Long-lasting rescue of schizophrenia-relevant cognitive impairments via risperidone-loaded microPlates

Abstract

Schizophrenia is a disorder characterized by cognitive impairment and psychotic symptoms that fluctuate over time and can only be mitigated with the chronic administration of antipsychotics. Here, we propose biodegradable microPlates made of PLGA for the sustained release of risperidone over several weeks. Two microPlate configurations - short: 20 × 20 × 10 μm; tall: 20 × 20 × 20 μm - are engineered and compared to conventional ~ 10 μm PLGA microspheres in terms of risperidone loading and release. Tall microPlates realize the slowest release documenting a 35% risperidone delivery at 100 days with a residual rate of 30 ng/ml. Short microPlates and microspheres present similar release profiles with over 50% of the loaded risperidone delivered within the first 40 days. Then, the therapeutic efficacy of one single intraperitoneal injection of risperidone microPlates is compared to the daily administration of free risperidone in heterozygous knockout mice for dysbindin-1, a clinically relevant mouse model of cognitive and psychiatric liability. In temporal order object recognition tasks, mice treated with risperidone microPlates outperform those receiving free risperidone up to 2, 4, 8, and 12 weeks of observation. This suggests that the sustained release of antipsychotics from one-time microPlate deposition can rescue cognitive impairment in dysbindin mice for up to several weeks. Overall, these results demonstrate that risperidone-loaded microPlates are a promising platform for improving cognitive symptoms associated to schizophrenia. Moreover, the long-term efficacy with one single administration could be of clinical relevance in terms of patient's compliance and adherence to the treatment regimen. Single injection of long-acting risperidone-loaded µPL ameliorates the dysbindin-induced deficit in a clinically relevant mouse model of cognitive and psychiatric liability for up to 12 weeks.

Keywords: Drug delivery; Long-acting formulations; Microparticles; Risperidone; Schizophrenia.

Fig. 1

μPL fabrication process, morphological and dimensional characterization. (a) Sequential steps in the fabrication of 20 × 20 × 10 and 20 × 20 × 20 μm μPL. A silicon master template is fabricated via direct laser writing and replicated into a PDMS template, whose pattern is then transferred into a sacrificial PVA template. This PVA template is loaded with the polymeric paste constituting the final μPL and enclosing the payload. μPL are released and collected upon dissolution in DI water of the sacrificial PVA template (from left to right). (b) SEM micrographs of short and (c) tall μPL showing the characteristic dimensions of 20 × 20 × 10 and 20 × 20 × 20 μm. (Scale bar: 10 μm). (d) Size characterization of short and (e) tall μPL via Multisizer analyses. (f) Cross-section profile of short and (g) tall μPL acquired by optical profilometer showing the thickness of the μPL. No significant differences were highlighted between empty and RSP-μPL

Fig. 2

Degradation of μPL under physiological conditions. (a) SEM images representing the degradation of short and (b) tall μPL over time. (c) Degradation of short and (d) tall μPL analyzed via the Multisizer

Fig. 3

Pharmacological characterization of μPL. (a) RSP loading into short µPL, tall μPL, and µS. (b) RSP encapsulation into short µPL, tall μPL, and µSpheres. Statistical significance was determined by one-way ANOVA: **p < 0.01 tall µPL vs short µPL, ***p < 0.001 µS vs sort µPL and µS vs tall µPL. (c) 40-day cumulative release profiles of RSP from short µPL, tall µPL, and µS (37 °C in PBS). (d) Cumulative and (e) daily release profiles of RSP from short and tall μPL (37 °C in PBS). Green and black lines in (d) represent the Weibull function fitting; 95% confident band. Data are expressed as the mean ± standard deviation (n = 3). Statistical significance was determined by one-way ANOVA: *p < 0.05, ***p < 0.001, §p < 0.0001, #p < 0.00001. Details of the statistical analysis are reported in Table S2

Fig. 4

Single injection of short RSP-μPL improves cognitive abilities of Dys ± in mice in the TOR task. Each experimental group received free vehicle (n = 7, dark gray bars) or free risperidone (n = 7, light grey bars) for 14 days, and short empty (n = 6, white bars) or RSP-μPL (n = 6, black bars) only once on day 0. (a) Experimental timeline. (b) Discrimination index showed by Dys ± mice during the 5-min test phase 2 weeks post-treatment. (c) Discrimination index showed by Dys ± receiving either empty or RSP-μPL during the 5-min test phase 4 weeks post treatment. The values are the means ± s.e.m. One-way ANOVA: treatment effect *p < 0.05, **p < 0.005

Fig. 5

Single injection of tall μPL improves the cognitive abilities of Dys ± mice in the TOR task. Each experimental group (n = 6) received either empty or RSP-μPL only once on day 0 and were tested in the TOR task at 2-, 4-, 8-, and 12-week post-injection. (a) Experimental timeline. (b) Discrimination index showed by mice during the 5-min test phase at 2, (c) 4, (d) 8, and (e) 12 weeks, respectively. The values are the means ± s.e.m. Two-way ANOVA: treatment effect *p < 0.05, **p < 0.01, ***p < 0.001. At 2- and 4-week post-injection, the discrimination performance was affected by the treatment (2 weeks – treatment effect: F_{(1, 13)} = 7256, p = 0,0184; 4 weeks – treatment effect: F_{(1, 13)} = 20.55, p = 0,0006), at 8- and 12-week post-injection the discrimination performance was impacted mainly by the genotype (8 weeks – genotype effect: F_(1,13) = 6.506, p = 0.0242; 12 weeks – genotype effect: F_(1,13) = 7.739, p = 0.0156)

Fig. 6

Single injection of tall μPL improves the cognitive abilities of Dys ± mice in the TOR task. Each experimental group received either empty (Dys + / + n = 6, Dys ± n = 10) or RSP-μPL (Dys + / + n = 6, Dys ± n = 10) only once on day 0 and were tested in the TOR task at 8- and 12-week post-injection. (a) Experimental timeline. (b) Discrimination index showed by mice during the 5-min test phase at 8, (c) 12 weeks, respectively. The values are the means ± s.e.m. Two-way ANOVA: treatment effect **p < 0.01, ***p < 0.001