Water-in-Water Emulsions, Ultralow Interfacial Tension, and Biolubrication

Open AccessCCS ChemistryRESEARCH ARTICLE6 Jun 2022Water-in-Water Emulsions, Ultralow Interfacial Tension, and Biolubrication Yitong Wang, Jin Yuan, Yunpeng Zhao, Ling Luxuan Guo, Lei Feng, Jiwei Cui, Shuli Dong, Shanhong Wan, Weimin Liu, Heinz Hoffmann, Kiet Tieu Jingcheng Hao Wang Key Laboratory of Colloid Interface Chemistry (Ministry Education) & State Crystal Materials, Shandong University, Jinan, 250100 Google Scholar More articles by this author , Yuan Zhao Department Orthopedics, Qilu Hospital, Cheeloo College Medicine, 250012 Guo Feng Cui Dong Wan Faculty Engineering Information Sciences, University Wollongong, NSW 2522 Solid Lubrication, Lanzhou Institute Chemical Physics, Chinese Academy 730000 Liu Hoffmann Physikalische Chemie I, Bayreuth Universität, D-95447 *Corresponding author: E-mail Address: [email protected] https://doi.org/10.31635/ccschem.021.202101028 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail A water-in-water (W/W) emulsion consists droplets formed the spontaneous liquid–liquid separation two immiscible aqueous phases. The inherent properties W/W interfaces, low or ultralow interfacial tension (?W/W = 1–1000 ?N/m) a large thickness several nanometers, beget poor stability emulsions. Herein, we report nanofibril emulsifier having Schiff base reactivity generate emulsion. has superior (stable > 6 months) because collagen nanofibrils, acting as stabilizer emulsions, can simultaneously satisfy requirements size overall coverage ratio phase interfaces. emulsions ?W/W ?10 ?N/m were used synthetic synovial fluids, showing lubrication performance with coefficient friction in range 0.003–0.011, which been demonstrated be suitable for joint lubrication. An intraarticular injection assessment further confirmed protective effect on articular cartilage vivo. Our study reveals mechanism stabilization opens up possibility osteoarthritis (OA) treatment using biolubrication effects lubricated artificial implant surfaces. Download figure PowerPoint Introduction extremely (COF) between interfaces relative motion an organism facilitates their daily use.1,2 Among them, are typical excellent is mainly attributable fluid (SF).3,4 Smooth elastic cushion vibration connected bones during movements, viscous SF also plays vital role lubricating Lubrication failure induced from degeneration leads wear thus (OA).5,6 primary choice OA treatment, replacement surgery, not only high cost causes great pain patients, but may limit rejection. In addition, abrasive particles generated degradation materials cause around dissolve loosen.7,8 ideal substitute material, bulk hydrogel, investigated its many similarities cartilage.9,10 However, challenges meeting both hydrogel strength drastically practical application materials. case, developing highly efficient biocompatible SFs provide alternative solution treat OA, it remains challenge. put forward incompatible polymer solutions, dextran polyethylene glycol (PEG) nanofibrils (Scheme 1), serve (SSFs). Considering that no research SSFs reported, analysis presented. (1) have such microgels11 brushes,12 products covalent cross-linking polymers, biosafety discussed, address concern. Compared oil-containing biocompatibility favorable.13 (2) thermodynamic instability all-aqueous significantly various fields.14 work, exhibited greater than months. (3) Although there cross-linked structure polymer-like microgels, amount water inside smooth character stabilizing greatly buffer stress protect cartilage. (4) It well known biopolyelectrolytes main components SFs.15 Scheme 1 | Schematic stabilized mPEG-collagen SFs. Analogous biological systems, combination natural protein, polysaccharide dextran, hydrophilic PEG ligands might promising design simultaneous biomimetic treatment. Moreover, recent studies shown liquid-like membraneless compartments eukaryotic cells, through (LLPS), driven proteins, nucleic acids, other biomacromolecules. After formed, macromolecules exist forms, one concentration state solution, higher form “droplets” whose morphology similar work. Thus, our suggests new strategy construction arthritis incorporating proteins surrounding, expanding types theoretical basis intracellular separation. Experimental Methods Materials chemicals For preparation stock (500 kDa) (8 obtained J&K Scientific Ltd. (Beijing, China). Collagen was purchased Chengdu Kele Biotechnology Co., (Chengdu, Methoxy glycol-acetaldehyde (mPEG-ALD) synthesized Shanghai Yayi (Shanghai, Fluorescein isothiocyanate (FITC)-dextran, tris, polyacrylic acid (PAA) Sigma-Aldrich Sodium tripolyphosphate (TPP) provided Aladdin Reagent Salts required system, CaCl2, NaCl, NaHCO3, KCl, K2HPO4·3H2O, MgCl2·6H2O, Na2SO4, NaN3, NaH2PO4, Sinopharm All analytical grade without purification. pH adjusted adding aliquots M NaOH HCl. experiments deionized (18.25 M?, Milli-Q, Millipore, Shanghai, Synthesis characterization prepared reaction. To obtain uniform transparent 50 mg dissolved 5 mL 0.2 acetic stirred at room temperature more 48 h. mixture 5.0 (near isoelectric point (PI) collagen, 4.9–5.0) mPEG-ALD added into beaker 12 Then reaction sealed maintained 25 °C disruption formation nanofibrils. reacting h, resultant dialyzed dialysis tube (molecular cut-off 8 3 days remove unreacted mPEG-ALD. throughout Preparation Stock solutions mixing certain amounts PEG, vessel stirring until dissolved. final 1–12 wt % 1.9–8.6 0.05–0.20 suspension. volume fraction varied 10% 80% changing compositions. diameter droplets, rate homogenization kept 1500 rpm min. fluorescence microscopy observation, FITC-dextran replaced dextran. biomineralization body (2.5 mM 136.8 4.2 1.5 0.5 Tris, 3.08 mg/mL PAA, 2.5 TPP, 7.4), biomineralized after incubation 72 Emulsion monitored demixing phases observable under microscope. Measurement tensions coexisting dextran- PEG-rich measured spinning drop interface tensiometer (TX500, USA KINO Industry Ltd., Boston, MA). density lower phase, served external spinning. 1–2 ?L droplet injected glass capillary insert filled denser dextran-rich phase. continued expand along axis rotation rotating horizontally. speed continuously length four times longer width. tension, ?, calculated Vonnegut equation measuring width cylindrical stick capillary. Characterization 1H NMR (400 MHz) spectra detected Bruker Avance 400 spectrometer (Bruker, Karlsruhe, Germany). scanning electron images freeze-dried gold coating observed (SEM; Zeiss G300, Atomic force (AFM) performed Dimension ICON operating PeakForce Tapping Mode. collected scan frequency Hz resolution 512 × pixels. microscope (Zeiss Axioskop 40, fluorescent recorded Axio observer 3, Wide-angle X-ray diffraction (WAXD) X’Pert3 powder diffractometer (PANalytical, Almelo, Netherlands) XPK-900 situ solid cell (Anton Paar, Graz, Austria) 10° < ? 70°. test conventional pin-on-disk reciprocating tribometer (Tribometer UMT-2, Center Tribology, Beijing, China) recording (?). frictional pair realized pressing upper running ball against settled disk. distance sliding cycle mm constant applying different normal loads (from 10 N) assisted software. elastomeric poly(dimethylsiloxane) (PDMS) hemisphere mm. disk silica wafer-plated titanium. coefficients average value each cycle. tests repeated three coefficient. Biocompatibility hMSCs Enhanced Green Fluorescent Protein (EGFP)-human mesenchymal stem cells (hMSC)-TERT cultured Dulbecco’s modified Eagle’s medium (DMEM) supplemented fetal bovine serum (FBS) 1% penicillin–streptomycin (P/S). Cells 5% CO2 atmosphere 37 °C. Besides, growth visualized Invitrogen EVOS FL Auto Cell Imaging System. 24, 48, h cocultivation medium, Counting Kit-8 (CKK-8, Dojindo, Kumamoto, Japan) evaluate proliferation According manufacturer’s protocol, CCK-8 diluted 1:10 then incubate incubator. Afterwards, absorbance 450 nm plate reader (Victor X5, PerkinElmer, Akron, OH). all samples, replicates tested. culture, activity levels lactate dehydrogenase (LDH), cytosolic enzyme normally indicator cellular toxicity, culture media damage. protocol (Roche Diagnostics, Mannheim, Germany), LDH assessing formazan product 490 via X5). background. 96-well toxicity control, while treated Triton X-100 marked high-toxicity control. percentages eq. 1: Cytotoxicity exp . ? control 100 animal models Male Sprague-Dawley rats (7 weeks age, 200–250 g) Charles River Co. animals week acclimatization. housed pairs temperature-controlled (21–22 °C) 12-h light/12-h dark male surgical destabilization medial meniscus (DMM) right knee. Specifically, DMM surgery sectioning meniscotibial ligament sham operation incision cutaneous muscular planes baseline. mice had undergone randomly divided groups: group, phosphate-buffered saline (PBS) group. given injections PBS killed 4-week mark. Dissected joints processed either histopathological analysis. accordance Institutional Animal Care Use Committee (IACUC) guidelines approved IACUC committees University. Results Discussion Stabilization Despite numerous applications including bioreactors, food formulations, delivery bioactive agents, templates synthesis microgel particles, still limited amphiphilic stabilizers adsorbed interfaces.16 Instead traditional molecules, larger colloidal protein-conjugate particles,17 cellulose nanocrystals,18 pH-sensitive microgels,19 reported adsorb even conditions tension.20 geometrical constraints packed often ratios,21 paper, produce employed protein produced near PI (4.9?5.0).22 Supporting Figure S1 1a demonstrate success resulting (mPEG-collagen) periodic clearly seen AFM image. line profiles five colors corresponding 1b. periodicity nanofibril, ranging 64.9 68.5 nm, quotient fiber bump number. distribution nanofibers Gaussian fitting (Figure 1c) show these 65.9 consistent well-known D-banded (the 68 nm) assembled tropocollagen.23 This process induces molecules improve solubility preserve bioactivity PEGylation. ratio. (a) image (b) colored lines (a). (c) (d) OP cPEG 8.0 varying cdex 0.05 (1), 0.10 (2), 0.15 (3), 0.20 (4). (e) adsorption (f) concentrations mPEG-collagen, increases linearly (top). total area fibril (bottom). level needed stabilize determined 0.05, 0.10, 0.15, %. Using optical (OP), well-defined spherical structures sizes function concentration. 1d, observe becomes smaller increasing mPEG-collagen; principle applicable fractions. There question whether will like surfactants absorbing oil/water though low. We ? values tensiometer, following (eq 2): / 4 ? ? ? 2 R details measurement calculation Note S2. series values, 5.5 18.0 %, measured. As 1e, weight fraction, increase. remain almost 10?5 N/m cdextran 14 1e shows behaving surfactant, effectively reduce tension. concluded adsorbs reduction attributed directional mPEG-collagen. establish examined use native emulsifier. macroscopic appearance mixtures S3a. blank showed within bottom top. case implying cannot influence emulsification tendency PEG/dextran mixtures. undergoes dynamic desorption interface. key stable overcome Brownian movement stabilizer. energy (?G) related capacity ?G depends (R), ?W/W, contact angle (?), 3: G ? W ( cos ) Only if much thermal kinetic (?E) firmly bonded prerequisite findings S3, most extreme ?r2 3.14 (1.5 nm/2)2 1.767 10?23 J. orders magnitude (?E kT 1.38 300 10?21 J) small nm.24 amorphous S3b point. Native effective barrier prevent fusion. when satisfying did lead microphotograph displaying complete absence coalescence S3c). results fractions (?dex) 0.1 mPEG S1f. At concentrations, cover entire droplet. When coalesce, gather merged droplets. sufficiently large, spreads out evenly over before delays occurrence Ostwald ripening These follow basic rule systems. ?dex (S) calculated, eq 4: S ? dex ? (4)where R? 1f, A, m2) independent reason why revealed. specific concentration, constant, increases, insufficient Droplet fusion occurs larger. linear increase providing estimated values: per gram 53.49 m2, m2 requires 0.01869 g determine composition presence prepared. inversion occurred 50% stacking. green continuous dextran-in-PEG <50% 2a). contrast, 50%, PEG-in-dextran 2b). Fluorescence FITC-modified nanofibrils: 6.3 1.9 (b). (cPEG %) day 40 (g). Size days, (h), respectively. explored being incubated 7 reduced, relatively (?0.20 %). little change S4). Figures 2c, 2d, 2f, 2g). regular structures, began fuse. enhanced explained free coalescence. adjacent must they fuse If takes place, physical barriers, enter 3.