Serum-Free B27/Neurobasal Neuronal Maintenance Culture

• Neurobasal medium with B27 supplement is the core serum-free maintenance medium for primary neuronal culture;
• Published protocols commonly add L-glutamine or GlutaMAX, and some protocols include glutamate only during early plating or early culture.

• Papain or trypsin can be used for enzymatic dissociation of embryonic or neonatal neural tissue, and poly-D-lysine, poly-L-lysine, laminin, Matrigel, PuraMatrix, or glial feeder/sandwich supports have been used as attachment or survival-support substrates depending on the protocol and cell density.

• Neuronal identity and culture purity have been assessed with neuron-specific markers including neurofilament 200, neuron-specific enolase, MAP2, βIII-tubulin, and NeuN;
• Glial contamination has been assessed with GFAP;
• Dopaminergic phenotype has been assessed with tyrosine hydroxylase;
• Synaptic maturation has been assessed with synaptophysin, GluR1, GABA_Aβ, and NMDA-R1 immunoreactivity.

• Reported culture workflows use sterile dissection instruments, cell-culture plates or glass coverslips, incubators for mammalian cell culture, phase-contrast microscopy for morphology, fluorescence microscopy for immunocytochemistry, and, when functional maturation is evaluated, patch-clamp recording, calcium imaging, or microelectrode arrays.

• Prepare dissociated neurons from the reported source tissue only within the validated model range: embryonic rat hippocampus, cortex, striatum, substantia nigra, septum, fetal hindbrain, neonatal dentate gyrus, neonatal cerebellum, or similar published rodent neuronal preparations;
• Avoid extrapolating unsupported tissue ages or species-specific parameters.

• Coat the culture surface with a published neuronal attachment support such as poly-D-lysine/poly-L-lysine with or without laminin, Matrigel, PuraMatrix, or a glial feeder/sandwich configuration;
• Low-density cultures are particularly dependent on coverslip overlay, sandwich culture, three-dimensional support, or trophic support from feeder layers.

• Prepare maintenance medium as Neurobasal plus B27 with glutamine or GlutaMAX when reported;
• For low-density long-term rat hippocampal cultures, Neurobasal/B27/L-glutamine combined with PuraMatrix and a sandwich coverslip supported cultures for >2 months without a glial feeder layer.

• Dissect target neural tissue, remove non-target tissue, enzymatically dissociate the tissue with papain or trypsin as reported, gently triturate to generate a single-cell suspension, and plate cells onto the prepared substrate in serum-free Neurobasal/B27-based medium or in a protocol-specific short initial plating condition followed by transfer to serum-free Neurobasal/B27.

• Use plating densities supported by the literature rather than arbitrary density choices: Brewer et al. reported B27/Neurobasal hippocampal neuron survival above 60% at ≥160 cells/mm² and >90% 4-week viability at 640 cells/mm², while lower-density systems required coverslip overlay, sandwich culture, PuraMatrix, or glial feeder support.

• Maintain cultures in serum-free Neurobasal/B27-based medium for days to weeks depending on the experimental endpoint;
• Published endpoints include 4-day survival assays, 10-day fetal hindbrain differentiation, 2-week dopaminergic phenotype maintenance, 3-week cortical/hippocampal neuronal branching, 4-week hippocampal/cortical survival, and >2-month low-density hippocampal culture under PuraMatrix sandwich conditions.

• Assess culture success by phase-contrast morphology, neuronal marker immunostaining, glial marker immunostaining, survival or viability measurements, neurite length or branching, and, where relevant, synaptic marker staining, calcium imaging, patch-clamp recording, or microelectrode-array activity.

• Use biological replicates from independent dissections or culture preparations when reported, compare serum-free B27/Neurobasal cultures with literature-relevant controls such as serum-containing medium, MEM-based medium, glial feeder or no-feeder conditions, or alternative defined supplements, and interpret reduced survival at low density as a condition-dependent limitation rather than a universal failure of the medium.

Low survival in sparse cultures:

Published work shows that isolated neurons below common plating-density thresholds have lower survival unless additional local trophic support or physical overlay is provided.
Solution
Increase plating density within the validated range, add a coverslip overlay, use sandwich culture, or use PuraMatrix-based sandwich support when using low-density hippocampal neurons.

Excess glial expansion:

Serum-containing medium promotes glial proliferation in neuronal cultures.
Solution
Maintain neurons in serum-free Neurobasal/B27-based conditions when the goal is neuron-enriched culture, because Brewer et al. reported <0.5% glial growth under optimized B27/Neurobasal conditions.

Poor reproducibility between B27-based cultures:

Defined supplements can vary in neuronal support, and NS21 work attributed much of the variability to albumin source and transferrin form.
Solution
Use a consistent supplement lot or consider a published defined alternative such as NS21 when supplement variability is experimentally problematic.

B27/Neurobasal is unsuitable for oxidative-stress experiments:

B27/Neurobasal contains antioxidant components that can interfere with free-radical injury studies.
Solution
Use a published alternative such as the NM-2 mixture when the study specifically requires reduced antioxidant influence while retaining neuronal survival and low glial proliferation.