Abstract:An aqueous liposome coated silk microsphere suspension is an effective lubricant, providing a low friction coefficient, minimizing surface wear, and avoiding degradation even over relatively prolonged cycling conditions. It is proposed that the lubricating properties of the silk microspheres are a result of an efficient rolling mechanism.
“…Besides, the lubrication performance of GelMA@DMA-MPC is better than GelMA, which further reduces COF synergistically via hydration lubrication of the zwitterionic phosphocholine groups in the copolymers [ 19 ]. Additionally, it is speculated that the DMA-MPC coating layer may also behave as a “lubricant” between the microspheres, and consequently it avoids jamming of the microspheres in the rolling process, which is favorable for lubrication [ 39 , 40 ]. Fig.…”
The occurrence of osteoarthritis (OA) is highly associated with the reduced lubrication property of the joint, where a progressive and irreversible damage of the articular cartilage and consecutive inflammatory response dominate the mechanism. In this study, bioinspired by the super-lubrication property of cartilage and catecholamine chemistry of mussel, we successfully developed injectable hydrogel microspheres with enhanced lubrication and controllable drug release for OA treatment. Particularly, the lubricating microspheres (GelMA@DMA-MPC) were fabricated by dip coating a self-adhesive polymer (DMA-MPC, synthesized by free radical copolymerization) on superficial surface of photo-crosslinked methacrylate gelatin hydrogel microspheres (GelMA, prepared via microfluidic technology), and encapsulated with an anti-inflammatory drug of diclofenac sodium (DS) to achieve the dual-functional performance. The tribological test and drug release test showed the enhanced lubrication and sustained drug release of the GelMA@DMA-MPC microspheres. In addition, the functionalized microspheres were intra-articularly injected into the rat knee joint with an OA model, and the biological tests including qRT-PCR, immunofluorescence staining assay, X-ray radiography and histological staining assay all revealed that the biocompatible microspheres provided significant therapeutic effect against the development of OA. In summary, the injectable hydrogel microspheres developed herein greatly improved lubrication and achieved sustained local drug release, therefore representing a facile and promising technique for the treatment of OA.
“…Besides, the lubrication performance of GelMA@DMA-MPC is better than GelMA, which further reduces COF synergistically via hydration lubrication of the zwitterionic phosphocholine groups in the copolymers [ 19 ]. Additionally, it is speculated that the DMA-MPC coating layer may also behave as a “lubricant” between the microspheres, and consequently it avoids jamming of the microspheres in the rolling process, which is favorable for lubrication [ 39 , 40 ]. Fig.…”
The occurrence of osteoarthritis (OA) is highly associated with the reduced lubrication property of the joint, where a progressive and irreversible damage of the articular cartilage and consecutive inflammatory response dominate the mechanism. In this study, bioinspired by the super-lubrication property of cartilage and catecholamine chemistry of mussel, we successfully developed injectable hydrogel microspheres with enhanced lubrication and controllable drug release for OA treatment. Particularly, the lubricating microspheres (GelMA@DMA-MPC) were fabricated by dip coating a self-adhesive polymer (DMA-MPC, synthesized by free radical copolymerization) on superficial surface of photo-crosslinked methacrylate gelatin hydrogel microspheres (GelMA, prepared via microfluidic technology), and encapsulated with an anti-inflammatory drug of diclofenac sodium (DS) to achieve the dual-functional performance. The tribological test and drug release test showed the enhanced lubrication and sustained drug release of the GelMA@DMA-MPC microspheres. In addition, the functionalized microspheres were intra-articularly injected into the rat knee joint with an OA model, and the biological tests including qRT-PCR, immunofluorescence staining assay, X-ray radiography and histological staining assay all revealed that the biocompatible microspheres provided significant therapeutic effect against the development of OA. In summary, the injectable hydrogel microspheres developed herein greatly improved lubrication and achieved sustained local drug release, therefore representing a facile and promising technique for the treatment of OA.
“…For example, the lubricin mimic 23, 25, 45 lubricants afford μ kinetic values ranging 0.1–0.3 on cartilage, while the liposomes 26 exhibit μ kinetic values ranging 0.02–0.1 and phospholipid coated silk microspheres range 0.02–0.06. 27 A high molecular weight lubricious polymer with poly(2‐methyl‐2‐oxazoline) sidechains gives μ kinetic values spanning 0.02–0.1. 28 The 2.8M TEG biolubricant provides superior lubrication even after the interstitial fluid pressure has subsided, indicating the viscous lubricant is superior to healthy BSF and saline under these loading conditions.…”
Section: Discussionmentioning
confidence: 99%
“…Although it is difficult to compare μ values directly between torsional and linearly oscillating configurations, our results with saline are within an order of magnitude of these prior reports. For example, the lubricin mimic ,, lubricants afford μ kinetic values ranging 0.1–0.3 on cartilage, while the liposomes exhibit μ kinetic values ranging 0.02–0.1 and phospholipid-coated silk microspheres range 0.02–0.06 . A high-molecular-weight lubricious polymer with poly(2-methyl-2-oxazoline) side chains gives μ kinetic values spanning 0.02–0.1 .…”
Section: Discussionmentioning
confidence: 99%
“…Toward this goal, we are investigating high-molecular-weight polyelectrolytes as viscous biolubricants for cartilage. Several classes of cartilage protectants are under preclinical investigation and include lubricin , and lubricin mimics, − liposomes, phospholipid-coated silk microspheres, and high-molecular-weight lubricious polymers, , the latter of which can form viscous aqueous solutions due to polymer chain entanglement and/or cross-linking. From a tribological design perspective, a viscous lubricant creates a thin film between the cartilage surfaces to ensure that a pressurized fluid film more easily forms.…”
A poly(7-oxanorbornene-2-carboxylate) polymer containing pendent triethyleneglycol (TEG) chains of 2.8 MDa (“2.8M TEG”) was synthesized and evaluated for long-term lubrication and wear reduction of ex vivo bovine cartilage as well as for synovitis in rats and dogs after intra-articular administration. Bovine cartilage surfaces were tested under torsional friction for 10,080 rotations while immersed in either saline, bovine synovial fluid (BSF), or 2.8M TEG. For each solution, coefficient of friction (μ), changes in surface roughness, and lost cartilage glycosaminoglycan were compared. To directly compare 2.8M TEG and BSF, additional samples were tested sequentially in BSF, BSF, 2.8M TEG, and then BSF. Finally, another set of samples were tested twice in saline to induce surface roughness and then tested in BSF, Synvisc, or 2.8M TEG to determine each treatment’s effect on worn cartilage. Next, male Lewis rats were injected in one knee with 2.8M TEG or saline and evaluated for effects on gait, and female beagles were injected with either 2.8M TEG or saline in one knee, and their synovial tissues analyzed for inflammation by H&E staining. Treatment with 2.8M TEG lowers μ, lessens surface roughness, and minimizes glycosaminoglycan loss compared to saline. The 2.8M TEG also reduces μ compared to BSF in pairwise testing and on worn cartilage surfaces. Injection of 2.8M TEG in rat or beagle knees gives comparable effects to treatment with saline, and does not cause significant synovitis.
“…With excellent injectability and biocompatibility, HMs can act similar to ball bearings to reduce friction at sliding interfaces via a rolling mechanism, making them attractive candidates for biolubricants (5,(7)(8)(9)(10). The surface lubrication properties of rolling elements can notably affect their rolling performances (8,11,12). Hydration layers formed by the interaction of water molecules with charged ions or zwitterions can substantially reduce friction (13).…”
Introducing hydration layers to hydrogel microspheres (HMs) by coating the surface with liposomes can effectively reduce friction. However, the lubrication can be inactivated when the surface coatings are damaged. To endow HMs with the ability to form self-renewable hydration layers and maintain cellular homeostasis, rapamycin-liposome–incorporating hyaluronic acid–based HMs (RAPA@Lipo@HMs) were created using microfluidic technology and photopolymerization processes. The RAPA@Lipo@HMs improve joint lubrication by using a smooth rolling mechanism and continuously exposing liposomes on the outer surface to form self-renewable hydration layers via frictional wear. In addition, the released autophagy activator (rapamycin)–loaded cationic liposomes can target negatively charged cartilage through electrostatic interactions and maintain cellular homeostasis by increasing autophagy. Furthermore, the in vivo data showed that the RAPA@Lipo@HMs can alleviate joint wear and delay the progression of osteoarthritis. The RAPA@Lipo@HMs can provide efficient lubrication and potentially alleviate friction-related diseases such as osteoarthritis.
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