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Research Papers

Development of Chitosan and Polylactic Acid Based Methotrexate Intravitreal Micro-Implants to Treat Primary Intraocular Lymphoma: An In Vitro Study

[+] Author and Article Information
Soumyarwit Manna

Department of Mechanical and
Materials Engineering,
University of Cincinnati,
Cincinnati, OH 45220

James J. Augsburger, Zelia M. Correa

Department of Ophthalmology,
University of Cincinnati,
Cincinnati, OH 45220

Julio A. Landero

Department of Chemistry,
University of Cincinnati,
Cincinnati, OH 45220

Rupak K. Banerjee

Department of Mechanical and
Materials Engineering,
University of Cincinnati,
593 Rhodes Hall,
Cincinnati, OH 45221
e-mail: Rupak.banerjee@uc.edu

1Corresponding author.

Contributed by the Bioengineering Division of ASME for publication in the Journal of Biomechanical Engineering. Manuscript received August 4, 2013; final manuscript received December 1, 2013; accepted manuscript posted December 7, 2013; published online February 5, 2014. Editor: Victor H. Barocas.

J Biomech Eng 136(2), 021018 (Feb 05, 2014) (15 pages) Paper No: BIO-13-1349; doi: 10.1115/1.4026176 History: Received August 04, 2013; Revised December 01, 2013; Accepted December 07, 2013

Primary intraocular lymphoma (PIOL) is an uncommon but clinically and pathologically distinct form of non-Hodgkin's lymphoma. It provides a therapeutic challenge because of its diverse clinical presentations and variable clinical course. Currently available treatments for PIOL include intravenous multiple drug chemotherapy, external beam radiation therapy, and intravitreal methotrexate (MTX) injection. Each intravitreal injection of MTX is associated with potentially toxic peaks and subtherapeutic troughs of intraocular MTX concentration. Repetitive injections are required to maintain therapeutic levels of MTX in the eye. A sustained release drug delivery system is desired for optimized therapeutic release (0.2–2.0 μg/day) of MTX for over a period of 1 month to achieve effective treatment of PIOL. This study reports development of a unique intravitreal micro-implant, which administers therapeutic release of MTX over a period of 1 month. Chitosan (CS) and polylactic acid (PLA) based micro-implants are fabricated for different MTX loadings (10%, 25%, and 40% w/w). First, CS and MTX mixtures are prepared for different drug loadings, and lyophilized in Tygon® tubing to obtain CS-MTX fibers. The fibers are then cut into desired micro-implant lengths and dip coated in PLA for a hydrophobic surface coating. The micro-implant is characterized using optical microscopy, scanning electron microscopy (SEM), time of flight-secondary ion mass spectroscopy (ToF-SIMS), and differential scanning calorimetry (DSC) techniques. The release rate studies are carried out using a UV-visible spectrophotometer. The total release durations for 10%, 25%, and 40% w/w uncoated CS-MTX micro-implants are only 19, 29, and 32 h, respectively. However, the therapeutic release durations for 10%, 25%, and 40% w/w PLA coated CS-MTX micro-implants significantly improved to 58, 74, and 66 days, respectively. Thus, the PLA coated CS-MTX micro-implants are able to administer therapeutic release of MTX for more than 50 days. The release kinetics of MTX from the coated micro-implants is explained by (a) the Korsmeyer–Peppas and zero order model fit (R2 ∼ 0.9) of the first 60% of the drug release, which indicates the swelling of polymer and initial burst release of the drug; and (b) the first order and Higuchi model fit (R2 ∼ 0.9) from the tenth day to the end of drug release, implying MTX release in the therapeutic window depends on its concentration and follows diffusion kinetics. The PLA coated CS-MTX micro-implants are able to administer therapeutic release of MTX for a period of more than 1 month. The proposed methodology could be used for improved treatment of PIOL.

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Figures

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Fig. 1

(a) Longitudinal view of PLA-coated micro-implant. (b) Longitudinal view of uncoated micro-implant. (c) Cross-sectional view of PLA-coated micro-implant showing PLA coating on the edge. (d) Cross-sectional view of uncoated micro-implant. (scale bar = 500 μm).

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Fig. 2

SEM images of longitudinal view showing the surface of (a) uncoated micro-implant at 26×, (b) uncoated micro-implant at 80×, (c) uncoated micro-implant at 200×, (d) coated micro-implant at 26×, (e) coated micro-implant at 80×, (f) coated micro-implant at 200×

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Fig. 3

SEM images of the cross section of (a) uncoated micro-implant at 80×, (b) uncoated micro-implant at 200×, (c) uncoated micro-implant at 500×, (d) PLA coated micro-implant at 80×, (e) PLA coated micro-implant at 200×, (f) PLA coated micro-implant at 500×

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Fig. 4

SEM images of the longitudinal view of uncoated micro-implants (a) placebo at 50×, (b) 10% MTX at 50×, (c) 25% MTX at 50×, (d) 40% MTX at 50×, (e) placebo at 500×, (f) 10% MTX at 500×, (g) 25% MTX at 500×, (h) 40% MTX at 500×

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Fig. 5

SEM images of the cross section of uncoated micro-implants (a) placebo at 80×, (b) 10% MTX at 80×, (c) 25% MTX at 80×, (d) 40% MTX at 80×, (e) placebo at 500×, (f) 10% MTX at 500×, (g) 25% MTX at 500×, (h) 40% MTX at 500×

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Fig. 6

TOF-SIMS spectra of PLA (MW 150,000), PLA coated 40% CS-MTX micro-implant, and uncoated 40% CS-MTX micro-implant

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Fig. 7

Characteristic DSC curve of a PLA coated micro-implant showing the Tg around 50 °C

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Fig. 8

(a) Characteristic MTX UV-Vis Spectra for different concentrations. (b) Calibration curve for MTX peak at 258 nm. (c) Calibration curve of MTX peak at 302 nm. (d) Calibration curve for MTX peak at 372 nm.

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Fig. 9

(a) Release rate curves from uncoated Chitosan-MTX micro-implants with different drug loadings. (b) Release rate curves from uncoated Chitosan-MTX micro-implants with different drug loadings in the therapeutic window (shaded region). (c) Cumulative drug release profile from uncoated Chitosan-MTX micro-implants.

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Fig. 10

(a) Release rate curves from PLA coated Chitosan-MTX micro-implants with different drug loadings. (b) Release rate curves from PLA coated Chitosan-MTX micro-implants with different drug loadings in the therapeutic window (shaded region). (c) Cumulative drug release profile from PLA coated Chitosan-MTX micro-implants.

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Fig. 11

Fitting of MTX release from the coated micro-implants using (a) Korsmeyer–Peppas equation (for the first 60% of drug release) and (b) first order equation (from the tenth day to the end of therapeutic drug release)

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