Specific Bioimaging Research Articles

Inherently targeted estradiol-derived carbon dots for selective killing of ER (+) breast cancer cells via oridonin-triggered p53 pathway activation.

One of the most prevalent cancers globally is breast cancer and approximately two thirds of the breast cancers are hormone receptor positive with estrogen receptors (ER) being a prominent target. Notably, p53 that controls several cellular functions and prevents tumor formation, gets suppressed in breast cancers. Reactivation of p53 can lead to cell cycle arrest as well as apoptosis. Therefore, targeting the estrogen receptor for selective delivery of anticancer drugs that can reactivate p53 in ER (+) breast cancers can be a crucial method in breast cancer therapy. Herein, we have designed and developed estradiol-derived inherently targeted specific carbon dots (E2-CA-CD) from 17β-estradiol and citric acid following a solvothermal method. The synthesized carbon dots were characterized using spectroscopic and microscopic techniques. The water soluble, intrinsically fluorescent E2-CA-CD showed excellent biocompatibility in MCF-7, MDA-MB-231 as well as NIH3T3 cells and demonstrated target specific bioimaging in ER (+) MCF-7 cells due to the overexpressed ER receptors. Furthermore, oridonin, a well-known hydrophobic anticancer drug capable of upregulating the p53 pathway, was loaded on the carbon dots to increase its bioavailability. E2-CA-CD-Ori caused ∼2.2 times higher killing in ER (+) MCF-7 cells compared to ER (-) MDA-MB-231 cells and normal cells NIH3T3. Also, E2-CA-CD-Ori showed ∼3 fold better killing in MCF-7 cells compared to native oridonin. E2-CA-CD-Ori-induced killing of MCF-7 cells took place through the early to late apoptotic pathway along with the elevation of the intracellular ROS level. Importantly, E2-CA-CD-Ori triggered the activation of the p53 pathway in MCF-7 cells, which in turn induced apoptosis involving the upregulation of Bax and downregulation of Bcl-2 leading to the selective and efficient killing of ER (+) MCF-7 cells.

Synthesis, structure, photophysical property, stability of tetraphenylethylene-based boranil, and applications in cell imaging

A new family of tetraphenylethylene-based N,O-chelated boranil complexes (TPE-BAs) with aggregation-induced emission (AIE) characteristics were developed. X-ray crystallographic analysis indicated that the terminal substituents on the aniline moiety significantly affected the intermolecular stacking mode, thereby influencing the photophysical properties. The stabilities of these compounds are closely related to the substituents on the aniline moiety. Electron-donor-substituted TPE-BA-OMe exhibited the best stability, whereas the electron-acceptor-substituted compounds exhibited poor stability. Benefitting from its AIE properties and suitable lipophilicity, TPE-BA-OMe served as an excellent fluorescent probe for the specific bioimaging of lipid droplets in living cells.

An emerging spectrum of therapeutic targets for Alzheimer's disease.

Development of effective preventative and therapeutic measures for Alzheimer's disease has been unsuccessful because of the long and subtly symptomatic preclinical period, difficulties obtaining tissue and biochemical data from living patients, and the many complex underlying pathogenic processes. Recent applications of sensitive specific bioimaging techniques, analyses of RNAs and proteins of neural cell-derived extracellular vesicles in blood, and sophisticated genetic procedures in cellular and rodent models have yielded hopeful new therapeutic targets. These newer targets are described here in relation to their neural cellular location, potential genetic modifications and possible pharmacological approaches.

Disulfide bond cross-linked three-dimensional graphitic carbon nitride nanocomposites with glutathione responsive fluorescence for cancer-cell specific bioimaging

The polymeric graphitic carbon nitride (g-C3N4) nanomaterials with non-toxicity, high stability, and photoluminescence property have promising application in bioimaging and biosensing. In this work, smart three-dimensional (3D) disulfide bond cross-linked g-C3N4 (CL-g-C3N4) nanocomposites with glutathione (GSH)-responsive fluorescence property were designed and developed for cancer cell-specific imaging. The g-C3N4 layered nanosheets with an average lateral size of 80–120 nm and mean thickness of ca. 0.5–1.0 nm were fabricated and used as building blocks. By combining several g-C3N4 nanosheets with non-fluorescent redox-sensitive disulfide bond-contained cross-linker, CL-g-C3N4 nanocomposites with a hydrodynamic particle size of ca. 270.5 nm were synthesized. The fluorescence of the CL-g-C3N4 nanocomposites was initially quenched due to the assembly of 2D g-C3N4 nanosheets into 3D structured nanocomposite caused by the crosslinking process. However, upon stirring them in a GSH solution with a concentration of 2 mM, which simulates the content in the cytoplasm of cells, the fluorescence was recovered to 89.3 % of its original intensity. This recovery was achieved through a thiol-disulfide exchange reaction, highlighting the GSH-responsive fluorescence recovery property of the nanocomposites. The cellular uptake traced images of CL-g-C3N4 in human cervix carcinoma (HeLa) cancer cells exhibited almost 3.5 times higher fluorescence intensity than that in human embryonic kidney (HEK 293 T) healthy cells owing to higher GSH concentration in cancer cells than that in healthy cells. The constructed CL-g-C3N4 nanocomposites should hold great promise as a fluorescence detector of cancer cells for early cancer diagnose.

Toward the Next Frontiers of Vibrational Bioimaging.

Chemical imaging based on vibrational contrasts can extract molecular information entangled in complex biological systems. To this end, nonlinear Raman scattering microscopy, mid-infrared photothermal (MIP) microscopy, and atomic force microscopy (AFM)-based force-detected photothermal microscopies are emerging with better chemical sensitivity, molecular specificity, and spatial resolution than conventional vibrational methods. Their utilization in bioimaging applications has provided biological knowledge in unprecedented detail. This Perspective outlines key methodological developments, bioimaging applications, and recent technical innovations of the three techniques. Representative biological demonstrations are also highlighted to exemplify the unique advantages of obtaining vibrational contrasts. With years of effort, these three methods compose an expanding vibrational bioimaging toolbox to tackle specific bioimaging needs, benefiting many biological investigations with rich information in both label-free and labeling manners. Each technique will be discussed and compared in the outlook, leading to possible future directions to accommodate growing needs in vibrational bioimaging.

Hyaluronic acid-magnetic fluorescent polydopamine/gold-based fluorescent probe for bioimaging of CD44 over-expressed cancer cells

CD44 is a transmembrane glycoprotein (P-glycoprotein) that expressed in a large scale on the surface membrane of breast cancer cells. The CD44 receptor has been employed for various medial aims such as imaging, drug delivery, and etc. In the present work, the surface of citrate-capped gold nanoparticles (cit-AuNPs) was modified with magnetic polydopamine nanoparticles to provide fluorescent nanocomposite and amine groups for attachment to hyaluronic acid (HA) molecules. HA molecules have been bonded to the surface of fluorescent polydopamine nanoparticles (FPNPs) via the formation of amide bonds between carboxyl (COOH) group of HA and amine groups of the FPNPs. Due to the presence of the HA molecules, the MNPs-FPNPs/AuNPs/HA can attach to the CD44-overexpressed MCF-7 cells with high specificity and could be employed for bioimaging aims. Fluorescence microscopy was applied for bioimaging of the MNPs-FPNPs/AuNPs/HA internalized cancer cells. Obtained results offered that the MNPs-FPNPs/AuNPs/HA can especially and efficiently internalize to the cells and differentiate CD44-positive cancer cells and normal cells of HFFF-2 cells. Also, the MNPs-FPNPs/AuNPs/HA has a biocompatible nature with the toxic levels around 250 μg/mL levels. As a conclusion, the MNPs-FPNPs/AuNPs/HA is a good candidate for specific bioimaging applications of CD44−overexpressed MCF-7 cancer cells with high physicochemical stability and advantageous spectral features.

Quantitative Single‐Molecule Electrochemiluminescence Bioassay

AbstractA single‐molecule electrochemiluminescence bioassay is developed here which allows imaging and direct quantification of single biomolecules. Imaging single biomolecules is realized by localizing the electrochemiluminescence events of the labeled molecules. Such an imaging system allows mapping the spatial distribution of biomolecules with electrochemiluminescence and contains quantitative single‐molecule insights. We further quantify biomolecules by spatiotemporally merging the repeated reactions at one molecule site and then counting the clustered molecules. The proposed single‐molecule electrochemiluminescence bioassay is used to detect carcinoembryonic antigen, showing a limit of detection of 67 attomole concentration which is 10 000 times better than conventional electrochemiluminescence bioassays. This spatial resolution and sensitivity enable single‐molecule electrochemiluminescence bioassay a new toolbox for both specific bioimaging and ultrasensitive quantitative analysis.

Quantitative Single-Molecule Electrochemiluminescence Bioassay.

A single-molecule electrochemiluminescence bioassay is developed here which allows imaging and direct quantification of single biomolecules. Imaging single biomolecules is realized by localizing the electrochemiluminescence events of the labeled molecules. Such an imaging system allows mapping the spatial distribution of biomolecules with electrochemiluminescence and contains quantitative single-molecule insights. We further quantify biomolecules by spatiotemporally merging the repeated reactions at one molecule site and then counting the clustered molecules. The proposed single-molecule electrochemiluminescence bioassay is used to detect carcinoembryonic antigen, showing a limit of detection of 67 attomole concentration which is 10 000 times better than conventional electrochemiluminescence bioassays. This spatial resolution and sensitivity enable single-molecule electrochemiluminescence bioassay a new toolbox for both specific bioimaging and ultrasensitive quantitative analysis.

Construction of a Stimuli-Responsive DNAzyme-Braked DNA Nanomachine for the Amplified Imaging of miRNAs in Living Cells and Mice

Construction of a Stimuli-Responsive DNAzyme-Braked DNA Nanomachine for the Amplified Imaging of miRNAs in Living Cells and Mice

Engineering BODIPY-based near-infrared nanoparticles with large Stokes shifts and aggregation-induced emission characteristics for organelle specific bioimaging.

Lipid droplets (LDs) and lysosomes, as two important subcellular organelles, play specific and indispensable roles in various cellular processes. The development of efficient LD- and lysosome-specific fluorescent bio-probes is of great importance. However, current commercial lipid droplet- (LD) and lysosome-specific fluorescent specific bio-probes often suffer from the aggregation-caused quenching (ACQ) effect, short absorption and emission wavelengths, poor photostability and low specificity. Herein, a typical ACQ luminogen BODIPY was directly conjugated to strong electron donating triarylamine units at its α-positions, giving near-infrared (NIR) fluorescent materials TPAB and 2TPAB with aggregation-induced emission (AIE). Both TPAB and 2TPAB nanoparticles were obtained by self-assembly, and showed NIR emissions, large Stokes shifts, good photostability and two-photon absorption. These nanoparticles presented remarkable bioimaging performances and were shown to specifically localize in LDs or lysosomes, respectively, depending on the number of triarylamine units attached. They have been successfully used to detect endogenous LD overproduction, and monitor abnormal activities of LDs/lysosomes, as well as real-time track the lipophagy process in cells. Their far NIR emission and two-photon excitation further supported their promising bioimaging application for lipid droplet tracking in liver tissue and live zebrafish larvae. Our work here enriches BODIPY based NIR AIE dyes and provides organelle specific bio-probes which are superior to currently used commercial ones.

Folic Acid Functionalized Carbon Dot/Polypyrrole Nanoparticles for Specific Bioimaging and Photothermal Therapy.

Polypyrrole nanoparticles (PPy-NPs) with excellent near-infrared absorption are commonly used as photothermal therapy (PTT) agents; however, PTT using PPy-NPs has a limitation in that it is difficult to maximize their therapeutic effect because of the lack of specific targeting. In this study, to overcome the difficulty of targeting, folic acid functionalized carbon dots (FA-CDs) with bright green fluorescence properties were combined with carboxylated PPy-NPs via the EDC/NHS coupling reaction to yield a PTT imaging agent. The synthesized FA-CD/PPy-NPs with excellent photostability performed folate receptor (FR) positive HeLa cancer cell imaging by green fluorescence signals of FA-CDs and exhibited high cell viability (above 90%) even at 500 μg/mL. The viability of HeLa cells incubated with 200 μg/mL FA-CD/PPy-NPs was dramatically decreased to 25.02 ± 1.85% by NIR laser irradiation, through photothermal therapeutic effects of FA-CD/PPy-NPs with high photothermal conversion efficiency (η = 40.80 ± 1.54%). The cancer cell death by FA-CD/PPy-NPs was confirmed by fluorescence imaging of FA-CDs as well as live/dead cell staining assay (calcein-AM/PI). These results demonstrate that the FA-CD/PPy-NPs can be utilized as multifunctional theranostic agents for specific bioimaging and treatment of FR-positive cancer cells.

Controllable Growth and Assembling Strategies Based on Nanomaterials for Targeted and Precise Therapy of Malignant Cancers

What is the most favorite and original chemistry developed in your research group??The sensitive detection methods and specific bioimaging strategies for tumor biomarkers, as well as the diagnosis‐therapy integration strategies of malignant cancers.How do you get into this specific field? Could you please share some experiences with our readers?I have entered this field for more than 10 years. Till now, cancer remains a major human health problem. Thus, the research about cancer diagnosis and therapy is quite important and interesting. Therefore, our group transferred our research attentions to this field.How do you supervise your students?In our group, we try our best to give every student the chance to demonstrate his talents and abilities. They could freely express their ideas or questions in our weekly seminar. Also I encourage the students to review the updated literature and have a clear understanding of the work they did.What is the most important personality for scientific research?I think the creativity and dedication to the research are very important for the scientific research.What's your hobbies? What's your favorite book(s)?Swimming and walking are my hobbies. I like to read some history books.How do you keep balance between research and family?A successful researcher should keep good balance between research and family. Usually, I try to elevate my work efficiency to finish all the work during the working time. Then, I have full time to be with my family.Who influences you mostly in your life?My doctoral adviser, professor Hongyuan Chen.What is your favorite journal(s)?Chemical Society Reviews and Journal of the American Chemical Society.Could you please give us some advices on improving Chinese Journal of Chemistry?Encourage the innovative submissions and endow the editor‐in‐chief with larger discretion.In the past decades, nanomaterials have achieved great development and received wide application in various fields. Nanomaterials‐based cancer therapy strategies brought great prospects and chance. Recently, we have developed controllable growth and assembling strategies based on nanomaterials for chemotherapy, photodynamic therapy, photothermal therapy and gene therapy. For chemotherapy, we modified DNA or RNA‐based nanostructures including DNA network, DNA sphere and RNA nanoflowers on the surface of magnetic nanoparticles (MNPs), gold nanoparticles (AuNPs) and mesoporous silica nanoparticles (MSPs) to develop feasible drug delivery systems, which could achieve the targeted therapy and controllable release. Especially, we developed telomerase‐ responsive drug delivery systems to achieve the highly‐localized chemotherapy. Furthermore, we established novel photodynamic nanotheranostic agents based on upconversion nanoparticles (UCNPs), which owned enhanced energy transfer efficiencies and improved production amount of reactive oxygen species (ROSs). For the photothermal therapy, we investigated novel composite nanomaterials to increase the ability of light‐to‐heat conversion. Finally, we also investigated the application of the RNA‐involved hydrogel in gene therapy. These developed strategies proved the great potential and application of nanomaterials in cancer therapy.

A benzothiadiazole-quinoline hybrid sensor for specific bioimaging and surgery procedures in mice

The work describes the design, synthesis, characterization and biological application (bioimaging) of a new hybrid and fluorescent 2,1,3-benzothiadiazole-quinoline sensor. Both photophysical data of the designed compound and DFT calculations have indicated its high stability and have pointed to its possible efficient application as a bioprobe for bioimaging experiments. The new sensor has been designed to display lipophilic character being capable of selectively stain lipid bodies independent whether live and fixed cancer cells were used. The fluorescent sensor has also been tested as a specific bioimaging marker for C. elegans (complex multicellular model) and has showed far better selectivity in the worm than the commercially available BODIPY. A live mice has been submitted to a surgery procedure and the adipocytes (lipid-rich) cells have been differentiated from standard cells. Experiments using high fat fed mice have enabled a high-resolution 3D image reconstruction. Also, in another surgery procedure, hepatocyte cells could have been successfully followed in the blood flow using the designed sensor in a multistaining procedure alongside with a commercially available blue emitting nuclei marker.

Monodisperse Core-Shell NaYF4:Yb3+/Er3+@NaYF4:Nd3+-PEG-GGGRGDSGGGY-NH2 Nanoparticles Excitable at 808 and 980 nm: Design, Surface Engineering, and Application in Life Sciences.

Lanthanide-doped upconversion nanoparticles (UCNPs) have a unique capability of upconverting near-infrared (NIR) excitation into ultraviolet, visible, and NIR emission. Conventional UCNPs composed of NaYF4:Yb3+/Er3+(Tm3+) are excited by NIR light at 980 nm, where undesirable absorption by water can cause overheating or damage of living tissues and reduce nanoparticle luminescence. Incorporation of Nd3+ ions into the UCNP lattice shifts the excitation wavelength to 808 nm, where absorption of water is minimal. Herein, core-shell NaYF4:Yb3+/Er3+@NaYF4:Nd3+ nanoparticles, which are doubly doped by sensitizers (Yb3+ and Nd3+) and an activator (Er3+) in the host NaYF4 matrix, were synthesized by high-temperature coprecipitation of lanthanide chlorides in the presence of oleic acid as a stabilizer. Uniform core (24 nm) and core-shell particles with tunable shell thickness (~0.5–4 nm) were thoroughly characterized by transmission electron microscopy (TEM), energy-dispersive analysis, selected area electron diffraction, and photoluminescence emission spectra at 808 and 980 nm excitation. To ensure dispersibility of the particles in biologically relevant media, they were coated by in-house synthesized poly(ethylene glycol) (PEG)-neridronate terminated with an alkyne (Alk). The stability of the NaYF4:Yb3+/Er3+@NaYF4:Nd3+-PEG-Alk nanoparticles in water or 0.01 M PBS and the presence of PEG on the surface were determined by dynamic light scattering, ζ-potential measurements, thermogravimetric analysis, and FTIR spectroscopy. Finally, the adhesive azidopentanoyl-modified GGGRGDSGGGY-NH2 (RGDS) peptide was immobilized on the NaYF4:Yb3+/Er3+@NaYF4:Nd3+-PEG-Alk particles via Cu(I)-catalyzed azide-alkyne cycloaddition. The toxicity of the unmodified core-shell NaYF4:Yb3+/Er3+@NaYF4:Nd3+, NaYF4:Yb3+/Er3+@NaYF4:Nd3+-PEG-Alk, and NaYF4:Yb3+/Er3+@NaYF4:Nd3+-PEG-RGDS nanoparticles on both Hep-G2 and HeLa cells was determined, confirming no adverse effect on their survival and proliferation. The interaction of the nanoparticles with Hep-G2 cells was monitored by confocal microscopy at both 808 and 980 nm excitation. The NaYF4:Yb3+/Er3+@NaYF4:Nd3+-PEG-RGDS nanoparticles were localized on the cell membranes due to specific binding of the RGDS peptide to integrins, in contrast to the NaYF4:Yb3+/Er3+@NaYF4:Nd3+-PEG-Alk particles, which were not engulfed by the cells. The NaYF4:Yb3+/Er3+@NaYF4:Nd3+-PEG-RGDS nanoparticles thus appear to be promising as a new non-invasive probe for specific bioimaging of cells and tissues. This development makes the nanoparticles useful for diagnostic and/or, after immobilization of a bioactive compound, even theranostic applications in the treatment of various fatal diseases.

Multifunctional AuI -based AIEgens: Manipulating Molecular Structures and Boosting Specific Cancer Cell Imaging and Theranostics.

Gold(I) N-heterocyclic carbene (AuI -NHC) complexes have emerged as potential anticancer agents owing to their high cytotoxicity and stability. Integration of their above unique functions with customized aggregation-induced emission (AIE) luminogens to achieve specific bioimaging and efficient theranostics to cancer is highly desirable but is rarely studied. Now, a series of novel AuI -NHC compounds were developed with AIE characteristics. A complex with a PPh3 ligand was selected out as it could achieve both prominent specific imaging of various cancer cells and efficient inhibition of their growth with negligible toxic effects on normal cells due to the targeting binding and strong inhibition towards thioredoxin reductase. This complex could also act as a powerful radiosensitizer to boost the anticancer efficacy with performance superior to that of popularly used auranofin. It holds great potential as a specific and effective theranostic drug in cancer diagnosis and precise therapy.

Multifunctional AuI‐based AIEgens: Manipulating Molecular Structures and Boosting Specific Cancer Cell Imaging and Theranostics

AbstractGold(I) N‐heterocyclic carbene (AuI‐NHC) complexes have emerged as potential anticancer agents owing to their high cytotoxicity and stability. Integration of their above unique functions with customized aggregation‐induced emission (AIE) luminogens to achieve specific bioimaging and efficient theranostics to cancer is highly desirable but is rarely studied. Now, a series of novel AuI‐NHC compounds were developed with AIE characteristics. A complex with a PPh3 ligand was selected out as it could achieve both prominent specific imaging of various cancer cells and efficient inhibition of their growth with negligible toxic effects on normal cells due to the targeting binding and strong inhibition towards thioredoxin reductase. This complex could also act as a powerful radiosensitizer to boost the anticancer efficacy with performance superior to that of popularly used auranofin. It holds great potential as a specific and effective theranostic drug in cancer diagnosis and precise therapy.

The unusual physicochemical properties of azulene and azulene-based compounds

Azulene, an isomer of naphthalene, has become one of hot chemical structures in the research field of functional materials, due to its anti-Kasha’s rule emissions and unusual physicochemical properties (e.g., photophysical, electrochemical, and photoelectrochemical properties). In the past, the synthesis of azulene-based compounds is relatively inconvenient. Recently, there have been more and more reports about the synthesis strategies of the azulene-based compounds for finely tuning the physicochemical properties. In this article, we introduce several synthetic methods for kinds of azulene-based compounds which has unusual physicochemical properties. With these convenient methods and unique physicochemical properties, azulene-based compounds can be applied into many fields such as specific bioimaging, advanced molecular switches, organic field-effect transistor (OFET), organic light emitting diode (OLED), solar cells, and so forth. And these properties are also summarized here.

A structure optimized fluorescent probe for highly sensitive monitoring drug induced lysosomal pH value changes

Lysosomes generally maintain the weak acidic microenvironment, to ensure highly efficient activity and functions of hydrolytic enzymes and proteins. Aberrations of the lysosomal pH may result in cellular functional changes and influence human physiology, possibly causing serious diseases. Small-molecular fluorescent probes based imaging techniques capable of providing information on target locations are considerably appreciated. Herein, by reducing the size of the typical lysosome targetable group 4-(2-aminoethyl) morpholine, we rationally designed a rhodamine analogue probe Ly-HN2AM with N-Aminomorpholine as the ring-closed switch and the lysosome targetable moiety for visualizing lysosomal pH changes. With the benefit of constructing multi-pentacyclic intramolecular hydrogen bond when binding with the H+, Ly-HN2AM gives a highly sensitive response towards pH values ranging from 4.79 to 6.07, with a remarkable higher pKa 5.35 over the typical 4-(2-aminoethyl) morpholine modified probes. The new probe was successfully applied to visualize pH value changes in lysosome-associated physiological and pathological processes with excellent photostability and low cytotoxicity, indicating the potential applications of lysosome specific bioimaging.

Simultaneous sensing of ferritin and apoferritin proteins using an iron-responsive dye and evaluation of physiological parameters associated with serum iron estimation.

An iron-responsive optical probe has been developed for simultaneous sensing of both ferritin and apoferritin proteins at pH 7.4 in water. The compound showed an exclusive response (turn-off signal) towards ferritin among a wide range of proteins even at nanomolar concentration. In contrast, apoferritin dissociates the preformed iron complex and revives the green colored fluorescence of the native probe (turn-on signal). Subsequently, various parameters associated with the serum iron level are evaluated, which are beneficial for clinical diagnosis of many iron-related diseases, including anemia. Estimation of iron was achieved in a wide range of edible plant materials as well as pharmaceutical formulations. Subsequently, different kinds of natural water samples were screened for quantification of soluble iron contents. In addition to traditional spectroscopic tools, dye-coated paper strips were developed as an alternative strategy for onsite 'instrument-free' detection of iron. Highly specific bioimaging of Fe3+ was achieved in cervical cancer cells (HeLa).

Inhibitor-conjugated harmonic nanoparticles targeting fibroblast activation protein.

The recent progress in the engineering of nanosized inorganic materials presenting tailored physical properties and reactive surface for post-functionalization has opened promising avenues for the use of nanoparticles (NPs) in diagnosis and therapeutic intervention. Surface decoration of metal oxide NPs with ligands modulating circulation time, cellular uptake, affinity and extravasation through active targeting led to efficient cancer specific bioimaging probes. The most relevant cancer biomarkers studied so far include surface and transmembrane cancer cell receptors. More recently, tumor microenvironments and more specifically the fibroblastic element of the tumor stroma have emerged as a valuable target for diagnosis and treatment of several types of cancers. In this study, a low molecular weight ligand targeting fibroblast activation protein α (FAP), which is specifically expressed by activated fibroblasts of the tumor stroma, was synthesized. This ligand demonstrated nanomolar inhibition of FAP with high selectivity with respect to prolyl oligopeptidase (PREP) and dipeptidyl peptidase (DPP) IV, as well as good biocompatibility toward a human lung tissue model. Bismuth ferrite (BFO) harmonic nanoparticles (HNPs) conjugated to this ligand showed target-specific association to FAP as demonstrated by reverse ELISA-type assay using Human Fibroblast Activation Protein alpha/FAP Alexa Fluor® 594-conjugated Antibody and multiphoton multispectral microscopy experiments. These functionalized HNPs may provide new nanocarriers to explore the role of FAP in tumorigenesis and to target the fibroblastic component of the tumor microenvironment.