UF Pre-Concentration for Muscle Tissue-Derived EV Isolation via ExoFaster-500

1. Overview

This application note evaluates the performance of ultrafiltration (UF) pre-concentration prior to size-exclusion chromatography (SEC) isolation of extracellular vesicles (EVs) from mouse quadriceps tissue conditioned medium using the ExoFaster-500 platform. EV yields and purity from un-concentrated crude conditioned medium and UF-concentrated samples were compared via UV absorbance profiling (A260/A280) and nanoparticle tracking analysis (NTA), demonstrating that UF pre-concentration drastically improves EV detection and recoverable particle output for low-biomass muscle tissue specimens.

2. Materials & Isolation Protocol

2.1 Sample Preparation from Mouse Skeletal Muscle

1. Sacrifice mice and dissect 0.5–1 g quadriceps muscle tissue per biological replicate.

2. Mince tissue into ~2 mm fragments, then incubate in serum-free high-glucose DMEM at a ratio of 1 mL medium per 0.1 g tissue for 24 h at 37 °C to generate tissue conditioned medium.

3. Clarify conditioned medium by centrifugation at 2000 × g for 30 min to remove tissue debris and cell fragments; collect clarified supernatant.

2.2 Two Sample Loading Regimens

• Group 1 (No UF Pre-Concentration): Clarified muscle conditioned medium loaded directly onto ExoFaster-500 without volume reduction.

• Group 2 (UF Pre-Concentration): Clarified supernatant transferred to ultrafiltration tubes, concentrated at 4000–5000 × g, room temperature for 20–40 min to reduce 17 mL starting medium to 500 μL retentate. Concentrated retentate may be stored at 4 °C overnight prior to SEC loading; repeated freeze-thaw cycles are prohibited to prevent protein precipitation.

2.3 SEC Isolation on ExoFaster-500

All samples were separated using ExoFaster-500 SEC columns with standard 1 VN loading mode (500 μL injection volume) to collect serial elution fractions.

2.4 Characterisation Assays

1. UV Spectrophotometry: A260, A280 absorbance and A260/A280 ratio measured for each elution fraction to track vesicle and soluble protein elution profiles.

2. Nanoparticle Tracking Analysis (NTA): Quantification of EV particle concentration, total soluble protein concentration, and particle-to-protein purity ratio from pooled target EV fractions.

3. Results

3.1 SEC Elution Absorbance Profiles (Group 1 vs Group 2)

UV absorbance readings of serial elution fractions 5–14 were compared between direct loading (Group 1) and UF pre-concentrated loading (Group 2), with core EV-containing fractions highlighted (Fractions 7–8):

Fraction	Group 1 (No Pre-Concentration)			Group 2 (UF Pre-Concentration)
	A260	A280	A260/A280	A260	A280	A260/A280
5	-0.115	0.022	-5.292	-0.082	0.022	-3.770
6	-0.128	0.012	-10.311	-0.082	0.040	-2.055
7	-0.097	0.028	-3.495	0.083	0.175	0.473
8	-0.065	0.053	-1.240	0.232	0.370	0.626
9	-0.081	0.040	-2.023	0.247	0.483	0.512
10	-0.070	0.051	-1.385	0.242	0.605	0.400
11	-0.088	0.072	-1.217	0.344	0.801	0.429
12	-0.029	0.097	-0.303	0.474	1.011	0.469
13	-0.060	0.118	-0.507	0.545	1.159	0.470
14	-0.024	0.156	-0.157	0.616	1.245	0.495

Key observations:

1. Group 1 direct loading generated negligible positive absorbance signals across all fractions, with all A260 values remaining negative and no distinct elution peak corresponding to EV populations.

2. Group 2 UF-preconcentrated samples produced clear, elevated A260 and A280 signals starting at Fraction 7, consistent with the expected elution window for intact extracellular vesicles on ExoFaster-500. Stable A260/A280 ratios (0.40–0.63) throughout target fractions confirmed consistent vesicle-containing eluate.

   
   

3.2 NTA Quantification of UF Pre-Concentrated EV Fractions (Group 2)

Pooled target EV eluates from UF pre-concentrated Group 2 were characterised via NTA and BCA protein assay to assess particle yield and purity:

Metric	Group 2 (UF Pre-Concentration)
Particle Concentration	5.02 × 10¹⁰ particles/mL
Total Protein Concentration	0.18 mg/mL
Particle-to-Protein Purity Ratio	2.77 × 10⁸ particles/μg protein

High particle-to-protein ratio verified the ExoFaster-500 SEC platform effectively separates intact EVs from soluble tissue-derived protein contaminants after UF pre-concentration, delivering high-purity EV preparations suitable for downstream functional and omics analysis.

4. Conclusion & Recommended Workflow

For EV isolation from mouse quadriceps muscle tissue conditioned medium using ExoFaster-500 SEC:

1. Ultrafiltration pre-concentration is strongly recommended prior to SEC loading for low-EV-abundance tissue culture samples. Direct processing of un-concentrated conditioned medium fails to produce detectable EV elution profiles on the ExoFaster-500 system.

2. Concentrate clarified tissue conditioned medium to 500 μL via 4000–5000 × g ultrafiltration at room temperature for 20–40 min, then separate using 1 VN standard loading parameters on ExoFaster-500.

3. Target EV fractions correspond to Fractions 7–8 with stable A260/A280 absorbance ratios, yielding high-purity EV populations with particle-to-protein ratios above 2 × 10⁸ particles/μg protein.