Measurement of Blood Dilution during Lancet-Free Blood Sampling.

In this paper, we report on a fluorescent and colorimetric system for measuring the dilution of capillary blood released by a needle-free jet injector. Jet injection uses a high-speed liquid jet to penetrate tissue, and in the process can release capillary blood that can be collected for performing blood tests. In this way, blood sampling can be performed without the use of a lancet. However, any injectate that mixes with the collected blood dilutes the sample and may significantly impact subsequent analyses. By adding the fluorescent marker indocyanine green to the injected liquid, the fraction of injectate mixed into the collected blood can be measured. The incorporation of colorimetry allows our system to also correct for the impact of hematocrit on fluorescence. The results from this system show that it can determine the dilution of blood that has been diluted by up to 10 %, the upper limit of dilution typically observed in lancet-free blood sampling via jet injection.Clinical Relevance- Blood samples can be collected by jet injection without significant dilution, avoiding the need for lancing.

Minimally invasive capillary blood sampling methods.

INTRODUCTION: Whole blood samples, including arterial, venous, and capillary blood, are regularly used for disease diagnosis and monitoring. The global Covid-19 pandemic has highlighted the need for a more resilient screening capacity. Minimally invasive sampling techniques, such as capillary blood sampling, are routinely used for point of care testing in the home healthcare setting and clinical settings such as the Intensive Care Unit with less pain and wounding than conventional venepuncture. AREAS COVERED: In this manuscript, we aim to provide a overview of state-of-the-art of techniques for obtaining samples of capillary blood. We first review both established and novel methods for releasing blood from capillaries in the skin. Next, we provide a comparison of different capillary blood sampling methods based on their mechanism, testing site, puncture size, cost, wound geometry, healing, and perceptions of pain. Finally, we overview established and new methods for enhancing capillary blood collection. EXPERT OPINION: We expect that microneedles will prove to be a preferred option for paediatric blood collection. The ability of microneedles to collect a capillary blood sample without pain will improve paediatric healthcare outcomes. Jet injection may prove to be a useful method for facilitating both blood collection and drug delivery.