Develop and Evaluate a Dose Calculation Strategy Using Electron Density Maps from Spectral CT

PURPOSE/OBJECTIVE(S)

The conventional method of estimating relative electron density using Hounsfield Units (HUs) is prone to errors resulting from various factors such as energy spectrum, exposure, scanner/patient conditions, etc. Specific calibration is needed for each acquisition protocol. To overcome these limitations, dual energy CT has been extensively researched for its accuracy in dose calculation using tube potential switching techniques. A dual layer design offers a different approach to acquire spectral images using single data acquisitions. This study aims to develop and evaluate a dose calculation method using electron density maps generated directly from a dual layer detector scanner.

MATERIALS/METHODS

A phantom with tissue equivalent inserts was scanned using different scanner configurations on a dual layer detector scanner. The electron density of 17 inserts ranged from 0.668 - 5.663 × 1023 m-23. The energy dependent attenuation curves were generated and translated into values of Compton and photoelectric components, which were used to calculate ED values. The ED values were compared to normal values provided by the vendor for each insert. The generated ED maps were normalized to the ED of water and used as the input for dose calculations without CT images. Dosimetry plans were generated on the phantom for two different field sizes (10 × 10 cm2 and 3 × 3 cm2) at gantry angles of 0 and 90 degrees using a 6 MV Monte Carlo engine. The dose distributions were compared between the conventional HU to ED calibration approach with CT images and the direct calculation using the calculated ED map.

RESULTS

The results showed that compared to the conventional HU to ED map, the ED map generated from spectral CT had a relative ED that was about 0.02 lower and was more uniform, with smaller standard deviations. The ED map was closer to the nominal value in low-density regions, while the HU converted ED map was closer to the nominal value in high-density regions. The dose distributions between the two ED approaches were almost identical, with a maximum deviation of around 1% for both field sizes at deeper depths.

CONCLUSION

In conclusion, a dual layer detector scanner can provide an accurate estimation of ED maps. We showed that the dose calculation using the generated ED map is highly accurate using a phantom. This method provides an alternative strategy for dose calculation that eliminates the need for HU to ED calibration and enables the use of the ED map directly.

An Aptamer-Functionalized DNA Circuit to Establish an Artificial Interaction between T Cells and Cancer Cells

Nongenetic strategies that enable control over the cell-cell interaction network would be highly desired, particularly in T cell-based cancer immunotherapy. In this work, we developed an aptamer-functionalized DNA circuit to modulate the interaction between T cells and cancer cells. This DNA circuit was composed of recognition-then-triggering and aggregation-then-activation modules. Upon recognizing target cancer cells, the triggering strand was released to induce aggregation of immune receptors on the T cell surface, leading to an enhancement of T cell activity for effective cancer eradication. Our results demonstrated the feasibility of this DNA circuit for promoting target cancer cell-directed stimulation of T cells, which, consequently, enhanced their killing effect on cancer cells. This DNA circuit, as a modular strategy to modulate intercellular interactions, could lead to a new paradigm for the development of nongenetic T cell-based immunotherapy.

Aptamer-Functionalized Nanovaccines: Targeting In Vivo DC Subsets for Enhanced Antitumor Immunity

Cancer vaccines, which directly pulsed in vivo dendritic cells (DCs) with specific antigens and immunostimulatory adjuvants, showed great potential for cancer immunoprevention. However, most of them were limited by suboptimal outcomes, mainly owing to overlooking the complex biology of DC phenotypes. Herein, based on adjuvant-induced antigen assembly, we developed aptamer-functionalized nanovaccines for in vivo DC subset-targeted codelivery of tumor-related antigens and immunostimulatory adjuvants. We chose two aptamers, iDC and CD209, and tested their performance on DC targeting. Our results verified that these aptamer-functionalized nanovaccines could specifically recognize circulating classical DCs (cDCs), a subset of DCs capable of priming naïve T cells, noting that iDC outperformed CD209 in this regard. With excellent cDC-targeting capability, the iDC-functionalized nanovaccine induced potent antitumor immunity, leading to effective inhibition of tumor occurrence and metastasis, thus providing a promising platform for cancer immunoprevention.

[Combined resection of thoracic and abdominal organ clusters: a series of 50 cases]

Objective: To examine the technique and effect of combined thoracic and abdominal organ clusters resection. Methods: From February 2019 to August 2021, totally 50 cases of combined thoracoabdominal organ cluster resection were completed at Transplant Medical Center, the Second Affiliated Hospital of Guangxi Medical University from donation after brain death donors. There were 47 males and 3 females, aging (34.8±12.3) years (range: 5 to 55 years). The length of hospital stay(M(IQR)) was 4(4) days (range: 2 to 43 days), the length of tube time was 4(2) days (range: 1 to 43 days). Through the midsternal incision and the abdominal grand cross incision, the cold perfusion was performing simultaneously when the perfusion lines of each target organ was established respectively. The combined resection was performed with the diaphragm as the boundary and the organ cluster as the unit. The heart and lung were separated on site and sent to the transplant hospital, and the abdominal organ cluster was directly preserved and returned to our hospital for further separation and repair. Results: Totaly 21 hearts, 47 pairs of lungs, 49 livers, 47 pairs of kidneys and 11 pancreas were harvested by this surgical treatment. The resection time was (32.6±6.5) minutes (range: 19 to 50 minutes), with no hot ischemia time. There was no accidental injury that affected organ quality and function. Heart transplantation was performed in 17 cases, combined heart-kidney transplantation in 2 cases, double lung transplantation in 43 cases, single lung transplantation in 6 cases, liver transplantation in 41 cases, combined liver-pancreas-duodenal cluster transplantation in 1 case, combined liver-kidney transplantation in 3 cases, combined pancreas-kidney transplantation in 9 cases, and kidney transplantation in 74 cases. Conclusion: Simultaneous perfusion and combined resection of thoracic and abdominal organ clusters for donation after brain death donors are feasible and effective.

Aptamer-Based Analysis and Manipulation of the Protein Activity in Living Cells

Directly analyzing and precisely manipulating the activity of target proteins without altering their natural structure and expression would be essential to decoding many protein-dominant cellular processes. To meet this goal, we used streptavidin as the carrier to develop an aptamer-based nanoplatform for monitoring the activation process of specific proteins in living cells. Our results showed that this nanoplatform could efficiently enter the cellular cytoplasm and specifically report the presence of RelA in the activated state. Meanwhile, with incorporation of a photoresponsive module, this aptamer-based nanoplatform was able to manipulate the nuclear translocation behavior of active RelA, enabling control over related downstream signaling events.

Photolytic Removal of Red Blood Cell Membranes Camouflaged on Nanoparticles for Enhanced Cellular Uptake and Combined Chemo-Photodynamic Inhibition of Cancer Cells

Biomimetic therapeutics offer great potential for drug delivery that avoids immune recognition. However, the coated cell membrane usually hinders the cellular uptake of nanoparticles; thus, structure-changeable formulations have attracted increasing attention. Herein, we report photolytic pyropheophorbide a (PA)-inserted red blood cell (RBC) membrane-camouflaged curcumin dimeric prodrug (CUR₂-TK)-poly(lactic-co-glycolic acid) (PLGA) nanoparticles [(CUR₂-TK)-PLGA@RBC-PA] for enhanced cancer therapy. In these nanoparticles, the inner core was constructed using PLGA and loaded with our synthesized reactive oxygen species (ROS)-responsive cleavable curcumin dimeric prodrug (CUR₂-TK). The nanoparticles generated ROS in response to the light irradiation attributed to the incorporated PA. The ROS further triggered the lysis of the cell membrane and exposed the nanoparticles for enhanced tumor cellular uptake, and the ROS also cleaved CUR₂-TK for controlled CUR drug release. Moreover, the ROS performed photodynamic therapy (PDT). The chemotherapy and PDT produced a combined effect in the treatment of cancer cells, thus enhancing anticancer therapeutic efficacy.

Metal-organic frameworks for virus detection

Virus severely endangers human life and health, and the detection of viruses is essential for the prevention and treatment of associated diseases. Metal-organic framework (MOF), a novel hybrid porous material which is bridged by the metal clusters and organic linkers, has become a promising biosensor platform for virus detection due to its outstanding properties including high surface area, adjustable pore size, easy modification, etc. However, the MOF-based sensing platforms for virus detection are rarely summarized. This review systematically divided the detection platforms into nucleic acid and immunological (antigen and antibody) detection, and the underlying sensing mechanisms were interpreted. The nucleic acid sensing was discussed based on the properties of MOF (such as metal ion, functional group, geometry structure, size, porosity, stability, etc.), revealing the relationship between the sensing performance and properties of MOF. Moreover, antibodies sensing based on the fluorescence detection and antigens sensing based on molecular imprinting or electrochemical immunoassay were highlighted. Furthermore, the remaining challenges and future development of MOF for virus detection were further discussed and proposed. This review will provide valuable references for the construction of sophisticated sensing platform for the detection of viruses, especially the 2019 coronavirus.

Aptamer-Based Targeted Drug Delivery Systems: Current Potential and Challenges

Aptamers are single-stranded DNA or RNA with 20-100 nucleotides in length that can specifically bind to target molecules via formed three-dimensional structures. These innovative targeting molecules have attracted an increasing interest in the biomedical field. Compared to traditional protein antibodies, aptamers have several advantages, such as small size, high binding affinity, specificity, good biocompatibility, high stability and low immunogenicity, which all contribute to their wide application in the biomedical field. Aptamers can bind to the receptors on the cell membrane and mediate themselves or conjugated nanoparticles to enter into cells. Therefore, aptamers can be served as ideal targeting ligands for drug delivery. Since their excellent properties, different aptamer-mediated drug delivery systems had been developed for cancer therapy. This review provides a brief overview of recent advances in drug delivery systems based on aptamers. The advantages, challenges and future prospectives are also discussed.

Aptamer-Pyropheophorbide a Conjugates with Tumor Spheroid Targeting and Penetration Abilities for Photodynamic Therapy

Pyropheophorbide a (Pyro) is a widely used photosensitizer for photodynamic therapy (PDT). However, poor water solubility, aggregation-induced fluorescence quenching, and lack of selectivity to targeted cells seriously limit its application. In this work, we prepared aptamer-Pyro conjugates (APCs) by linking Pyro to hydrophilic nucleic acid aptamer to enhance its water solubility and endow it with protein tyrosine kinase 7 (PTK7) overexpressed tumor spheroid specific targeting and penetration abilities for photodynamic therapy. The molecular conjugate was successfully synthesized and dissolved well in an aqueous solution. The APCs showed strong near-infrared fluorescence in the aqueous solution and produced singlet oxygen both in the solution and cells under laser irradiation, indicating its generation of singlet oxygen during PDT was guaranteed. Owing to the cancer cell targeting ability of the aptamer, the APCs specifically bound with PTK7 overexpressed cancerous cells and showed fluorescence signal for tumor cell imaging and diagnosis. The APCs exhibited favorable enhanced phototoxicity to target tumor cells compared with control cells. More importantly, due to the small size of the molecular conjugate, the APCs efficiently penetrated into the interior of multicellular tumor spheroids (MCTS) and caused cell damage. All these results indicated that the robust aptamer-Pyro conjugate is a promising selective tumor-targeting and penetrable molecule for cancer photodynamic therapy.

Dynamic DNA Assemblies in Biomedical Applications

Deoxyribonucleic acid (DNA) has been widely used to construct homogeneous structures with increasing complexity for biological and biomedical applications due to their powerful functionalities. Especially, dynamic DNA assemblies (DDAs) have demonstrated the ability to simulate molecular motions and fluctuations in bionic systems. DDAs, including DNA robots, DNA probes, DNA nanochannels, DNA templates, etc., can perform structural transformations or predictable behaviors in response to corresponding stimuli and show potential in the fields of single molecule sensing, drug delivery, molecular assembly, etc. A wave of exploration of the principles in designing and usage of DDAs has occurred, however, knowledge on these concepts is still limited. Although some previous reviews have been reported, systematic and detailed reviews are rare. To achieve a better understanding of the mechanisms in DDAs, herein, the recent progress on the fundamental principles regarding DDAs and their applications are summarized. The relative assembly principles and computer-aided software for their designing are introduced. The advantages and disadvantages of each software are discussed. The motional mechanisms of the DDAs are classified into exogenous and endogenous stimuli-triggered responses. The special dynamic behaviors of DDAs in biomedical applications are also summarized. Moreover, the current challenges and future directions of DDAs are proposed.

Tumor microenvironment and NIR laser dual-responsive release of berberine 9-O-pyrazole alkyl derivative loaded in graphene oxide nanosheets for chemo-photothermal synergetic cancer therapy

A berberine 9-O-pyrazole alkyl derivative, a chemical compound (called B3) previously synthesized by our group, shows anti-cancer activity. However, B3 lacks targeting cytotoxicity to cancer cells, leading to obvious toxic side effects on normal cells. To solve this problem, here, we prepared a drug delivery system, namely, AS1411-GO/B3 for tumor targeting, in which nano-graphene oxide (GO) sheets were employed as the drug carrier, and the aptamer AS1411 was conjugated onto GO for tumor targeting. GO also had a photothermal effect, which helped the release of B3 from GO as well as the thermal cytotoxicity to cells. We found that the release of B3 could respond to acid conditions, indicating that the tumor intracellular environment could promote the release of B3, thus allowing it to perform chemotherapy effects. This system could also release B3 in response to photothermal heating, moreover, combined photothermal therapy and chemotherapy to improve the anticancer activity was achieved. This AS1411-GO/B3 platform with chemo-photothermal synergetic therapy provides a very promising treatment for tumors.

Technical Note: Evaluation of the systematic accuracy of a frameless, multiple image modality guided, linear accelerator based stereotactic radiosurgery system

PURPOSE

To evaluate the total systematic accuracy of a frameless, image guided stereotactic radiosurgery system.

METHODS

The localization accuracy and intermodality difference was determined by delivering radiation to an end-to-end prototype phantom, in which the targets were localized using optical surface monitoring system (OSMS), electromagnetic beacon-based tracking (Calypso®), cone-beam CT, "snap-shot" planar x-ray imaging, and a robotic couch. Six IMRT plans with jaw tracking and a flattening filter free beam were used to study the dosimetric accuracy for intracranial and spinal stereotactic radiosurgery treatment.

RESULTS

End-to-end localization accuracy of the system evaluated with the end-to-end phantom was 0.5 ± 0.2 mm with a maximum deviation of 0.9 mm over 90 measurements (including jaw, MLC, and cone measurements for both auto and manual fusion) for single isocenter, single target treatment, 0.6 ± 0.4 mm for multitarget treatment with shared isocenter. Residual setup errors were within 0.1 mm for OSMS, and 0.3 mm for Calypso. Dosimetric evaluation based on absolute film dosimetry showed greater than 90% pass rate for all cases using a gamma criteria of 3%/1 mm.

CONCLUSIONS

The authors' experience demonstrates that the localization accuracy of the frameless image-guided system is comparable to robotic or invasive frame based radiosurgery systems.

[Epidemic profile of mumps in China during 2004-2013]

OBJECTIVE

To analyze the epidemiological characteristics of mumps in China from 2004 to 2013.

METHODS

Data of mump cases occurring between 2004 and 2013 were gathered from the national notifiable disease reporting system in China (excluding Hong Kong, Macao, and Taiwan); only cases classified as "final card" , laboratory confirmed, or clinical diagnosis were included. Descriptive epidemiology techniques were used to analyze features of sex, age, trends over time, and geography.

RESULTS

Average incidence of mumps between 2004 to 2013 was 24.20/100 000. Peaks were in 2011 and 2012, with incidence 33.9/100 000 (454 385/1.340 million) and 35.6/100 000 (479 518/1.347 million). Two seasonal peaks occurred regularly in years, one from April to July in the first year, and the other from November to January in the next year. During the study period, provinces with the highest incidence were Ningxia, Tibet, Xinjiang, and Guangxi; incidences were 72.1/100 000 (4 425/6.13 million), 48.5/100 000 (1 396/3 million), 51.7/100 000 (10 887/21.04 million), and 40.8/100 000 (19 179/46.99 million), respectively. Guangdong (28 078), Sichuan (21 924), Guangxi (21 616), and Zhejiang (20 000) provinces reported the highest number of mumps cases. Beijing, Tianjin, and Shanghai showed a consistently low incidence. Mumps cases occurred primarily among children aged 5-9 years, with incidence ranging from 118.2/100 000 to 281.4/100 000. In 2004-2008, the peak age was 6-8 years (174.1/100 000) and in 2009-2013, peak age was 5-7 years (234.5/100 000).

CONCLUSION

The highest incidences of mumps in China were reported in 2011 and 2012, with children of school age constituting the majority of cases.