Pharmaceutical Research

, Volume 33, Issue 10, pp 2433–2444 | Cite as

Comparative Study of Poly (ε-Caprolactone) and Poly(Lactic-co-Glycolic Acid) -Based Nanofiber Scaffolds for pH-Sensing

  • Wenjun Di
  • Ryan S. Czarny
  • Nathan A. Fletcher
  • Melissa D. Krebs
  • Heather A. ClarkEmail author
Research Paper



This study aims to develop biodegradable and biocompatible polymer-based nanofibers that continuously monitor pH within microenvironments of cultured cells in real-time. In the future, these fibers will provide a scaffold for tissue growth while simultaneously monitoring the extracellular environment.


Sensors to monitor pH were created by directly electrospinning the sensor components within a polymeric matrix. Specifically, the entire fiber structure is composed of the optical equivalent of an electrode, a pH-sensitive fluorophore, an ionic additive, a plasticizer, and a polymer to impart mechanical stability. The resulting poly(ε-caprolactone) (PCL) and poly(lactic-co-glycolic acid) (PLGA) based sensors were characterized by morphology, dynamic range, reversibility and stability. Since PCL-based nanofibers delivered the most desirable analytical response, this matrix was used for cellular studies.


Electrospun nanofiber scaffolds (NFSs) were created directly out of optode material. The resulting NFS sensors respond to pH changes with a dynamic range centered at 7.8 ± 0.1 and 9.6 ± 0.2, for PCL and PLGA respectively. NFSs exhibited multiple cycles of reversibility with a lifetime of at least 15 days with preservation of response characteristics. By comparing the two NFSs, we found PCL-NFSs are more suitable for pH sensing due to their dynamic range and superior reversibility.


The proposed sensing platform successfully exhibits a response to pH and compatibility with cultured cells. NSFs will be a useful tool for creating 3D cellular scaffolds that can monitor the cellular environment with applications in fields such as drug discovery and tissue engineering.


electrospinning nanofibers pH detection poly(lactic-co-glycolic acid) poly(ε-caprolactone) 



Chromoionophore II




Sodium tetrakis(3,5-bis(trifluoromethyl)phenyl]borate)


Poly(ε-caprolactone) electrospun nanofiber scaffold


Poly(lactic-co-glycolic acid) electrospun nanofiber scaffold





We thank Dr. Guoxin Rong for critical reading of this manuscript. This research is supported by National Institute of Health (NIH) under grant RO1NS081641.

Supplementary material

11095_2016_1987_MOESM1_ESM.pdf (440 kb)
ESM 1 (PDF 439 kb)


  1. 1.
    Lee MY, Kumar RA, Sukumaran SM, Hogg MG, Clark DS, Dordick JS. Three-dimensional cellular microarray for high-throughput toxicology assays. Proc Natl Acad Sci U S A. 2008;105(1):59–63.CrossRefPubMedGoogle Scholar
  2. 2.
    Hongisto V, Jernstrom S, Fey V, Mpindi JP, Sahlberg KK, Kallioniemi O, et al. High-Throughput 3D Screening Reveals Differences in Drug Sensitivities between Culture Models of JIMT1 Breast Cancer Cells. Plos One. 2013 23;8(10). English.Google Scholar
  3. 3.
    Fu K, Pack DW, Klibanov AM, Langer R. Visual evidence of acidic environment within degrading poly(lactic-co-glycolic acid) (PLGA) microspheres. Pharmaceut Res. 2000;17(1):100–6. English.CrossRefGoogle Scholar
  4. 4.
    Lynn DM, Amiji MM, Langer R. pH-responsive polymer microspheres: rapid release of encapsulated material within the range of intracellular pH. Angew Chem Int Ed. 2001;40(9):1707–10. English.CrossRefGoogle Scholar
  5. 5.
    Miller WM, Blanch HW, Wilke CR. A kinetic analysis of hybridoma growth and metabolism in batch and continuous suspension culture: Effect of nutrient concentration, dilution rate, and pH (Reprinted from Biotechnology and Bioengineering, vol 32, pg 947-965, 1988). Biotechnol Bioeng. 2000;67(6):853–71. English.CrossRefPubMedGoogle Scholar
  6. 6.
    Kinlen PJ, Heider JE, Hubbard DE. A solid-state Ph sensor-based on a nafion-coated iridium oxide indicator electrode and a polymer-based silver-chloride reference electrode. Sensors Actuators B Chem. 1994;22(1):13–25. English.CrossRefGoogle Scholar
  7. 7.
    Gill E, Arshak K, Arshak A, Korostynska O. Mixed metal oxide films as pH sensing materials. Microsyst Technol. 2008;14(4-5):499–507. English.CrossRefGoogle Scholar
  8. 8.
    Liu Y, Cui TH. Ion-sensitive field-effect transistor based pH sensors using nano self-assembled polyelectrolyte/nanoparticle multilayer films. Sensors Actuators B Chem. 2007;123(1):148–52. English.CrossRefGoogle Scholar
  9. 9.
    Bratov A, Abramova N, Ipatov A. Recent trends in potentiometric sensor arrays-a review. Anal Chim Acta. 2010;678(2):149–59. English.CrossRefPubMedGoogle Scholar
  10. 10.
    Mistlberger G, Crespo GA, Bakker E. Ionophore-based optical sensors. Annu Rev Anal Chem. 2014;7:483–512. English.CrossRefGoogle Scholar
  11. 11.
    Askim JR, Mahmoudi M, Suslick KS. Optical sensor arrays for chemical sensing: the optoelectronic nose. Chem Soc Rev. 2013;42(22):8649–82. English.CrossRefPubMedGoogle Scholar
  12. 12.
    Thomas JA, Buchsbaum RN, Zimniak A, Racker E. Intracellular pH measurements in Ehrlich ascites tumor cells utilizing spectroscopic probes generated in situ. Biochemistry. 1979;18(11):2210–8.CrossRefPubMedGoogle Scholar
  13. 13.
    Lin HJ, Szmacinski H, Lakowicz JR. Lifetime-based pH sensors: indicators for acidic environments. Anal Biochem. 1999;269(1):162–7. English.CrossRefPubMedGoogle Scholar
  14. 14.
    Sanders R, Draaijer A, Gerritsen HC, Houpt PM, Levine YK. Quantitative Ph imaging in cells using confocal fluorescence lifetime imaging microscopy. Anal Biochem. 1995;227(2):302–8. English.CrossRefPubMedGoogle Scholar
  15. 15.
    Clark HA, Kopelman R, Tjalkens R, Philbert MA. Optical nanosensors for chemical analysis inside single living cells. 2. Sensors for pH and calcium and the intracellular application of PEBBLE sensors. Anal Chem. 1999;71(21):4837–43. English.CrossRefPubMedGoogle Scholar
  16. 16.
    Clark HA, Barker SLR, Brasuel M, Miller MT, Monson E, Parus S, et al. Subcellular optochemical nanobiosensors: probes encapsulated by biologically localised embedding (PEBBLEs). Sensors Actuators B Chem. 1998;51(1–3):12–6. English.CrossRefGoogle Scholar
  17. 17.
    Xu H, Aylott JW, Kopelman R. Fluorescent nano-PEBBLE sensors designed for intracellular glucose imaging. Analyst. 2002;127(11):1471–7. English.CrossRefPubMedGoogle Scholar
  18. 18.
    Haugland R. The handbook: a guide to fluorescent probes and labeling technologies: invitrogen corporation; 2005.Google Scholar
  19. 19.
    Buhlmann P, Pretsch E, Bakker E. Carrier-based ion-selective electrodes and bulk optodes. 2. Ionophores for potentiometric and optical sensors. Chem Rev. 1998;98(4):1593–687. English.CrossRefPubMedGoogle Scholar
  20. 20.
    Bakker E, Buhlmann P, Pretsch E. Carrier-based ion-selective electrodes and bulk optodes. 1. General characteristics. Chem Rev. 1997;97(8):3083–132. English.CrossRefPubMedGoogle Scholar
  21. 21.
    Dubach JM, Das S, Rosenzweig A, Clark HA. Visualizing sodium dynamics in isolated cardiomyocytes using fluorescent nanosensors. Proc Natl Acad Sci U S A. 2009;106(38):16145–50. English.CrossRefPubMedPubMedCentralGoogle Scholar
  22. 22.
    Xie XJ, Bakker E. Ion selective optodes: from the bulk to the nanoscale. Anal Bioanal Chem. 2015;407(14):3899–910. English.CrossRefPubMedGoogle Scholar
  23. 23.
    Ruckh TT, Mehta AA, Dubach JM, Clark HA. Polymer-Free Optode Nanosensors for Dynamic, Reversible, and Ratiometric Sodium Imaging in the Physiological Range. Sci Rep-Uk. 2013;3. English.Google Scholar
  24. 24.
    Kohn DH, Sarmadi M, Helman JI, Krebsbach PH. Effects of pH on human bone marrow stromal cells in vitro: implications for tissue engineering of bone. J Biomed Mater Res. 2002;60(2):292–9. English.CrossRefPubMedGoogle Scholar
  25. 25.
    Crapo PM, Gilbert TW, Badylak SF. An overview of tissue and whole organ decellularization processes. Biomaterials. 2011;32(12):3233–43. English.CrossRefPubMedPubMedCentralGoogle Scholar
  26. 26.
    Sung HJ, Meredith C, Johnson C, Galis ZS. The effect of scaffold degradation rate on three-dimensional cell growth and angiogenesis. Biomaterials. 2004;25(26):5735–42. English.CrossRefPubMedGoogle Scholar
  27. 27.
    Miller JS, Stevens KR, Yang MT, Baker BM, Nguyen DH, Cohen DM, et al. Rapid casting of patterned vascular networks for perfusable engineered three-dimensional tissues. Nat Mater. 2012;11(9):768–74. Pubmed Central PMCID: 3586565.CrossRefPubMedPubMedCentralGoogle Scholar
  28. 28.
    Chen RR, Mooney DJ. Polymeric growth factor delivery strategies for tissue engineering. Pharm Res. 2003;20(8):1103–12. English.CrossRefPubMedGoogle Scholar
  29. 29.
    Yang J, Yamato M, Kohno C, Nishimoto A, Sekine H, Fukai F, et al. Cell sheet engineering: recreating tissues without biodegradable scaffolds. Biomaterials. 2005;26(33):6415–22. English.CrossRefPubMedGoogle Scholar
  30. 30.
    Ding B, Wang MR, Wang XF, Yu JY, Sun G. Electrospun nanomaterials for ultrasensitive sensors. Mater Today. 2010;13(11):16–27. English.CrossRefGoogle Scholar
  31. 31.
    Huang ZM, Zhang YZ, Kotaki M, Ramakrishna S. A review on polymer nanofibers by electrospinning and their applications in nanocomposites. Compos Sci Technol. 2003;63(15):2223–53. English.CrossRefGoogle Scholar
  32. 32.
    Agarwal S, Wendorff JH, Greiner A. Use of electrospinning technique for biomedical applications. Polymer. 2008;49(26):5603–21. English.CrossRefGoogle Scholar
  33. 33.
    Wang XY, Drew C, Lee SH, Senecal KJ, Kumar J, Sarnuelson LA. Electrospun nanofibrous membranes for highly sensitive optical sensors. Nano Lett. 2002;2(11):1273–5. English.CrossRefGoogle Scholar
  34. 34.
    Abedalwafa M, Wang FJ, Wang L, Li CJ. Biodegradable poly-epsilon-caprolactone (Pcl) for tissue engineering applications: a review. Rev Adv Mater Sci. 2013;34(2):123–40. English.Google Scholar
  35. 35.
    Karp JM, Shoichet MS, Davies JE. Bone formation on two-dimensional poly(DL-lactide-co-glycolide) (PLGA) films and three-dimensional PLGA tissue engineering scaffolds in vitro. J Biomed Mater Res A. 2003;64(2):388–96.CrossRefPubMedGoogle Scholar
  36. 36.
    Rowley JA, Madlambayan G, Mooney DJ. Alginate hydrogels as synthetic extracellular matrix materials. Biomaterials. 1999;20(1):45–53. English.CrossRefPubMedGoogle Scholar
  37. 37.
    Bashur CA, Dahlgren LA, Goldstein AS. Effect of fiber diameter and orientation on fibroblast morphology and proliferation on electrospun poly(D,L-lactic-co-glycolic acid) meshes. Biomaterials. 2006;27(33):5681–8. English.CrossRefPubMedGoogle Scholar
  38. 38.
    Eagle H. Buffer combinations for mammalian cell culture. Science. 1971;174(4008):500–3.CrossRefPubMedGoogle Scholar
  39. 39.
    Salis A, Ninham BW. Models and mechanisms of Hofmeister effects in electrolyte solutions, and colloid and protein systems revisited. Chem Soc Rev. 2014;43(21):7358–77. English.CrossRefPubMedGoogle Scholar
  40. 40.
    Wulf E, Deboben A, Bautz FA, Faulstich H, Wieland T. Fluorescent Phallotoxin, a tool for the visualization of cellular actin. Proc Natl Acad Sci U S A. 1979;76(9):4498–502. English.CrossRefPubMedPubMedCentralGoogle Scholar
  41. 41.
    Qin Y, Bakker E. Quantitive binding constants of H(+)-selective chromoionophores and anion ionophores in solvent polymeric sensing membranes. Talanta. 2002;58(5):909–18.CrossRefPubMedGoogle Scholar
  42. 42.
    Bright GR, Fisher GW, Rogowska J, Taylor DL. Fluorescence ratio imaging microscopy. Methods Cell Biol. 1989;30:157–92. English.CrossRefPubMedGoogle Scholar
  43. 43.
    Takahashi A, Camacho P, Lechleiter JD, Herman B. Measurement of intracellular calcium. Physiol Rev. 1999;79(4):1089–125. English.PubMedGoogle Scholar
  44. 44.
    Buranda T, Wu Y, Perez D, Chigaev A, Sklar LA. Real-time partitioning of octadecyl rhodamine B into bead-supported lipid bilayer membranes revealing quantitative differences in saturable binding sites in DOPC and 1:1:1 DOPC/SM/cholesterol membranes. J Phys Chem B. 2010;114(3):1336–49. English.CrossRefPubMedPubMedCentralGoogle Scholar
  45. 45.
    Yoo JW, Mitragotri S. Polymer particles that switch shape in response to a stimulus. Proc Natl Acad Sci U S A. 2010;107(25):11205–10. English.CrossRefPubMedPubMedCentralGoogle Scholar
  46. 46.
    Zeng XQ, Latimer ML, Xiao ZL, Panuganti S, Welp U, Kwok WK, et al. Hydrogen gas sensing with networks of ultrasmall palladium nanowires formed on filtration membranes. Nano Lett. 2011;11(1):262–8. English.CrossRefPubMedGoogle Scholar
  47. 47.
    Zolnik BS, Burgess DJ. Effect of acidic pH on PLGA microsphere degradation and release. J Control Release. 2007;122(3):338–44.CrossRefPubMedGoogle Scholar
  48. 48.
    Pitt CG, Gratzl MM, Kimmel GL, Surles J, Schindler A. Aliphatic polyesters II. The degradation of poly (DL-lactide), poly (epsilon-caprolactone), and their copolymers in vivo. Biomaterials. 1981;2(4):215–20.CrossRefPubMedGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  • Wenjun Di
    • 1
  • Ryan S. Czarny
    • 2
  • Nathan A. Fletcher
    • 2
  • Melissa D. Krebs
    • 2
  • Heather A. Clark
    • 1
    Email author
  1. 1.Department of Pharmaceutical SciencesNortheastern UniversityBostonUSA
  2. 2.Chemical and Biological EngineeringColorado School of MinesGoldenUSA

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