In the diagnostics of diabetes, specific targeting of drugs (e.g., liraglutide) to insulin-deficient β-cells with their simultaneous noninvasive imaging is currently needed. In this report, liraglutide (LGL)-conjugated poly(methyl vinyl ether-alt-maleic acid) (PMVEMA)-coated core-shell NaYF4:Yb,Er,Fe@NaYF4:Nd upconversion nanoparticles (CS-UCNPs) have been developed, thoroughly physicochemically characterized, and evaluated in vivo. Novel codoping of Fe2+, Yb3+, and Er3+ ions in the host NaYF4 induced upconversion emission in the red region at both 980 and 808 nm excitation, making the particles suitable for deep-tissue imaging. Surface functionalization with PMVEMA provided colloidal stability and facilitated covalent conjugation with LGL, enabling targeted binding to GLP-1 receptors on pancreatic β-cells, increasing glucose-stimulated insulin secretion from isolated Langerhans islets. Biocompatibility of CS-UCNP@PMVEMA-LGL nanoparticles was confirmed by the trypan blue dye exclusion assay. When the fluorescent dye Flamma was conjugated to the nanoparticles, in vivo fluorescence imaging revealed significantly enhanced accumulation of CS-UCNP@PMVEMA-LGL-Flamma nanoparticles in the pancreas 24 h after intramuscular injection compared with intravenous administration, with luminescence intensity approximately doubled. The improved pancreatic targeting efficiency was attributed to enhanced binding to GLP-1 receptors. Confocal microscopy and elemental analysis confirmed receptor-mediated uptake of the nanoparticles by internalization and their localization within pancreatic β-cells. These findings highlight the potential of CS-UCNP@PMVEMA-LGL nanoparticles as biocompatible targetable imaging agents with future applications in pancreatic diagnostics.

• Keywords
• Flamma, diabetes, liraglutide, nanoparticles, poly(methyl vinyl ether-alt-maleic acid), theranostics, upconversion,
• MeSH
• Insulin-Secreting Cells metabolism   drug effects   MeSH
• Diabetes Mellitus, Experimental * drug therapy   diagnostic imaging   MeSH
• Fluorides MeSH
• Insulin metabolism   MeSH
• Humans MeSH
• Liraglutide * chemistry   pharmacology   MeSH
• Maleates * chemistry   MeSH
• Mice MeSH
• Nanoparticles * chemistry   MeSH
• Polyvinyls chemistry   MeSH
• Theranostic Nanomedicine * methods   MeSH
• Yttrium MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Fluorides MeSH
• Insulin MeSH
• Liraglutide * MeSH
• Maleates * MeSH
• Polyvinyls MeSH
• sodium yttriumtetrafluoride MeSH Browser
• Yttrium MeSH

The anti-Stokes emission of photon upconversion nanoparticles (UCNPs) facilitates their use as labels for ultrasensitive detection in biological samples as infrared excitation does not induce autofluorescence at visible wavelengths. The detection of extremely low-abundance analytes, however, remains challenging as it is impossible to completely avoid nonspecific binding of label conjugates. To overcome this limitation, we developed a novel hybridization complex transfer technique using UCNP labels to detect short nucleic acids directly without target amplification. The assay involves capturing the target-label complexes on an initial solid phase, then using releasing oligonucleotides to specifically elute only the target-UCNP complexes and recapturing them on another solid phase. The nonspecifically adsorbed labels remain on the first solid phase, enabling background-free, ultrasensitive detection. When magnetic microparticles were used as the first solid phase in a sample volume of 120 μL, the assay achieved a limit of detection (LOD) of 310 aM, a 27-fold improvement over the reference assay without transfer. Moreover, the additional target-specific steps introduced in the complex transfer procedure improved the sequence specificity of the complex transfer assay compared with the reference assay. The suitability for clinical analysis was confirmed using spiked plasma samples, resulting in an LOD of 190 aM. By increasing the sample volume to 600 μL and using magnetic preconcentration, the LOD was improved to 46 aM. These results highlight the importance of background elimination in achieving ultralow LODs for the analysis of low-abundance biomarkers.

• MeSH
• Nucleic Acid Hybridization MeSH
• Humans MeSH
• Limit of Detection MeSH
• Luminescence MeSH
• Luminescent Measurements * methods   MeSH
• Nanoparticles * chemistry   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

Photodynamic therapy (PDT) has the potential to cure pancreatic cancer with minimal side effects. Visible wavelengths are primarily used to activate hydrophobic photosensitizers, but in clinical practice, these wavelengths do not sufficiently penetrate deeper localized tumor cells. In this work, NaYF4:Yb3+,Er3+,Fe2+ upconversion nanoparticles (UCNPs) were coated with polymer and labeled with meta-tetra(hydroxyphenyl)chlorin (mTHPC; temoporfin) to enable near-infrared light (NIR)-triggered PDT of pancreatic cancer. The coating consisted of alendronate-terminated poly[N,N-dimethylacrylamide-co-2-aminoethylacrylamide]-graft-poly(ethylene glycol) [P(DMA-AEM)-PEG-Ale] to ensure the chemical and colloidal stability of the particles in aqueous physiological fluids, thereby also improving the therapeutic efficacy. The designed particles were well tolerated by the human pancreatic adenocarcinoma cell lines CAPAN-2, PANC-1, and PA-TU-8902. After intratumoral injection of mTHPC-conjugated polymer-coated UCNPs and subsequent exposure to 980 nm NIR light, excellent PDT efficacy was achieved in tumor-bearing mice.

• MeSH
• Acrylamides chemistry   MeSH
• Photochemotherapy * methods   MeSH
• Photosensitizing Agents * chemistry   pharmacology   MeSH
• Infrared Rays MeSH
• Colloids chemistry   MeSH
• Humans MeSH
• Mesoporphyrins * chemistry   pharmacology   MeSH
• Mice, Inbred BALB C MeSH
• Mice, Nude MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• Pancreatic Neoplasms * drug therapy   pathology   MeSH
• Nanoparticles chemistry   MeSH
• Polyethylene Glycols * chemistry   MeSH
• Polymers chemistry   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Acrylamides MeSH
• Photosensitizing Agents * MeSH
• Colloids MeSH
• Mesoporphyrins * MeSH
• Polyethylene Glycols * MeSH
• Polymers MeSH
• temoporfin MeSH Browser

Dot-blot immunoassays are widely used for the user-friendly detection of clinical biomarkers. However, the majority of dot-blot assays have only limited sensitivity and are only used for qualitative or semiquantitative analysis. To overcome this limitation, we have employed labels based on photon-upconversion nanoparticles (UCNPs) that exhibit anti-Stokes luminescence and can be detected without optical background interference. First, the dot-blot immunoassay on a nitrocellulose membrane was optimized for the quantitative analysis of human serum albumin (HSA), resulting in a limit of detection (LOD) of 0.19 ng/mL and a signal-to-background ratio (S/B) of 722. Commercial quantum dots were used as a reference label, reaching the LOD of 4.32 ng/mL and the S/B of 3, clearly indicating the advantages of UCNPs. In addition, the potential of UCNP-based dot-blot for real sample analysis was confirmed by analyzing spiked urine samples, reaching the LOD of 0.24 ng/mL and recovery rates from 79 to 123%. Furthermore, we demonstrated the versatility and robustness of the assay by adapting it to the detection of two other clinically relevant biomarkers, prostate-specific antigen (PSA) and cardiac troponin (cTn), reaching the LODs in spiked serum of 9.4 pg/mL and 0.62 ng/mL for PSA and cTn, respectively. Finally, clinical samples of patients examined for prostate cancer were analyzed, achieving a strong correlation with the reference electrochemiluminescence immunoassay (recovery rates from 89 to 117%). The achieved results demonstrate that UCNPs are highly sensitive labels that enable the development of dot-blot immunoassays for quantitative analysis of low-abundance biomarkers.

• MeSH
• Biomarkers * blood   urine   analysis   MeSH
• Immunoassay methods   MeSH
• Quantum Dots chemistry   MeSH
• Humans MeSH
• Serum Albumin, Human analysis   urine   MeSH
• Limit of Detection * MeSH
• Nanoparticles * chemistry   MeSH
• Prostate-Specific Antigen * blood   analysis   MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Biomarkers * MeSH
• Serum Albumin, Human MeSH
• Prostate-Specific Antigen * MeSH

Upconverting nanoparticles are interesting materials that have the potential for use in many applications ranging from solar energy harvesting to biosensing, light-triggered drug delivery, and photodynamic therapy (PDT). One of the main requirements for the particles is their surface modification, in our case using poly(methyl vinyl ether-alt-maleic acid) (PMVEMA) and temoporfin (THPC) photosensitizer to ensure the colloidal and chemical stability of the particles in aqueous media and the formation of singlet oxygen after NIR irradiation, respectively. Codoping of Fe2+, Yb3+, and Er3+ ions in the NaYF4 host induced upconversion emission of particles in the red region, which is dominant for achieving direct excitation of THPC. Novel monodisperse PMVEMA-coated upconversion NaYF4:Yb3+,Er3+,Fe2+ nanoparticles (UCNPs) with chemically bonded THPC were found to efficiently transfer energy and generate singlet oxygen. The cytotoxicity of the UCNPs was determined in the human pancreatic adenocarcinoma cell lines Capan-2, PANC-01, and PA-TU-8902. In vitro data demonstrated enhanced uptake of UCNP@PMVEMA-THPC particles by rat INS-1E insulinoma cells, followed by significant cell destruction after excitation with a 980 nm laser. Intratumoral administration of these nanoconjugates into a mouse model of human pancreatic adenocarcinoma caused extensive necrosis at the tumor site, followed by tumor suppression after NIR-induced PDT. In vitro and in vivo results thus suggest that this nanoconjugate is a promising candidate for NIR-induced PDT of cancer.

• Keywords
• pancreatic tumor, photodynamic therapy, temoporfin, upconversion,
• Publication type
• Journal Article MeSH

Upconverting nanoparticles (UCNPs) are of particular interest in nanomedicine for in vivo deep-tissue optical cancer bioimaging due to their efficient cellular uptake dependent on polymer coating. In this study, particles, ca. 25 nm in diameter, were prepared by a high-temperature coprecipitation of lanthanide chlorides. To ensure optimal dispersion of UCNPs in aqueous milieu, they were coated with three different polymers containing reactive groups, i.e., poly(ethylene glycol)-alendronate (PEG-Ale), poly(N,N-dimethylacrylamide-co-2-aminoethylacrylamide)-alendronate (PDMA-Ale), and poly(methyl vinyl ether-co-maleic acid) (PMVEMA). All the particles were characterized by TEM, DLS, FTIR, and spectrofluorometer to determine the morphology, hydrodynamic size and ξ-potential, composition, and upconversion luminescence. The degradability/dissolution of UCNPs in water, PBS, DMEM, or artificial lysosomal fluid (ALF) was evaluated using an ion-selective electrochemical method and UV-Vis spectroscopy. The dissolution that was more pronounced in PBS at elevated temperatures was decelerated by polymer coatings. The dissolution in DMEM was relatively small, but much more pronounced in ALF. PMVEMA with multiple anchoring groups provided better protection against particle dissolution in PBS than PEG-Ale and PDMA-Ale polymers containing only one reactive group. However, the cytotoxicity of the particles depended not only on their ability to rapidly degrade, but also on the type of coating. According to MTT, neat UCNPs and UCNP@PMVEMA were toxic for both rat cells (C6) and rat mesenchymal stem cells (rMSCs), which was in contrast to the UCNP@Ale-PDMA particles that were biocompatible. On the other hand, both the cytotoxicity and uptake of the UCNP@Ale-PEG particles by C6 and rMSCs were low, according to MTT assay and ICP-MS, respectively. This was confirmed by a confocal microscopy, where the neat UCNPs were preferentially internalized by both cell types, followed by the UCNP@PMVEMA, UCNP@Ale-PDMA, and UCNP@Ale-PEG particles. This study provides guidance for the selection of a suitable nanoparticle coating with respect to future biomedical applications where specific behaviors (extracellular deposition vs. cell internalization) are expected.

• Keywords
• degradation, lanthanides, luminescence, nanoparticles, upconversion,
• MeSH
• Alendronate MeSH
• Rats MeSH
• Nanoparticles * chemistry   MeSH
• Polyethylene Glycols chemistry   MeSH
• Polymers * chemistry   MeSH
• Water MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Alendronate MeSH
• Polyethylene Glycols MeSH
• Polymers * MeSH
• Water MeSH