Erythrocyte-Inspired Discoidal Polymeric Nanoconstructs Carrying Tissue Plasminogen Activator for the Enhanced Lysis of Blood Clots

Abstract

Tissue plasminogen activator (tPA) is the sole approved therapeutic molecule for the treatment of acute ischemic stroke. Yet, only a small percentage of patients could benefit from this life-saving treatment because of medical contraindications and severe side effects, including brain hemorrhage, associated with delayed administration. Here, a nano therapeutic agent is realized by directly associating the clinical formulation of tPA to the porous structure of soft discoidal polymeric nanoconstructs (tPA-DPNs). The porous matrix of DPNs protects tPA from rapid degradation, allowing tPA-DPNs to preserve over 70 % of the tPA original activity after 3 h of exposure to serum proteins. Under dynamic conditions, tPA-DPNs dissolve clots more efficiently than free tPA, as demonstrated in a microfluidic chip where clots are formed mimicking in vivo conditions. At 60 min post treatment initiation, the clot area reduces by half (57 + 8 %) with tPA-DPNs, whereas a similar result (56 + 21 %) is obtained only after 90 min for free tPA. In murine mesentery venules, the intravenous administration of 2.5 mg/kg of tPA-DPNs resolves almost 90 % of the blood clots, whereas a similar dose of free tPA successfully recanalize only about 40 % of the treated vessels. At about 1/10 of the clinical dose (1.0 mg/kg), tPA-DPNs still effectively dissolve 70 % of the clots, whereas free tPA works efficiently only on 16 % of the vessels. In vivo, discoidal tPA-DPNs outperform the lytic activity of 200 nm spherical tPA-coated nanoconstructs in terms of both percentage of successful recanalization events and clot area reduction. The conjugation of tPA with preserved lytic activity, the deformability and blood circulating time of DPNs together with the faster blood clot dissolution would make tPA-DPNs a promising nanotool for enhancing both potency and safety of thrombolytic therapies.

Targeted Delivery of Plasminogen Activators for Thrombolytic Therapy: An Integrative Evaluation

“…Activity of immobilized PAs may be compromised due to steric hindrance; whereas for protected PAs, the local concentration at the target is greatly dependent on the release kinetics or the strategy of controlled release. There have been liposomal preparations [11,16,17,18,19,20] and polymeric nanocomposite [21,22] developed and achieved target thrombolysis in vivo , as shown in Figure 2. The protection may extend its half-life [20], allowing PAs to be administered from a remote site in circulation such as vein [11,16,17,18].…”

“…Activity retention after immobilization can be defined as the percentage of activity of immobilized PA compared with that of PA added initially. This method is simple with good reproducibility, and thus often used in optimization of the nanocomposites during preparation [11,12,14,21,22,26,30,34]. However, plasminogen is a much bigger molecule in structure, and therefore, interaction of plasminogen and PAs may not be as free as the small substrate.…”

Engineered microparticles and nanoparticles for fibrinolysis

“…Rather than using blood cells, Colasuonno et al. synthesized discoidal polymeric nanoconstruct (DPN) mimics shaped like RBC and functionalized with tPA . The DPN are 1 μm in diameter, 0.4 μm in height, biconcave, and can be synthesized from either PEG or PLGA.…”

“…28 Rather than using blood cells, Colasuonno et al synthesized discoidal polymeric nanoconstruct (DPN) mimics shaped like RBC and functionalized with tPA. 56 The DPN are 1 μm in diameter, 0.4 μm in height, biconcave, and can be synthesized from either PEG or PLGA. Tissue plasminogen activator discoidal polymeric nanoconstructs have a fibrinolytic activity roughly 50% higher than free tPA at 10% the free tPA concentration.…”

Applications of Nanotechnology in the Diagnosis and Therapy of Stroke

“…As recently reviewed, 86,87 nanotechnology has the potential to offer innovative solutions, which address the shortfalls of rt-PA. For example, dramatic prolongation of rt-PA half-life has been achieved by encapsulation of rt-PA in PEG-modified liposomes, 88 in zinc-stabilized gelatin nanoparticles, 89 in the porous structure of soft discoidal polymeric nanoconstructs (tPA-DPNs) 90 or by shielding rt-PA from plasma inactivation by complexing with albumin, then recovering its local thrombolytic activity by release-triggers such as heparin or thrombin. 86,91 Improved clot penetration, leading to better thrombolysis and subsequent dose reduction was achieved by rt-PA encapsulation in biocompatible polymers such as synthetic polylactic-co-glycolytic acid combined with natural polysaccharides like chitosan.…”