Background & Aims

Chronic neuropathic pain has catapulted serious impacts both in economic and public health sectors due to various underlying mechanisms associated with it. Dorsal root ganglia (DRG), a cluster of neurons, play a major role in the alleviation and maintenance of such painful conditions. Ongoing research on the dysregulation of short non-coding nucleotides known as microRNAs in DRG neurons demonstrate that these caused polarization of macrophages to pro-inflammatory or M1 macrophages causing pain signal generation. Repolarization of these to M2 can induce therapy. Another line of treatment is via use of ion channel blockers that inhibit the conductivity and excitability of neurons associated. But naked delivery of these are limited due to rapid clearance, degradation and reduction of half-life. This study is based on sustained delivery of these small molecules to the DRG target sites using biomaterials such as chitosan, poly-lactic-co-glycolic acid (PLGA) and a thermosensitive hydrogel.

Methods

Chitosan nanoparticles are prepared via ionic gelation or inotropic gelation method using low molecular weight chitosan and sodium tripolyphosphate as a cross-linking agent. On the other hand, polylactic-co-glycolic acid (PLGA) nanoparticles are prepared via double emulsion (water/oil/water) using homogenisation and sonication, followed by solvent evaporation. Preparation of hydrogels followed Michael addition reaction between thiolated hyaluronic acid and vinyl sulfonated polyethylene glycol (PEG)/HPMAm -1,2 lactate triblock co-polymer.

Results

After optimising the processing parameters for the chitosan nanoparticle preparation, microRNA or miR-21 antagomir loaded nanoparticles were prepared of the sizes ranging from 108 nm to 120 nm with polydispersity index (PDI) of 0.1 to 0.2 and zeta potential ranging from 20 to 26 mV. Stability studies at room temperature showed that these are stable over a period of 1 to 2 months. BIII 890 CL (novel sodium channel inhibitor) loaded PLGA nanoparticles were prepared via water/oil/water double emulsion technique using sonication followed by solvent evaporation to obtain particles of the size ranging from 160 to 173 nm with PDI of 0.1 and a zeta potential of -28mV. For the formation of hydrogel PEG/HPMAm-1,2 lactate triblock co-polymer was vinyl sulfonated to obtain a 9% degree of substitution and 98.65% yield with cloud point determined to be at 26 degree celsius. It was then loaded with sodium channel blocker and was cross-linked using thiolated hyaluronic acid at 37 degrees to form gel.

Conclusions

Synthesised nanoparticles and the hydrogels are promising vectors in terms of size and yield respectively. Stability studies indicate that the formulated biomaterials are stable over period of several weeks to months. Ongoing release studies using Ultraviolet-Visible spectroscopy indicate the efficiency and loading capacity of these biomaterials. Results of the surface morphological analysis along with ongoing cytotoxicity studies on cell lines demonstrate that these are future state of the art carrier systems to bypass the current challenges and limitations.

References

1) Strickland IT, Richards L, Holmes FE, Wynick D, Uney JB, Wong LF. Axotomy-Induced miR-21 Promotes Axon Growth in Adult Dorsal Root Ganglion Neurons. PLoS One. 2011 Aug 10;6(8):e23423.

2) Yu B, Zhou S, Qian T, Wang Y, Ding F, Gu X. Altered microRNA expression following sciatic nerve resection in dorsal root ganglia of rats. Acta Biochim Biophys Sin (Shanghai). 2011 Nov 1;43(11):909–15.

3) Tewes F, Munnier E, Antoon B, Ngaboni Okassa L, Cohen-Jonathan S, Marchais H, et al. Comparative study of doxorubicin-loaded poly(lactide-co-glycolide) nanoparticles prepared by single and double emulsion methods. European Journal of Pharmaceutics and Biopharmaceutics. 2007 Jun;66(3):488–92.

4) Cruz KP, Patricio BFC, Pires VC, Amorim MF, Pinho AGSF, Quadros HC, et al. Development and Characterization of PLGA Nanoparticles Containing 17-DMAG, an Hsp90 Inhibitor. Front Chem. 2021 May 13;9.

5) Dubbini A, Censi R, Butini ME, Sabbieti MG, Agas D, Vermonden T, et al. Injectable hyaluronic acid/PEG-p(HPMAm-lac)-based hydrogels dually cross-linked by thermal gelling and Michael addition. Eur Polym J. 2015 Nov;72:423–37

Presenting Author

Stefan Jackson

Poster Authors

Stefan Jackson

PhD

University of Camerino

Lead Author

E-mail

Topics

  • Models: Chronic Pain - Neuropathic