Queen's University of Belfast, School of Pharmacy, Belfast BT9 7BL, UK.
Int J Pharm. 2012 Jul 1;430(1-2):89-97. doi: 10.1016/j.ijpharm.2012.03.036. Epub 2012 Apr 2.
A major goal in vaccine development is elimination of the 'cold chain', the transport and storage system for maintenance and distribution of the vaccine product. This is particularly pertinent to liquid formulation of vaccines. We have previously described the rod-insert vaginal ring (RiR) device, comprising an elastomeric body into which are inserted lyophilised, rod-shaped, solid drug dosage forms, and having potential for sustained mucosal delivery of biomacromolecules, such as HIV envelope protein-based vaccine candidates. Given the solid, lyophilised nature of these insert dosage forms, we hypothesised that antigen stability may be significantly increased compared with more conventional solubilised vaginal gel format. In this study, we prepared and tested vaginal ring devices fitted with lyophilised rod inserts containing the model antigen bovine serum albumin (BSA). Both the RiRs and the gels that were freeze-dried to prepare the inserts were evaluated for BSA stability using PAGE, turbidimetry, microbial load, MALDI-TOF and qualitative precipitate solubility measurements. When stored at 4 °C, but not when stored at 40 °C/75% RH, the RiR formulation offered protection against structural and conformational changes to BSA. The insert also retained matrix integrity and release characteristics. The results demonstrate that lypophilised gels can provide relative protection against degradation at lower temperatures compared to semi-solid gels. The major mechanism of degradation at 40 °C/75% RH was shown to be protein aggregation. Finally, in a preliminary study, we found that addition of trehalose to the formulation significantly reduces the rate of BSA degradation compared to the original formulation when stored at 40 °C/75% RH. Establishing the mechanism of degradation, and finding that degradation is decelerated in the presence of trehalose, will help inform further development of RiRs specifically and polymer based freeze-dried systems in general.
疫苗开发的一个主要目标是消除“冷链”，即疫苗产品的运输和储存系统。这对于液体疫苗制剂尤为重要。我们之前描述过杆状插入式阴道环（RiR）装置，它由一个弹性体组成，其中插入了冻干的、棒状的、固体药物剂型，具有持续输送生物大分子（如 HIV 包膜蛋白疫苗候选物）的潜力。鉴于这些插入剂型是固体、冻干的，我们假设与更传统的溶解阴道凝胶剂型相比，抗原稳定性可能会显著提高。在这项研究中，我们制备并测试了装有冻干棒状插入物的阴道环装置，该插入物含有模型抗原牛血清白蛋白（BSA）。RiR 和用于制备插入物的冻干凝胶都使用 PAGE、浊度测定法、微生物负载、MALDI-TOF 和定性沉淀溶解度测量法来评估 BSA 稳定性。当储存在 4°C 时，而不是储存在 40°C/75%RH 时，RiR 制剂可防止 BSA 的结构和构象变化。插入物还保留了基质完整性和释放特性。结果表明，与半固体凝胶相比，冻干凝胶在较低温度下可以提供相对保护，防止降解。在 40°C/75%RH 下，主要的降解机制是蛋白质聚集。最后，在一项初步研究中，我们发现与原始配方相比，在 40°C/75%RH 下储存时，配方中添加海藻糖可显著降低 BSA 降解的速度。确定降解机制，并发现海藻糖的存在会减缓降解速度，这将有助于进一步开发 RiR 以及一般的聚合物冻干系统。
