本研究中我們目標首以建立電噴灑式氣相奈米粒子流動分析儀(ES-DMA)，並開發適用之分析方法，以期具有測量膠體奈米材料於水溶液相的粒徑分布、濃度及對應膠體穩定性之能力。我們可針對所處的環境條件(如pH值，溶液中鹽類濃度，以及溶液相內與存在之大分子交互作用等)，量測對應之粒徑分布及數量濃度產生的變化，進而定量上分析膠體奈米材料在不同環境下膠體穩定性之變化。 研究中主要選用的材料為奈米銀粒子(silver nanoparticle, AgNP)，並分二階段進行探討。第一階段探討未擔載之奈米銀及牛血清蛋白(BSA)改質之奈米銀，在酸性環境下之膠體穩定性。我們利用ES-DMA測量不同酸性環境中AgNPs及BSA-AgNPs的粒徑分佈情形及粒徑大小隨時間的變化，並根據結果推測聚集和溶解反應的程度，以及計算BSA吸附的厚度及表面吸附密度。同時，我們也以穿透式電子顯微鏡(TEM)觀察AgNPs表面的變化，分析AgNPs溶解的過程。根據實驗的結果，AgNP在酸性環境下快速聚集形成多聚物，而表面也會受到硝酸腐蝕而溶解。相較之下，BSA-AgNPs則受到BSA吸附層(corona)保護而減慢粒子聚集的速度，使AgNPs能穩定存在於溶液中，且BSA corona亦會阻擋硝酸與AgNPs接觸，因此BSA-AgNPs並沒有明顯的溶解現象發生。
第二階段我們針對奈米銀粒子於溶液相中發生之溶解現象進行深入的動力學探討。定量上我們比較不同粒徑(20nm、30nm及60nm)AgNPs之聚集與溶解效應，以期了解膠體銀粒徑大小對其穩定性之影響。除了先前所探討的酸鹼度之外，我們也藉由調整溶液中鹽類濃度來探討溶液中離子強度對於AgNPs在聚集以及溶解動力學上的影響。我們也利用硫醇基化聚乙二醇 (SH-PEG)做為中性電之高分子配體，並與之前BSA做比較，以探討不同吸附分子會對奈米銀粒子產生之影響。根據實驗結果計算，粒徑較大的AgNPs其聚集速度較慢。此外，隨著環境的鹽類濃度提高，AgNPs聚集速度則加快。相較之下，以SH-PEG改質後，SH-PEG-AgNPs可阻擋鹽類與AgNPs反應，因此聚集及溶解程度均減少；然而，SH-PEG無法阻擋硝酸與AgNPs反應，因此在酸性條件下SH-PEG-AgNPs會逐漸溶解使粒徑變小。
除了AgNP之外，研究結果顯示我們可利用ES-DMA分析其他功能性膠體奈米材料，如2-D氧化石墨烯(GO)、TiO2奈米粒子、孔性金屬-有機配位聚合物(metal-organic framework, MOF)和奈米金粒子等材料之膠體穩定性。初步結果顯示藉由量測其尺寸上之變化，我們可以評估其穩定性以及可能對應之功能性和毒性影響，做為未來工作相關研究之基礎。

Silver nanoparticle (AgNP) is widely used in our daily life, including consumer goods, clothes, electronics, and also many emerging technology in biomedical applications (e.g., carriers, sensors). In this study, we investigated the colloidal stability of AgNPs under acidic and/or highly ionic environments, and the subsequent interaction with the plasma protein to their colloidal stability. Electrospray-differential mobility analysis was used to characterize the particle size distributions and the number concentrations of AgNPs. Transmission electron microscopy was employed orthogonally to provide visualization of AgNPs. For unconjugated AgNPs, the particles size was increased by aggregation as increasing the acidity and/or ionic strength, accompanied with a change of morphology due to acid-induced interfacial dissolution, but aggregation and dissolution were both shown to be insignificant for bovine serum albumin-functionalized AgNPs. This work provides a generic method to analyze colloidal stability of surface functionalized AgNPs over various formulation chemistry and environment conditions (e.g., cell culture media and natural water).

1. Nam, J., et al., Surface engineering of inorganic nanoparticles for imaging and therapy. Advanced Drug Delivery Reviews, 2013. 65(5): p. 622-648.
2. Liu, J.Y. and R.H. Hurt, Ion Release Kinetics and Particle Persistence in Aqueous Nano-Silver Colloids. Environmental Science & Technology, 2010. 44(6): p. 2169-2175.
3. Zook, J.M., et al., Measuring Agglomerate Size Distribution and Dependence of Localized Surface Plasmon Resonance Absorbance on Gold Nanoparticle Agglomerate Size Using Analytical Ultracentrifugation. Acs Nano, 2011. 5(10): p. 8070-8079.
4. Hou, W.B. and S.B. Cronin, A Review of Surface Plasmon Resonance-Enhanced Photocatalysis. Advanced Functional Materials, 2013. 23(13): p. 1612-1619.
5. Liu, L., et al., Mechanism of Shape Evolution in Ag Nanoprisms Stabilized by Thiol-Terminated Poly(ethylene glycol): An in Situ Kinetic Study. Chemistry of Materials, 2013. 25(21): p. 4206-4214.
6. Shannahan, J.H., et al., Silver Nanoparticle Protein Corona Composition in Cell Culture Media. PLoS ONE, 2013. 8(9): p. e74001.
7. Tai, J.-T., et al., Protein–Silver Nanoparticle Interactions to Colloidal Stability in Acidic Environments. Langmuir, 2014.
8. Reidy, B., et al., Mechanisms of Silver Nanoparticle Release, Transformation and Toxicity: A Critical Review of Current Knowledge and Recommendations for Future Studies and Applications. Materials, 2013. 6(6): p. 2295-2350.
9. Glover, R.D., J.M. Miller, and J.E. Hutchison, Generation of Metal Nanoparticles from Silver and Copper Objects: Nanoparticle Dynamics on Surfaces and Potential Sources of Nanoparticles in the Environment. ACS Nano, 2011. 5(11): p. 8950-8957.
10. Walters, C., E. Pool, and V. Somerset, Aggregation and dissolution of silver nanoparticles in a laboratorybased freshwater microcosm under simulated environmental conditions. Toxicological and Environmental Chemistry, 2013. 95(10): p. 1690-1701.
11. Yang, X.-H., et al., Catalytic formation of silver nanoparticles by bovine serum albumin protected-silver nanoclusters and its application for colorimetric detection of ascorbic acid. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2013. 106(0): p. 224-230.
12. Ostermeyer, A.-K., et al., Influence of Bovine Serum Albumin and Alginate on Silver Nanoparticle Dissolution and Toxicity to Nitrosomonas europaea. Environmental Science & Technology, 2013. 47(24): p. 14403-14410.
13. Li, X., J.J. Lenhart, and H.W. Walker, Aggregation Kinetics and Dissolution of Coated Silver Nanoparticles. Langmuir, 2012. 28(2): p. 1095-1104.
14. Grade, S., et al., Serum albumin reduces the antibacterial and cytotoxic effects of hydrogel-embedded colloidal silver nanoparticles. RSC Advances, 2012. 2(18): p. 7190-7196.
15. Tsai, D.H., et al., Adsorption and Conformation of Serum Albumin Protein on Gold Nanoparticles Investigated Using Dimensional Measurements and in Situ Spectroscopic Methods. Langmuir, 2011. 27(6): p. 2464-2477.
16. Martin, M.N., et al., Dissolution, Agglomerate Morphology, and Stability Limits of Protein-Coated Silver Nanoparticles. Langmuir, 2014. 30(38): p. 11442-11452.
17. Masrahi, A., A. VandeVoort, and Y. Arai, Effects of Silver Nanoparticle on Soil-Nitrification Processes. Archives of Environmental Contamination and Toxicology, 2014. 66(4): p. 504-513.
18. Pettibone, J.M., J. Gigault, and V.A. Hackley, Discriminating the States of Matter in Metallic Nanoparticle Transformations: What Are We Missing? Acs Nano, 2013. 7(3): p. 2491-2499.
19. Li, X. and J.J. Lenhart, Aggregation and Dissolution of Silver Nanoparticles in Natural Surface Water. Environmental Science & Technology, 2012. 46(10): p. 5378-5386.
20. Bilberg, K., et al., In Vivo Toxicity of Silver Nanoparticles and Silver Ions in Zebrafish (Danio rerio). Journal of Toxicology, 2012. 2012: p. 9.
21. Pease Iii, L.F., Physical analysis of virus particles using electrospray differential mobility analysis. Trends in Biotechnology, 2012. 30(4): p. 216-224.
22. Suvajyoti Guha, M.L., Michael J. Tarlov and Michael R. Zachariah, Electrospray–differential mobility analysis of bionanoparticles. Cell press, 2012.
23. Zook, J., et al., Measuring silver nanoparticle dissolution in complex biological and environmental matrices using UV–visible absorbance. Analytical and Bioanalytical Chemistry, 2011. 401(6): p. 1993-2002.
24. Ho, C.-M., et al., Oxidative Dissolution of Silver Nanoparticles by Biologically Relevant Oxidants: A Kinetic and Mechanistic Study. Chemistry – An Asian Journal, 2010. 5(2): p. 285-293.
25. Dominguez-Medina, S., et al., Adsorption of a Protein Monolayer via Hydrophobic Interactions Prevents Nanoparticle Aggregation under Harsh Environmental Conditions. ACS Sustainable Chemistry & Engineering, 2013. 1(7): p. 833-842.
26. Li, M., et al., Method for determining the absolute number concentration of nanoparticles from electrospray sources. Langmuir, 2011. 27(24): p. 14732-9.
27. Li, M.D., et al., Quantification and Compensation of Nonspecific Analyte Aggregation in Electrospray Sampling. Aerosol Science and Technology, 2011. 45(7): p. 849-860.
28. Tsai, D.H., et al., Hydrodynamic Fractionation of Finite Size Gold Nanoparticle Clusters. Journal of the American Chemical Society, 2011. 133(23): p. 8884-8887.
29. Tsai, D.H., et al., Aggregation kinetics of colloidal particles measured by gas-phase differential mobility analysis. Langmuir, 2009. 25(1): p. 140-6.
30. Hunter, R.J., Zeta Potential in Colloid Science. 1988, San Diego, CA, USA: Academic Press.
31. Liu, J., et al., Capabilities of Single Particle Inductively Coupled Plasma Mass Spectrometry for the Size Measurement of Nanoparticles: A Case Study on Gold Nanoparticles. Analytical Chemistry, 2014. 86(7): p. 3405-3414.
32. Elzey, S., et al., Real-time size discrimination and elemental analysis of gold nanoparticles using ES-DMA coupled to ICP-MS. Analytical and Bioanalytical Chemistry, 2013. 405(7): p. 2279-2288.
33. Fabricius, A.-L., et al., ICP-MS-based characterization of inorganic nanoparticles—sample preparation and off-line fractionation strategies. Analytical and Bioanalytical Chemistry, 2014. 406(2): p. 467-479.
34. Tsai, D.H., et al., Controlled Formation and Characterization of Dithiothreitol-Conjugated Gold Nanoparticle Clusters. Langmuir, 2014. 30(12): p. 3397-3405.
35. Tsai, D.H., et al., Quantitative Determination of Competitive Molecular Adsorption on Gold Nanoparticles Using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy. Langmuir, 2011. 27(15): p. 9302-9313.
36. Williams, K.R., et al., The Binding Constant for Complexation of Bilirubin to Bovine Serum Albumin. An Experiment for the Biophysical Chemistry Laboratory. Journal of Chemical Education, 2002. 79(1): p. 115.
37. Russel, W.B., D.A. Saville, and W.R. Schowalter, Colloidal Dispersions. 1989: Cambridge University Press.
38. Hinds, W.C., Aerosol Technology: Properties, Behavior, and Measurement of Airborne Particles. Second ed. 1999: John Wiley & Sons.
39. Berg, J.C., An Introduction to Interfaces and Colloids :The Bridge to Nanoscience 2010, Singapore: World Scientific.
40. MOJCA PAVLIN, V.B.B., Stability of Nanoparticle Suspensions in Different Biologically Relevant Media. Digest Journal of Nanomaterials & Biostructures, 2012. 7.
41. Tai, J.-T., et al., Quantifying Nanosheet Graphene Oxide Using Electrospray-Differential Mobility Analysis. Analytical Chemistry, 2015. 87(7): p. 3884-3889.