Radionuclide-functionalized drug delivery vehicles capable of being imaged via positron emission tomography (PET) are of increasing interest in the biomedical field as they can reveal the in vivo behavior of encapsulated therapeutics with high sensitivity. However, the majority of current PET-guided theranostic agents suffer from poor retention of radiometal over time, low drug loading capacities, and time-limited PET imaging capability. To overcome these challenges, we have developed hollow microcapsules with a thin (<100 nm) multilayer shell as advanced theranostic delivery systems for multiday PET tracking in vivo. The 3 μm capsules were fabricated via the aqueous multilayer assembly of a natural antioxidant, tannic acid (TA), and a poly(N-vinylpyrrolidone) (PVPON) copolymer containing monomer units functionalized with deferoxamine (DFO) to chelate the 89 Zr radionuclide, which has a half-life of 3.3 days. We have found using radiochromatography that (TA/PVPON-DFO) 6 capsules retained on average 17% more 89 Zr than their (TA/PVPON) 6 counterparts, which suggests that the covalent attachment of the DFO to PVPON provides stable 89 Zr chelation. In vivo PET imaging studies performed in mice demonstrated that excellent stability and imaging contrast were still present 7 days postinjection. Animal biodistribution analyses showed that capsules primarily accumulated in the spleen, liver, and lungs with negligible accumulation in the femur, with the latter confirming the stable binding of the radiotracer to the capsule walls. The application of therapeutic ultrasound (US) (60 s of 20 kHz US at 120 W cm −2 ) to Zr-functionalized capsules could release the hydrophilic anticancer drug doxorubicin from the capsules in the therapeutic amounts. Polymeric capsules with the capability of extended in vivo PET-based tracking and US-induced drug release provide an advanced platform for development of precisiontargeted therapeutic carriers and could aid in the development of more effective drug delivery systems.

Nucleic acid therapeutics have the potential to be the most effective disease treatment strategy due to their intrinsic precision and selectivity for coding highly specific biological processes. However, freely administered nucleic acids of any type are quickly destroyed or rendered inert by a host of defense mechanisms in the body. In this work, we address the challenge of using nucleic acids as drugs by preparing stimuli responsive poly(methacrylic acid)/poly(N-vinylpyrrolidone) (PMAA/PVPON)n multilayer hydrogel capsules loaded with ~7 kDa G-quadruplex DNA. The capsules are shown to release their DNA cargo on demand in response to both enzymatic and ultrasound (US)-triggered degradation. The unique structure adopted by the G-quadruplex is essential to its biological function and we show that the controlled release from the microcapsules preserves the basket conformation of the oligonucleotide used in our studies. We also show that the (PMAA/PVPON) multilayer hydrogel capsules can encapsulate and release ~450 kDa double stranded DNA. The encapsulation and release approaches for both oligonucleotides in multilayer hydrogel microcapsules developed here can be applied to create methodologies for new therapeutic strategies involving the controlled delivery of sensitive biomolecules. Our study provides a promising methodology for the design of effective carriers for DNA vaccines and medicines for a wide range of immunotherapies, cancer therapy and/or tissue regeneration therapies in the future.

We developed a multipart laboratory experiment on the synthesis of freestanding hydrogels for junior to senior undergraduate students. In this experiment series that runs over the course of multiple 3-h lab periods, small everyday objects belonging to the students are reproduced as hydrogels by first creating negative templates in thermally cured poly(dimethylsiloxane) molds (PDMS), followed by simultaneous photopolymerization and cross-linking using N-vinylpyrrolidone and poly(ethylene glycol) diacrylate in the molds. After being cured at room temperature, the molds are bisected and the objects are recovered. Second, the students optimize the synthesis of poly(N-vinylpyrrolidone)/ poly(ethylene glycol) diacrylate (PVPON/PEGDA) hydrogels via UV-induced polymerization in test-batch scale quartered Petri dishes. Next, using the optimized hydrogel synthesis and the molds from part one, PVPON/PEGDA replicas of their objects are obtained by simultaneous photopolymerization and cross-linking in a UV cross-linking device. Finally, students present their results, methodology, and proposals for industrial scaleup to the class. The students are encouraged by steady progress toward their goal of making a freestanding hydrogel replica of their object and applying their knowledge toward developing a reproduceable protocol. They learn to control synthetic parameters including mixing ratios, polymerization time, and UV intensity as well as readjusting their synthesis procedure based on their understanding of structure−property concepts. This experience provides students with an introduction to polymer synthesis and methodologies familiar to both academic research and industry, which builds confidence in their ability to conduct independent research and development.