A NEW BIFUNCTIONAL CHELATING AGENT α,ε-N,N'-BIS(L-CYSTEINYL)-L-LYSINE FOR RADIOLABELLING OF MONOCLONAL ANTIBODIES WITH TECHNETIUM-99M

α,ε-N,N'-bis(L-cysteinyl)-L-lysine was synthesized and char- acterized for the first time.It was then employed as a bifunctional chelating agent to chelate technetium-99m and subsequently conjugated to fragment F(ab')_2 of anti-gastric tumor monoclonal antibody 3G9.The radiolabelled antibody was satisfactorily stable and immunoreactive.

LABELLING OF METALLOTHIONEIN WITH ^(99m)Tc

99mTc-labelled metallothionein (99mTc-MT) was prepared through both direct and transcomplexation labelling approaches. Buffer systems and a variety of other parameters in the direct labelling procedure were studied in detail. High radiolabelling yields of 93-96% and the specific radioactivity of 3.7 MB/μg were obtained under optimal conditions by the direct labelling method. The prepared 99mTc-MT was stable in vitro. The chelate-exchange kinetics of MT with 99mTc-glucohepatonate and 99mTc-citrate were also studied. Biodistribution and imaging studies showed that 99mTc-MT was accumulated in the animal kidneys at an exceptionally high level, indicating that 99mTc-MT might be a potential renal imaging agent.

Reductive Amination with [¹¹C]Formaldehyde: A Versatile Approach to Radiomethylation of Amines

Carbon-11 radiolabeled amines constitute a very important class of radioligands that are widely used for positron emission tomography (PET) imaging. Radiolabeling of amines is often achieved through radiomethylation using [11C]CH3I or [11C]CH3OTf under basic conditions in a strictly anhydrous environment. Functional groups such as hydroxyl and carboxyl groups that are often present in the molecules are normally base sensitive and require protection and deprotection, which substantially prolongs and complicates the radiolabeling process. Here we report a versatile approach to a series of C-11 radiolabeled amines prepared through reductive amination using [11C]formaldehyde. Using a variety of substrates bearing different functional groups, we demonstrate the general utility of this method. In contrast to conventional radiomethylation methods, the reductive amination using [11C]formaldehyde can be carried out in an aqueous environment relatively quickly without the need of protection of base-sensitive functional groups.

Radiolabeling of lacosamide using highly purified rhenium-188 as a prospective brain theranostic agent

Rhenium-188 is prospectively effective for both diagnosis and radiotherapy as it appropriately emits gamma rays and beta particles.Lacosamide(LCM)is a newly approved antiepileptic medication for focal drug-resistant epilepsy.Rhenium-188 was separated with high elution yield and high purity using the new 188W/188Re generator based on the ZrSiW gel matrix.188Re-LCM was prepared with high radiochemical yield and high purity.Biodistribution of 188Re-LCM in normal Swiss albino mice was investigated to determine its utility as a potential brain therapy agent.The 188W/188Re generator was used to obtain 188Re based on the ZrSi188W gel matrix,and the chemical,radiochemical,and radionuclidic purity of the obtained 188Re was determined using inductively coupled plasma optical emission spectrometry(ICP-AES),a paper chromatography technique,and high-purity germanium(HPGe)detection,respectively,to assess its validity for LCM labeling.Various factors,such as the pH,reaction time,and LCM quantity,were therefore studied in order to improve the yield and purity of 188Re-LCM,as determined by various chromatographic techniques such as electrophoresis,thin layer chromatography(TLC),and highpressure liquid chromatography(HPLC).188Re was obtained with a high elution yield(75±3%)and a low 188W breakthrough(0.001±0.0001%).The maximum radiochemical yield of 188Re-LCM(87.5±1.8%)was obtained using 50 ll LCM(4 mM),250 ll stannous chloride(4.4 mM)at pH 4,100 ll 188Re(37 MBq),within 30 min,at room temperature(25±3C),as determined by TLC,electrophoresis,and HPLC techniques.Biodistribution analysis showed that 188Re-LCM was primarily localized in the brain(5.1%)with a long residence time(240 min).

Studies on the Thiol Components of Isolated Nuclei

The thiol components of the nonhistone proteins prepared from isolated nuclei from rat liver, regenerating liver and hepatoma 223 cells have been investigated after reaction with radio labelled N-ethylmaleimide and 5-5’-dithiobis-(2-nitrobenzoic acid) (DTNB). The labelled adducts formed were examined by isoelectric focusing analysis in polyacrylamide gel and the distribution of the radiolabels within sliced portions of the gels determined. In the case of the 14C labelled NEM adduct the label was found to be spread amongst numerous protein components within the gel however, in the case of the 35S labelled DTNB adducts, only a small proportion of the label was found in the protein material which was retained in the acidic isoelectric point (pI) region of the gel. The bulk of the 35S labelled adduct (56% - 60%) was found to have migrated into the anode solution (10 mM phosphoric acid). This could be adsorbed onto a hydrophobic resin (XAD2) resin and eluted with methanol. Gel filtration chromatographic analysis of this adduct material on BioGel P2, (exclusion limit 1500 daltons) showed low molecular weight components to be present. Slightly different patterns were obtained for these nuclei, each containing several 35S components with molecular weights greater than the Ellman reagent itself. These 35S labelled thiol components did not contain any protein, peptide or amino acid components indicating strongly that a novel species of thiols could be present in these nuclei bound within the non-histone protein matrices.

Expression and radiolabeling of Cas9 protein

As a robust platform for genome editing,CRISPR/Cas9 is currently being explored for engineering biology or therapeutics,yet means for quantitative detection of Cas9 proteins remain to be fully realized.Here,we expressed Cas9 proteins and developed a novel detection method that traced Cas9 based on radiolabeled iodine.Through optimizing the reaction conditions of reaction time,temperature and cycles,we obtained ^(125)I-Cas9 of high labeling yield.The prepared ^(125)I-Cas9 was stable in various media and preserved excellent genome editing efficiency.Thus,our strategy provides a convenient and efficient tool for further tracing biological behaviors of Cas9 proteins in living systems.

Natural product-based radiopharmaceuticals:Focus on curcumin and its analogs,flavonoids,and marine peptides

Natural products provide a bountiful supply of pharmacologically relevant precursors for the development of various drug-related molecules,including radiopharmaceuticals.However,current knowledge regarding the importance of natural products in developing new radiopharmaceuticals remains limited.To date,several radionuclides,including gallium-68,technetium-99m,fluorine-18,iodine-131,and iodine-125,have been extensively studied for the synthesis of diagnostic and therapeutic radiopharmaceuticals.The availability of various radiolabeling methods allows the incorporation of these radionuclides into bioactive molecules in a practical and efficient manner.Of the radiolabeling methods,direct radioiodination,radiometal complexation,and halogenation are generally suitable for natural products owing to their simplicity and robustness.This review highlights the pharmacological benefits of curcumin and its analogs,flavonoids,and marine peptides in treating human pathologies and provides a perspective on the potential use of these bioactive compounds as molecular templates for the design and development of new radiopharmaceuticals.Additionally,this review provides insights into the current strategies for labeling natural products with various radionuclides using either direct or indirect methods.

Peptides Radiofluorination: Main Methods and Highlights

Peptides have an important role in organism and its high quantity present in tumors leading to development of radiolabeled peptides for tumor-specific imaging. Once the traditional methodologies used for radiofluorination do not work with peptides, due to their harsh conditions, other radiolabeling strategies had to be developed to supply the need. Direct radiofluorination is either an inefficient method, and the use of bidirectional groups, or prosthetic groups, is needed to enable the binding between the radionuclide fluorine-18 and a peptide functionalized. New peptides radiolabeling strategies have been developed sourcing increase the synthesis yield, its chemoselectivity, and the binding stability, and reduce the total process time and the number of steps required. The progress of radiofluorination methodologies led to development of the amidation, acylation, imidation, and alkylation techniques, the use of thiol groups, photochemical conjugation, chemoselective reactions, and “click chemistry”, in addition to use of FDG molecule and heteroatoms as linkers. This paper presents the main strategies used for peptides radiofluorination, presenting their positive and negative points, and the prosthetic groups most used in each method.

An Experimental Study of Myocardial Viability with Myocardial Contrast Echocardiography

Background Myocardial blood flow(MBF) can be quantified with myocardial contrast echocardiography (MCE) during a venous infusion of microbubble. A minimal MBF is required to maintain cell membrane integrity and myocardial viability in ischemic condition. Thus, we hypothesized that MCE could be used to assess myocardial viability by the determination of MBF. Methods and ResultsMCE was performed at 4 hours after ligation of proximal left anterior descending coronary artery in 7 dogs with constant venous infusions of microbubbles. The video intensity versus pulsing interval plots derived from each myocardial pixel were fitted to an exponential function: y=A(1-e-βt), where y is Ⅵ at pulsing interval t, A reflects microvascular cross - sectional area (or myocardial blood volume), and βreflects mean myocardial microbubble velocity. The product of A·β represents MBF. MBF was also obtained by ra-diolabeled microsphere method servered as reference. MBF derived by radiolabeled microsphere - method in the regions of normal, ischemia and infarction was 1.5+0.3, 0.7+0.3, 0. 3+0. 2 mL @ min-1@ g-1 respectively. The product of A·β obtained by MCE in those regions was 52. 46±15. 09, 24. 36±3. 89, 3. 74 ±3. 80 respectively. There was good correlation between normalized MBF and the normalized A·β ( r = 0. 81, P=0. 001). Conclusions MCE has an ability to determine myocardial viability in myocardial infarction canine model.

A general method for assaying homo-and hetero-transglycanase activities that act on plant cell-wall polysaccharides

Transglycanases（endotransglycosylases） cleave a polysaccharide（donor-substrate） in mid-chain, and then transfer a portion onto another poly-or oligosaccharide（acceptor-substrate）. Such enzymes contribute to plant cellwall assembly and/or re-structuring. We sought a general method for revealing novel homo- and hetero-transglycanases, applicable to diverse polysaccharides and oligosaccharides, separating transglycanase-generated3 Hpolysaccharides from unreacted3H-oligosaccharides—the former immobilized（on filter-paper, silica-gel or glassfiber）,the latter eluted. On filter-paper, certain polysaccharides [e.g.（1!3, 1!4）-b-D-glucans] remained satisfactorily adsorbed when water-washed; others（e.g. pectins） were partially lost. Many oligosaccharides（e.g. arabinan-, galactan-, xyloglucan-based） were successfully eluted in appropriate solvents, but others（e.g. [3H]xylohexaitol, [3H]mannohexaitol[3H]cellohexaitol） remained immobile. On silica-gel, all3 Holigosaccharides left an immobile ‘ghost’ spot（contaminating any3H-polysaccharides）, which was diminished but not prevented by additives e.g. sucrose or Triton X-100. The best stratum was glassfiber（GF）, onto which the reactionmixture was dried then washed in 75% ethanol. Washing led to minimal loss or lateral migration of3H-polysaccharides if conducted by slow percolation of acidified ethanol. The effectiveness of GF-blotting was well demonstrated for Chara vulgaris transb-mannanase. In conclusion, our novel GF-blotting technique ef ficiently frees transglycanase-generated3H-polysaccharides from unreacted3H-oligosaccharides,enabling high-throughput screening of multiple postulated transglycanase activities utilising chemically diverse donorand acceptor-substrates.

Isolation of ^(212)Pb from natural thorium for targeted alpha-therapy

Targeted alpha-therapy(TAT) is increasingly attractive due to its extraordinary antitumor efficacy.However,the supply of α-emitters for TAT is insufficient and under control by a limited number of countries.^(212)Pb is a promising α-emitter with an optimal half-life(10.6 h) and favored decay chain.Of interest,^(212)Pb can be extracted directly from natural thorium,which may be abundant in the mining waste of rare-earth,uranium,etc.Indeed,radioactive thorium waste has been a longstanding environmental challenge that needs immediate action.Developing an on-demand and facile process to isolate ^(212)Pb from natural thorium would be ideal to meet the above challenges,yet is difficult.In theory,the ratio of ^(212)Pb tonatTh is below 10^(-13)in commercially available thorium salts.As a pilot study,2.2 MBq of ^(212)Pb was successfully extracted from a 5 L solution of thorium nitrate by using a Pb-selective resin.The radiochemical purity of ^(212)Pb is over 99.9% according to gamma-ray analysis.The purified^(212)Pb was applied to radiolabel a couple of peptides used in clinics(i.e.PSMA,TATE and FAPI-04),and the radiochemical yields are>85%.Of note,^(212)Pb can be repeatedly separated from the thorium solution every 2 days.In summary,a practical and scalable method was developed to isolate^(212)Pb for potentially clinical use,which may be of great importance as it does not require either cyclotron or nuclear reactor.

^(64)Cu radiolabeled nanomaterials for positron emission tomography(PET)imaging

The prevalence of positron emission tomography(PET)imaging has advanced biomedical applications for its ultrahigh sensitivity,deep tissue penetration and quantitative visualization of diseases in vivo.^(64)Cu with ideal half-life and decay characteristics has been designed as radioactive probes for disease diagnosis.The currently reported ^(64)Cu-labeled nanomaterials have the advantages of long circulation time in serum,good biocompatibility and mature preparation methods,and have been used in vivo PET imaging,biodistribution and pharmacokinetic monitoring,and imaging guided therapy.At the same time,suitable carrier characteristics and radiolabeling strategies are particularly important in the ^(64)Cu PET imaging process.In this review,we summarize different imaging probe designs and ^(64)Cu radiolabeling strategies,as well as their eventual applications in biomedicine.The potential challenges and prospects of ^(64)Cu labeled nanomaterials are also described,which provides broad prospects for radiolabeling strategies and further applications.

General synthesis of silica-based yolk/shell hybrid nanomaterials and in vivo tumor vasculature targeting

Multifunctional yolk/shell-structured hybrid nanomaterials have attracted increasing interest as theranostic nanoplatforms for cancer imaging and therapy. However, because of the lack of suitable surface engineering and tumor targeting strategies, previous research has focused mainly on nanostructure design and synthesis with few successful examples showing active tumor targeting after systemic administration. In this study, we report the general synthetic strategy of chelator-free zirconium-89 （89Zr）-radiolabeled, TRC105 antibody-conjugated, silica-based yolk/sheU hybrid nanopartides for in vivo tumor vasculature targeting. Three types of inorganic nanoparticles with varying morphologies and sizes were selected as the internal cores, which were encapsulated into single hollow mesoporous silica nanosheUs to form the yolk/sheU-structured hybrid nanopartides. As a proof-of-concept, we demonstrated successful surface functionalization of the nanoparticles with polyethylene glycol, TRC105 antibody （specific for CD105/endoglin）, and ~Zr （a positron-emitting radioisotope）, and enhanced in vivo tumor vasculature-targeted positron emission tomography imaging in 4T1 murine breast tumor-bearing mice. This strategy could be applied to the synthesis of other types of yolk/shell theranostic nanoparticles for tumor- targeted imaging and drug delivery.

Noninvasive Detection and Imaging of Matrix Metalloproteinases for Cancer Diagnosis

Matrix metalloproteinases(MMPs)are important cancer biomarkers and the sensitive detection of MMPs is of great importance to improve clinical diagnosis and therapy of cancer at its early stage.Molecular imaging,including fluorescent optical imaging,radiolabeled imaging,and magnetic resonance imaging,is a powerful tool to visualize and characterize biological processes at the cellular and molecular level.The recognition of MMPs via imaging strategies by utilizing MMP-responsive probes has been a hot pursuit in recent years.Probes designed for MMP detection commonly have two features:(1)off-thenon state in detection signal response to the appearance of MMPs,which has been applied in optical imaging and magnetic resonance imaging;(2)specific retention upon sensing MMPs,which has been applied in radiolabeled imaging.The development of theory and technology in the field of biomarker probes will be beneficial to the accurate diagnosis and effective treatment of cancer.

Radiosynthesis of [^(18)F]ArylSCF2H Using Aryl Boronic Acids, S-(Chlorofluoromethyl) benzenesulfonothioate and [^(18)F]Fluoride

Herein,we report a mild and practical protocol for the copper-catalyzed chlorofluoromethylthiolation of(hetero)aryl boronic acids with the novel reagent PhSO2SCFClH.The resulting products are amenable to halogen-exchange^(18)F-fluorination with cyclotronproduced[^(18)F]fluoride affording[^(18)F]ArSCF2H.This process highlights the combined value of reagent development and(hetero)aryl boron precursors for radiochemistry by adding the[^(18)F]SCF2H group to the list of^(18)F-motifs within reach for positron emission tomography studies.