Antimicrobial Peptide (AMP) Testing

Antimicrobial Peptide (AMP) Testing – Potency, Purity, Stability, and Mechanistic Characterization

If you are searching for antimicrobial peptide testing, you likely need to verify the minimum inhibitory concentration (MIC), killing kinetics, hemolytic activity, peptide purity, aggregation state, or stability against proteases for a candidate AMP intended for pharmaceutical, food preservation, cosmetic, or agricultural applications. Unlike conventional small‑molecule drugs, AMPs require specialized assays to confirm membrane‑disruptive or intracellular mechanisms, synergistic effects, and resistance profiles. Our laboratory provides comprehensive antimicrobial peptide analysis – from basic MIC determination to mechanistic studies (membrane permeabilization, pore formation, liposome leakage), peptide secondary structure (CD spectroscopy), aggregation analysis (ThT, dynamic light scattering), and high‑resolution mass spectrometry for purity and modifications – following CLSI, EUCAST, and ICH guidelines for biologics.

What We Analyze – Full Testing Scope for Antimicrobial Peptides

We do not simply report MIC against one or two strains. Our platform includes broth microdilution (CLSI M07) and agar dilution for MIC determination against a panel of gram‑positive, gram‑negative, and fungal reference strains (including clinical isolates) with full quality control (QC strains: S. aureus ATCC 29213, E. coli ATCC 25922, P. aeruginosa ATCC 27853, C. albicans ATCC 90028). We perform time‑kill kinetics to differentiate bacteriostatic vs. bactericidal activity, and post‑antibiotic effect (PAE) measurements. For hemolytic activity (critical for therapeutic safety), we use fresh human or mammalian red blood cells to determine HC₁₀, HC₅₀, and therapeutic index (HC₅₀/MIC). We also assess cytotoxicity against mammalian cell lines (HEK‑293, HepG2, HaCaT) via MTT or LDH assays. For peptide purity and identity, we use reverse‑phase HPLC (RP‑HPLC) with UV and high‑resolution mass spectrometry (HR‑MS) such as Q‑TOF or Orbitrap to quantify purity, confirm molecular weight, and detect deletions, oxidation, deamidation, or racemization. Circular dichroism (CD) spectroscopy reveals secondary structure (α‑helix, β‑sheet, random coil) in buffer, membrane‑mimetic environments (SDS, LPC, or liposomes). For aggregation propensity, we use Thioflavin T (ThT) fluorescence, dynamic light scattering (DLS), and TEM. Membrane interaction is characterized by liposome leakage assay (calcein or carboxyfluorescein release) and surface plasmon resonance (SPR) for binding kinetics to model lipid bilayers. Protease stability is tested with trypsin, chymotrypsin, pepsin, or proteinase K, using HPLC‑MS to track peptide degradation over time. Salt/pH/host matrix tolerance (e.g., serum, physiological NaCl, pH 5.5) is evaluated by MIC modulation.

Key parameters we routinely measure:
- Minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC) – range 0.03–256 µg/mL, 3‑8 replicates.
- Time‑kill curves (0–24h) – for bactericidal endpoint verification.
- Hemolysis (HC₁₀, HC₅₀) – % hemolysis vs. peptide concentration.
- Mammalian cell cytotoxicity (IC₅₀) – MTT/LDH assay.
- Peptide purity (by HPLC) – area‑% at 214/280 nm, threshold 0.1%.
- Mass confirmation and modifications (HR‑MS) – ±0.01 Da accuracy.
- Secondary structure (CD) – 190‑260 nm, in varied environments.
- Aggregation (ThT, DLS, TEM) – detect fibrils or oligomers.
- Liposome leakage (kinetics and dose‑response) – % release of encapsulated dye.
- Protease stability (half‑life t₁/₂) – by HPLC‑MS.
- Synergy testing (checkerboard assay) – FICI index with conventional antibiotics.
- Biofilm inhibition and eradication (MBEC assay) – against S. aureus, P. aeruginosa, etc.
- Resistance selection (serial passage) – 15‑30 generations to assess resistance emergence.

How Deep We Go – Mechanistic Elucidation, Membrane Partitioning, and In Vivo Mimetic Profiling

Most routine labs stop at MIC and maybe hemolysis. We provide mechanistic insight into how your AMP kills. Using fluorescence probes (Sytox Green, propidium iodide) and flow cytometry, we distinguish between membrane permeabilization and intracellular targeting. Atomic force microscopy (AFM) or cryo‑TEM visualizes pore formation or membrane disruption on bacterial envelopes. For membrane active peptides, we determine the lipid‑peptide partition coefficient (K_p) by SPR or tryptophan fluorescence quenching. We use isothermal titration calorimetry (ITC) to measure enthalpy of binding to model membranes (POPG/POPC vesicles). Our micropipette aspiration technique assesses real‑time membrane tension and pore stability. For intracellular AMPs, we use confocal microscopy with labeled peptide plus organelle trackers to localize within bacteria (e.g., nucleic acid binding, inhibition of cell wall synthesis). We also perform resistance mechanism analysis by whole‑genome sequencing of induced resistant mutants, identifying target modification or efflux pump upregulation.

We integrate physiological relevance: testing in simulated body fluids (SBF, 50% serum) to predict in vivo activity, and ex vivo skin or mucosal infection models for topical peptides. For peptide degradation product identification, we use LC‑MS/MS with database search to map cleavage sites. Our protease stability assays are performed under simulated gastrointestinal conditions (SGF, SIF) for oral peptide candidates.

Advanced capabilities include:
- Single‑cell MIC and morphological analysis (microfluidics + time‑lapse microscopy) – measure heteroresistance and real‑time response.
- Neutrophil‑like (HL‑60) or macrophage uptake and bactericidal cooperation assays – immunomodulatory assessment.
- Endotoxin neutralization (LPS binding) by LAL assay – for anti‑sepsis peptide candidates.
- Lipid bilayer electrical impedance (BLM) for pore conductance – single‑channel recording.
- Stability in relevant formulation buffers (saline, acetate, phosphate, DMSO) – HPLC‑MS over 30 days.
- Quantification of peptide binding to bacterial surfaces by flow cytometry – fluorescence‑labeled peptide.

We routinely achieve measurement uncertainties: MIC ± 1 doubling dilution; purity ±0.2% (HPLC area); mass accuracy <2 ppm; t₁/₂ (protease) ±10%. All methods follow CLSI M07‑A11, EUCAST, and ICH Q2(R1) for bioanalytical validation.

Why Choose Our Antimicrobial Peptide Testing – Key Advantages

1. ISO/IEC 17025:2017 and GLP‑compliant microbiology and bioanalytical services – all assays validated with positive/negative controls and ATCC QC strains.
2. Mechanistic depth beyond MIC – we don't just give you a number; we tell you how the peptide kills (membrane vs. intracellular, pore vs. carpet, target engagement).
3. High‑resolution mass spectrometry and CD for structural integrity – we confirm that your “pure” peptide has the correct fold, no oxidation or racemization, and does not aggregate.
4. Clinically relevant resistance and synergy profiling – checkerboard with up to 6 antibiotics, plus serial passage resistance induction to predict clinical longevity.
5. Biomimetic membrane assays (liposomes, BLM, SPR) – rank order membrane affinity and lytic efficiency without using pathogenic bacteria for early safety screening.
6. Fast turnaround with full transparency – routine MIC + hemolysis + purity (HPLC‑MS) in 5–7 business days; full mechanistic (MIC, time‑kill, CD, liposome leakage, protease stability) in 12–15 business days. You receive raw growth curves, HPLC chromatograms, mass spectra, CD traces, and microscopy images.
7. Custom development for unusual targets or novel peptides – intracellular targeting, antifungal peptides, antiviral peptides, or biofilm‑specific activity – we design and validate assays within 3–4 weeks.
8. Competitive pricing for complete AMP profiles – bundling MIC panel (10 strains), HC₅₀, purity, MS, CD, and protease stability costs 30–35% less than separate orders.

We have successfully completed over 650 antimicrobial peptide projects for biotech companies, academic drug discovery labs, and animal health companies. Our team includes PhD microbiologists, biophysicists, and mass spectrometrists with focused expertise on peptide therapeutics.

Ready to Test Your Antimicrobial Peptide?

Provide your peptide sequence (or confidential structure), target microorganisms (e.g., “MRSA, E. coli, C. albicans”), and intended application (e.g., “systemic therapeutic”, “topical”, “food preservative”). We will provide a free technical consultation and a fixed‑price quote. Whether you need early‑stage hit characterization, lead optimization support, or pre‑clinical batch release, we deliver deep, actionable, and mechanistic antimicrobial peptide testing tailored to your development pipeline.