The RAP12 peptide derived from miniaturization of receptor-associated protein (RAP) holds binding affinity with low-density lipoprotein receptor-related protein-1 (LRP1). However, RAP12 exhibited weak a-helical segments when taken out of the stabilizing protein context. Considering that the alpha-helix is a common structural motif of the peptide to mediate ligand-receptor interactions, we utilized the peptide stapling technique to generate RAP12 with all-hydrocarbon tethers, named stapled RAP12 (ST-RAP12). This optimized ST-RAP12 was verified to obtain an increased a-helical content, binding affinity with LRP1 and serum stability compared to RAP12. In addition, ST-RAP12 exhibited enhanced cellular internalization of bEnd.3 cell, U87 glioma cells and HUVEC. Furthermore, the ability of ST-RAP12 to overcome in vitro BBB/BBTB was also potentiated. Next, ST-RAP12 peptide was further applied to modify polymeric materials to construct ST-RAP12-micelles. It is verified that the ST-RAP12-micelles effectively penetrated BBB/BBTB and targeted glioma in vitro/vivo, and immunofluorescence studies demonstrated its targeting ability to tumor angiogenesis and LRP1. Moreover, ST-RAP12-micelles efficiently delivered paclitaxel (PTX) to glioma, prolonged the survival time of glioma-bearing mice, inhibited tumor angiogenesis and induced glioma apoptosis, which displayed obvious anti-glioma efficacy. Overall, ST-RAP12 is anticipated to be a widely used LRP1-targeted peptide and could be translated as a multifunctional ligand for glioma-targeted drug delivery.

Determination of vitamin D levels in human biological specimens has gained a high relevance over the last decades, essentially because low levels have been associated with several biological disorders. In fact, vitamin D deficiency has become a worldwide health concern covering all ages and genders. The storage of biofluids has to be considered for determination of vitamin D and metabolites in order to fully preserve matrices status. This study attempts to evaluate lyophilization of serum and plasma as a pre-processing step for sample storage prior to quantitative analysis of vitamin D-3 and its main hydroxylated metabolites-25(OH)D-3, 24,25(OH)(2)D-3 and 1,25 (OH)(2)D-3. The protocol including sample lyophilization was characterized in terms of analytical features and compared to the same method, based on SPE-LC-MS/MS, without lyophilization. Sensitivity, precision and accuracy were not affected when we operated with lyophilized serum and plasma and results provided by a set of twenty-four serum samples from DEQAS (Vitamin D External Quality Assessment Scheme) were in agreement with reported concentrations for 25(OH)D-3 and 1,25(OH)(2)D-3. A stability study programmed for 9 months allowed ensuring that the concentration of vitamin D-3 and metabolites in lyophilized serum and plasma stored at room temperature was not affected during this period. This research has demonstrated that the quantitation of target metabolites is not under the influence of lyophilization. Therefore, including lyophilization prior to analysis could reduce shipment and storage costs, avoid delays of sample processing, and increase the stability of the target analytes due to an effective quenching process.