Turner Paul A, Thiele Jeffrey S, Stegemann Jan P
a Department of Biomedical Engineering , University of Michigan , Ann Arbor , MI , USA.
J Biomater Sci Polym Ed. 2017 Nov;28(16):1826-1846. doi: 10.1080/09205063.2017.1354672. Epub 2017 Jul 20.
Controlled release of growth factors allows the efficient, localized, and temporally-optimized delivery of bioactive molecules to potentiate natural physiological processes. This concept has been applied to treatments for pathological states, including chronic degeneration, wound healing, and tissue regeneration. Peptide microspheres are particularly suited for this application because of their low cost, ease of manufacture, and interaction with natural remodeling processes active during healing. The present study characterizes gelatin microspheres for the entrapment and delivery of growth factors, with a focus on tailored protein affinity, loading capacity, and degradation-mediated release. Genipin crosslinking in PBS and CHES buffers produced average microsphere sizes ranging from 15 to 30 microns with population distributions ranging from about 15 to 60 microns. Microsphere formulations were chosen based on properties important for controlled transient and spatial delivery, including size, consistency, and stability. The microsphere charge affinity was found to be dependent on gelatin type, with type A (GelA) carriers consistently having a lower negative charge than equivalent type B (GelB) carriers. A higher degree of crosslinking, representative of primary amine consumption, resulted in a greater negative net charge. Gelatin type was found to be the strongest determinant of degradation, with GelA carriers degrading at higher rates versus similarly crosslinked GelB carriers. Growth factor release was shown to depend upon microsphere degradation by proteolytic enzymes, while microspheres in inert buffers showed long-term retention of growth factors. These studies illuminate fabrication and processing parameters that can be used to control spatial and temporal release of growth factors from gelatin-based microspheres.
生长因子的控释能够实现生物活性分子的高效、局部且时间优化的递送，从而增强自然生理过程。这一概念已应用于包括慢性退变、伤口愈合和组织再生在内的病理状态的治疗。肽微球因其成本低、易于制造以及与愈合过程中活跃的自然重塑过程相互作用，特别适合用于此应用。本研究对用于包裹和递送生长因子的明胶微球进行了表征，重点关注定制的蛋白质亲和力、负载能力和降解介导的释放。在磷酸盐缓冲盐水（PBS）和2-（2-羟乙基）氨基乙磺酸（CHES）缓冲液中进行京尼平交联，产生的微球平均尺寸为15至30微米，群体分布范围约为15至60微米。基于对可控的瞬时和空间递送重要的特性，包括尺寸、稠度和稳定性，选择了微球配方。发现微球电荷亲和力取决于明胶类型，A型（GelA）载体始终比同等的B型（GelB）载体具有更低的负电荷。更高程度的交联代表伯胺消耗，导致更大的净负电荷。发现明胶类型是降解的最强决定因素，与类似交联的GelB载体相比，GelA载体降解速度更快。生长因子的释放显示取决于蛋白水解酶对微球的降解，而在惰性缓冲液中的微球显示生长因子的长期保留。这些研究阐明了可用于控制基于明胶的微球中生长因子的空间和时间释放的制造和加工参数。
