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Limited actionable data is one of the main constraints for urban local bodies and regulatory agencies to improve air quality. Emission inventories and source apportionment are important components of air quality management. However, they provide limited information about the location of pollution sources and how the sources are changing dynamically. To overcome these limitations, a field reconnaissance survey and hyperlocal monitoring through low-cost sensors were conducted for one of the hotspots in Delhi. Field reconnaissance survey helps identify and geolocate dispersed pollution sources (unpaved roads, road dust, biomass and waste burning, construction activities, etc.). The operation of the survey includes route planning, training of field surveyors, field survey, data quality control and analysis. Through the survey, 786 dispersed sources of 14 distinct types were identified. Construction and Demolition waste, potholes, road dust and garbage dumps constitute 40 % of the sources. The concerned agencies and sub-departments were mapped through consultation with stakeholders, and sources were prioritised based on factors like population density, predominant wind direction, etc. A network of low-cost sensors is also being deployed, taking the different land use categories within the hotspot into consideration to study the impact of tackling these dispersed sources. The present approach was found to be both cost as well time effective and has the potential to scale and can be used for other scientific applications like spatial bias correction in air quality models. The approach can also be used to develop targeted strategies for improving air quality and mitigating the negative impacts of air pollution on human health and the environment.

The incorporation of non-covalent albumin binding moieties (ABMs) into radiotracers results in increased circulation time, leading to a higher uptake in the target tissues such as the tumor, and, in some cases, reduced kidney retention. We previously developed [18F]AlF NOTA-K(ABM)-αvβ6-BP, where αvβ6-BP is a peptide with high affinity for the cell surface receptor integrin αvβ6 that is overexpressed in several cancers, and the ABM is an iodophenyl-based moiety. [18F]AlF NOTA-K(ABM)-αvβ6-BP demonstrated prolonged blood circulation compared to the non-ABM parent peptide, resulting in high, αvβ6-targeted uptake with continuously improving detection of αvβ6(+) tumors using PET/CT. To further extend the imaging window beyond that of fluorine-18 (t1/2 = 110 min) and to investigate the pharmacokinetics at later time points, we radiolabeled the αvβ6-BP with copper-64 (t1/2 = 12.7 h). Two peptides were synthesized without (1) and with (2) the ABM and radiolabeled with copper-64 to yield [64Cu]1 and [64Cu]2, respectively. The affinity of [natCu]1 and [natCu]2 for the integrin αvβ6 was assessed by enzyme-linked immunosorbent assay. [64Cu]1 and [64Cu]2 were evaluated in vitro (cell binding and internalization) using DX3puroβ6 (αvβ6(+)), DX3puro (αvβ6(-)), and pancreatic BxPC-3 (αvβ6(+)) cells, in an albumin binding assay, and for stability in both mouse and human serum. In vivo (PET/CT imaging) and biodistribution studies were done in mouse models bearing either the paired DX3puroβ6/DX3puro or BxPC-3 xenograft tumors. [64Cu]1 and [64Cu]2 were synthesized in ≥97% radiochemical purity. In vitro, [natCu]1 and [natCu]2 maintained low nanomolar affinity for integrin αvβ6 (IC50 = 28 ± 3 and 19 ± 5 nM, respectively); [64Cu]1 and [64Cu]2 showed comparable binding to αvβ6(+) cells (DX3puroβ6: ≥70%, ≥42% internalized; BxPC-3: ≥19%, ≥12% internalized) and ≤3% to the αvβ6(-) DX3puro cells. Both radiotracers were ≥98% stable in human serum at 24 h, and [64Cu]2 showed a 6-fold higher binding to human serum protein than [64Cu]1. In vivo, selective uptake in the αvβ6(+) tumors was observed with tumor visualization up to 72 h for [64Cu]2. A 3-5-fold higher αvβ6(+) tumor uptake of [64Cu]2 vs [64Cu]1 was observed throughout, at least 2.7-fold improved BxPC-3-to-kidney and BxPC-3-to-blood ratios, and 2-fold improved BxPC-3-to-stomach ratios were noted for [64Cu]2 at 48 h. Incorporation of an iodophenyl-based ABM into the αvβ6-BP ([64Cu]2) prolonged circulation time and resulted in improved pharmacokinetics, including increased uptake in αvβ6(+) tumors that enabled visualization of αvβ6(+) tumors up to 72 h by PET/CT imaging.

The use of low-cost sensors (LCS) in air quality monitoring has been gaining interest across all walks of society, including community and citizen scientists, academic research groups, environmental agencies, and the private sector. Traditional air monitoring, performed by regulatory agencies, involves expensive regulatory-grade equipment and requires ongoing maintenance and quality control checks. The low-price tag, minimal operating cost, ease of use, and open data access are the primary driving factors behind the popularity of LCS. This study discusses the role and associated challenges of PM2.5 sensors in monitoring air quality. We present the results of evaluations of the PurpleAir (PA.) PA-II LCS against regulatory-grade PM2.5 federal equivalent methods (FEM) and the development of sensor calibration algorithms. The LCS calibration was performed for 2 to 4 weeks during December 2019–January 2020 in Raleigh, NC, and Delhi, India, to evaluate the data quality under different aerosols loadings and environmental conditions. This exercise aims to develop a robust calibration model that uses PA measured parameters (i.e., PM2.5, temperature, relative humidity) as input and provides bias-corrected PM2.5 output at an hourly scale. Thus, the calibration model relies on simultaneous measurements of PM2.5 by FEM as target output during the calibration model development process. We applied various statistical and machine learning methods to achieve a regional calibration model. The results from our study indicate that, with proper calibration, we can achieve bias-corrected PM2.5 data using PA sensors within 12 % percentage mean absolute bias at hourly and within 6 % for a daily average. Our study also suggests that pre-deployment calibrations developed at local or regional scales should be performed for the PA sensors to correct data from the field for scientific data analysis.

PurposeThe αvβ6-BP peptide selectively targets the integrin αvβ6, a cell surface receptor recognized as a prognostic indicator for several challenging malignancies. Given that the 4-[18F]fluorobenzoyl (FBA)-labeled peptide is a promising PET imaging agent, radiolabeling via aluminum [18F]fluoride chelation and introduction of an albumin binding moiety (ABM) have the potential to considerably simplify radiochemistry and improve the pharmacokinetics by increasing biological half-life.ProceduresThe peptides NOTA-αvβ6-BP (1) and NOTA-K(ABM)-αvβ6-BP (2) were synthesized on solid phase, radiolabeled with aluminum [18F]fluoride, and evaluated in vitro (integrin ELISA, albumin binding, cell studies) and in vivo in mouse models bearing paired DX3puroβ6 [αvβ6(+)]/DX3puro [αvβ6(-)], and for [18F]AlF 2, BxPC-3 [αvβ6(+)] cell xenografts (PET imaging, biodistribution).ResultsThe peptides were radiolabeled in 23.0 ± 5.7% and 22.1 ± 4.4% decay-corrected radiochemical yield, respectively, for [18F]AlF 1 and [18F]AlF 2. Both demonstrated excellent affinity and selectivity for integrin αvβ6 by ELISA (IC50(αvβ6) = 3-7nM vs IC50(αvβ3) > 10μM) and in cell binding studies (51.0 ± 0.7% and 47.2 ± 0.7% of total radioactivity bound to DX3puroβ6 cells at 1h, respectively, vs. ≤ 1.2% to DX3puro for both compounds). The radiotracer [18F]AlF 1 bound to human serum at 16.3 ± 1.9%, compared to 67.5 ± 1.0% for the ABM-containing [18F]AlF 2. In vivo studies confirmed the effect of the ABM on blood circulation (≤ 0.1% ID/g remaining in blood for [18F]AlF 1 as soon as 1h p.i. vs. > 2% ID/g for [18F]AlF 2 at 6h p.i.) and higher αvβ6(+) tumor uptake (4h: DX3puroβ6; [18F]AlF 1: 3.0 ± 0.7% ID/g, [18F]AlF 2: 7.2 ± 0.7% ID/g; BxPC-3; [18F]AlF 2: 10.2 ± 0.1% ID/g).ConclusionBoth compounds were prepared using standard chemistries; affinity and selectivity for integrin αvβ6 in vitro remained unaffected by the albumin binding moiety. In vivo, the albumin binding moiety resulted in prolonged circulation and higher αvβ6-targeted uptake.

The purpose of this study was to develop and evaluate two αvβ6-targeted fluorescent imaging agents. The integrin subtype αvβ6 is significantly upregulated in a wide range of epithelial derived cancers, plays a key role in invasion and metastasis, and expression is often located at the invasive edge of tumors. αvβ6-targeted fluorescent imaging agents have the potential to guide surgical resection leading to improved patient outcomes. Both imaging agents were based on the bi-PEGylated peptide NH2-PEG28-A20FMDV2-K16R-PEG28 (1), a peptide that has high affinity and selectivity for the integrin αvβ6: (a) 5-FAM-X-PEG28-A20FMDV2-K16R-PEG28 (2), and (b) IRDye800-PEG28-A20FMDV2-K16R-PEG28 (3). Peptides were synthesized using solid-phase peptide synthesis and standard Fmoc chemistry. Affinity for αvβ6 was evaluated by ELISA. In vitro binding, internalization, and localization of 2 was monitored using confocal microscopy in DX3puroβ6 (αvβ6+) and DX3puro (αvβ6−) cells. The in vivo imaging and ex vivo biodistribution of 3 was evaluated in three preclinical mouse models, DX3puroβ6/DX3puro and BxPC-3 (αvβ6+) tumor xenografts and a BxPC-3 orthotopic pancreatic tumor model. Peptides were obtained in > 99% purity. IC50 values were 28 nM (2) and 39 nM (3). Rapid αvβ6-selective binding and internalization of 2 was observed. Fluorescent intensity (FLI) measurements extracted from the in vivo images and ex vivo biodistribution confirmed uptake and retention of 3 in the αvβ6 positive subcutaneous and orthotopic tumors, with negligible uptake in the αvβ6-negative tumor. Blocking studies with a known αvβ6-targeting peptide demonstrated αvβ6-specific binding of 3. Two fluorescence imaging agents were developed. The αvβ6-specific uptake, internalization, and endosomal localization of the fluorescence agent 2 demonstrates potential for targeted therapy. The selective uptake and retention of 3 in the αvβ6-positive tumors enabled clear delineation of the tumors and surgical resection indicating 3 has the potential to be utilized during image-guided surgery.

The incorporation of non-covalent albumin binding moieties (ABMs) into radiotracers results in increased circulation time, leading to a higher uptake in the target tissues such as the tumor, and, in some cases, reduced kidney retention. We previously developed [

National Clean Air Programme (NCAP), launched in 2019, is India's flagship program for better air quality in 122 cities. This review evaluates the scientific, legislative, financial, and institutional framework of the 102 publicly available clean air action plans submitted under NCAP. We assessed the robustness of the plans using the background information on pollution sources and their contribution; legal backing for the clean air action plan; cost of measures; and existing institutional accountability regime. We used the tally chart method for estimating city-specific and sector-specific mitigation measures, the number of actions under the purview of various implementation agencies, and the number of institutional, physical, and promotional interventions in the plans. Transport and road dust together cover 50% of action points, followed by interventions for the industries. Domestic cooking and heating is mentioned as a source only in 42 plans for a total of 2% of the action points. Institutional nature of the interventions was observed in 74% of the action points, using the language “overseeing, planning, proposing, preparing, investigating, identifying, ensuring, strengthening, training, studying, and engaging”. We also identified the plans that contained information on source contributions, an outline of financial requirements for executing the plans and measures for mitigating pollution from regional sources. Only 25% of the plans integrated information on the relative source contributions to formulate control strategies. Even fewer plans outlined the financial requirements for executing the plans. The institutional and administrative arrangements for ensuring inter-departmental and regional alignment in air pollution mitigation strategies are absent. We close the review with recommendations which include mandating regular updates for emission and pollution loads, granting greater fiscal autonomy for Urban Local Bodies to maintain the infrastructure necessary for sustaining air quality benefits, and moving from city-centric to airshed-centric air quality management.

PURPOSE: The α(v)β(6)-BP peptide selectively targets the integrin α(v)β(6), a cell surface receptor recognized as a prognostic indicator for several challenging malignancies. Given that the 4-[(18)F] fluorobenzoyl (FBA)-labeled peptide is a promising PET imaging agent, radiolabeling via aluminum [(18)F]fluoride chelation and introduction of an albumin binding moiety (ABM) have the potential to considerably simplify radiochemistry and improve the pharmacokinetics by increasing biological half-life. PROCEDURES: The peptides NOTA-α(v)β(6)-BP (1) and NOTA-K(ABM)-α(v)β(6)-BP (2) were synthesized on solid phase, radiolabeled with aluminum [(18)F]fluoride, and evaluated in vitro (integrin ELISA, albumin binding, cell studies) and In vivo in mouse models bearing paired DX3puroβ6 [α(v)β(6)(+)]/DX3puro [α(v)β(6)(−)], and for [(18)F]AlF 2, BxPC-3 [α(v)β(6)(+)] cell xenografts (PET imaging, biodistribution). RESULTS: The peptides were radiolabeled in 23.0 ± 5.7 % and 22.1 ± 4.4 % decay-corrected radiochemical yield, respectively, for [(18)F]AlF 1 and [(18)F]AlF 2. Both demonstrated excellent affinity and selectivity for integrin α(v)β(6) by ELISA (IC(50)(α(v)β(6)) = 3–7 nM vs IC(50)(α(v)β(3)) > 10 μM) and in cell binding studies (51.0 ± 0.7 % and 47.2 ± 0.7 % of total radioactivity bound to DX3puroβ6 cells at 1 h, respectively, vs. ≤ 1.2 % to DX3puro for both compounds). The radiotracer [(18)F]AlF 1 bound to human serum at 16.3 ± 1.9 %, compared to 67.5 ± 1.0 % for the ABM-containing [(18)F]AlF 2. In vivo studies confirmed the effect of the ABM on blood circulation (≤ 0.1 % ID/g remaining in blood for [(18)F]AlF 1 as soon as 1 h p.i. vs. > 2 % ID/g for [(18)F]AlF 2 at 6 h p.i.) and higher α(v)β(6)(+) tumor uptake (4 h: DX3puroβ6; [(18)F]AlF 1: 3.0 ± 0.7 % ID/g, [(18)F]AlF 2: 7.2 ± 0.7 % ID/g; BxPC-3; [(18)F]AlF 2: 10.2 ± 0.1 % ID/g). CONCLUSION: Both compounds were prepared using standard chemistries; affinity and selectivity for integrin α(v)β(6) in vitro remained unaffected by the albumin binding moiety. In vivo, the albumin binding moiety resulted in prolonged circulation and higher α(v)β(6)-targeted uptake.

The purpose of this study was to develop and evaluate two αPeptides were synthesized using solid-phase peptide synthesis and standard Fmoc chemistry. Affinity for αPeptides were obtained in 99% purity. ICTwo fluorescence imaging agents were developed. The α

This article was updated to correct the axes in Figures 4e and 5d.

A series of phosphoramidate-based prostate specific membrane antigen (PSMA) inhibitors of increasing lipophilicity were synthesized (4, 5, and 6), and their fluorine-18 analogs were evaluated for use as positron emission tomography (PET) imaging agents for prostate cancer. To gain insight into their modes of binding, they were also cocrystallized with the extracellular domain of PSMA. All analogs exhibited irreversible binding to PSMA with IC50 values ranging from 0.4 to 1.3 nM. In vitro assays showed binding and rapid internalization (80-95%, 2 h) of the radiolabeled ligands in PSMA(+) cells. In vivo distribution demonstrated significant uptake in CWR22Rv1 (PSMA(+)) tumor, with tumor to blood ratios of 25.6:1, 63.6:1, and 69.6:1 for [(18)F]4, [(18)F]5, and [(18)F]6, respectively, at 2 h postinjection. Installation of aminohexanoic acid (AH) linkers in the phosphoramidate scaffold improved their PSMA binding and inhibition and was critical for achieving suitable in vivo imaging properties, positioning [(18)F]5 and [(18)F]6 as favorable candidates for future prostate cancer imaging clinical trials.

© 2015 American Chemical Society. Solid tumors are hypoxic with altered metabolism, resulting in secretion of acids into the extracellular matrix and lower relative pH, a feature associated with local invasion and metastasis. Therapeutic and diagnostic agents responsive to this microenvironment may improve tumor-specific delivery. Therefore, we pursued a general strategy whereby caged small-molecule drugs or imaging agents liberate their parent compounds in regions of low interstitial pH. In this manuscript, we present a new acid-labile prodrug method based on the glycosylamine linkage, and its application to a class of positron emission tomography (PET) imaging tracers, termed [18F]FDG amines. [18F]FDG amines operate via a proposed two-step mechanism, in which an acid-labile precursor decomposes to form the common radiotracer 2-deoxy-2-[18F]fluoro-d-glucose, which is subsequently accumulated by glucose avid cells. The rate of decomposition of [18F]FDG amines is tunable in a systematic fashion, tracking the pKaof the parent amine. In vivo, a 4-phenylbenzylamine [18F]FDG amine congener showed greater relative accumulation in tumors over benign tissue, which could be attenuated upon tumor alkalinization using previously validated models, including sodium bicarbonate treatment, or overexpression of carbonic anhydrase. This new class of PET tracer represents a viable approach for imaging acidic interstitial pH with potential for clinical translation.

Introduction In this study, a structurally modified phosphoramidate scaffold, with improved prostate-specific membrane antigen (PSMA) avidity, stability and in vivo characteristics, as a PET imaging agent for prostate cancer (PCa), was prepared and evaluated. Methods p-Fluorobenzoyl-aminohexanoate and 2-(3-hydroxypropyl)glycine were introduced into the PSMA-targeting scaffold yielding phosphoramidate 5. X-ray crystallography was performed on the PSMA/5 complex. [ 18 F]5 was synthesized, and cell uptake and internalization studies were conducted in PSMA(+) LNCaP and CWR22Rv1 cells and PSMA(−) PC-3 cells. In vivo PET imaging and biodistribution studies were performed at 1 and 4h post injection in mice bearing CWR22Rv1 tumor, with or without blocking agent. Results The crystallographic data showed interaction of the p -fluorobenzoyl group with an arene-binding cleft on the PSMA surface. In vitro studies revealed elevated uptake of [ 18 F]5 in PSMA(+) cells (2.2% in CWR22Rv1 and 12.1% in LNCaP) compared to PSMA(−) cells (0.08%) at 4h. In vivo tumor uptake of 2.33% ID/g and tumor-to-blood ratio of 265:1 was observed at 4h. Conclusions We have successfully synthesized, radiolabeled and evaluated a new PSMA-targeted PET agent. The crystal structure of the PSMA/5 complex highlighted the interactions within the arene-binding cleft contributing to the overall complex stability. The high target uptake and rapid non-target clearance exhibited by [ 18 F]5 in PSMA(+) xenografts substantiates its potential use for PET imaging of PCa. Advances in Knowledge The only FDA-approved imaging agent for PCa, Prostascint®, targets PSMA but suffers from inherent shortcomings. The data acquired in this manuscript confirmed that our new generation of [ 18 F]-labeled PSMA inhibitor exhibited promising in vivo performance as a PET imaging agent for PCa and is well-positioned for subsequent clinical trials. Implications for Patient Care Our preliminary data demonstrate that this tracer possesses the required imaging characteristics to be sensitive and specific for PCa imaging in patients at all stages of the disease.

The enzyme-biomarker prostate-specific membrane antigen (PSMA) is an active target for imaging and therapeutic applications for prostate cancer. The internalization of PSMA has been shown to vary with inhibitors' mode of binding: irreversible, slowly reversible, and reversible.In the present study, PSMA-targeted clickable derivatives of an irreversible phosphoramidate inhibitor DBCO-PEG(4) -CTT-54 (IC(50) = 1.0 nM) and a slowly reversible phosphate inhibitor, DBCO-PEG(4) -CTT-54.2 (IC(50) = 6.6 nM) were clicked to (99m) Tc(CO)(3) -DPA-azide to assemble a PSMA-targeted SPECT agent. The selectivity, percent uptake, and internalization of these PSMA-targeted SPECT agents were evaluated in PSMA-positive and PSMA-negative cells.In vitro studies demonstrated that PSMA-targeted SPECT agents exhibited selective cellular uptake in the PSMA-positive LNCaP cells compared to PSMA-negative PC3 cells. More importantly, it was found that (99m) Tc(CO)(3) -DPA-DBCO-PEG(4) -CTT-54 based on an irreversible PSMA inhibitor core, exhibited greater uptake and internalization than (99m) Tc(CO)(3) -DPA-DBCO-PEG(4) -CTT-54.2 constructed from a slowly reversible PSMA inhibitor core.We have demonstrated that a PSMA-targeted SPECT agent can be assembled efficiently using copper-less click chemistry. In addition, we demonstrated that mode of binding has an effect on internalization and percent uptake of PSMA-targeted SPECT agents; with the irreversible targeting agent demonstrating superior uptake and internalization in PSMA+ cells. The approach demonstrated in this work now supports a modular approach for the assembly of PSMA-targeted imaging and therapeutic agents.

Prostate-specific membrane antigen (PSMA) is highly up-regulated in prostate tumor cells, providing an ideal target for imaging applications of prostate cancer. CTT-1297 (IC50 = 27 nM) is an irreversible phosphoramidate inhibitor of PSMA that has been conjugated to the CB-TE1K1P chelator for incorporation of Cu-64. The resulting positron emission tomography (PET) agent, [(64)Cu]ABN-1, was evaluated for selective uptake both in vitro and in vivo in PSMA-positive cells of varying expression levels. The focus of this study was to assess the ability of [(64)Cu]ABN-1 to detect and distinguish varying levels of PSMA in a panel of prostate tumor-bearing mouse models.CTT-1297 was conjugated to the CB-TE1K1P chelator using click chemistry and radiolabeled with Cu-64. Internalization and binding affinity of [(64)Cu]ABN-1 was evaluated in the following cell lines having varying levels of PSMA expression: LNCaP late-passage LNCaP early passage ≈ C4-2B CWR22rv1 and PSMA-negative PC-3 cells. PET/X-ray computed tomography imaging was performed in NCr nude mice with subcutaneous tumors of the variant PSMA-expressing cell lines.[(64)Cu]ABN-1 demonstrated excellent uptake in PSMA-positive cells in vitro, with ∼80 % internalization at 4 h for each PSMA-positive cell line with uptake (fmol/mg) correlating to PSMA expression levels. The imaging data indicated significant tumor uptake in all models. The biodistribution for late-passage LNCaP (highest PSMA expression) demonstrated the highest specific uptake of [(64)Cu]ABN-1 with tumor-to-muscle and tumor-to-blood ratios of 30 ± 11 and 21 ± 7, respectively, at 24 h post-injection. [(64)Cu]ABN-1 cleared through all tissues except for PSMA-positive kidneys.[(64)Cu]ABN-1 demonstrated selective uptake in PSMA-positive cells and tumors, which correlated to the level of PSMA expression. The data reported herein suggest that [(64)Cu]ABN-1 will selectively target and image variant PSMA expression and in the future will serve as a non-invasive method to follow the progression of prostate cancer in men.

BACKGROUND Prostate-specific membrane antigen (PSMA) remains an active target for imaging and therapeutic applications for prostate cancer. METHODS In the present study, an irreversible phosphoramidate inhibitor, CTT-54 (IC50 = 14 nM), has been modified to deliver 99mTc-(CO)3-DTPA as a SPECT imaging payload to PSMA+ cells in vivo and in vitro. Percent uptake, competitive binding, and internalization will evaluate the imaging agent in vitro. Preliminary biodistribution and imaging will be utilized for in vivo evaluation. RESULTS In vitro studies demonstrate that the radiotracer 99mTc-(CO)3-DTPA-CTT-54 exhibits increasing cellular uptake in the PSMA+ LNCaP cells over time. More importantly, it was found that 99mTc-(CO)3-DTPA-CTT-54 is rapidly internalized into LNCaP cells, presumably through the PSMA enzyme-inhibitor complex. In a pilot biodistribution study, increasing accumulation of the radiotracer in LNCaP xenografts was observed from 2 to 4 hr and significant clearance from non-target tissues. CONCLUSIONS While DTPA may not represent the ideal chelate structure for 99mTc(CO)3, the data provides proof-of-concept support for the development of a next-generation phosphoramidate-based PSMA inhibitor-conjugates for use as SPECT imaging agents. Prostate 72:904–912, 2012. © 2011 Wiley Periodicals, Inc.

The fac-Re(OH2)3(CO)3+ moiety was investigated with a known bidentate ligand, acetylactone (acac) and amine based ligands in a 2 + 1 and tridentate approach. In the 2 + 1 approach, the fac-Re(CO)3(acac)(OH2) was reacted with ethylamine to yield the monomer version fac-Re(CO)3(acac)(NH2Et), 1. Based on the Schiff base condensation of a ketone and a primary amine, a tridentate ligand approach for fac-Re(OH2)3(CO)3+ utilizing the reactivity of acac and diamine ligands (1,2 ethylene, 1,3 propylene, 1,4 butylene) was explored in a didactic manner: 1) an in situ ligand synthesis approach reacting fac-Re(CO)3(acac)(OH2) with the diamine (2 + 2 = 3) or 2) direct complexation of fac-Re(OH2)3(CO)3+ with the prepared ligand. The results observed with rhenium complexes were characterized by standard chemical analysis and X-ray analysis.

The fac -M (CO) 3 + (M = Re, 99m Tc) moiety was investigated with a known bidentate ligand, acetylacetone (acac) and imidazole based ligands in a 2 + 1 and tridentate approach. In the 2 + 1 approach, the fac -Re(CO) 3 (acac)(OH 2 ) was reacted with imidazole or 1-methylimidazole to yield a unique anionic μ-bridging imidazol-1-ide dimer fac -[(imidazol-1-ide)-bis-( fac -acetylacetonatotricarbonylrhenium (I)], 1 , or the monomer version fac -M(CO) 3 (acac)(1-methylimidazole), 2 , respectively. Based on the Schiff base condensation of a ketone and a primary amine, a tridentate ligand approach for fac -M ( OH 2 ) 3 (CO) 3 + utilizing the reactivity of acac and histamine was explored in a didactic manner: (1) an in situ ligand synthesis approach reacting fac -M(CO) 3 (acac)(OH 2 ) with histamine (2 + 2 = 3) that led to the formation of an unexpected dimer μ-acachistimine, compound, 3 , or (2) direct complexation of fac -M ( OH 2 ) 3 (CO) 3 + with the prepared ligand acachistimine, 4 , to yield the monomer product fac -M(CO) 3 (acachistimine), 5 . The results observed with rhenium complexes characterized by standard chemical analysis and X-ray analysis correlated with the radioactive experiments conducted with 99 m Tc (CO) 3 + .

Prostate cancer (PCa) is the second most common cause of cancer death among American men after lung cancer. Unfortunately, current therapies do not provide effective treatments for patients with advanced, metastatic, or hormone refractory disease. Therefore, we seek to generate therapeutic agents for a novel PCa treatment strategy by delivering a suicide enzyme (yCDtriple) to a cell membrane bound biomarker found on PCa cells (prostate-specific membrane antigen (PSMA)). This approach has resulted in a new PCa treatment strategy reported here as inhibitor-directed enzyme prodrug therapy (IDEPT). The therapeutic agents described were generated using a click chemistry reaction between the unnatural amino acid (p-azidophenylalanine (pAzF)) incorporated into yCDtriple and the dibenzylcyclooctyne moiety of our PSMA targeting agent (DBCO-PEG4-AH2-TG97). After characterization of the therapeutic agents, we demonstrate significant PCa cell killing of PSMA-positive cells. Importantly, we demonstrate that this click chemistry approach can be used to efficiently couple a therapeutic protein to a targeting agent and may be applicable to the ablation of other types of cancers and/or malignancies.

Prostate-specific membrane antigen (PSMA) remains an active target for imaging and therapeutic applications for prostate cancer.In the present study, an irreversible phosphoramidate inhibitor, CTT-54 (IC50 = 14 nM), has been modified to deliver 99mTc-(CO)3-DTPA as a SPECT imaging payload to PSMA+ cells in vivo and in vitro. Percent uptake, competitive binding, and internalization will evaluate the imaging agent in vitro. Preliminary biodistribution and imaging will be utilized for in vivo evaluation.In vitro studies demonstrate that the radiotracer 99mTc-(CO)3-DTPA-CTT-54 exhibits increasing cellular uptake in the PSMA+ LNCaP cells over time. More importantly, it was found that 99mTc-(CO)3-DTPA-CTT-54 is rapidly internalized into LNCaP cells, presumably through the PSMA enzyme-inhibitor complex. In a pilot biodistribution study, increasing accumulation of the radiotracer in LNCaP xenografts was observed from 2 to 4 hr and significant clearance from non-target tissues.While DTPA may not represent the ideal chelate structure for 99mTc(CO)3, the data provides proof-of-concept support for the development of a next-generation phosphoramidate-based PSMA inhibitor-conjugates for use as SPECT imaging agents.

Facile reactivity of hydrazides and aldehydes was explored as potential coupling partners for incorporation into M(CO)(3) (M = Re, (99m)Tc) based radiopharmaceuticals. Both 'click, then chelate' and 'prelabel, then click' synthetic routes produced identical products in high yields and lacked metal-hydrazide/-hydrazone interactions, highlighting the potential of this click strategy.