Multicomponent Injectable Hydrogels for Antigen-Specific Tolerogenic Immune Modulation.

Biomaterial scaffolds that enrich and modulate immune cells in situ can form the basis for potent immunotherapies to elicit immunity or reëstablish tolerance. Here, the authors explore the potential of an injectable, porous hydrogel to induce a regulatory T cell (Treg) response by delivering a peptide antigen to dendritic cells in a noninflammatory context. Two methods are described for delivering the BDC peptide from pore-forming alginate gels in the nonobese diabetic mouse model of type 1 diabetes: encapsulation in poly(lactide-co-glycolide) (PLG) microparticles, or direct conjugation to the alginate polymer.

Click-Crosslinked Injectable Gelatin Hydrogels.

Injectable gelatin hydrogels formed with bioorthogonal click chemistry (ClickGel) are cell-responsive ECM mimics for in vitro and in vivo biomaterials applications. Gelatin polymers with pendant norbornene (GelN) or tetrazine (GelT) groups can quickly and spontaneously crosslink upon mixing, allowing for high viability of encapsulated cells, establishment of 3D elongated cell morphologies, and biodegradation when injected in vivo.

Vaccines Combined with Immune Checkpoint Antibodies Promote Cytotoxic T-cell Activity and Tumor Eradication.

We demonstrate that a poly(lactide-co-glycolide) (PLG) cancer vaccine can be used in combination with immune checkpoint antibodies, anti-CTLA-4 or anti-PD-1, to enhance cytotoxic T-cell (CTL) activity and induce the regression of solid B16 tumors in mice. Combination therapy obviated the need for vaccine boosting and significantly skewed intratumoral reactions toward CTL activity, resulting in the regression of B16 tumors up to 50 mm(2) in size and 75% survival rates. These data suggest that combining material-based cancer vaccines with checkpoint antibodies has the potential to mediate tumor regression in humans.

Injectable cryogel-based whole-cell cancer vaccines.

A biomaterial-based vaccination system that uses minimal extracorporeal manipulation could provide in situ enhancement of dendritic cell (DC) numbers, a physical space where DCs interface with transplanted tumour cells, and an immunogenic context. Here we encapsulate GM-CSF, serving as a DC enhancement factor, and CpG ODN, serving as a DC activating factor, into sponge-like macroporous cryogels. These cryogels are injected subcutaneously into mice to localize transplanted tumour cells and deliver immunomodulatory factors in a controlled spatio-temporal manner.

Injectable, spontaneously assembling, inorganic scaffolds modulate immune cells in vivo and increase vaccine efficacy.

Implanting materials in the body to program host immune cells is a promising alternative to transplantation of cells manipulated ex vivo to direct an immune response, but doing so requires a surgical procedure. Here we demonstrate that high-aspect-ratio, mesoporous silica rods (MSRs) injected with a needle spontaneously assemble in vivo to form macroporous structures that provide a 3D cellular microenvironment for host immune cells. In mice, substantial numbers of dendritic cells are recruited to the pores between the scaffold rods.

Local delivery of VEGF and SDF enhances endothelial progenitor cell recruitment and resultant recovery from ischemia.

Biomaterials may improve outcomes of endothelial progenitor-based therapies for the treatment of ischemic cardiovascular disease, due to their ability to direct cell behavior. We hypothesized that local, sustained delivery of exogenous vascular endothelial growth factor (VEGF) and stromal cell-derived factor (SDF) from alginate hydrogels could increase recruitment of systemically infused endothelial progenitors to ischemic tissue, and subsequent neovascularization. VEGF and SDF were found to enhance in vitro adhesion and migration of outgrowth endothelial cells (OECs) and circulating angiogenic cells (CACs), two populations of endothelial progenitors, by twofold to sixfold, and nearly doubled recruitment to both ischemic and nonischemic muscle tissue in vivo.

Refilling drug delivery depots through the blood.

Local drug delivery depots have significant clinical utility, but there is currently no noninvasive technique to refill these systems once their payload is exhausted. Inspired by the ability of nanotherapeutics to target specific tissues, we hypothesized that blood-borne drug payloads could be modified to home to and refill hydrogel drug delivery systems. To address this possibility, hydrogels were modified with oligodeoxynucleotides (ODNs) that provide a target for drug payloads in the form of free alginate strands carrying complementary ODNs.

Comparison of biomaterial delivery vehicles for improving acute retention of stem cells in the infarcted heart.

Cell delivery to the infarcted heart has emerged as a promising therapy, but is limited by very low acute retention and engraftment of cells. The objective of this study was to compare a panel of biomaterials to evaluate if acute retention can be improved with a biomaterial carrier. Cells were quantified post-implantation in a rat myocardial infarct model in five groups (n = 7-8); saline injection (current clinical standard), two injectable hydrogels (alginate, chitosan/β-glycerophosphate (chitosan/ß-GP)) and two epicardial patches (alginate, collagen).

Identification of immune factors regulating antitumor immunity using polymeric vaccines with multiple adjuvants.

The innate cellular and molecular components required to mediate effective vaccination against weak tumor-associated antigens remain unclear. In this study, we used polymeric cancer vaccines incorporating different classes of adjuvants to induce tumor protection, to identify dendritic cell (DC) subsets and cytokines critical to this efficacy. Three-dimensional, porous polymer matrices loaded with tumor lysates and presenting distinct combinations of granulocyte macrophage colony-stimulating factor (GM-CSF) and various Toll-like receptor (TLR) agonists affected 70% to 90% prophylactic tumor protection in B16-F10 melanoma models.

Injectable, porous, and cell-responsive gelatin cryogels.

The performance of biomaterials-based therapies can be hindered by complications associated with surgical implant, motivating the development of materials systems that allow minimally invasive introduction into the host. In this study, we created cell-adhesive and degradable gelatin scaffolds that could be injected through a conventional needle while maintaining a predefined geometry and architecture. These scaffolds supported attachment, proliferation, and survival of cells in vitro and could be degraded by recombinant matrix metalloproteinase-2 and -9.

Noninvasive imaging reveals inhibition of ovarian cancer by targeting CXCL12-CXCR4.

Patients with metastatic ovarian cancer continue to have a dismal prognosis, emphasizing the need for new strategies to identify and develop new molecular targets for therapy. Chemokine CXCL12 and its receptor CXCR4 are upregulated in metastatic ovarian cancer cells and the intraperitoneal tumor microenvironment. CXCL12-CXCR4 signaling promotes multiple steps in proliferation and dissemination of ovarian cancer cells, suggesting that targeted inhibition of this pathway will limit tumor progression.

Secreted CXCL12 (SDF-1) forms dimers under physiological conditions.

Chemokine CXCL12 (CXC chemokine ligand 12) signalling through CXCR (CXC chemokine receptor) 4 and CXCR7 has essential functions in development and underlies diseases including cancer, atherosclerosis and autoimmunity. Chemokines may form homodimers that regulate receptor binding and signalling, but previous studies with synthetic CXCL12 have produced conflicting evidence for homodimerization. We used bioluminescence imaging with GL (Gaussia luciferase) fusions to investigate dimerization of CXCL12 secreted from mammalian cells.

In vivo imaging of ligand receptor binding with Gaussia luciferase complementation.

Studies of ligand-receptor binding and the development of receptor antagonists would benefit greatly from imaging techniques that translate directly from cell-based assays to living animals. We used Gaussia luciferase protein fragment complementation to quantify the binding of chemokine (C-X-C motif) ligand 12 (CXCL12) to chemokine (C-X-C motif) receptor 4 (CXCR4) and CXCR7. Studies established that small-molecule inhibitors of CXCR4 or CXCR7 specifically blocked CXCL12 binding in cell-based assays and revealed differences in kinetics of inhibiting chemokine binding to each receptor.

Resident workload, pager communications, and quality of care.

With the recent regulations limiting resident work hours, it has become more important to understand how residents spend their time. The volume and content of the pages they receive provide a valuable source of information that give insight into their workload and help identify inefficiencies in hospital communication. We hypothesized that above a certain workload threshold, paging data would suggest breakdowns in communication and implications for quality of care.

Effects of smoking on survival for patients with end-stage liver disease.

Background: Smokers with chronic liver disease can become eligible for transplantation, but some insurers refuse reimbursement pending smoking cessation.

Study Design: Our hypothesis is that liver transplantation candidates and recipients who smoke have inferior survival compared with nonsmokers. Using a retrospective cohort study design, three Cox proportional hazards models were constructed to determine covariate-adjusted mortality from transplantation evaluation and transplantation based on smoking status at evaluation, transplantation, and posttransplantation followup.