{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,26]],"date-time":"2026-02-26T06:37:06Z","timestamp":1772087826745,"version":"3.50.1"},"reference-count":51,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,2,16]],"date-time":"2026-02-16T00:00:00Z","timestamp":1771200000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Shandong Provincial Key Research and Development Program","award":["No. 2024CXGC010612"],"award-info":[{"award-number":["No. 2024CXGC010612"]}]},{"name":"The Natural Science Foundation of Shandong Province","award":["ZR2024QB011"],"award-info":[{"award-number":["ZR2024QB011"]}]},{"name":"Young Scholars Program of Shandong University","award":["Zhang X. 11190082364061"],"award-info":[{"award-number":["Zhang X. 11190082364061"]}]},{"name":"Young Scholars Program of Shandong University","award":["Qiu X. 11190082364060"],"award-info":[{"award-number":["Qiu X. 11190082364060"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>Hydrogel fluorescent microspheres function as versatile tracers with applications spanning across biomedicine, complex plasma systems, hydrodynamics, and drug delivery. However, the controlled release of fluorescent material in hydrogel microspheres is challenging to achieve. The fluorescent hydrogel microsphere (namely poly(ethylene glycol) diacrylate@rhodamine B-tannic acid, PEGDA@RhB-TA) was fabricated by incorporating tannic acid and RhB into PEGDA microspheres. The stable encapsulation and responsive release of RhB can be achieved by leveraging the non-covalent interactions between TA and RhB. RhB was stably encapsulated within PEGDA microspheres through noncovalent interactions (hydrophobic interactions, hydrogen bonding, \u03c0\u2013\u03c0, and ion\u2013\u03c0 interactions) between RhB and TA. Both molecular dynamics simulations by GROMACS and experimental results confirmed the noncovalent binding mechanisms between RhB and TA. The microspheres retained RhB following 24 h immersion in a highly concentrated salt solution (1 M NaCl) and exhibited minimal RhB release (7.1%) under heating at 80 \u00b0C for 24 h. However, PEGDA@RhB-TA microspheres underwent rapid RhB release in a 50% v\/v ethanol\u2013water solution, liberating 73% of the encapsulated dye within 24 h. TA within the PEGDA@RhB-TA microsphere acts as a molecular lock by forming non-covalent interactions with RhB, significantly enhancing the stability of encapsulated RhB, and enabling the responsive release of RhB under specific conditions. Upon introduction into a microfluidic chip, PEGDA@RhB-TA microspheres enable the calculation of flow velocity through position tracking using high-speed camera imaging and fluorescence microscopy. These microspheres overcome the dual challenges of tracer stability and controlled release, making them suitable for fluid tracing and measuring flow rates.<\/jats:p>","DOI":"10.3390\/polym18040493","type":"journal-article","created":{"date-parts":[[2026,2,16]],"date-time":"2026-02-16T14:09:54Z","timestamp":1771250994000},"page":"493","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Stable Encapsulation and Responsive Release of Dyes via Noncovalent Molecular Lock Strategy: A Case Study of Rhodamine B Based Fluorescent Hydrogel Microspheres"],"prefix":"10.3390","volume":"18","author":[{"given":"Shuo","family":"Meng","sequence":"first","affiliation":[{"name":"Key Laboratory of Colloid and Interface Chemistry of the Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Chuanyu","family":"Dang","sequence":"additional","affiliation":[{"name":"Shandong Kunda Biotech Co., Ltd., Linyi 276400, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiaoyong","family":"Qiu","sequence":"additional","affiliation":[{"name":"Key Laboratory of Colloid and Interface Chemistry of the Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jianhua","family":"Chen","sequence":"additional","affiliation":[{"name":"Beijing Fleming Technology Co., Ltd., Beijing 102600, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ruiheng","family":"Yao","sequence":"additional","affiliation":[{"name":"Center for Advanced Jet Engineering Technologies (CaJET), Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education, School of Mechanical Engineering, Shandong University, Jinan 250061, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuquan","family":"Wang","sequence":"additional","affiliation":[{"name":"Center for Advanced Jet Engineering Technologies (CaJET), Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education, School of Mechanical Engineering, Shandong University, Jinan 250061, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Luxing","family":"Wei","sequence":"additional","affiliation":[{"name":"Center for Advanced Jet Engineering Technologies (CaJET), Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education, School of Mechanical Engineering, Shandong University, Jinan 250061, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jun","family":"Huang","sequence":"additional","affiliation":[{"name":"Center for Advanced Jet Engineering Technologies (CaJET), Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education, School of Mechanical Engineering, Shandong University, Jinan 250061, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8607-6801","authenticated-orcid":false,"given":"Xiaolai","family":"Zhang","sequence":"additional","affiliation":[{"name":"Key Laboratory of Colloid and Interface Chemistry of the Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"13932","DOI":"10.1021\/acs.langmuir.3c01478","article-title":"Optimizing the production of hydrogel microspheres using microfluidic chips: The influence of surface treatment on droplet formation mechanism","volume":"39","author":"Zhang","year":"2023","journal-title":"Langmuir"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"475","DOI":"10.1016\/j.colsurfb.2016.12.043","article-title":"Inherently fluorescent polystyrene microspheres for coating, sensing and cellular imaging","volume":"152","author":"Qu","year":"2017","journal-title":"Colloids Surf. B"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"3556","DOI":"10.1021\/bm1010273","article-title":"Versatile polymer microspheres for injection therapy: Aspects of fluoroscopic traceability and biofunctionalization","volume":"11","author":"Saralidze","year":"2010","journal-title":"Biomacromolecules"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"16404","DOI":"10.1103\/PhysRevE.75.016404","article-title":"Fluorescent microspheres as tracer particles in dusty plasmas","volume":"75","author":"Miksch","year":"2007","journal-title":"Phys. Rev. E"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"82","DOI":"10.1007\/s00348-023-03624-9","article-title":"Investigation of turbulent superstructures in Rayleigh-B\u00e9nard convection by Lagrangian particle tracking of fluorescent microspheres","volume":"64","author":"Weiss","year":"2023","journal-title":"Exp. Fluids"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"99034","DOI":"10.1039\/C6RA15401H","article-title":"Electrospraying magnetic-fluorescent bifunctional Janus PLGA microspheres with dual rare earth ions fluorescent-labeling drugs","volume":"6","author":"Li","year":"2016","journal-title":"RSC Adv."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"23244","DOI":"10.1021\/jp4045836","article-title":"Poly(ethylene oxide) and polystyrene encapsulated quantum dots: Highly fluorescent, functionalizable, and ultrastable in aqueous media","volume":"117","author":"Kloust","year":"2013","journal-title":"J. Phys. Chem. C"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"101400","DOI":"10.1016\/j.fpsl.2024.101400","article-title":"A sprayable and rapidly cross-linked hydrogel membrane for fruit preservation","volume":"46","author":"Wei","year":"2024","journal-title":"Food Packag. Shelf Life"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1016\/j.colsurfa.2015.03.048","article-title":"Adsorption and removal of rhodamine B from aqueous solution by tannic acid functionalized graphene","volume":"477","author":"Liu","year":"2015","journal-title":"Colloid Surf. A"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"299","DOI":"10.1016\/j.ecoenv.2018.09.009","article-title":"Tannic acid functionalized graphene hydrogel for organic dye adsorption","volume":"165","author":"Tang","year":"2018","journal-title":"Ecotoxicol. Environ. Saf."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"166303","DOI":"10.1016\/j.cej.2025.166303","article-title":"Manipulating the wastewater\u2019s ion composition to assist in the adsorption of organophosphate esters (OPEs)","volume":"520","author":"Li","year":"2025","journal-title":"Chem. Eng. J."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1129","DOI":"10.1016\/j.neuron.2018.08.011","article-title":"Molecular dynamics simulation for all","volume":"99","author":"Hollingsworth","year":"2018","journal-title":"Neuron"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"114653","DOI":"10.1016\/j.foodres.2024.114653","article-title":"Application of the molecular dynamics simulation GROMACS in food science","volume":"190","author":"Yu","year":"2024","journal-title":"Food Res. Int."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"259","DOI":"10.1021\/acsbiomaterials.4c01762","article-title":"Data-Driven framework for the prediction of PEGDA hydrogel mechanics","volume":"11","author":"Tang","year":"2024","journal-title":"ACS Biomater. Sci. Eng."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"158615","DOI":"10.1016\/j.cej.2024.158615","article-title":"Anti-inflammatory MXene- and tannic acid-based synthetic-natural hybrid hydrogel for diabetic wound treatment by electrostimulation","volume":"503","author":"Liu","year":"2025","journal-title":"Chem. Eng. J."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"212","DOI":"10.1016\/j.jlumin.2016.11.052","article-title":"Fluorescent probe encapsulated hydrogel microsphere for selective and reversible detection of Hg2+","volume":"183","author":"Song","year":"2017","journal-title":"J. Lumin."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"39662","DOI":"10.1039\/D0RA07318K","article-title":"Injectable microfluidic hydrogel microspheres based on chitosan and poly(ethylene glycol) diacrylate (PEGDA) as chondrocyte carriers","volume":"10","author":"Lin","year":"2020","journal-title":"RSC Adv."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"132453","DOI":"10.1016\/j.ijbiomac.2024.132453","article-title":"Antibacterial; antioxidant, Cr(VI) adsorption and dye adsorption effects of biochar-based silver nanoparticles-sodium alginate-tannic acid composite gel beads","volume":"271","author":"Feng","year":"2024","journal-title":"Int. J. Biol. Macromol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"e54743","DOI":"10.1002\/app.54743","article-title":"Selective filtration of dye by tannic acid-molybdenum disulfide composite nanofiltration membrane","volume":"141","author":"Li","year":"2023","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"5648","DOI":"10.1063\/1.464913","article-title":"Density-functional thermochemistry. III. The role of exact exchange","volume":"98","author":"Becke","year":"1993","journal-title":"J. Chem. Phys."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"580","DOI":"10.1002\/jcc.22885","article-title":"Multiwfn: A multifunctional wavefunction analyzer","volume":"33","author":"Lu","year":"2011","journal-title":"J. Comput. Chem."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"10269","DOI":"10.1021\/j100142a004","article-title":"A well-behaved electrostatic potential based method using charge restraints for deriving atomic charges: The RESP model","volume":"97","author":"Bayly","year":"2002","journal-title":"J. Phys. Chem."},{"key":"ref_23","unstructured":"Lu, T. (2026, February 12). Sobtop, Version [1.0(dev3)]. Available online: http:\/\/sobereva.com\/soft\/Sobtop."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"213","DOI":"10.1007\/BF00533485","article-title":"The influence of polarization functions on molecular orbital hydrogenation energies","volume":"28","author":"Hariharan","year":"1973","journal-title":"Theor. Chim. Acta"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"2257","DOI":"10.1063\/1.1677527","article-title":"Self-Consistent molecular orbital methods. XII. further extensions of Gaussian-Type basis sets for use in molecular orbital studies of organic molecules","volume":"56","author":"Hehre","year":"1972","journal-title":"J. Chem. Phys."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1016\/j.softx.2015.06.001","article-title":"GROMACS: High performance molecular simulations through multi-level parallelism from laptops to supercomputers","volume":"1\u20132","author":"Abraham","year":"2015","journal-title":"SoftwareX"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"712","DOI":"10.1002\/prot.21123","article-title":"Comparison of multiple AMBER force fields and development of improved protein backbone parameters","volume":"65","author":"Hornak","year":"2006","journal-title":"Proteins Struct. Funct. Bioinf."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"014101","DOI":"10.1063\/1.2408420","article-title":"Canonical sampling through velocity rescaling","volume":"126","author":"Bussi","year":"2008","journal-title":"J Chem Phys."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"114017","DOI":"10.1063\/5.0020514","article-title":"Pressure control using stochastic cell rescaling","volume":"153","author":"Bernetti","year":"2020","journal-title":"J. Chem. Phys."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"8577","DOI":"10.1063\/1.470117","article-title":"A smooth particle mesh Ewald method","volume":"103","author":"Essmann","year":"1995","journal-title":"J. Chem. Phys."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"10089","DOI":"10.1063\/1.464397","article-title":"Particle mesh Ewald: An N\u22c5log(N) method for Ewald sums in large systems","volume":"98","author":"Darden","year":"1993","journal-title":"J. Chem. Phys."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1016\/0263-7855(96)00018-5","article-title":"VMD: Visual molecular dynamics","volume":"14","author":"Humphrey","year":"1996","journal-title":"J. Mol. Graph."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"449","DOI":"10.1517\/17460441.2015.1032936","article-title":"The MM\/PBSA and MM\/GBSA methods to estimate ligand-binding affinities","volume":"10","author":"Genheden","year":"2015","journal-title":"Expert Opin. Drug Discov."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"6281","DOI":"10.1021\/acs.jctc.1c00645","article-title":"gmx_MMPBSA: A new tool to perform end-state free energy calculations with GROMACS","volume":"17","author":"Valiente","year":"2021","journal-title":"J. Chem. Theory Comput."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"105717","DOI":"10.1016\/j.foodhyd.2020.105717","article-title":"Tannic acid-assisted cross-linked nanoparticles as a delivery system of eugenol: The characterization, thermal degradation and antioxidant properties","volume":"104","author":"Jia","year":"2020","journal-title":"Food Hydrocoll."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"35066","DOI":"10.1021\/acsami.5c03066","article-title":"Skin barrier restoration by waste-derived multifunctional adhesive hydrogel based on tannin-modified chitosan","volume":"17","author":"Ferri","year":"2025","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"119962","DOI":"10.1016\/j.carbon.2024.119962","article-title":"Visually monitoring of wear damage and interfacial corrosion in lubricant coating enabled by MXene@Rhodamine B fluorophores","volume":"234","author":"Wang","year":"2025","journal-title":"Carbon"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"2309317","DOI":"10.1002\/smll.202309317","article-title":"A 3D cross-linked metal-organic framework (MOF)-derived polymer electrolyte for dendrite-free solid-state lithium-ion batteries","volume":"20","author":"Zhou","year":"2023","journal-title":"Small"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"2500976","DOI":"10.1002\/smll.202500976","article-title":"Crystallization-Induced network growth for enhancing hydrogel mechanical properties","volume":"21","author":"Liu","year":"2025","journal-title":"Small"},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Song, B., Yang, L., Han, L., and Jia, L. (2019). Metal ion-chelated tannic acid coating for hemostatic dressing. Materials, 12.","DOI":"10.3390\/ma12111803"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"560","DOI":"10.1002\/jbm.b.32856","article-title":"Preparation and properties of tannic acid cross-linked collagen scaffold and its application in wound healing","volume":"101B","author":"Natarajan","year":"2012","journal-title":"J. Biomed. Mater. Res. Part B"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"4491","DOI":"10.1021\/acs.macromol.3c00611","article-title":"Urea as a hydrogen bond producer for fabricating mechanically very strong hydrogels","volume":"56","author":"Wu","year":"2023","journal-title":"Macromolecules"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"199","DOI":"10.1016\/j.chemphys.2018.09.014","article-title":"The dependence of hydrophobic interactions on solute size","volume":"516","author":"Sun","year":"2019","journal-title":"Chem. Phys."},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Liu, Y., Chen, Y., and Sun, Q. (2024). The dependence of hydrophobic interactions on the shape of solute surface. Molecules, 29.","DOI":"10.3390\/molecules29112601"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/j.colsurfa.2012.10.055","article-title":"Effect of solvent polarity on the assembly behavior of PVP coated rhodium nanoparticles","volume":"417","author":"Gacem","year":"2013","journal-title":"Colloid Surf. A"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"e2301826","DOI":"10.1002\/adhm.202301826","article-title":"Novel natural carrier-free self-assembled nanoparticles for treatment of ulcerative colitis by balancing immune microenvironment and intestinal barrier","volume":"12","author":"Gao","year":"2023","journal-title":"Adv. Healthc. Mater."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"163247","DOI":"10.1016\/j.apsusc.2025.163247","article-title":"Molecular dynamics simulation study on adsorption of imidazoline and quinoline derivatives on Fe (001) surface","volume":"700","author":"Li","year":"2025","journal-title":"Appl. Surf. Sci."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"9478","DOI":"10.1021\/acs.chemrev.9b00055","article-title":"End-Point binding free energy calculation with MM\/PBSA and MM\/GBSA: Strategies and applications in drug design","volume":"119","author":"Wang","year":"2019","journal-title":"Chem. Rev."},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Gilli, G., and Gilli, P. (2009). The Nature of the Hydrogen Bond: Outline of a Comprehensive Hydrogen Bond Theory, Oxford University Press.","DOI":"10.1093\/acprof:oso\/9780199558964.001.0001"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"1144","DOI":"10.1126\/science.7761829","article-title":"Classical electrostatics in biology and chemistry","volume":"268","author":"Honig","year":"1995","journal-title":"Science"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"11372","DOI":"10.1039\/D3TB01817B","article-title":"An underwater stable and durable gelatin composite hydrogel coating for biomedical applications","volume":"11","author":"Wei","year":"2023","journal-title":"J. Mater. Chem. B"}],"container-title":["Polymers"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/4\/493\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,2,26]],"date-time":"2026-02-26T05:28:32Z","timestamp":1772083712000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/4\/493"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,2,16]]},"references-count":51,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2026,2]]}},"alternative-id":["polym18040493"],"URL":"https:\/\/doi.org\/10.3390\/polym18040493","relation":{},"ISSN":["2073-4360"],"issn-type":[{"value":"2073-4360","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,2,16]]}}}