The paper-based immunoassay for point-of-care diagnostics is widely used due to its low cost and portability over traditional lab-based assays. Lateral-flow immunoassay (LFA) is the most well-established paper-based assay since it is rapid and easy to use. However, the disadvantage of LFA is its lack of sensitivity in some cases where a large sample volume is required, limiting its use as a diagnostic tool. To improve the sensitivity of LFA, we previously reported on the concentration of analytes into one of the two bulk phases of an aqueous two-phase system (ATPS) prior to detection. In this study, we preserved the advantages of LFA while significantly improving upon our previous proof-of-concept studies by employing a novel approach of concentrating gold nanoparticles, a common LFA colorimetric indicator. By conjugating specific antibodies and polymers to the surfaces of the particles, these gold nanoprobes (GNPs) were able to capture target proteins in the sample and subsequently be concentrated within 10 min at the interface of an ATPS solution comprised of polyethylene glycol, potassium phosphate, and phosphate-buffered saline. These GNPs were then extracted and applied directly to LFA. By combining this prior ATPS interface extraction with LFA, the detection limit of LFA for a model protein was improved by 100-fold from 1 ng/μL to 0.01 ng/μL. Additionally, we examined the behavior of the ATPS system in fetal bovine serum and synthetic urine to more closely approach real-world applications. Despite using more complex matrices, ATPS interface extraction still improved the detection limit by 100-fold within 15 to 25 min, demonstrating the system’s potential to be applied to patient samples.

We previously investigated the intracellular trafficking properties of our novel poly(L-glutamate)60-b-poly(L-leucine)20 (E60L20) vesicles (EL vesicles) conjugated to transferrin (Tf). In this study, we expand upon our previous work by investigating the drug encapsulation, release, and efficacy properties of our novel EL vesicles for the first time. After polyethylene glycol (PEG) was conjugated to the vesicles for steric stability, doxorubicin (DOX) was successfully encapsulated in the vesicles using a modified pH-ammonium sulfate gradient method. Tf was subsequently conjugated to the vesicles to provide active targeting to cancer cells and a mode of internalization into the cells. These Tfconjugated, DOX-loaded, PEGylated EL (Tf-DPEL) vesicles exhibited colloidal stability and were within the allowable size range for passive and active targeting. A mathematical model was then derived to predict drug release from the Tf-DPEL vesicles by considering diffusive and convective mass transfer of DOX. Our mathematical model reasonably predicted our experimentally measured release profile with no fitted parameters, suggesting that the model could be used in the future to manipulate drug carrier properties to alter drug release profiles. Finally, an in vitro cytotoxicity assay was used to demonstrate that the Tf-DPEL vesicles exhibited enhanced drug carrier efficacy in comparison to its non-targeted counterpart. We are grateful for the insightful comments from the reviewers, and have addressed all of the concerns. A detailed summary of our responses to the comments has been uploaded as the "Lee et al Response to Reviewers" file. IJP AUTHOR CHECKLISTDear Author, It frequently happens that on receipt of an article for publication, we find that certain elements of the manuscript, or related information, is missing. This is regrettable of course since it means there will be a delay in processing the article while we obtain the missing details.In order to avoid such delays in the publication of your article, if accepted, could you please run through the list of items below and make sure you have completed the items. Note that the text bolded in blue represents text that has been added to our original document, and text bolded in red with the strikethrough represents text that has been removed. Overall Manuscript Details Reviewer 11. In the Introduction (Line 55), the author claimed that the commercial DOX liposome technology has limitations, such as instability and short circulation half-life of the vesicles in the body. But this manuscript did not contain any in vitro and in vivo stability data about the Tf-DPEL, such as stability in PBS buffer or plasma. The detailed data of Tf-DPEL should be added in.We thank the reviewer for this point regarding vesicle stability. We have removed this line from the Introduction as this was not within the scope of this paper. Introduction (Line 52-56)DOXIL® is currently FDA approved for treating Kaposi's sarcoma and recurrent ovarian cancer, and is under clinical trials for ...