Physicochemical properties and micro-interaction between micro-nanoparticles and anterior corneal multilayer biological interface film for improving drug delivery efficacy: the transformation of tear film turnover mode.

Recently, various novel drug delivery systems have been developed to overcome ocular barriers in order to improve drug efficacy. We have previously reported that montmorillonite (MT) microspheres (MPs) and solid lipid nanoparticles (SLNs) loaded with the anti-glaucoma drug betaxolol hydrochloride (BHC) exhibited sustained drug release and thus intraocular pressure (IOP) lowering effects. Here, we investigated the effect of physicochemical particle parameters on the micro-interactions with tear film mucins and corneal epithelial cells. Results showed that the MT-BHC SLNs and MT-BHC MPs eye drops significantly prolonged the precorneal retention time due to their higher viscosity and lower surface tension and contact angle compared with the BHC solution, with MT-BHC MPs exhibiting the longest retention due to their stronger hydrophobic surface. The cumulative release of MT-BHC SLNs and MT-BHC MPs was up to 87.78% and 80.43% after 12 h, respectively. Tear elimination pharmacokinetics study further confirmed that the prolonged precorneal retention time of the formulations was due to the micro-interaction between the positively charged formulations and the negatively charged tear film mucins. Moreover, the area under the IOP reduction curve (AUC) of MT-BHC SLNs and MT-BHC MPs was 1.4 and 2.5 times that of the BHC solution. Accordingly, the MT-BHC MPs also exhibit the most consistent and long-lasting IOP-lowering effect. Ocular irritation experiments showed no significant toxicity of either. Taken together, MT MPs may have the potential for more effective glaucoma treatment.

A receptor-based bioadsorbent to target advanced glycation end products in chronic kidney disease.

The accumulation of advanced glycation end products (AGEs) has been reported to be a major contributor to chronic systemic inflammation. AGEs are not efficiently removed by hemodialysis or the kidney of a chronic kidney disease (CKD) patient. The goal of this study was to develop a receptor for AGEs (RAGE)-based bioadsorbent device that was capable of removing endogenous AGEs from human blood. The extracellular domain of RAGE was immobilized onto agarose beads to generate the bioadsorbent. The efficacy of AGE removal from saline, serum, and whole blood; biological effects of AGE reduction; and hemocompatibility and stability of the bioadsorbent were investigated. The bioadsorbent bound AGE-modified bovine serum albumin (AGE-BSA) with a binding capacity of 0.73 ± 0.07 mg AGE-BSA/mL bioadsorbent. The bioadsorbent significantly reduced the concentration of total AGEs in serum isolated from end-stage kidney disease patients by 57%. AGE removal resulted in a significant reduction of vascular cell adhesion molecule-1 expression in human endothelial cells and abolishment of osteoclast formation in osteoclast progenitor cells. A hollow fiber device loaded with bioadsorbent-reduced endogenous AGEs from recirculated blood to 36% of baseline levels with no significant changes in total protein or albumin concentration. The bioadsorbent maintained AGE-specific binding capacity after freeze-drying and storage for 1 year. This approach provides the foundation for further development of soluble RAGE-based extracorporeal therapies to selectively deplete serum AGEs from human blood and decrease inflammation in patients with diabetes and/or CKD.

The processivity of kinesin-2 motors suggests diminished front-head gating.

Kinesin-2 motors, which are involved in intraflagellar transport and cargo transport along cytoplasmic microtubules, differ from motors in the canonical kinesin-1 family by having a heterodimeric rather than homodimeric structure and possessing a three amino acid insertion in their neck linker domain. To determine how these structural features alter the chemomechanical coupling in kinesin-2, we used single-molecule bead experiments to measure the processivity and velocity of mouse kinesin-2 heterodimer (KIF3A/B) and the engineered homodimers KIF3A/A and KIF3B/B and compared their behavior to Drosophila kinesin-1 heavy chain (KHC). Single-motor run lengths of kinesin-2 were 4-fold shorter than those of kinesin-1. Extending the kinesin-1 neck linker by three amino acids led to a similar reduction in processivity. Furthermore, kinesin-2 processivity varied inversely with ATP concentration. Stochastic simulations of the kinesin-1 and kinesin-2 hydrolysis cycles suggest that "front-head gating," in which rearward tension prevents ATP binding to the front head when both heads are bound to the microtubule, is diminished in kinesin-2. Because the mechanical tension that underlies front-head gating must be transmitted through the neck linker domains, we propose that the diminished coordination in kinesin-2 is a result of its longer and, hence, more compliant neck linker element.

The two motor domains of KIF3A/B coordinate for processive motility and move at different speeds.

KIF3A/B, a kinesin involved in intraflagellar transport and Golgi trafficking, is distinctive because it contains two nonidentical motor domains. Our hypothesis is that the two heads have distinct functional properties, which are tuned to maximize the performance of the wild-type heterodimer. To test this, we investigated the motility of wild-type KIF3A/B heterodimer and chimaeric KIF3A/A and KIF3B/B homodimers made by splicing the head of one subunit to the rod and tail of the other. The first result is that KIF3A/B is processive, consistent with its transport function in cells. Secondly, the KIF3B/B homodimer moves at twice the speed of the wild-type motor but has reduced processivity, suggesting a trade-off between speed and processivity. Third, the KIF3A/A homodimer moves fivefold slower than wild-type, demonstrating distinct functional differences between the two heads. The heterodimer speed cannot be accounted for by a sequential head model in which the two heads alternate along the microtubule with identical speeds as in the homodimers. Instead, the data are consistent with a coordinated head model in which detachment of the slow KIF3A head from the microtubule is accelerated roughly threefold by the KIF3B head.