Rational Design of Pectin-Chitosan Polyelectrolyte Nanoparticles for Enhanced Temozolomide Delivery in Brain Tumor Therapy

Abstract

Conventional chemotherapeutic approaches currently used for brain tumor treatment have low efficiency in targeted drug delivery and often have non-target toxicity. Development of stable and effective drug delivery vehicles for the most incurable diseases is one of the urgent biomedical challenges. We have developed polymer nanoparticles (NPs) with improved temozolomide (TMZ) delivery for promising brain tumor therapy, performing a rational design of polyelectrolyte complexes of oppositely charged polysaccharides of cationic chitosan and anionic pectin. The NPs' diameter (30 to 330 nm) and zeta-potential (-29 to 73 mV) varied according to the initial mass ratios of the biopolymers. The evaluation of nanomechanical parameters of native NPs demonstrated changes in Young's modulus from 58 to 234 kPa and adhesion from -0.3 to -3.57 pN. Possible mechanisms of NPs' formation preliminary based on ionic interactions between ionogenic functional groups were proposed by IR spectroscopy and dynamic rheology. The study of the parameters and kinetics of TMZ sorption made it possible to identify compounds that most effectively immobilize and release the active substance in model liquids that simulate the internal environment of the body. A polyelectrolyte carrier based on an equal ratio of pectin-chitosan (0.1% by weight) was selected as the most effective for the delivery of TMZ among a series of obtained NPs, which indicates a promising approach to the treatment of brain tumors.

Keywords: biomaterials; blood–brain barrier; brain tumors; carbohydrates; drug delivery systems; nanocarrier; polysaccharides; temozolomide; viscoelastic properties.

Figure 1

(a) The structural formula of the uncharged and charged forms of chitosan. The presented polysaccharide can contain both types of glucosamine residues connected by O-glycoside bonds simultaneously. (b) The general scheme of pectins’ structure: various modifications of galacturonic acid in pectins. The figure is based on [3].

Figure 2

(a) A phase diagram of polyelectrolyte solutions. The red color indicates compositions for which there was no NP formation observed. The compositional region of the nanoscale PECs is highlighted in green. (b) High-resolution TEM images of initial PEC compositions: 1—chitosan at 0.5 wt.%, pectin at 0.1 wt.%; 2—chitosan at 0.1 wt.%, pectin at 0.1 wt.%.

Figure 3

(a) Three-dimensional AFM images with the correlation of NPs’ sizes and Young’s modulus obtained with a mass ratio of pectin to chitosan at 0.1:0.1, 0.1:0.3, and 0.1:0.5; (b,d) type of Young’s modulus and (c,e) adhesion distributions of stechiometric ratio of pectin and chitosan of NPs. Statistical differences were designated as significant if the p-values were less than 0.05 (* p ≤ 0.05) or less than 0.0005 (**** p ≤ 0.0001). The Kruskal-Wallis test was used to assess the differences between two independent samples. All abbreviations of the obtained NP samples are presented below in Table 1.

Figure 4

IR spectra of powders of (1) chitosan and (2) pectin, (3) NP-01-01 NPs, (4) sample with ratio of pectin to chitosan of 0.5 wt.%:0.1 wt.%, and (5) NP-01-05.

Figure 5

Plots of storage (black curves) and loss moduli (red curves) and complex viscosity (blue curves) as a function of shear stress frequency: (a) NPs-01-01, (b) NPs-01-03, (c) NPs-01-05. Point of transition region from a solid-like to liquid-like state marked by blue circles. Plots of shear stress versus the shear rate: (d) NPs-01-01, (e) NPs-01-03, (f) NPs-01-05. For plots d-f, black curves correspond to compositions without TMZ, and red curves correspond to PEC immobilized with drugs.

Figure 6

Effect of mass ratio of pectin–chitosan on adsorption kinetics of TMZ by NPs: (a) TMZ immobilization to pectin–chitosan particles; (b) TMZ immobilization rate to pectin–chitosan particles.

Figure 7

(a) Pseudo first-order kinetic and (b) pseudo second-order kinetic model fit for TMZ sorption onto pectin–chitosan NPs.

Figure 8

(a) Freundlich and (b) BET isotherms for TMZ adsorption on pectin–chitosan NPs.

Figure 9

Cumulative release profile (%) of TMZ from pectin–chitosan NPs to different media at various ratios of pectin to chitosan: (a) NP-01-01; (b) NP-01-05.

Figure 10

Release rate of TMZ from pectin–chitosan NPs at various ratios of pectin to chitosan: (a) into the MCF; (b) into the MBPF.

Figure 11

Overall efficiency of the pectin–chitosan–TMZ system. All data are presented as means and standard errors of the mean (M ± SEM). Circle mark—individual data points for MCF (in red). Square mark—individual data points for MBPF (in green). Triangle mark—individual data points for water (in blue).