Ambara Rachmat Pradipta

Pyrene excimer-based fluorescent probes for chemoselective detection of acrolein have been developed by leveraging a [4+4] cycloaddition dimerization between unsaturated aldehydes and 1,2-amino alcohol derivatives. Building on our previously reported Probe A, which features an ethanolamine skeleton and a pyrene fluorophore, we designed and synthesized a series of second-generation probes (Probes B–E) that report acrolein binding through pyrene excimer emission. Using serine- and glycine-derived building blocks, we established concise synthetic routes that enable facile preparation of these probes in high overall yields. We identified optimized cycloaddition dimerization conditions under which a small amount of acetic acid promotes conjugated imine formation and affords a rapid and pronounced increase in excimer fluorescence. Reactivity studies with a panel of α,β-unsaturated aldehydes revealed that, compared with the first-generation probe bearing a terminal primary amine, second-generation 1,2-amino alcohol probes in which the primary amine is located at an internal secondary carbon exhibit enhanced chemoselectivity for acrolein while maintaining favorable sensitivity. We further optimized extraction and reaction conditions for Probe D and demonstrated quantitative detection of cell-derived acrolein by monitoring acrolein concentration-dependent excimer fluorescence in organic extracts from hydrogen peroxide–treated RAW264.7 cells.

Synthetic chemistry within living systems offers a transformative strategy for precision medicine by enabling the targeted generation of therapeutic agents directly at disease sites. Carbon monoxide (CO), an endogenous gasotransmitter upregulated in many cancer phenotypes, represents a unique yet underexploited chemical feedstock for such intracellular synthesis. However, the intrinsically low reactivity of CO necessitates transition-metal mediation, which is typically compromised by rapid deactivation by intracellular thiols such as glutathione (GSH). Here, we present a biocompatible albumin-palladacycle complex (APC) platform that harnesses endogenous CO for two distinct functions: the detection of CO levels and the in situ synthesis of cytotoxic phenanthridinone derivatives—a privileged scaffold found in potent poly(ADP-ribose) polymerase (PARP) and topoisomerase inhibitors. Central to this design is a coumarin anchor that directs the palladium center into the hydrophobic binding pocket of albumin, shielding it from thiol-mediated poisoning while facilitating cellular uptake via endocytosis. We demonstrate that this system effectively detects elevated CO in cancer cells and, in a parallel application, enables the in situ synthesis of pharmacologically active agents. Although the associated cytotoxicity is modest, the approach nonetheless suppresses cancer cell growth. This study considerably advances the proof of concept for “therapeutic in vivo synthetic chemistry,” in which disease-associated metabolites are repurposed as structural building blocks for both diagnostic and therapeutic applications.

Acrolein is the simplest α,β-unsaturated aldehyde, and its selective hydrogenation on metal surfaces is of fundamental interest. Here, we investigate the adsorption structures of acrolein molecules on Cu(111) by scanning tunneling microscopy. At low temperatures, chemisorbed and physisorbed monomers as well as dimers are observed. The thermally most stable chemisorbed monomer is assigned to 12 symmetry-equivalent adsorption orientations on Cu(111). The observed asymmetry between the C=C and C=O groups provides microscopic insight into the adsorption geometries relevant to selective hydrogenation.

Zwitterionic heterocycles hold significant therapeutic potential; however, their application is often hindered by poor membrane permeability and limited target‐cell selectivity. Here, we report an innovative strategy for the in situ synthesis of these compounds within cancer cells, using a rationally designed precursor that is nontoxic, non‐ionic, and membrane permeable. The synthesis is initiated by endogenous acrolein, an oncometabolite elevated in cancer cells, which triggers a cascade involving 1,3‐dipolar cycloaddition, diazo formation, carbamate cleavage, imine formation, intramolecular 6π‐azaelectrocyclization, oxidative aromatization, and ester hydrolysis. We validated this methodology in human lung adenocarcinoma (A549) cells, where the in situ‐synthesized zwitterionic heterocycle exhibited anticancer activity. Conversely, its pre‐synthesized congener showed minimal cytotoxicity, underscoring the poor membrane permeability of the zwitterionic form. Precursor optimization resulted in a lead compound that, upon administration to A549 cells, converted into a cytotoxic zwitterionic heterocycle with a half‐maximal inhibitory concentration (IC ₅₀ ) of 6.2 µM. The lead precursor showed exceptional selectivity, with no cytotoxicity in normal human diploid (TIG3) cells. This selectivity arises because healthy cells contain low acrolein levels, insufficient to trigger the activation cascade. Our approach effectively addresses the key therapeutic challenges associated with zwitterionic heterocycles.

Zwitterionic heterocycles hold significant therapeutic potential; however, their application is often hindered by poor membrane permeability and limited target‐cell selectivity. Here, we report an innovative strategy for the in situ synthesis of these compounds within cancer cells, using a rationally designed precursor that is nontoxic, non‐ionic, and membrane permeable. The synthesis is initiated by endogenous acrolein, an oncometabolite elevated in cancer cells, which triggers a cascade involving 1,3‐dipolar cycloaddition, diazo formation, carbamate cleavage, imine formation, intramolecular 6π‐azaelectrocyclization, oxidative aromatization, and ester hydrolysis. We validated this methodology in human lung adenocarcinoma (A549) cells, where the in situ‐synthesized zwitterionic heterocycle exhibited anticancer activity. Conversely, its pre‐synthesized congener showed minimal cytotoxicity, underscoring the poor membrane permeability of the zwitterionic form. Precursor optimization resulted in a lead compound that, upon administration to A549 cells, converted into a cytotoxic zwitterionic heterocycle with a half‐maximal inhibitory concentration (IC ₅₀ ) of 6.2 µM. The lead precursor showed exceptional selectivity, with no cytotoxicity in normal human diploid (TIG3) cells. This selectivity arises because healthy cells contain low acrolein levels, insufficient to trigger the activation cascade. Our approach effectively addresses the key therapeutic challenges associated with zwitterionic heterocycles.

The intracellular polymerization of synthetic macromolecules presents a unique method for modifying cell behavior, enabling real‐time imaging, and enhancing therapeutic effectiveness. However, most current strategies rely on external catalysts or non‐physiological triggers, often lacking target‐cell specificity. Here, we report a cancer‐selective intracellular cyclodimerization cascade polymerization driven solely by endogenous acrolein, an oncometabolite overproduced in malignant cells. Acrolein plays dual roles as a polymerization initiator through imine formation and as a structural component of the resulting polymer. We designed a meta ‐phenylene‐bis(2‐aminoethanol) monomer that incorporates an aggregation‐induced emission (AIE)‐active tetraphenylethylene unit. In acrolein‐rich cancer cells, condensation between the aminoethanol groups and acrolein generates imines, which then undergo a spontaneous, catalyst‐free cyclodimerization cascade, yielding eight‐membered 1,5‐diazacyclooctane polymers that embed native acrolein. This polymerization triggers robust AIE fluorescence “turn‐on”, facilitating high‐contrast imaging of malignant cells with minimal background in healthy cells. We demonstrated selective fluorescence in multiple cancer cell lines and applied this platform to freshly resected human breast tumor samples, showing its utility for rapid intraoperative assessment. This strategy establishes a versatile toolkit for precision diagnostics, engineered intracellular materials, and next‐generation therapeutics.

The intracellular polymerization of synthetic macromolecules presents a unique method for modifying cell behavior, enabling real‐time imaging, and enhancing therapeutic effectiveness. However, most current strategies rely on external catalysts or non‐physiological triggers, often lacking target‐cell specificity. Here, we report a cancer‐selective intracellular cyclodimerization cascade polymerization driven solely by endogenous acrolein, an oncometabolite overproduced in malignant cells. Acrolein plays dual roles as a polymerization initiator through imine formation and as a structural component of the resulting polymer. We designed a meta ‐phenylene‐bis(2‐aminoethanol) monomer that incorporates an aggregation‐induced emission (AIE)‐active tetraphenylethylene unit. In acrolein‐rich cancer cells, condensation between the aminoethanol groups and acrolein generates imines, which then undergo a spontaneous, catalyst‐free cyclodimerization cascade, yielding eight‐membered 1,5‐diazacyclooctane polymers that embed native acrolein. This polymerization triggers robust AIE fluorescence “turn‐on”, facilitating high‐contrast imaging of malignant cells with minimal background in healthy cells. We demonstrated selective fluorescence in multiple cancer cell lines and applied this platform to freshly resected human breast tumor samples, showing its utility for rapid intraoperative assessment. This strategy establishes a versatile toolkit for precision diagnostics, engineered intracellular materials, and next‐generation therapeutics.

Pharmacokinetics of pro-FTY and its effect on lymphocytes and tumor suppression in mice. A, BALB/c and control (Ct) mice implanted with the 4T1 breast cancer cell line were treated three times with FTY720 and pro-FTY, and tumor volumes were measured. B, pStat3 expression in representative tumors from BALB/c mice administered the 4T1 breast cancer cell line after treatment with FTY720 or pro-FTY. Scale bars, 25 μm. C and D, Pro-FTY, FTY720, and FTY-P levels in tumor and plasma samples from BALB/c mice were quantified by mass spectrometry on d1 (C) and d3 (D) after the last pro-FTY drug administration. E–N, Blood counts were performed the day after the last dose of drug was administered: white blood cells (WBC; E), red blood cells (RBC; F), hemoglobin (HGB; G), hematocrit (HCT; H), platelets (PLT; I), lymphocytes (LYM; J), neutrophils (NEU; K), eosinophils (EOS; L), basophils (BAS; M), and monocytes (MON; N). O, CD4+ and CD8+ lymphocyte abundances were measured by flow cytometry. P, Serum IL-6 levels were determined by performing ELISAs. Q and R, With the PDX mouse model, the effect of pro-FTY was evaluated by measuring tumor volumes (Q) over time and tumor weights (R) when the mice were euthanized. *, P < 0.05 vs. control. S, Body weights of the mice in each group during the treatment period.

Dose–response curves for the indicated drugs in multidrug-resistant breast cancer cell lines. A–H, Dose–response curves and IC50 values of doxorubicin (A and B), paclitaxel (C and D), FTY720 (E and F), and pro-FTY (G and H) were determined in MCF-7 and MCF-7R cells (A and C–E) and MDA-MB-231 and MDA-MB-231R cells (B, D, F, and H) by performing WST-8 assays. ND, not determined.

Pro-FTY, a novel anticancer prodrug that is converted to its active form (FTY720) after reacting with acrolein, which is overproduced in breast cancer cells. A, Synthesis of pro-FTY. FTY720 was reacted with compound 1 to synthesize pro-FTY. B, Schematic representation of the reaction of pro-FTY with acrolein in cancer cells to produce the active drug, FTY720, which can block S1P signaling. C, Acrolein expression in breast cancer tissue and normal breast tissue. Fluorescence microscopy images of acrolein expression in cancer (c) tissue and normal (n) breast tissue labeled with the CTS probe (red) and 4′,6-diamidino-2-phenylindole (DAPI; blue). Scale bars, 100 nm. D–G, Dose–response bar graphs for each drug in breast cancer and normal mammary cell lines. The IC50 values of FTY720 (D) and pro-FTY (E) were determined using the MDA-MB-468 breast cancer cell line by performing WST-8 assays, and the IC50 values of FTY720 (F) and pro-FTY (G) were determined in the noncancer, mammary epithelial cell line, MCF-10A.