Technical Specification: Transfection Reagents¶
1. Product Range¶
Solarbio offers two transfection reagent formulations designed for different cell type requirements. Solarfect (T2100) is a multi-component lipid formulation optimized for established cell lines. Liposomal Transfection Reagent (T2200) uses an advanced liposome formulation for primary cells and difficult-to-transfect types.
| Product | SKU | Cargo Type | Cell Types | Format |
|---|---|---|---|---|
| Solarfect Transfection Reagent | T2100 | Plasmid DNA, siRNA | HEK293, HeLa, CHO, HepG2, A549, NIH/3T3 | 1 mL, 2 mL |
| Liposomal Transfection Reagent | T2200 | Plasmid DNA, siRNA | Primary cells, stem cells, difficult-to-transfect (HUVEC, MSC, neurons) | 1 mL, 2 mL |
2. Technical Parameters¶
2.1 Solarfect (T2100)¶
| Parameter | Specification |
|---|---|
| Transfection efficiency (HEK293, 24 h) | >80% (GFP reporter, flow cytometry) |
| Cytotoxicity (HEK293 at recommended dose) | <10% (MTT assay, 48 h) |
| siRNA knockdown efficiency | >70% (48 h, 20 nM siRNA, qPCR readout) |
| DNA amount (24-well) | 0.5–1 μg per well |
| siRNA amount (24-well) | 10–100 pmol per well |
| Reagent-to-DNA ratio (v/w) | 2–3:1 (μL reagent : μg DNA) |
| Optimal cell confluency at transfection | 70–90% |
| Serum compatibility | Works in serum-containing medium (no change needed) |
| Antibiotic compatibility | Avoid during transfection (penicillin/streptomycin) |
| Storage | 2–8°C, 12 months |
| Complex formation time | 15–20 min at RT |
2.2 Liposomal Transfection Reagent (T2200)¶
| Parameter | Specification |
|---|---|
| Transfection efficiency (HUVEC, 48 h) | >60% (GFP reporter) |
| Transfection efficiency (MSC, 72 h) | >40% (GFP reporter) |
| Cytotoxicity (HUVEC at recommended dose) | <15% (MTT assay) |
| siRNA knockdown efficiency (primary cells) | >60% (48–72 h, 50 nM siRNA) |
| DNA amount (24-well) | 0.5–1 μg per well |
| Reagent-to-DNA ratio (v/w) | 3–4:1 (μL reagent : μg DNA) |
| Optimal cell confluency | 60–80% |
| Serum compatibility | Reduced serum (Opti-MEM or serum-free) for complex formation |
| Storage | 2–8°C, 12 months |
| Complex formation time | 15–30 min at RT |
3. Mechanism of Action¶
Lipid-based transfection reagents consist of cationic lipids (e.g., DOTMA, DOTAP) and neutral co-lipids (typically DOPE) formulated into liposomes. The transfection mechanism proceeds through five distinct steps:
Step 1 — Complex formation: Cationic liposomes interact electrostatically with negatively charged nucleic acids (DNA or siRNA) to form lipoplexes. The net positive charge of the complex facilitates interaction with the negatively charged cell surface.
Step 2 — Cellular uptake: Lipoplexes bind to the anionic cell surface proteoglycans (heparan sulfate) and are internalized primarily via clathrin-mediated endocytosis, with minor contributions from caveolin-mediated uptake and macropinocytosis.
Step 3 — Endosomal escape: The key limiting step. The fusogenic lipid DOPE undergoes a lamellar-to-hexagonal phase transition at acidic pH in the endosome, destabilizing the endosomal membrane and releasing nucleic acid into the cytoplasm. Approximately 1–5% of internalized nucleic acid escapes the endosome.
Step 4 — Intracellular trafficking: Plasmid DNA must traverse the cytoplasm and enter the nucleus. Nuclear entry occurs during mitosis when the nuclear envelope breaks down. siRNA remains in the cytoplasm for RISC loading.
Step 5 — Expression/silencing: Plasmid DNA transcription produces mRNA, followed by translation. siRNA is loaded into the RNA-induced silencing complex (RISC), guiding sequence-specific mRNA cleavage.
4. Protocol Overview — Plasmid DNA Transfection (24-well Plate)¶
| Step | Detail | Time |
|---|---|---|
| Seed cells | 5×10⁴ cells/well in 500 μL complete medium | Day 1 |
| Culture | Grow to 70–90% confluency | 24 h |
| DNA dilution | 0.5–1 μg DNA in 50 μL Opti-MEM or PBS | Day 2 |
| Reagent dilution | 1.5–3 μL reagent in 50 μL Opti-MEM | Day 2 |
| Complex formation | Mix diluted DNA + reagent; pipette gently | 15–20 min at RT |
| Add to cells | Add 100 μL complexes directly to cells; swirl gently | — |
| Medium change | Optional (if serum-free complexes); change after 4–6 h | — |
| Readout | GFP/mCherry: 24–48 h; Luciferase: 24–72 h | Day 3–4 |
5. Transfection Efficiency by Cell Type¶
| Cell Line | Reagent | Optimal Ratio (μL:μg) | Efficiency (%) | Viability (%) |
|---|---|---|---|---|
| HEK293 | T2100 | 2:1 | 85–92 | >95 |
| HeLa | T2100 | 3:1 | 75–85 | >90 |
| CHO-K1 | T2100 | 2:1 | 70–80 | >90 |
| HepG2 | T2100 | 3:1 | 55–70 | >85 |
| A549 | T2100 | 3:1 | 60–75 | >90 |
| NIH/3T3 | T2100 | 2:1 | 65–80 | >95 |
| HUVEC (primary) | T2200 | 3:1 | 55–70 | >85 |
| MSC (primary) | T2200 | 4:1 | 35–50 | >75 |
| Primary neurons | T2200 | 4:1 | 20–35 | >70 |
| Jurkat (suspension) | T2100 | 2:1 | 50–65 | >80 |
| RAW 264.7 | T2100 | 3:1 | 30–45 | >75 |
6. Optimization Guide¶
6.1 Parameter Matrix¶
| Parameter | Recommended Range | Strategy |
|---|---|---|
| DNA amount (24-well) | 0.25–2 μg | Titrate in 2-fold increments; measure both efficiency and viability |
| Reagent:DNA ratio | 1:1 to 5:1 (v/w) | Test 1:1, 2:1, 3:1, 4:1; higher ratios may increase efficiency but reduce viability |
| Cell density | 50–90% confluency | Lower density → higher efficiency, lower viability; higher density → lower efficiency, higher viability |
| DNA quality | A₂₆₀/A₂₈₀ 1.8–2.0 | Endotoxin-free maxiprep recommended; avoid RNA contamination |
| Serum during transfection | 0–10% | Complex formation in serum-free medium; add to cells with or without serum |
6.2 Critical Factors¶
| Factor | Impact | Recommendation |
|---|---|---|
| Antibiotics | Cationic lipids increase membrane permeability → antibiotics enter cells → cytotoxicity | Omit penicillin/streptomycin during transfection |
| Passage number (primary cells) | High passage → reduced efficiency | Use passages 2–6 for primary cells |
| DNA purity | Impurities (phenol, ethanol, endotoxin) → cytotoxicity | Endotoxin-free maxiprep; A₂₆₀/A₂₈₀ 1.8–2.0 |
| siRNA concentration | High concentration → off-target effects | Use 10–50 nM for well-characterized siRNA; validate with 2 independent sequences |
| Medium change timing | Prolonged complex incubation → toxicity | For sensitive cells: change medium after 4–6 h |
7. Troubleshooting¶
| Issue | Possible Cause | Solution |
|---|---|---|
| Low efficiency, acceptable viability | Reagent:DNA ratio too low; cell confluency too high | Increase ratio; reduce seeding density |
| Low efficiency, low viability | Reagent:DNA ratio too high; complexes toxic | Reduce ratio; change medium after 4 h; use fewer complexes |
| Cell death after transfection | Antibiotic present; DNA impure; cells too sparse | Omit antibiotics; purify DNA; increase cell density |
| High cell death in primary cells | T2100 too harsh for sensitive cells | Switch to T2200; reduce complex volume |
| No GFP expression | Plasmid quality issues; promoter not active in cell type | Verify plasmid map; check cell-specific promoter activity; include positive control (CMV-GFP) |
| siRNA no knockdown | Low delivery; target sequence weak | Increase siRNA to 50 nM; test 2–3 independent siRNAs; qRT-PCR confirmation |
8. Cross-References¶
- ▶ Related Protocol: Cell Culture Protocol
- ▶ Related Protocol: Competent Cell Transformation
- ▶ See also: Cell Proliferation Assay Kits
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