Jianjun Cheng

Reversible Cell‐Specific Drug Delivery with Aptamer‐Functionalized Liposomes

cis-Diamminedichloroplatinum(II) (cisplatin) is a potent chemotherapeutic agent for the treatment of a broad range of cancerous tumors. 2] Despite its excellent antitumor efficacy, the major drawbacks of cisplatin include its lack of tumor specificity and severe side effects. In addition, certain tumor-cell types develop resistance to cisplatin from exposure to the drug. Strategies that allow the delivery of cisplatin specifically to tumor cells are highly desirable. Several strategies have been reported for the delivery of cisplatin specifically to tumor sites, the most common of which is to use antibody (Ab) recognition against different cell-surface targets. The binding of Abs to the cell-membrane receptors triggers receptor-mediated endocytosis, with the result of improved therapeutic efficacy. Despite this success, the use of Abs as cell-specific homing agents poses significant challenges. Ab conjugations are difficult to control and typically show poor site specificity for the conjugation and inconsistent binding affinity. The antibody-based drugdelivery system also tends to be immunogenic, so it requires extra humanization steps, which make it more difficult for clinical application. Nucleic acid based aptamers provide excellent alternatives to antibodies as cell-specific agents. They are singlestranded oligonucleotides identified through an in vitro selection process, termed system evolution of ligands by exponential enrichment (SELEX), to bind the target molecules selectively. 12] Many aptamers identified by SELEX have nearly identical binding affinity and specificity to those of Abs. Aptamers are much easier to prepare and to scale up. They are generally considered nonimmunogenic and can be gradually degraded by nucleases and cleared from the blood to cause minimal system toxicity. Functionalizations of aptamers to facilitate site-specific conjugation are also straightforward. Thus, aptamers are promising targeting ligands and have been used in targeted drug-delivery systems, most of which are block-copolymer nanoparticles. Although these new nanotechnology-based platforms look promising, the clinical benefit of nanoparticles for targeted cancer therapy is yet to be demonstrated. Liposomes are by far the most successful drug-delivery systems; a number of liposome-based systems have been approved by the US Food and Drug Administration for disease treatment in the clinic. Liposomes have been shown to increase the plasma residence time of aptamers. Previous efforts on liposomal drug delivery have focused on developing long-circulating liposomes that target cancerous tumor tissues through the enhanced permeation and retention (EPR) effect, 34] a passive targeting mechanism. However, cancer targeting entirely based on EPR still has undesirable systemic side effects and suboptimal antitumor efficacy: clinical studies of a cisplatin-containing liposome showed only poor to moderate therapeutic efficacy. 38] Delivery vehicles with active tumor-targeting capability could, in principle, improve this significantly. Personalized chemotherapy is an unmet challenge in cancer treatment. Despite the existence of rough empirical dosage guidelines, the individual patient response can deviate strongly from average behavior. This problem is especially acute for chemotherapy agents, for which drug overdosage can have severe consequences. At present, once an initial dosage is administered, the side effects and drug effectiveness can no longer be modulated if there are no “antidotes” to the treatment. However, the discovery of good antidotes or neutralizers for each individual drug molecule is not an easy task, if even practical. Moreover, there are no known ways to “multiplex” different antidotes to control complex treatment profiles with multiple drugs. We report here the controlled formulation of aptamerconjugated, cisplatin-encapsulating multifunctional liposomes. Cancer-cell-specific targeting and drug delivery are demonstrated by using this delivery platform. Furthermore, we also show for the first time that a complementary DNA (cDNA) of the aptamer can function as an antidote to disrupt [*] R. Tong, A. Mishra, Prof. G. C. L. Wong, Prof. J. Cheng, Prof. Y. Lu Department of Materials Science and Engineering University of Illinois at Urbana-Champaign 1304 W. Green Street, Urbana, IL 61801 (USA) Fax: (+ 1)217-333-2736 E-mail: gclwong@illinois.edu jianjunc@illinois.edu Homepage: http://www.matse.illinois.edu/faculty/wong/profile.html http://www.matse.illinois.edu/faculty/cheng/profile.html Dr. Z. Cao, W. Xu, Prof. Y. Lu Department of Chemistry University of Illinois at Urbana-Champaign 600 S. Mathews Avenue, Urbana, IL 61801 (USA) Fax: (+ 1)217-244-3186 E-mail: yi-lu@illinois.eduyi-lu@illinois.edu Homepage: http://www.chemistry.illinois.edu/faculty/Yi_Lu.html [] Z.C. and R.T. contributed equally to this work.

Anticancer Polymeric Nanomedicines

Polymers play important roles in the design of delivery nanocarriers for cancer therapies. Polymeric nanocarriers with anticancer drugs conjugated or encapsulated, also known as polymeric nanomedicines, form a variety of different architectures including polymer‐drug conjugates, micelles, nanospheres, nanogels, vesicles, and dendrimers. This review focuses on the current state of the preclinical and clinical investigations of polymer‐drug conjugates and polymeric micelles. Recent progress achieved in some promising fields, such as site‐specific protein conjugation, pH‐sensitive polymer‐drug conjugates, polymer nanoparticles for targeted cancer therapy, stimuli‐responsive polymeric micelles, polymeric vesicles, and dendrimer‐based anticancer nanomedicines, will be highlighted.

Dynamic urea bond for the design of reversible and self-healing polymers

Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-ureas) capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials.

Bioresorbable silicon electronic sensors for the brain

Many procedures in modern clinical medicine rely on the use of electronic implants in treating conditions that range from acute coronary events to traumatic injury. However, standard permanent electronic hardware acts as a nidus for infection: bacteria form biofilms along percutaneous wires, or seed haematogenously, with the potential to migrate within the body and to provoke immune-mediated pathological tissue reactions. The associated surgical retrieval procedures, meanwhile, subject patients to the distress associated with re-operation and expose them to additional complications. Here, we report materials, device architectures, integration strategies, and in vivo demonstrations in rats of implantable, multifunctional silicon sensors for the brain, for which all of the constituent materials naturally resorb via hydrolysis and/or metabolic action, eliminating the need for extraction. Continuous monitoring of intracranial pressure and temperature illustrates functionality essential to the treatment of traumatic brain injury; the measurement performance of our resorbable devices compares favourably with that of non-resorbable clinical standards. In our experiments, insulated percutaneous wires connect to an externally mounted, miniaturized wireless potentiostat for data transmission. In a separate set-up, we connect a sensor to an implanted (but only partially resorbable) data-communication system, proving the principle that there is no need for any percutaneous wiring. The devices can be adapted to sense fluid flow, motion, pH or thermal characteristics, in formats that are compatible with the body’s abdomen and extremities, as well as the deep brain, suggesting that the sensors might meet many needs in clinical medicine.

Translocation of HIV TAT peptide and analogues induced by multiplexed membrane and cytoskeletal interactions

Cell-penetrating peptides (CPPs), such as the HIV TAT peptide, are able to translocate across cellular membranes efficiently. A number of mechanisms, from direct entry to various endocytotic mechanisms (both receptor independent and receptor dependent), have been observed but how these specific amino acid sequences accomplish these effects is unknown. We show how CPP sequences can multiplex interactions with the membrane, the actin cytoskeleton, and cell-surface receptors to facilitate different translocation pathways under different conditions. Using “nunchuck” CPPs, we demonstrate that CPPs permeabilize membranes by generating topologically active saddle-splay (“negative Gaussian”) membrane curvature through multidentate hydrogen bonding of lipid head groups. This requirement for negative Gaussian curvature constrains but underdetermines the amino acid content of CPPs. We observe that in most CPP sequences decreasing arginine content is offset by a simultaneous increase in lysine and hydrophobic content. Moreover, by densely organizing cationic residues while satisfying the above constraint, TAT peptide is able to combine cytoskeletal remodeling activity with membrane translocation activity. We show that the TAT peptide can induce structural changes reminiscent of macropinocytosis in actin-encapsulated giant vesicles without receptors.

Investigating the optimal size of anticancer nanomedicine

Significance Understanding the interdependency of physiochemical properties of nanomedicine (NM) in correlation to its biological response and function is crucial for additional development of anticancer NM. Here, we prepared monodisperse drug–silica nanoconjugates in three distinct sizes (20, 50, and 200 nm) with other physiochemical properties controlled to be identical to investigate size-dependent biodistribution, tumor tissue penetration and clearance, and anticancer efficacy in various tumor models. We also developed a mathematical model of the spatiotemporal distribution of NM within a tumor to gain insight into the size-dependent interaction with tumor. Our studies show clear evidence that there is an optimal size of anticancer NM and that NM with the optimal size has the highest tumor retention integrated over time. Nanomedicines (NMs) offer new solutions for cancer diagnosis and therapy. However, extension of progression-free interval and overall survival time achieved by Food and Drug Administration-approved NMs remain modest. To develop next generation NMs to achieve superior anticancer activities, it is crucial to investigate and understand the correlation between the physicochemical properties of NMs (particle size in particular) and their interactions with biological systems to establish criteria for NM optimization. Here, we systematically evaluated the size-dependent biological profiles of three monodisperse drug–silica nanoconjugates (NCs; 20, 50, and 200 nm) through both experiments and mathematical modeling and aimed to identify the optimal size for the most effective anticancer drug delivery. Among the three NCs investigated, the 50-nm NC shows the highest tumor tissue retention integrated over time, which is the collective outcome of deep tumor tissue penetration and efficient cancer cell internalization as well as slow tumor clearance, and thus, the highest efficacy against both primary and metastatic tumors in vivo.

Spatiotemporal controlled delivery of nanoparticles to injured vasculature.

There are a number of challenges associated with designing nanoparticles for medical applications. We define two challenges here: (i) conventional targeting against up-regulated cell surface antigens is limited by heterogeneity in expression, and (ii) previous studies suggest that the optimal size of nanoparticles designed for systemic delivery is approximately 50–150 nm, yet this size range confers a high surface area-to-volume ratio, which results in fast diffusive drug release. Here, we achieve spatial control by biopanning a phage library to discover materials that target abundant vascular antigens exposed in disease. Next, we achieve temporal control by designing 60-nm hybrid nanoparticles with a lipid shell interface surrounding a polymer core, which is loaded with slow-eluting conjugates of paclitaxel for controlled ester hydrolysis and drug release over approximately 12 days. The nanoparticles inhibited human aortic smooth muscle cell proliferation in vitro and showed greater in vivo vascular retention during percutaneous angioplasty over nontargeted controls. This nanoparticle technology may potentially be used toward the treatment of injured vasculature, a clinical problem of primary importance.

Protein corona significantly reduces active targeting yield

When nanoparticles (NPs) are exposed to the biological environment, their surfaces become covered with proteins and biomolecules (e.g. lipids). Here, we report that this protein coating, or corona, reduces the targeting capability of surface engineered NPs by screening the active sites of the targeting ligands.

Reversible three-state switching of multicolor fluorescence emission by multiple stimuli modulated FRET processes within thermoresponsive polymeric micelles

toachieve nanoscale control and accurate location of chromo-phores, leading to the modulation of luminescence efficiencythrough the enhancement or restriction of fluorescenceresonance energy transfer (FRET) processes. In view of themicroenvironment complexity in certain bio-applicationssuch as imaging, biosensing, and clinical diagnosis, it ishighly desirable to combine the concept of external stimuli-triggered activation/deactivation of specific emitting fluoro-phores to achieve higher temporal and spatial detectionresolution. Although thereare a few examples of luminescentpolymeric assemblies and nanoparticles exhibiting two-stateswitching of luminescence,

Preclinical efficacy of the camptothecin-polymer conjugate IT-101 in multiple cancer models.

Preclinical efficacy of i.v. IT-101, a nanoparticulate conjugate of 20(S)-camptothecin and a cyclodextrin-based polymer, was investigated in several mouse xenografts. The effects of different multiple dosing schedules on tumor growth of LS174T colon carcinoma xenografts are elucidated. All multiple dosing schedules administered over 15 to 19 days resulted in enhanced efficacy compared with untreated or single-dose groups. Further improvements in antitumor efficacy were not observed when the dosing frequency was increased from three weekly doses to five doses at 4-day intervals or 5 days of daily dosing followed by 2 days without dosing repeated in three cycles using similar cumulative doses. This observation was attributed to the extended release characteristics of camptothecin from the polymer. Antitumor efficacy was further evaluated in mice bearing six different s.c. xenografts (LS174T and HT29 colorectal cancer, H1299 non–small-cell lung cancer, H69 small-cell lung cancer, Panc-1 pancreatic cancer, and MDA-MB-231 breast cancer) and one disseminated xenograft (TC71-luc Ewings sarcoma). In all cases, a single treatment cycle of three weekly doses of IT-101 resulted in a significant antitumor effect. Complete tumor regression was observed in all animals bearing H1299 tumors and in the majority of animals with disseminated Ewings sarcoma tumors. Importantly, IT-101 is effective in a number of tumors that are resistant to treatment with irinotecan (MDA-MB-231, Panc-1, and HT29), consistent with the hypothesis that polymeric drug conjugates may be able to overcome certain kinds of multidrug resistance. Taken together, these results indicate that IT-101 has good tolerability and antitumor activity against a wide range of tumors.