Development of 225Ac-doped biocompatible nanoparticles for targeted alpha therapy.

Targeted alpha therapy (TAT) relies on chemical affinity or active targeting using radioimmunoconjugates as strategies to deliver α-emitting radionuclides to cancerous tissue. These strategies can be affected by transmetalation of the parent radionuclide by competing ions in vivo and the bond-breaking recoil energy of decay daughters. The retention of α-emitting radionuclides and the dose delivered to cancer cells are influenced by these processes. Encapsulating α-emitting radionuclides within nanoparticles can help overcome many of these challenges. Poly(lactic-co-glycolic acid) (PLGA) nanoparticles are a biodegradable and biocompatible delivery platform that has been used for drug delivery. In this study, PLGA nanoparticles are utilized for encapsulation and retention of actinium-225 ([225Ac]Ac3+). Encapsulation of [225Ac]Ac3+ within PLGA nanoparticles (Zave = 155.3 nm) was achieved by adapting a double-emulsion solvent evaporation method. The encapsulation efficiency was affected by both the solvent conditions and the chelation of [225Ac]Ac3+. Chelation of [225Ac]Ac3+ to a lipophilic 2,9-bis-lactam-1,10-phenanthroline ligand ([225Ac]AcBLPhen) significantly decreased its release (< 2%) and that of its decay daughters (< 50%) from PLGA nanoparticles. PLGA nanoparticles encapsulating [225Ac]AcBLPhen significantly increased the delivery of [225Ac]Ac3+ to murine (E0771) and human (MCF-7 and MDA-MB-231) breast cancer cells with a concomitant increase in cell death over free [225Ac]Ac3+ in solution. These results demonstrate that PLGA nanoparticles have potential as radionuclide delivery platforms for TAT to advance precision radiotherapy for cancer. In addition, this technology offers an alternative use for ligands with poor aqueous solubility, low stability, or low affinity, allowing them to be repurposed for TAT by encapsulation within PLGA nanoparticles.

Isothiocyanate-Functionalized Bifunctional Chelates and fac-[M(I)(CO)3](+) (M = Re, (99m)Tc) Complexes for Targeting uPAR in Prostate Cancer.

Developing new strategies to rapidly incorporate the fac-[M(I)(CO)3](+) (M = Re, (99m)Tc) core into biological targeting vectors in radiopharmaceuticals continues to expand as molecules become more complex and as efforts to minimize nonspecific binding increase. This work examines a novel isothiocyanate-functionalized bifunctional chelate based on 2,2'-dipicolylamine (DPA) specifically designed for complexing the fac-[M(I)(CO)3](+) core. Two strategies (postlabeling and prelabeling) were explored using the isothiocyanate-functionalized DPA to determine the effectiveness of assembly on the overall yield and purity of the complex with amine containing biomolecules. A model amino acid (lysine) examined (1) amine conjugation of isothiocyanate-functionalized DPA followed by complexation with fac-[M(I)(CO)3](+) (postlabeling) and (2) complexation of fac-[M(I)(CO)3](+) with isothiocyanate-functionalized DPA followed by amine conjugation (prelabeling). Conducted with stable Re and radioactive (99m)Tc analogs, both strategies formed the product in good to excellent yields under macroscopic and radiotracer concentrations. A synthetic peptide (AE105) which targets an emerging biomarker in CaP prognosis, urokinase-type plasminogen activator receptor (uPAR), was also explored using the isothiocyanate-functionalized DPA strategy. In vitro PC-3 (uPAR+) cell uptake assays with the (99m)Tc-labeled peptide (8a) showed 4.2 ± 0.5% uptake at 4 h. In a murine model bearing PC-3 tumor xenografts, in vivo biodistribution of 8a led to favorable tumor uptake (3.7 ± 0.7% ID/g) at 4 h p.i. with relatively low accumulation (<2% ID/g) in normal organs not associated with normal peptide excretion. These results illustrate the promise of the isothiocyanate-functionalized approach for labeling amine containing biological targeting vectors with fac-[M(I)(CO)3](+).

Influence of functionalized pyridine ligands on the radio/chemical behavior of [M(I)(CO)3](+) (M = Re and (99m)Tc) 2 + 1 complexes.

While a number of chelate strategies have been developed for the organometallic precursor fac-[M(I)(OH2)3(CO)3](+) (M = Re, (99m)Tc), a unique challenge has been to improve the overall function and performance of these complexes for in vivo and in vitro applications. Since its discovery, fac-[M(I)(OH2)3(CO)3](+) has served as an essential scaffold for the development of new targeted (99m)Tc based radiopharmaceuticals due to its labile aquo ligands. However, the lipophilic nature of the fac-[M(I)(CO)3](+) core can influence the in vivo pharmacokinetics and biodistribution of the complexes. In an effort to understand and improve this behavior, monosubstituted pyridine ligands were used to assess the impact of donor nitrogen basicity on binding strength and stability of fac-[M(I)(CO)3](+) in a 2 + 1 labeling strategy. A series of Re and (99m)Tc complexes were synthesized with picolinic acid as a bidentate ligand and 4-substituted pyridine ligands. These complexes were designed to probe the effect of pKa from the monodentate pyridine ligand both at the macro scale and radiochemical concentrations. Comparison of X-ray structural data and radiochemical solution experiments clearly indicate an increase in overall yield and stability as pyridine basicity increased.

Clickable, hydrophilic ligand for fac-[M(I)(CO)3](+) (M = Re/(99m)Tc) applied in an S-functionalized α-MSH peptide.

The copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction was used to incorporate alkyne-functionalized dipicolylamine (DPA) ligands (1 and 3) for fac-[M(I)(CO)3](+) (M = Re/(99m)Tc) complexation into an α-melanocyte stimulating hormone (α-MSH) peptide analogue. A novel DPA ligand with carboxylate substitutions on the pyridyl rings (3) was designed to increase the hydrophilicity and to decrease in vivo hepatobiliary retention of fac-[(99m)Tc(I)(CO)3](+) complexes used in single photon emission computed tomography (SPECT) imaging studies with targeting biomolecules. The fac-[Re(I)(CO)3(3)] complex (4) was used for chemical characterization and X-ray crystal analysis prior to radiolabeling studies between 3 and fac-[(99m)Tc(I)(OH2)3(CO)3](+). The corresponding (99m)Tc complex (4a) was obtained in high radiochemical yields, was stable in vitro for 24 h during amino acid challenge and serum stability assays, and showed increased hydrophilicity by log P analysis compared to an analogous complex with nonfunctionalized pyridine rings (2a). An α-MSH peptide functionalized with an azide was labeled with fac-[M(I)(CO)3](+) using both click, then chelate (CuAAC reaction with 1 or 3 followed by metal complexation) and chelate, then click (metal complexation of 1 and 3 followed by CuAAC with the peptide) strategies to assess the effects of CuAAC conditions on fac-[M(I)(CO)3](+) complexation within a peptide framework. The peptides from the click, then chelate strategy had different HPLC tR's and in vitro stabilities compared to those from the chelate, then click strategy, suggesting nonspecific coordination of fac-[M(I)(CO)3](+) using this synthetic route. The fac-[M(I)(CO)3](+)-complexed peptides from the chelate, then click strategy showed >90% stability during in vitro challenge conditions for 6 h, demonstrated high affinity and specificity for the melanocortin 1 receptor (MC1R) in IC50 analyses, and led to moderately high uptake in B16F10 melanoma cells. Log P analysis of the (99m)Tc-labeled peptides confirmed the enhanced hydrophilicity of the peptide bearing the novel, carboxylate-functionalized DPA chelate (10a') compared to the peptide with the unmodified DPA chelate (9a'). In vivo biodistribution analysis of 9a' and 10a' showed moderate tumor uptake in a B16F10 melanoma xenograft mouse model with enhanced renal uptake and surprising intestinal uptake for 10a' compared to predominantly hepatic accumulation for 9a'. These results, coupled with the versatility of CuAAC, suggests this novel, hydrophilic chelate can be incorporated into numerous biomolecules containing azides for generating targeted fac-[M(I)(CO)3](+) complexes in future studies.

99mTc-labeled cystine knot peptide targeting integrin αvß6 for tumor SPECT imaging.

Integrin αvß6 is overexpressed in a variety of cancers, and its expression is often associated with poor prognosis. Therefore, there is a need to develop affinity reagents for noninvasive imaging of integrin αvß6 expression since it may provide early cancer diagnosis, more accurate prognosis, and better treatment planning. We recently engineered and validated highly stable cystine knot peptides that selectively bind integrin αvß6 with no cross-reactivity to integrins αvß5, α5ß1, or αvß3, also known to be overexpressed in many cancers. Here, we developed a single photon emission computed tomography (SPECT) probe for imaging integrin αvß6 positive tumors. Cystine knot peptide, S02, was first conjugated with a single amino acid chelate (SAAC) and labeled with [(99m)Tc(H2O)3(CO)3](+). The resulting probe, (99m)Tc-SAAC-S02, was then evaluated by in vitro cell uptake studies using two αvß6 positive cell lines (human lung adenocarcinoma cell line HCC4006 and pancreatic cancer cell line BxPC-3) and two αvß6 negative cell lines (human lung adenocarcinoma cell line H838 and human embryonic kidney cell line 293T). Next, SPECT/CT and biodistribution studies were performed in nude mice bearing HCC4006 and H838 tumor xenografts to evaluate the in vivo performance of (99m)Tc-SAAC-S02. Significant differences in the uptake of (99m)Tc-SAAC-S02 were observed in αvß6 positive vs negative cells (P < 0.05). Biodistribution and small animal SPECT/CT studies revealed that (99m)Tc-SAAC-S02 accumulated to moderate levels in antigen positive tumors (∼2% ID/g at 1 and 6 h postinjection, n = 3 or 4/group). Moreover, the probe demonstrated tumor-to-background tissue ratios of 6.81 ± 2.32 (tumor-to-muscle) and 1.63 ± 0.18 (tumor-to-blood) at 6 h postinjection in αvß6 positive tumor xenografts. Co-incubation of the probe with excess amount of unlabeled S02 as a blocking agent demonstrated significantly reduced tumor uptake, which is consistent with specific binding to the target. Renal filtration was the main route of clearance. In conclusion, knottin peptides are excellent scaffolds for which to develop highly stable imaging probes for a variety of oncological targets. (99m)Tc-SAAC-S02 demonstrates promise for use as a SPECT agent to image integrin αvß6 expression in living systems.

Cu-free 1,3-dipolar cycloaddition click reactions to form isoxazole linkers in chelating ligands for fac-[M(I)(CO)3]+ centers (M = Re, 99mTc).

Isoxazole ring formation was examined as a potential Cu-free alternative click reaction to Cu(I)-catalyzed alkyne/azide cycloaddition. The isoxazole reaction was explored at macroscopic and radiotracer concentrations with the fac-[M(I)(CO)3](+) (M = Re, (99m)Tc) core for use as a noncoordinating linker strategy between covalently linked molecules. Two click assembly methods (click, then chelate and chelate, then click) were examined to determine the feasibility of isoxazole ring formation with either alkyne-functionalized tridentate chelates or their respective fac-[M(I)(CO)3](+) complexes with a model nitrile oxide generator. Macroscale experiments, alkyne-functionalized chelates, or Re complexes indicate facile formation of the isoxazole ring. (99m)Tc experiments demonstrate efficient radiolabeling with click, then chelate; however, the chelate, then click approach led to faster product formation, but lower yields compared to the Re analogues.

PSMA-targeted SPECT agents: mode of binding effect on in vitro performance.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Targeting prostate cancer cells with PSMA inhibitor-guided gold nanoparticles.

Prostate-specific membrane antigen (PSMA) is a notable biomarker for diagnostic and therapeutic applications in prostate cancer. Gold nanoparticles (AuNPs) provide an attractive nanomaterial platform for combining a variety of targeting, imaging, and cytotoxic agents into a unified device for biomedical research. In this study, we present the generation and evaluation of the first AuNP system functionalized with a small molecule phosphoramidate peptidomimetic inhibitor for the targeted delivery to PSMA-expressing prostate cancer cells. The general approach involved the conjugation of streptavidin-coated AuNPs with a biotin-linked PSMA inhibitor (CTT54) to generate PSMA-targeted AuNPs. In vitro evaluations of these targeted AuNPs were conducted to determine PSMA-mediated and time-dependent binding to PSMA-positive LNCaP cells. The PSMA-targeted AuNPs exhibited significantly higher and selective binding to LNCaP cells compared to control non-targeted AuNPs, thus demonstrating the feasibility of this approach.

Photo-initiated thiol-ene click reactions as a potential strategy for incorporation of [M(I)(CO)3]+ (M = Re, (99m)Tc) complexes.

Click reactions offer a rapid technique to covalently assemble two molecules. In radiopharmaceutical construction, these reactions can be utilized to combine a radioactive metal complex with a biological targeting molecule to yield a potent tool for imaging or therapy applications. The photo-initiated radical thiol-ene click reaction between a thiol and an alkene was examined for the incorporation of [M(I)(CO)3](+) (M = Re, (99m)Tc) systems for conjugating biologically active targeting molecules containing a thiol. In this strategy, a potent chelate system, 2,2'-dipicolylamine (DPA), for [M(I)(CO)3](+) was functionalized at the central amine with a terminal alkene linker that was explored with two synthetic approaches, click then chelate and chelate then click, to determine the flexibility and applicability of the thiol-ene click reaction to specifically incorporate ligand systems and metal complexes with a thiol containing molecule. In the click then chelate approach, the thiol-ene click reaction was carried out with the DPA chelate followed by complexation with [M(I)(CO)3](+). In the chelate then click approach, the alkene functionalized DPA chelate was first complexed with [M(I)(CO)3](+) followed by the conduction of the thiol-ene click reaction. Initial studies utilized benzyl mercaptan as a model thiol for both strategies to generate the identical product from either route to provide information on reactivity and product formation. DPA ligands functionalized with two unique linker systems (allyl and propyl allyl ether) were prepared to examine the effect of the proximity of the chelate or complex on the thiol-ene click reaction. Both the thiol-ene click and coordination reactions with Re, (99m)Tc were performed in moderate to high yields demonstrating the potential of the thiol-ene click reaction for [M(I)(CO)3](+) incorporation into thiol containing biomolecules.

pH-controlled coordination mode rearrangements of "clickable" Huisgen-based multidentate ligands with [M(I)(CO)3]+ (M = Re, (99m)Tc).

The viability of the Huisgen cycloaddition reaction for clickable radiopharmaceutical probes was explored with an alkyne-functionalized 2-[(pyridin-2-ylmethyl)amino]acetic acid (PMAA) ligand system, 3, and fac-[M(I)(OH2)3(CO)3](+) (M = Re, (99m)Tc). Two synthetic strategies, (1) click, then chelate and (2) chelate, then click, were investigated to determine the impact of assembly order on the reactivity of the system. In the click, then chelate approach, fac-[M(I)(OH2)3(CO)3](+) was reacted with the PMAA ligand "clicked" to the benzyl azide, 5, to yield two unique coordination species, fac-[M(I)(CO)3(O,N(amine),N(py)-5)], M = Re (8), (99m)Tc (8A), and fac-[M(I)(CO)3(N(tri),N(amine),N(py)-5)], M = Re (9), (99m)Tc (9A), where coordination is through the triazole (N(tri)), central amine (N(amine)), pyridine (N(py)), or carboxylate (O). Depending on the reaction pH, different ratios of complexes 8(A) and 9(A) were observed, but single species were obtained of (O,N(amine),N(py)) coordination, 8(A), in basic pHs (>9) and (N(tri),N(amine),N(py)) coordination, 9(A), in slightly acidic pHs (<4). In the chelate, then click approach, the (O,N(amine),N(py)) coordination of [M(I)(CO)3](+) was preorganized in the alkyne-functionalized fac-[M(I)(CO)3(O,N(amine),N(py)-3)], M = Re (6), (99m)Tc (6A), followed by standard Cu(I)-catalyzed Huisgen "click" conditions at pH ≈ 7.4, where the (O,N(amine),N(py)) coordination mode remained unchanged upon formation of the triazole product in the clicked molecule. Despite the slow substitution kinetics of the low-spin d(6) metal, the coordination modes (O,N(amine),N(py)) and (N(tri),N(amine),N(py)) were found to reversibly intraconvert between 8(A) and 9(A) based upon changes in pH that mirrored the (O,N(amine),N(py)) coordination in basic pHs and (N(tri),N(amine),N(py)) coordination in acidic pHs. Comparison of the Re and (99m)Tc analogs also revealed faster intraconversion between the coordination modes for (99m)Tc.

A phosphoramidate-based prostate-specific membrane antigen-targeted SPECT agent.

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.

Novel, cysteine-modified chelation strategy for the incorporation of [M(I)(CO)(3)](+) (M = Re, (99m)Tc) in an α-MSH peptide.

Engineering peptide-based targeting agents with residues for site-specific and stable complexation of radionuclides is a highly desirable strategy for producing diagnostic and therapeutic agents for cancer and other diseases. In this report, a model N-S-N(Py) ligand (3) and a cysteine-derived α-melanocyte stimulating hormone (α-MSH) peptide (6) were used as novel demonstrations of a widely applicable chelation strategy for incorporation of the [M(I)(CO)(3)](+) (M = Re, (99m)Tc) core into peptide-based molecules for radiopharmaceutical applications. The structural details of the core ligand-metal complexes as model systems were demonstrated by full chemical characterization of fac-[Re(I)(CO)(3)(N,S,N(Py)-3)](+) (4) and comparative high-performance liquid chromatography (HPLC) analysis between 4 and [(99m)Tc(I)(CO)(3)(N,S,N(Py)-3)](+) (4a). The α-MSH analogue bearing the N-S-N(Py) chelate on a modified cysteine residue (6) was generated and complexed with [M(I)(CO)(3)](+) to confirm the chelation strategy's utility when applied in a peptide-based targeting agent. Characterization of the Re(I)(CO)(3)-6 peptide conjugate (7) confirmed the efficient incorporation of the metal center, and the (99m)Tc(I)(CO)(3)-6 analogue (7a) was explored as a potential single photon emission computed tomography (SPECT) compound for imaging the melanocortin 1 receptor (MC1R) in melanoma. Peptide 7a showed excellent radiolabeling yields and in vitro stability during amino acid challenge and serum stability assays. In vitro B16F10 melanoma cell uptake of 7a reached a modest value of 2.3 ± 0.08% of applied activity at 2 h at 37 °C, while this uptake was significantly reduced by coincubation with a nonlabeled α-MSH analogue, NAPamide (3.2 µM) (P < 0.05). In vivo SPECT/X-ray computed tomography (SPECT/CT) imaging and biodistribution of 7a were evaluated in a B16F10 melanoma xenografted mouse model. SPECT/CT imaging clearly visualized the tumor at 1 h post injection (p.i.) with high tumor-to-background contrast. Blocking studies with coinjected NAPamide (10 mg per kg of mouse body weight) confirmed the in vivo specificity of 7a for MC1R-positive tumors. Biodistribution results with 7a yielded a moderate tumor uptake of 1.20 ± 0.09 percentage of the injected radioactive dose per gram of tissue (% ID/g) at 1 h p.i. Relatively high uptake of 7a was also seen in the kidneys and liver at 1 h p.i. (6.55 ± 0.36% ID/g and 4.44 ± 0.17% ID/g, respectively), although reduced kidney uptake was seen at 4 h p.i. (3.20 ± 0.48% ID/g). These results demonstrate the utility of the novel [M(I)(CO)(3)](+) chelation strategy when applied in a targeting peptide.

Elucidating the coordination chemistry of the radium ion for targeted alpha therapy.

The coordination chemistry of Ra2+ is poorly defined, hampering efforts to design effective chelators for 223Ra-based targeted alpha therapy. Here, we report the complexation thermodynamics of Ra2+ with the biomedically-relevant chelators DOTA and macropa. Our work reveals the highest affinity chelator to date for Ra2+ and advances our understanding of key factors underlying complex stability and selectivity for this underexplored ion.

Is handgrip strength a useful tool to detect slow walking speed in older Indian adults: A cross-sectional study among geriatric outpatients in a tertiary care hospital in South India.

Objectives: To determine whether handgrip strength can be used as a proxy for detecting slow walking speed in older adults. Measuring walking speed in older adults can be challenging as cognitive and functional decline may have a significant impact on test performance. Methods: Hundred subjects aged >/= 60 were recruited. Slow walking speed was defined as walking speed <1.0 m/s. Handgrip strength was measured using handheld dynamometer. Multiple linear regression analysis was used to determine the relationship between the two. Results: The mean age of the study participants was 67.8±6.2 years. There were 63 males and 37 females. The mean handgrip strength of the participants was 23±5.9 kgs. Older subjects had slow gait speed (r=-0.40, p<0.001) while patients with higher BMI (r=0.36, p<0.001), handgrip strength (r=0.72, p<0.001) and appendicular lean mass (r=0.53, p<0.001) had normal gait speed. On multiple linear regression analysis, only handgrip strength (OR 0.71; 95% CI 0.58-0.87, p=0.001) and nutritional status (OR 8.60; 95% CI 1.98 - 37.40, p=0.004) were found to have a significant association with walking speed. Conclusions: Our study shows that handgrip strength assessment can be used as a surrogate indicator for detecting slow walking speed. Large population studies are warranted to examine its validity.

Investigation of mixed oxidation state cyanide-bridged Re(V)oxo (acac(2)en/pn) and Re(I)(bipy)(CO)3 complexes.

A series of cyanide-bridged complexes that combine a low-valent photoacceptor rhenium(I) metal center with an electroactive midvalent rhenium(V) complex were prepared. The synthesis involved the preparation of novel asymmetric rhenium(V) oxo compounds, cis-Re(V)O(CN)(acac(2)en) (1) and cis-Re(V)O(CN)(acac(2)pn) (2), formed by reacting trans-[Re(V)O(OH(2))(acac(2)en)]Cl or trans-Re(V)O(acac(2)pn)Cl with [NBu(4)][CN]. The µ-bridged cyanide mixed-oxidation Re(V)-Re(I) complexes were prepared by incubating the asymmetric complexes, 1 or 2, with fac-[Re(I)(bipy)(CO)(3)][OTf] to yield cis-[Re(V)O(acac(2)en)(µ-CN-1κC:2κN)-fac-Re(I)(bipy)(CO)(3)][PF(6)] (3) and [cis-Re(V)O(acac(2)pn)(µ-CN-1κC:2κN)-fac-Re(I)(bipy)(CO)(3)][PF(6)] (4), respectively.

Acute colonic pseudo-obstruction in two patients admitted with severe acute respiratory syndrome-coronavirus-2 pneumonia.

We have described two cases of severe SARS-CoV-2 pneumonia presenting with acute colonic pseudo-obstruction with normal liver enzymes and serum lactate. These older adults presented predominantly with constitutional symptoms, silent hypoxia, distended abdomen, sluggish bowel sounds, and colonic dilatation supported by abdominal imaging (plain X-ray and computerized tomography of abdomen) to a tertiary care center in South India. Both patients received standard treatment for severe SARS-CoV-2 pneumonia and acute colonic pseudo-obstruction according to available guidelines but succumbed to complications during hospital stay. Acute colonic pseudo-obstruction in patients admitted with SARS-CoV-2 infection requires high index of suspicion as it warrants early mitigation by cessation of offending agents, optimizing electrolytes, and colonic decompression to prevent morbidity and mortality.

Psychological impact of infection with SARS-CoV-2 on health care providers: A qualitative study.

BACKGROUND: Rapid increase in severe acute respiratory syndrome coronavirus 2 (SAR-CoV-2) infection has also affected many health care providers (HCPs). This study aims to understand personal stories of HCPs affected by SARS-CoV-2, which could help with insights about ways to support them. METHODS: Using a phenomenological approach and purposive sampling method, we recruited participants for semi-structured interviews through a telephone. Data saturation was achieved by the 11th participant and two more interviews were performed to confirm the same. Interviews were transcribed, and a seven-step Colaizzi method was used to identify different themes. RESULTS: The psychological impact of SARS-CoV-2 on HCPs who tested positive can be summarized into four broad themes. These are challenges faced by HCPs, social concerns, experience of quarantine period, and positive experiences. Challenges they faced were about dealing with uncertainty, fear of spreading infection, and stigma. In the social concerns theme, what featured was concerns about family, social support from friends and hospital, and stigmatizing experience in neighborhood. In the quarantine experience theme, self-care and desperation to connect prominently colored their emotional and psychological experience. There were positive experiences also, which included personal strength, sense of gratitude, growth, and professional commitment. CONCLUSION: The personal stories of HCPs highlight that while they coped effectively during the recovery process, it may be important to address psychosocial factors of well-being as they worked with patients testing positive for SARS-CoV-2.

Prevalence and factors contributing to primary sarcopenia in relatively healthy older Indians attending the outpatient department in a tertiary care hospital: A cross-sectional study.

BACKGROUND: Literature is scarce on primary sarcopenia among Indian older adults. This study was aimed to estimate the prevalence of primary sarcopenia among older persons in India using the European Working Group on Sarcopenia in the Older People 2010 (EWGSOP) diagnostic criteria and to elucidate the factors leading to its development. METHODOLOGY: Two hundred twenty-seven subjects over 60 years of age attending the geriatric outpatient clinic were recruited for the study. Sarcopenia was diagnosed based on set criteria for gait speed, handgrip, and skeletal muscle mass assessment by dual-energy x-ray absorptiometry. RESULT: The prevalence of primary sarcopenia in the study population was 39.2% (n = 89). Male patients were more sarcopenic than women, 47% (n = 72) vs 23% (n = 17). Obese subjects (body mass index > 25 kg/m2) had a lower prevalence of sarcopenia (odds ratio = 0.10; 95% confidence interval = 0.05-0.19). There was no association between sarcopenia and other postulated risk factors like low vitamin D levels, dietary protein or carbohydrate intake, or sedentary lifestyle. CONCLUSION: Contrary to published data, primary sarcopenia appears to be higher among older Indians using presently available guidelines. Community studies with validated cutoffs suited for the Indian subcontinent may yield a lower prevalence of primary sarcopenia.

Diagnostic methods and identification challenges experienced in a Burkholderia contaminans outbreak occurred in a tertiary care centre.

BACKGROUND: Recently, a novel species contaminans belonging to the family Burkholderia cepacia complex (Bcc) is rising as a hospital pathogen. Detection of Burkholderia contaminans, a member of Bcc can be done only by MALDI TOF and sequencing techniques. We report the diagnostic challenges faced in an outbreak of bacteremia due to B. contaminans grown in diltiazem vials. METHOD: The department of microbiology notified the infection control team about a cluster of eleven patients with B. contaminans isolated from blood culture. An outbreak investigation was initiated by performing environmental surveillance and sterility testing of solutions given for the patients. Routine phenotypical methods for identification of species followed by MALDI-TOF and sequencing was performed to identify the pathogen. RESULTS: All the patients detected with B. contaminans were having cardiac disease and received diltiazem. Sterility testing of diltiazem vials given for the patient and an unopened vial of same batch has grown B. contaminans. Clonal typing has confirmed the sequence similarities between patient and solution isolates. CONCLUSION: Due to diagnostic challenge in identifying the species of Bcc, MALDI TOF and clonal typing remains the key diagnostic tools available to detect Bcc species at an earliest especially in an outbreak.

Applications of machine learning in acute care research.

Artificial intelligence has been successfully applied to numerous health care and non-health care-related applications and its use in emergency medicine has been expanding. Among its advantages are its speed in decision making and the opportunity for rapid, actionable deduction from unstructured data with that increases with access to larger volumes of data. Artificial intelligence algorithms are currently being applied to enable faster prognosis and diagnosis of diseases and to improve patient outcomes.1,2 Despite the successful application of artificial intelligence, it is still fraught with limitations and "unknowns" pertaining to the fact that a model's accuracy is dependent on the amount of information available for training the model, and the understanding of the complexity presented by current artificial intelligence and machine learning algorithms is often limited in many individuals outside of those involved in the field. This paper reviews the applications of artificial intelligence and machine learning to acute care research and highlights commonly used machine learning techniques, limitations, and potential future applications.