Supplementary Materialsgkaa034_Supplemental_Data files. filter systems with 100 000 NMWL from Millipore. Applying the focused exosome suspension on the 30% sucrose pillow performed the ultimate exosome purification by ultracentrifugation at 100 000 g. Exosome purification was verified by transmitting electron microscopy (TEM, Supplementary Amount S1). Enrichment of aptamer collection on exosomes produced from VCaP and LNCaP cells Five rounds of SELEX had been performed on VCaP and LNCaP exosomes produced from prostate cancers cell lines by ultracentrifugation. To be able to block nonspecific binding, exosomes had been pre-incubated with 10 l salmon sperm DNA (800 ng), 10 l candida tRNA (800 ng) in 160 1207283-85-9 l reaction buffer [1 PBS, 3 mM MgCl2, 0.5% Pluronic? F127 (Sigma), 1 mg/ml human being serum albumin (HSA)] for 20 min at 25C with shaking at 500 rpm. In the first step of enrichment (round 1), 20 l of a diverse library of 1011 ssODNs (5 ng) having a 35 nt random region was incubated in reaction buffer with 25 g in 180 l VCaP exosomes (positive selection: 25 g pre-incubated exosomes for 30 min at 25C with rotation (final volume: 200 l). Exosomes were then precipitated with 6% PEG8000 (precipitation protocol: 200 l 12% PEG8000 added to 200 l ODN-bound exosomes, 30 min incubation on snow, centrifuge at 16 000 ?g for 10 min at 4C, remove supernatant, resuspend in 200 l reaction buffer, centrifuge at 16?000 g for 10 min at 4C), and exosome-associated ssODNs were recovered by elution using 10 l?0.25 M NaOH, incubation for 10 min at 50C, shaking for 5C10 s at 550 rpm, addition of 10 l?0.25 M HCl, centrifugation at 16?000 ?g for 10 min. The supernatant was eliminated and the pellet was resuspend in 30 l reaction buffer. This ssODN pool was taken straight into PCR after round 1 (11), but for subsequent rounds of enrichment (rounds 2 C 5), the eluted ssODNs from positive selection were further incubated with 25 g LNCaP exosomes (bad selection). LNCaP exosomes were precipitated with 6% PEG8000 and then pelleted by centrifugation at 16?000 ?g for 10 min. The pellet was discarded and the unbound ssODNs from your supernatant were collected and incubated with a fresh aliquot of 25 g VCaP exosomes. Precipitation and two-step elution were again performed, with 6% PEG8000 and 0.25 M NaOH/HCl respectively. The eluted ssODN library was amplified by PCR, denatured to recover ssDNA and then purified. The amplified, enriched ssODN library was used as the starting material for the next round of 1207283-85-9 enrichment at an input of 1011 sequences. Enrichment was monitored by next-generation sequencing. Libraries after each round of enrichment were amplified by PCR with unique indexing primers for multiplex analysis by NGS 1207283-85-9 on an Illumina HiSeq2500 (Supplementary Number S2). Next-generation sequencing of ssODN-probed exosomes Exosome probing was performed by incubating 25 g VCaP and LNCaP exosomes, in duplicate, with 2 1010 copies (1?ng) enriched round 5 ssODN library for 30 min at 25C. Exosomes were precipitated with 6% PEG8000 and centrifuged at 16?000 g for 10 min. Supernatant was discarded and exosome pellets were resuspended in H2O. Exosome-associated ssODNs were amplified by PCR with unique indexing primers for multiplex analysis by NGS on an Illumina HiSeq2500. The nine sequences demonstrated in Number ?Number2B2B were selected based on a combination of collapse changes of at least 4.0 and normalized counts of at least 500 for probing on VCaP exosomes (positive samples). Normalized counts were obtained by dividing the raw counts by the total counts per sample and multiplying the result by the average sample count (Supplementary Figure S3). Open in a separate window Figure 2. Sequence identification and verification. (A) Library after five rounds of enrichment was used to probe MMP7 exosomes from VCaP and LNCaP cells in order to identify individual ODNs that bound preferably to exosomes from VCaP cells (blue). Per exosome type two probing reactions (replicates 1 and 2) were performed and bound ODNs were identified by NGS; each dot represents one unique sequence with counts from different samples on both axes. Yellow frame: comparison of counts from VCaP exosome replicates 1 and 2 with LNCaP exosome replicates 1 and 2. Red frame: magnification of the VCaP exosome replicate 2 versus LNCaP exosome replicate 1 distribution of counts. A higher degree of scattering indicates the selection of sequences with a higher affinity to one or the other sample. For details on the NGS results see Supplementary Figure S3. (B) Sequences were resynthesized and binding of co-precipitated ODNs to VCaP exosomes was verified by qPCR. Sequences of the.