{"id":6638,"date":"2026-07-09T11:27:59","date_gmt":"2026-07-09T15:27:59","guid":{"rendered":"https:\/\/neoaptamers.com\/?p=6638"},"modified":"2026-07-09T11:34:27","modified_gmt":"2026-07-09T15:34:27","slug":"kd-is-not-the-same-as-lod","status":"publish","type":"post","link":"https:\/\/neoaptamers.com\/fr\/kd-is-not-the-same-as-lod\/","title":{"rendered":"KD is not the same as LOD"},"content":{"rendered":"<p>In Biosensors, K<sub>D<\/sub> is not the same as LOD. Clients often ask if is it possible to obtain a limit of detection (LOD) for a target that is lower than the K<sub>D<\/sub> of the probe. The answer is yes, here we explain why.<\/p>\n<p>Let\u2019s say that the desired LOD for a target is 1 nM. This means that we need to be able to detect the presence of the target when it is present in a sample at this concentration. Let\u2019s consider this from the target\u2019s perspective, what proportion of a target at a concentration of 1 nM is bound by probes that have varying binding affinities?<\/p>\n<p>The figure below provides the binding trajectories for an aptamer binding to 1 nM target for varying K<sub>D<\/sub> values of the aptamer with 100 nM of aptamer immobilized on the biosensor.<\/p>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone wp-image-6642\" src=\"https:\/\/neoaptamers.com\/wp-content\/uploads\/2026\/07\/KD-binding-curve4.png\" alt=\"\" width=\"563\" height=\"478\" srcset=\"https:\/\/neoaptamers.com\/wp-content\/uploads\/2026\/07\/KD-binding-curve4.png 848w, https:\/\/neoaptamers.com\/wp-content\/uploads\/2026\/07\/KD-binding-curve4-300x255.png 300w, https:\/\/neoaptamers.com\/wp-content\/uploads\/2026\/07\/KD-binding-curve4-768x652.png 768w, https:\/\/neoaptamers.com\/wp-content\/uploads\/2026\/07\/KD-binding-curve4-14x12.png 14w\" sizes=\"(max-width: 563px) 100vw, 563px\" \/><\/p>\n<p>There are several things to note with this result:<\/p>\n<p>1 ) Equilibrium is achieved relatively rapidly, more rapidly the weaker the aptamer binds to the target.<\/p>\n<p>2) At a K<sub>D <\/sub>equivalent to the LOD (1e-9) almost 100% of the target is bound. At a K<sub>D<\/sub> 100X weaker (1e-7) 50% of the target is bound.<\/p>\n<p>The difference described in point 2 above sounds significant, but to understand sensitivity we need to flip the perspective from the target to the aptamer. It is the aptamer that we are relying on for signal not the target. We need to be able to distinguish the signal provided by the aptamer\/target complex in the presence of 1 nM target versus the absence of this signal in the absence of target. From this perspective we can rewrite point 2 above as follows:<\/p>\n<p>3) At a K<sub>D<\/sub> equivalent to the LOD (1e-9), 1% of the aptamer present in the sensor is complexed with target and providing a signal. At a K<sub>D <\/sub>100X weaker (1e-7) ,0.5% of the aptamer present in the sensor is providing a signal.<\/p>\n<p>When the problem is considered as described in point 3 the difference in binding affinity is not as large. This clearly shows that the basis of the LOD is much more heavily influenced by the sensitivity of the signal that the aptamer\/target complex provides. The binding affinity of the aptamer matters but the signal measured by the biosensor matters much more.<\/p>","protected":false},"excerpt":{"rendered":"<p>In Biosensors, KD is not the same as LOD. Clients often ask if is it possible to obtain a limit of detection (LOD) for a target that is lower than the KD of the probe. The answer is yes, here we explain why. Let\u2019s say that the desired LOD for a target is 1 nM.&hellip;&nbsp;<a href=\"https:\/\/neoaptamers.com\/fr\/kd-is-not-the-same-as-lod\/\" rel=\"bookmark\">Lire la suite &raquo;<span class=\"screen-reader-text\">KD is not the same as LOD<\/span><\/a><\/p>","protected":false},"author":1,"featured_media":6644,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"neve_meta_sidebar":"","neve_meta_container":"","neve_meta_enable_content_width":"off","neve_meta_content_width":70,"neve_meta_title_alignment":"","neve_meta_author_avatar":"","neve_post_elements_order":"","neve_meta_disable_header":"","neve_meta_disable_footer":"","neve_meta_disable_title":"","footnotes":""},"categories":[44],"tags":[45],"class_list":["post-6638","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-biosensors","tag-biosensors"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.9 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>KD is not the same as LOD<\/title>\n<meta name=\"description\" content=\"In Biosensors, KD is not the same as LOD. Clients often ask if is it possible to obtain a limit of detection (LOD) for a target that is lower than the KD\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/neoaptamers.com\/fr\/kd-is-not-the-same-as-lod\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"KD is not the same as LOD\" \/>\n<meta property=\"og:description\" content=\"In Biosensors, KD is not the same as LOD. Clients often ask if is it possible to obtain a limit of detection (LOD) for a target that is lower than the KD\" \/>\n<meta property=\"og:url\" content=\"https:\/\/neoaptamers.com\/fr\/kd-is-not-the-same-as-lod\/\" \/>\n<meta property=\"og:site_name\" content=\"neoaptamers\" \/>\n<meta property=\"article:published_time\" content=\"2026-07-09T15:27:59+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-07-09T15:34:27+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/neoaptamers.com\/wp-content\/uploads\/2026\/07\/KD-LOD-post-for-website.png\" \/>\n\t<meta property=\"og:image:width\" content=\"930\" \/>\n\t<meta property=\"og:image:height\" content=\"630\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"partyinfrance\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u00c9crit par\" \/>\n\t<meta name=\"twitter:data1\" content=\"partyinfrance\" \/>\n\t<meta name=\"twitter:label2\" content=\"Dur\u00e9e de lecture estim\u00e9e\" \/>\n\t<meta name=\"twitter:data2\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/neoaptamers.com\\\/kd-is-not-the-same-as-lod\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/neoaptamers.com\\\/kd-is-not-the-same-as-lod\\\/\"},\"author\":{\"name\":\"partyinfrance\",\"@id\":\"https:\\\/\\\/neoaptamers.com\\\/#\\\/schema\\\/person\\\/34934951075d3d931c9216ed7f568fe6\"},\"headline\":\"KD is not the same as LOD\",\"datePublished\":\"2026-07-09T15:27:59+00:00\",\"dateModified\":\"2026-07-09T15:34:27+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/neoaptamers.com\\\/kd-is-not-the-same-as-lod\\\/\"},\"wordCount\":374,\"publisher\":{\"@id\":\"https:\\\/\\\/neoaptamers.com\\\/#organization\"},\"image\":{\"@id\":\"https:\\\/\\\/neoaptamers.com\\\/kd-is-not-the-same-as-lod\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/neoaptamers.com\\\/wp-content\\\/uploads\\\/2026\\\/07\\\/KD-LOD-post-for-website.png\",\"keywords\":[\"Biosensors\"],\"articleSection\":[\"Biosensors\"],\"inLanguage\":\"fr-FR\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/neoaptamers.com\\\/kd-is-not-the-same-as-lod\\\/\",\"url\":\"https:\\\/\\\/neoaptamers.com\\\/kd-is-not-the-same-as-lod\\\/\",\"name\":\"KD is not the same as LOD\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/neoaptamers.com\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/neoaptamers.com\\\/kd-is-not-the-same-as-lod\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/neoaptamers.com\\\/kd-is-not-the-same-as-lod\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/neoaptamers.com\\\/wp-content\\\/uploads\\\/2026\\\/07\\\/KD-LOD-post-for-website.png\",\"datePublished\":\"2026-07-09T15:27:59+00:00\",\"dateModified\":\"2026-07-09T15:34:27+00:00\",\"description\":\"In Biosensors, KD is not the same as LOD. 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