment of these conditions,and a MAGL positron emission tomography(PET) probe would greatly facilitate preclinical and clinical development of MAGL inhibitors.Herein,we design and synthesize a small library of fluoropyridyl-containing MAGL inhibitor candidates.Pharmacological evaluation of these candidates by activity-based protein profiling identified 14 as a lead compound,which was then radiolabeled with fluorine-18 via a facile SNAr reaction to form 2-[^(18)F]fluoropyridine scaffold.Good blood-brain barrier permeability and high in vivo specific binding was demonstrated for radioligand [^(18)F]14(also named as [^(18)F]MAGL-1902).This work may serve as a roadmap for clinical translation and further design of potent 18F-labeled MAGL PET tracers.

Self-Assembly of Constrained Cyclic Peptides Controlled by Ring Size

The de novo design of new peptide assemblies that expands the repertoire of biomaterial nanostructures has been of a tremendous challenge.Hence,it is evident that a successful research achievement in this area would increase the understanding of molecular interactions in supramolecules and create novel scaffolds exploitable in biotechnology and synthetic biology.The manipulation of cyclic peptide self-assembly is particularly intriguing for this purpose.Herein,we report that a novel type of cyclic peptides,referred to as chiral tether constrained cyclic peptides(CCP),shows promising self-assembly properties.CCPs are the first example of a controllable assembly of all-L-α-cyclic peptides with different ring sizes.A noteworthy feature of the CCP system is good tolerance of different secondary structures,ring size,and peptide sequence.Based on this system,a variety of nanostructures could be constructed,which display different physical properties,rendering it an excellent platform for molecular interaction studies.Further,demonstrate potential applications of these peptide assemblies in bioimaging and energy storage.

Peptide-based nanomaterials:Self-assembly,properties and applications

Peptide-based materials that have diverse structures and functionalities are an important type of biomaterials.In former times,peptide-based nanomaterials with excellent stability were constructed through self-assembly.Compared with individual peptides,peptide-based self-assembly nanomaterials that form well-ordered superstructures possess many advantages such as good thermo-and mechanical stability,semiconductivity,piezoelectricity and optical properties.Moreover,due to their excellent biocompatibility and biological activity,peptide-based self-assembly nanomaterials have been vastly used in different fields.In this review,we provide the advances of peptide-based self-assembly nanostructures,focusing on the driving forces that dominate peptide self-assembly and assembly mechanisms of peptides.After that,we outline the synthesis and properties of peptide-based nanomaterials,followed by the applications of functional peptide nanomaterials.Finally,we provide perspectives on the challenges and future of peptide-based nanomaterials.

A multifunctional nanotheranostic agent potentiates erlotinib to EGFR wild-type non-small cell lung cancer

Epidermal growth factor receptor(EGFR)tyrosine kinase inhibitors(TKI),such as Erlotinib,have demonstrated remarkable efficacy in the treatment of non-small cell lung cancer(NSCLC)patients with mutated EGFR.However,the efficacy of EGFR-TKIs in wild-type(wt)EGFR tumours has been shown to be marginal.Methods that can sensitize Erlotinib to EGFR wild-type NSCLC remain rare.Herein,we developed a multifunctional superparamagnetic nanotheranostic agent as a novel strategy to potentiate Erlotinib to EGFR-wt NSCLCs.Our results demonstrate that the nanoparticles can co-escort Erlotinib and a vascular epithermal growth factor(VEGF)inhibitor,Bevacizumab(Bev),to EGFR-wt tumours.The nanotheranostic agent exhibits remarkable effects as an inhibitor of EGFR-wt tumour growth.Moreover,Bev normalizes the tumour embedded vessels,further promoting the therapeutic efficacy of Erlotinib.In addition,the tumour engagement of the nanoparticles and the vascular normalization could be tracked by magnetic resonance imaging(MRI).Collectively,our study,for the first time,demonstrated that elaborated nanoparticles could be employed as a robust tool to potentiate Erlotinib to EGFR-wt NSCLC,paving the way for imaging-guided nanotheranostics for refractory NSCLCs expressing EGFR wild-type genes.