Multifunctional polyelectrolyte multilayer films: combining mechanical resistance, biodegradability, and bioactivity

Abstract

Cross-linked polyelectrolyte multilayer films (CL PEM) have an increased rigidity and are mechanically more resistant than native (e.g., uncrosslinked) films. However, they are still biodegradable, which make them interesting candidates for biomedical applications. In this study, CL PEM films have been explored for their multifunctional properties as (i) mechanically resistant, (ii) biodegradable, and (iii) bioactive films. Toward this end, we investigated drug loading into CL chitosan/hyaluronan (CHI/HA) and poly(L-lysine)/hyaluronan (PLL/HA) films by simple diffusion of the drugs. Sodium diclofenac and paclitaxel were chosen as model drugs and were successfully loaded into the films. The effect of varying the number of layers in the (CHI/HA) films as well as the cross-linker concentration on diclofenac loading were studied. Diclofenac was released from the film in about 10 h. Paclitaxel was also found to diffuse within CL films. Its activity was maintained after loading in the CL films, and cellular viability could be reduced by about 55% over 3 days. Such a simple approach may be applied to other types of cross-linked films and to other drugs. These results prove that it is possible to design multifunctional multilayer films that combine mechanical resistance, biodegradability, and bioactivity properties into a single PEM architecture.

FIGURE 1

Chemical structures of (A) sodium diclofenac (B) paclitaxel (ta)

FIGURE 2

Influence of the number of layer pairs in the films on the diclofenac loaded concentration in cross-linked (CHI/HA)_i films (with i=12, 24 and 48). The diclofenac solution concentration in contact with the film was fixed at 1 mg/mL. (Error bars are SD of three PEM coated slides).

FIGURE 3

Influence of the cross-linker concentration EDC on the diclofenac loaded concentration in (CHI/HA)₂₄ films. The initial diclofenac concentration was the same as for Figure 2. (Error bars are SD of three PEM coated slides).

FIGURE 4

Diclofenac release curve in PBS from a (CHI/HA)₂₄ film. Results are expressed in terms of percentage of the total diclofenac concentration loaded in the film. (error bars are SD of three measurements but are not visible).

FIGURE 5

Confocal laser scanning (CLSM) image of a CL (PLL/HA)₂₄ film loaded with fluorescent paclitaxel (paclitaxelGreen 4888) at 20 μg/mL. The white line corresponds to the glass slide and the white arrow to the film thickness (approximately 4 μm).

FIGURE 6

Acid phosphatase (AP) activity for HT29 cells cultured on native or cross-linked (PLL/HA)₁₂ films after 24 hours. The error bars represent the standard deviation. The value of 100% has been arbitrary attributed to CL films (*** p<0.001).

FIGURE 7

Acid phosphatase (AP) activity for HT29 cells cultured on cross-linked (PLL/HA)₁₂ films loaded or not with paclitaxel, after different time periods of 24H, 48H and 72H in culture. The error bars represent the standard deviation. Two different representations are shown: (A) The value of 100% has been arbitrary attributed to CL films at 24H; (** p<0.01; *** p<0.001 versus control at 24H for control films or versus paclitaxel at 24H for paclitaxel loaded films). (B) The value of 100% has been arbitrary set at 100% for CL films at each time period (* p<0.05; ** p<0.01; *** p<0.001 versus controls, which are the CL films at time 24H, 48H, and 72H respectively.