Core-shell microparticles for protein sequestration and controlled release of a protein-laden core

Abstract

Development of multifunctional biomaterials that sequester, isolate, and redeliver cell-secreted proteins at a specific timepoint may be required to achieve the level of temporal control needed to more fully regulate tissue regeneration and repair. In response, we fabricated core-shell heparin-poly(ethylene-glycol) (PEG) microparticles (MPs) with a degradable PEG-based shell that can temporally control delivery of protein-laden heparin MPs. Core-shell MPs were fabricated via a re-emulsification technique and the number of heparin MPs per PEG-based shell could be tuned by varying the mass of heparin MPs in the precursor PEG phase. When heparin MPs were loaded with bone morphogenetic protein-2 (BMP-2) and then encapsulated into core-shell MPs, degradable core-shell MPs initiated similar C2C12 cell alkaline phosphatase (ALP) activity as the soluble control, while non-degradable core-shell MPs initiated a significantly lower response (85±19% vs. 9.0±4.8% of the soluble control, respectively). Similarly, when degradable core-shell MPs were formed and then loaded with BMP-2, they induced a ~7-fold higher C2C12 ALP activity than the soluble control. As C2C12 ALP activity was enhanced by BMP-2, these studies indicated that degradable core-shell MPs were able to deliver a bioactive, BMP-2-laden heparin MP core. Overall, these dynamic core-shell MPs have the potential to sequester, isolate, and then redeliver proteins attached to a heparin core to initiate a cell response, which could be of great benefit to tissue regeneration applications requiring tight temporal control over protein presentation.

Localized SDF-1α Delivery Increases Pro-Healing Bone Marrow-Derived Cells in the Supraspinatus Muscle Following Severe Rotator Cuff Injury

“…Second, as natively sulfated heparin possesses potent anti-coagulant properties and may present safety issues in vivo , we have incorporated N-desulfated heparin (Hep −N ) within our biomaterials, which exhibits diminished anti-coagulant properties while maintaining the ability to bind protein and protect protein bioactivity [18,22]. Lastly, though heparin and heparin derivatives have been successfully incorporated within bulk hydrogels for SDF-1α delivery [7,10,11,23], we and others have developed heparin-based microparticles (MPs) [18,24–26] as an injectable protein delivery method without exposure to free radicals that are required for in situ radically-polymerized hydrogels [27–29]. Furthermore, building on our previous work [19], we have incorporated dithiothreitol (DTT) within the MPs to vary the rate of hydrolytic degradation [30] and ultimately allow for more complete release of protein over time.…”

Design and applications of protein delivery systems in nanomedicine and tissue engineering

“…the "pre-fabrication loading" or "post-fabrication loading" which consists of loading the heparin NPs before PEG MPs formation or loading the final heparin NP/PEG MP system respectively, both done through adsorption [9]. This study showed that the pre-fabrication loading induced a similar C2C12 cell ALP activity while postfabrication loading induced 7-fold higher ALP activity compared to free rhBMP2.…”

“…Even if this technique is very common to obtain poly(lactic-coglycolic acid) (PLGA) [7] or chitosan (CHI) [8] particles, it can also be extended to many biological macromolecules as building blocks. For example, Rinker et al reported the synthesis of heparin MPs by mixing an aqueous solution of heparin in corn oil, which is the classic water-in-oil emulsion technique [9]. More interestingly, they used it again to entrap these heparin MPs in bigger MPs mainly composed of poly(ethylene glycol) (PEG).…”

Technological Approaches for Improving Vaccination Compliance and Coverage

“…There is an increasing interest in developing core-shell particles with hydrophilic cores to maintain the microenvironment and therefore the conformation and biological integrity of the antigen [147]. They can be formulated using W/O/W method, microfluidics, or by StampEd assembly of polymer layers (SEAL), a recently reported microfabrication approach based on 3D printing [148].…”