20 Dec 2022
UC San Diego wearable device could be used for both clinical practice and research.
A 2022 survey by SPIE noted that the impact of imaging hemoglobin molecules in particular could be substantial, with the technology likely to contribute to "the decentralization of healthcare [and] the deployment of wearable technologies for self-monitoring."
Engineers at the University of California, San Diego (UCSD) have now made a new contribution to this topic, by developing a wearable electronic patch able to monitor biomolecules including hemoglobin in deep tissues. The results were published in Nature Communications.
"The amount and location of hemoglobin in the body provide critical information about blood perfusion or accumulation in specific locations," said Sheng Xu of UCSD. "Our device shows great potential in close monitoring of high-risk groups, enabling timely interventions at urgent moments."
The patch is based on photoacoustic (PA) sensing, a technique exposing hemoglobin molecules to fast laser pulses and imaging the transient ultrasound pulses that are created. PA as a hemoglobin-mapping technology and an alternative to MRI or X-ray CT has been the subject of clinical research for more than a decade.
UCSD combined PA technology with the concept of a flexible wearable patch, analogous to other currently available devices which employ electrochemical or optical sensing modalities. In particular, the team's goal was to allow sensing of molecules in deep tissues, which have a stronger correlation with metabolic processes than those near the surface typically detected by existing patches.
Reaching the visceral organs: a grand challenge
The device integrates an array of 24 high-power 850-nanometer VCSEL sources distributed in four equally spaced columns and connected in series, with 240 piezoelectric transducer detectors located between the VCSEL columns.
"An array of VCSEL diodes and piezoelectric transducers interconnected by serpentine metal electrodes are encapsulated in an elastomeric matrix," said the project in its published paper. "The high-power VCSEL diodes can generate laser pulses that penetrate more than 2 centimeters into biological tissues and activate hemoglobin molecules to generate acoustic waves."
In trials the patch was applied to tissue phantoms and ex vivo porcine tissue in which blood flow was externally pumped, before being tested in vivo on volunteer subjects, where the depth penetration was measured at 1.1 centimeters. Three-dimensional mapping of hemoglobin with a submillimeter spatial resolution was achieved in these deep tissues, according to the UCSD team.
Future work will include the use of higher power VCSELs, since detection depth is limited by the optical intensity of the illumination. The project noted that PA imaging of the human heart remains "a grand challenge in the field," due to the distance between the organ and the outer skin of the body, but higher power sources could boost the detection depth to the regions of visceral organs.
"Continuous monitoring is critical for timely interventions to prevent life-threatening conditions from worsening quickly," said UCSD's Xiangjun Chen. "Wearable devices based on electrochemistry for biomolecules detection, not limited to hemoglobin, are good candidates for long-term wearable monitoring applications."
UC San Diego: Kifaa cha kuvaa kinaweza kutumika kwa mazoezi ya kliniki na utafiti Uchunguzi wa SPIE wa mwaka 2022 ulibainisha kuwa athari za picha za molekuli za hemoglobini zinaweza kuwa kubwa, na teknolojia hiyo inaweza kuchangia "kutengwa kwa huduma za afya [na] utumiaji wa teknolojia za kuvaa kwa ajili ya kujisimamia." Wataalamu wa Chuo Kikuu cha California, San Diego (UCSD) sasa wamefanya mchango mpya kwa mada hii, kwa kuendeleza patch ya elektroniki inayoweza kuvaliwa inayoweza kufuatilia biomolecules ikiwa ni pamoja na hemoglobin katika tishu za kina. Matokeo hayo yalichapishwa katika jarida la Nature Communications. "Kupima kiasi na eneo la hemoglobini katika mwili hutoa habari muhimu kuhusu mtiririko wa damu au mkusanyiko katika maeneo maalum, ""alisema Sheng Xu wa UCSD." "Kifaa chetu kinaonyesha uwezo mkubwa katika ufuatiliaji wa karibu wa vikundi vya hatari kubwa, kuwezesha uingiliaji wa wakati unaofaa katika nyakati za dharura". "Patch hii inategemea ""photoacoustic"" sensing, mbinu ya kufunua molekuli za hemoglobini kwa pulsi za laser na kuunda picha za pulsi za ultrasound zinazopita." Utafiti wa kimatibabu wa PEA kama teknolojia ya ramani ya hemoglobini na mbadala wa MRI au CT ya X-ray umekuwa kichwa cha utafiti wa kliniki kwa zaidi ya miaka kumi. UCSD ilijumuisha teknolojia ya PA na dhana ya patch inayoweza kuvaliwa, sawa na vifaa vingine vinavyopatikana kwa sasa ambavyo hutumia njia za kuhisi za umeme au za macho. Lengo la timu hiyo ni kugundua molekuli katika tishu za ndani, ambazo zina uhusiano mkubwa na michakato ya kimetaboliki kuliko zile zilizo karibu na uso, ambazo kwa kawaida zinagunduliwa na patches zilizopo. Vifaa vya VCSEL vimeunganishwa na safu ya vyanzo vya 24 vya nguvu za juu vya 850-nanometer, vilivyopangwa katika safu nne zilizogawanywa sawa na kuunganishwa kwa mfululizo, na vifaa vya 240 vya transducer ya piezoelectric, ziko kati ya safu za VCSEL. "Mfululizo wa diodes VCSEL na transducers piezoelectric interconnected na serpentine chuma electrodes ni encapsulated katika matrix elastomeric, "alisema mradi katika karatasi yake iliyochapishwa." "Diodes za nguvu za juu za VCSEL zinaweza kuzalisha pulsi za laser ambazo huingia zaidi ya sentimeta 2 ndani ya tishu za kibiolojia na kuamsha molekuli za hemoglobini kuzalisha mawimbi ya sauti. """ Katika majaribio, patch ilitumiwa kwenye tishu ya phantom na ex vivo tishu ya nguruwe ambayo mtiririko wa damu ulipigwa nje, kabla ya kupimwa in vivo kwenye masomo ya kujitolea, ambapo upenyezaji wa kina ulipimwa kwa sentimita 1.1. Utafiti wa 3D wa hemoglobini na azimio la submillimeter la nafasi ulifikiwa katika tishu hizi za kina, kulingana na timu ya UCSD. Kazi ya baadaye itajumuisha matumizi ya nguvu ya juu ya VCSEL, kwani kina cha kugundua kinapunguzwa na nguvu ya macho ya taa. Utafiti huo ulibainisha kuwa picha za PA za moyo wa binadamu bado ni changamoto kubwa katika uwanja huo, kwa sababu ya umbali kati ya kiungo na ngozi ya nje ya mwili, lakini vyanzo vya nguvu zaidi vinaweza kuongeza kina cha kugundua kwa maeneo ya viungo vya ndani. "Ufuatiliaji wa kuendelea ni muhimu kwa uingiliaji wa wakati unaofaa ili kuzuia hali zenye kutisha maisha zisiwe mbaya haraka, "alisema Xiangjun Chen wa UCSD." "Vifaa vinavyoweza kuvaliwa vinavyotegemea electrochemistry kwa ajili ya kugundua biomolecules, sio tu kwa hemoglobin, ni wagombea wazuri kwa matumizi ya muda mrefu ya ufuatiliaji wa kuvaa".