{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,3]],"date-time":"2026-03-03T06:03:27Z","timestamp":1772517807505,"version":"3.50.1"},"reference-count":30,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T00:00:00Z","timestamp":1772236800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001824","name":"Czech Science Foundation","doi-asserted-by":"publisher","award":["25-16155S"],"award-info":[{"award-number":["25-16155S"]}],"id":[{"id":"10.13039\/501100001824","id-type":"DOI","asserted-by":"publisher"}]},{"name":"OPJAK EXREGMED","award":["CZ02.01.01\/00\/22-008\/0004562"],"award-info":[{"award-number":["CZ02.01.01\/00\/22-008\/0004562"]}]},{"DOI":"10.13039\/501100001823","name":"MEYS CR","doi-asserted-by":"crossref","award":["LM2023050 Czech-BioImaging"],"award-info":[{"award-number":["LM2023050 Czech-BioImaging"]}],"id":[{"id":"10.13039\/501100001823","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Upconverting nanoparticles, which transform low-energy infrared radiation into high-energy visible or UV light, show great potential in today\u2019s technology. High-quality upconversion colloid (UCC) consisting of lanthanide-based nanoparticles with a diameter of ~10 nm was obtained using a combination of two processes: high-temperature coprecipitation and hydrothermal treatment in an autoclave. The UCC was then PEGylated with PEG-alendronate (PEG-Ale) to facilitate its dispersion in aqueous cell culture media intended for in vitro cell uptake assays. The surface modification of the nanoparticles increased both the colloidal stability in water and the upconversion emission by mitigating surface quenching. UCC@Ale-PEG was characterized by transmission and scanning electron microscopy, dynamic light scattering, and fluorescence microscopy detecting upconversion photoluminescence emission. The results of an in vitro assay revealed that this new generation of UCC can be internalized by various cell types, including epithelial cells and macrophages, upon several hours of exposure, suggesting broad application potential of this type of UCC in biomedicine, bioengineering, and environmental sciences.<\/jats:p>","DOI":"10.3390\/ijms27052302","type":"journal-article","created":{"date-parts":[[2026,3,2]],"date-time":"2026-03-02T12:39:56Z","timestamp":1772455196000},"page":"2302","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Upconversion Colloid for Tracking Cellular Uptake of Nanoparticles"],"prefix":"10.3390","volume":"27","author":[{"given":"Mykhailo","family":"Nahorniak","sequence":"first","affiliation":[{"name":"Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovsk\u00e9ho n\u00e1m. 2, 162 00 Prague, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6907-9701","authenticated-orcid":false,"given":"Daniel","family":"Hor\u00e1k","sequence":"additional","affiliation":[{"name":"Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovsk\u00e9ho n\u00e1m. 2, 162 00 Prague, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"David","family":"Liebl","sequence":"additional","affiliation":[{"name":"Imaging Methods Core Facility, BIOCEV, Faculty of Science, Charles University, Pr\u016fmyslov\u00e1 595, 252 50 Vestec, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dana","family":"Marekov\u00e1","sequence":"additional","affiliation":[{"name":"Institute of Experimental Medicine, Czech Academy of Sciences, V\u00edde\u0148sk\u00e1 1083, 142 20 Prague, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7622-5837","authenticated-orcid":false,"given":"Lucia","family":"Machov\u00e1 Urdz\u00edkov\u00e1","sequence":"additional","affiliation":[{"name":"Institute of Experimental Medicine, Czech Academy of Sciences, V\u00edde\u0148sk\u00e1 1083, 142 20 Prague, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hana","family":"Mackov\u00e1","sequence":"additional","affiliation":[{"name":"Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovsk\u00e9ho n\u00e1m. 2, 162 00 Prague, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Petra","family":"Prok\u0161ov\u00e1","sequence":"additional","affiliation":[{"name":"Imaging Methods Core Facility, BIOCEV, Faculty of Science, Charles University, Pr\u016fmyslov\u00e1 595, 252 50 Vestec, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5829-8362","authenticated-orcid":false,"given":"Ale\u0161","family":"Benda","sequence":"additional","affiliation":[{"name":"Imaging Methods Core Facility, BIOCEV, Faculty of Science, Charles University, Pr\u016fmyslov\u00e1 595, 252 50 Vestec, Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2747","DOI":"10.1039\/D3NR05450K","article-title":"Photophysics and its application in photon upconversion","volume":"16","author":"Zhang","year":"2024","journal-title":"Nanoscale"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"e06247","DOI":"10.1002\/adma.202506247","article-title":"Spatiotemporal self-encrypted interlock-cascade-hashing optical storage based on multicolor photochromic lithographic array","volume":"38","author":"Xu","year":"2025","journal-title":"Adv. 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