Abstract 627: Custom Vectra® Polaris™ fluorescent multiplex IHC panel identifies mature tertiary lymphoid structures in colorectal cancer

Introduction: Tertiary lymphoid structures (TLS) are promising prognostic indicators of positive outcomes for patients with solid tumors including colorectal cancer (CRC) [1]. Large-scale retrospective analysis shows patients with mature TLS in particular respond to PD-1/PD-L1 antibody treatment with improved objective response, progression-free and overall survival [2]. Since not all patients respond to PD-1/PD-L1 antibody treatment, identifying patients with mature TLS is clinically relevant as it enables selection of patients likely to respond to immune checkpoint blockade. Mature TLS are composed of T cells (CD3+), follicular B cells (CD20+), germinal center B cells (CD23+), and follicular dendritic cells (CD21+) [3]. The ability to identify and evaluate TLS is limited by detection methods which traditionally employ hematoxylin and eosin (H&E) staining for visual quantification of immune aggregates, potentially significantly underestimating their quantity [4]. Multiplexed fluorescent immunohistochemistry (IHC) detection assays have the capability to precisely quantify mature TLS within the TME. Colorectal cancer specimens expressing a dynamic range of TLS are stained with a novel custom Vectra® Polaris™ multiplex immunofluorescence panel detecting CD20, CD21, CD23, CD3 and pan-cytokeratin. Identification of mature TLS with CD3+CD20+CD21+ and CD3+CD20+CD23+ expression in the TME is reported.

Results: Vectra® Polaris™ TLS multiplex immunofluorescence panel successfully identified mature TLS in the TME of colorectal cancer patient samples. TLS were quantified via custom analytics algorithms generated with Indica HALO software.

Conclusion: Characteristics of TME immunity in colorectal cancer differentially impact an individual patient’s odds of survival [5]. The novel Vectra® Polaris™ multiplex assay in this study shows a detailed picture of mature TLS in patient cancer samples. Future applications of this panel include investigations of TLS associated with successful anti-tumor immune development and therapeutic response to treatment. [1] Oncoimmunology. 2020; 9(1): 1724763 [2] Nat Cancer. 2, 794-802 (2021) [3] Oncoimmunology. 2021; 10(1): 1900508. [4] Mod Pathol 2017 Sep;30(9):1204-1212. doi: 10.1038/modpathol.2017.43. [5] Cell. 2020 Sep 3;182(5):1341-1359.e19. doi: 10.1016/j.cell.2020.07.005

Citation Format: Sara G. Pollan, Arezoo Hanifi, James Hargrove, Erinn A. Parnell, Jessica Lin, Josette William Ragheb, Qingyan Au. Custom Vectra® Polaris™ fluorescent multiplex IHC panel identifies mature tertiary lymphoid structures in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 627.

Stability of two-dimensional potential flows using bicomplex numbers

The use of the complex velocity potential and the complex velocity is widely disseminated in the study of two-dimensional incompressible potential flows. The advantages of working with complex analytical functions made this representation of the flow ubiquitous in the field of theoretical aerodynamics. However, this representation is not usually employed in linear stability studies, where the representation of the velocity as real vectors is preferred by most authors, in order to allow the representation of the perturbation as the complex exponential function. Some of the classical attempts to use the complex velocity potential in stability studies suffer from formal errors. In this work, we present a framework that reconciles these two complex representations using bicomplex numbers. This framework is applied to the stability of the von Kármán vortex street and a generalized formula is found. It is shown that the classical results of the symmetric and staggered von Kármán vortex streets are just particular cases of the generalized dynamical system in bicomplex formulation.

51 A novel cross-site analysis of Vectra® Polaris™ multiplex fluorescence PD-1/PD-L1 immunohistochemistry on colorectal cancer with high and low microsatellite instability

Background

Colorectal cancer (CRC) is the third most diagnosed cancer in the United States with a projected 52,980 deaths in 2021.1 Microsatellite instability-high (MSI-H) CRCs with deficiencies in mismatch repair (MMR) are significantly associated with positive response to immunotherapy and improved outcomes when treated with immune checkpoint inhibitors. Programmed cell death ligand-1 (PD-L1) is an effective biomarker of MSI-H status to identify CRC patients who will respond to treatment, however, reproducible quantification of programmed cell death receptor-1 (PD-1)/PD-L1 in the tumor microenvironment (TME) across laboratory sites has been under-reported.2–3 In this study, our group directly addressed this issue by interrogating PD-1/PD-L1 cross-site at Akoya Biosciences and NeoGenomics Laboratories by employing the MOTiF™ PD-1/PD-L1 Panel kit along with the Vectra Polaris imaging system.

Methods

Serial sections from 40 CRC samples with known MSI status were stained at Akoya and NeoGenomics Laboratories using a modified MOTiF PD-1/PD-L1 Lung Panel Kit on the Leica BOND RX. Sections were scanned using the Vectra Polaris imaging system at both sites. Inter-site staining reproducibility was assessed using image analysis algorithms developed with inForm tissue analysis software. Cell counts and densities were calculated using the R-script package PhenoptrReports and correlations were plotted per marker.

Results

The average signal intensity for all markers/Opal fluorophores was within the recommended ranges of 10–30 normalized counts, with the exception of Polaris 780, which has an advised range of 1–10. This indicates the protocol stained successfully and reproducibly across all serial sections at both sites. Inter-site concordance analysis of cell densities for each marker yielded an average R2 value of ≥0.70. H-Score of PD-L1 quantified at the cell membrane trended with MSI status (stable/high).

Conclusions

This study demonstrated that the MOTiF PD-1/PD-L1 Panel kit imaged in conjunction with the Vectra Polaris is not only a reliable assay that can be run across different sites, based on the concordant cross-site data, but that re-optimization of the kit allows for the assay panel to be successfully adapted to other cancers, such as CRC, which can then capture biological differences across a multitude of samples.

References

American Cancer Society https://www.cancer.org/cancer/colon-rectal-cancer/about/key-statistics.html

Yi M, Jiao D, Xu H, Liu Q, Zhao W, Han X, et al. Biomarkers for predicting efficacy of PD-1/PD-L1 inhibitors. Mol Cancer 2018;17(1):129

Lemery S, Keegan P, Pazdur R. First FDA approval agnostic of cancer site - when a biomarker defines the indication. N Engl J Med 2017;377(15):1409–12.

Abstract 434: Characterizing viral mRNA and immuno-protein expression in head and neck squamous cell carcinoma using a novel automated RNAscope™/Polaris™ integrated assay

Background: Chronic viral infection can generate inflammatory microenvironments leading to neoplastic growth and cancer development. Cancer patients with chronic viral infection have been shown to exhibit worse outcomes compared to non-infected individuals. One such cohort, head and neck squamous cell carcinoma (HNSCC) patients infected with chronic human cytomegalovirus (CMV), have increased risk of death when receiving radiotherapy or radiochemotherapy. This is clinically significant as HNSCC already carries a high mortality rate and low response to surgery and chemotherapeutic treatment. The ability to detect and localize viral infection and immune response in the same patient tissues has been historically under-developed and may assist in stratifying patients for therapeutic intervention.

Methods: Immune infiltrate to tumor in CMV infected and non-infected samples was assessed in HNSCC patient tissue using RNAscope in-situ hybridization (ISH) probe to detect CMV mRNA and Vectra® Polaris™ automated multiplex protein detection of CD8, PD-L1, CD68 and panCK with OPAL dyes.

Results: We developed a novel automated RNAscope™/Vectra® Polaris™ integrated multiplex immunofluorescence (IF) assay with OPAL detection and quantification of signal using Indica HALO® algorithms. The results include quantitative and reproducible RNAscope fluorescent ISH counting, cell-by-cell expression profiles, multiplex protein quantification and whole-slide image analysis.

Conclusion: NeoGenomics Laboratories RNAscope™/Polaris™ integrated assay detects and quantifies CMV viral infection and protein expression of PD-L1 positive and negative cytotoxic T cells and macrophages within and adjacent to HNSCC tumor regions.

Citation Format: Sara Pollan, Arezoo Hanifi, Mate Nagy, Nicholas Stavrou, Erinn Parnell, Maricel Gozo, Nickolas Attanasio, Josette William, Qingyan Au. Characterizing viral mRNA and immuno-protein expression in head and neck squamous cell carcinoma using a novel automated RNAscope™/Polaris™ integrated assay [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 434.

Abstract 2143: Profiling exhausted T cells using Vectra® Polaris™multiplex immunofluorescence assay in HNSCC

Background: Head and neck squamous cell carcinoma (HNSCC) is a cancer with the ability to modulate the immune system to evade detection. It is the sixth most frequently diagnosed cancer with 550,000 new cases and 300,000 lives lost worldwide per year. New treatments for HNSCC are urgently needed as patients continue to experience a high mortality rate and low response to surgery and chemotherapeutic treatments. Part of the reason why HNSCC is difficult to treat is it upregulates the expression of immune-checkpoint signaling molecule TIGIT (T cell immunoreceptor with Ig and ITIM domains) to inhibit T cell activation in vivo. Emerging evidence shows TIGIT overexpression in the CD8+ and CD4+ T cells that infiltrate the tumor cells of HNSCC patients. TIGIT expression is also associated with up-regulation of immune-checkpoint ligands PD-1 (programmed cell death protein 1) and LAG-3 (lymphocyte-activation gene 3 aka CD223), markers of T-cell exhaustion. Altogether, activation of the TIGIT/PD-1/LAG-3 axis correlates with an immunosuppressive microenvironment as well as cancer development and progression. Although there is ample evidence that the upregulation of TIGIT decreases the immune response in HNSCC, only limited studies have been published that address the location, expression and co-expression of TIGIT, LAG-3 and PD-1 in the HNSCC microenvironment.

Methods: In this study, we sought to establish a robust report of immune cells in the tissue of patients with HNSCC. Using Vectra Polaris multiplex immunofluorescence (IF) assays, we studied T-cell exhaustion and T-cell expression in HNSCC patient tissue using a total of 9 markers essential in cancer immunology. Sequential tissue sections were stained in two panels of 6, an exhausted T cell panel comprised of TIGIT, PD-1, LAG-3, panCK, CD4 and CD8 and a T cell panel including CD3, FOXP3, CD45RO, panCK, CD4 and CD8.

Results: Multiplexing IF staining revealed a HNSCC histologic landscape characteristic of immune suppression in this study. The data demonstrated abundant T cells with TIGIT overexpression in the tissue microenvironment of HNSCC samples. Using Indica Halo algorithms, we quantified exhausted T cells (TIGIT+PD1+LAG3+CD4+CD3+, TIGIT+PD1+LAG3+CD8+CD3+), T helper cells (CD3+CD4+), T cytotoxic cells (CD3+CD8+), T regulatory cells (CD3+CD4+FoxP3), memory T-cells (CD3+CD4+CD45RO) and anergic T-cells (PD1+CD8+) within the tumor and the stromal regions.

Conclusion: Currently AB154, a fully humanized immunoglobulin G1 monoclonal antibody targeting human TIGIT is in phase I clinical trials in HNSCC patients and BGB-A1217, an anti-TIGIT monoclonal antibody in combination with anti-PD-1 monoclonal antibody Tislelizumab is in a Phase 1/1b clinical trial in patients with advanced solid tumors. The Vectra Polaris imaging reported in this study identifies T cell composition in the tumor microenvironment of patients facing high mortality.

Citation Format: Sara Pollan, Arezoo Hanifi, Mate Nagy, Nicholas Stavrou, Erinn Parnell, Maricel Gozo, Nickolas Attanasio, Josette William, Qingyan Au. Profiling exhausted T cells using Vectra® Polaris™multiplex immunofluorescence assay in HNSCC [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2143.

Abstract 497: Characterization of TIGIT expression using MultiOmyxTM hyperplexed immunofluorescence assay in solid tumors

TIGIT (T cell immunoreceptor with Ig and ITIM domains) is a recently identified immune-receptor that is expressed on T cells, natural killer (NK) cells and NKT cells. TIGIT has emerged as an important coinhibitory receptor. TIGIT expression on CD8+ tumor infiltrating lymphocytes (TILs) has been shown to be upregulated in solid cancers such as melanoma, colon cancer, and NSCLC and have been associated with a dysfunctional phenotype in TILs. TIGIT can also be activated on a subset of Regulatory T cells (Tregs) and may be critical in driving CD8+ T cell dysfunction. A second mechanism in which TIGIT inhibits immunosurveillance is through both competition and direct inhibition of CD226, impairing its ability to activate immunosurveillance. TIGIT has also been reported to inhibit T cell responses indirectly by triggering CD155 expression in dendritic cells (DCs), thereby preventing DC maturation. These findings render the TIGIT pathway as an attractive candidate for cancer immunotherapy In this study, we seek to use MultiOmyx hyperplexed immunofluorescence (IF) assay to exploit this new pathway and characterize the TIGIT expression in a total of 20 melanoma and NSCLC samples. The cancer FFPE slides will be stained with a 13-marker panel including TIGIT, CD226, CD155, CD3, CD4, CD8, FOXP3, CD56, CD45, CD11b, CD11c, PD1, LAG3, TIM3 and PanCK. This panel will enable the detection of TIGIT, CD226 and CD115 expression in the Melanoma and NSCLC samples. The TIGIT expression will be further characterized on different TILs including CD4+ helper T cells, CD8+ cytotoxic T cells, Tregs and NK cells. Using the MultiOmyx proprietary algorithm, we can quantify different subtypes of TIGIT expressing cells and measure the distance of different TIGIT expressing cells to the tumor. Increased expression of TIGIT and PD1 has been demonstrated in NSCLC and melanoma. Moreover, TIGIT+ Tregs have been reported to upregulate TIM-3 expression in mice tumor models. In this study, we will also evaluate the expression of TIGIT in conjunction with other coinhibitory receptors such as PD1, LAG3 and TIM3. The percentage of TILs that co-express TIGIT/PD1, TIGIT/LAG3 and TIGIT/TIM3 will be quantified and analyzed. Leveraging TIGIT in combination with other immune therapy may achieve more robust clinical outcomes. There are currently multiple phase I clinical trials using TIGIT monoclonal antibody (for instance, BMS-986207 by Bristol-Myers Squibb and MTIG7192A by Genetech) in combination with anti PD1/PDL1 antibodies in solid tumors. Our data can help provide more insight into how TIGIT modulate antitumor immunity in melanoma and NSCLC tumors. And the findings in this study can also be used to understand the synergistic effects between TIGIT and other coinhibitory receptors and help identify the additional opportunity for combination immunotherapy using checkpoint inhibitors.

Citation Format: Qingyan Au, Arezoo Hanifi, Erinn Parnell, Judy Kuo, Eric Leones, Flora Sahafi, Kathy Pham, RaghavKrishna Padmanabhan, Nicholas Hoe, Josette William. Characterization of TIGIT expression using MultiOmyxTM hyperplexed immunofluorescence assay in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 497.

Abstract 2256: Efficient large-scale cell classification and analysis for MultiOmyxTMassays: A deep learning approach

Traditional immunohistochemistry (IHC) techniques utilize one slide per biomarker. When clinical samples are precious and the number of serial sections is limited, comprehensive biomarker profiling becomes difficult with IHC. MultiOmyx is a proprietary, multiplexing methodology capable of staining up to 60 biomarkers on the same slide. The output of the assay enables quantitative profiling of tissues at a single cell level. The assay generates data for millions of cells with billions of queryable data points. To detect and classify cells efficiently at this large scale, we developed an image analysis framework using Deep Learning. Our framework consists of seven major steps: (1) manual annotation of a small subset of the nuclear staining channel (DAPI); (2) training of a fully convolutional neural network [1] on this annotation-set to generate a feature map identifying cell centers; (3) application of the trained network in (2) on the nuclear stain (DAPI) of the entire dataset to delineate individual cells; (4) manual annotation of a small subset of each of the other biomarker channels; (5) training of a convolutional neural network on these annotation-sets for binary classification of each of the biomarkers; (6) application of these classifiers to the entire dataset; (7) combination of the binary classification results to identify phenotypes of interest. For our output, we provide both visual label maps and classification summary tables for individual and co-localized biomarkers at the region of interest level and the entire slide level. In addition, combining the phenotype and location information allows us to visualize complex spatial relationships in the tissue.

The benefits of using this Deep Learning framework are greatly felt through increased time efficiency without a loss in accuracy, when compared to more traditional computer vision methods requiring high levels of parameter fine-tuning. For future work, we plan on fully automating the approach as more manual annotation-sets are generated.

Citation Format: Mate L. Nagy, Arezoo Hanifi, Ahalya Tirupsur, Geoffrey Wong, Jun Fang, Nicholas Hoe, Qingyan Au, Raghav K. Padmanabhan. Efficient large-scale cell classification and analysis for MultiOmyxTMassays: A deep learning approach [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2256.

Evaluation of Bacillus subtilis R0179 on gastrointestinal viability and general wellness: a randomised, double-blind, placebo-controlled trial in healthy adults

A probiotic formulation of Enterococcus faecium R0026 and Bacillus subtilis R0179 has been evaluated in previous clinical trials. However, B. subtilis R0179 has not been evaluated as a single probiotic strain or in combination with other strains at doses higher than 0.1×109 cfu. To establish oral dose-response tolerance and gastrointestinal (GI) viability of B. subtilis R0179, a randomised, double-blind, placebo-controlled trial in healthy adults (n=81; 18-50 years old) was conducted. Participants received B. subtilis R0179 at 0.1, 1.0 or 10×109 cfu/capsule/day or placebo for four weeks. General wellness was assessed using a daily questionnaire evaluating GI, cephalic, ear-nose-throat, behavioural, emetic, and epidermal symptoms. GI symptoms were further evaluated using a weekly gastrointestinal symptom rating scale (GSRS). GI transit viability of B. subtilis R0179 was assessed by plating and microbiota analysis by 16S rRNA at baseline, week 4 of the intervention and washout. General wellness and GI function were not affected by oral consumption of B. subtilis R0179 at any dose. Daily questionnaire syndrome scores were not different from baseline and did not exceed a clinically significant score of 1. GSRS syndrome scores were not different from baseline and ranged from 1.1±0.1 to 1.9±0.2. Faecal viable counts of B. subtilis R0179 demonstrated a dose response: the placebo group (1.1±0.1 log10 cfu/g) differed from 0.1×109 (4.6±0.1 log10 cfu/g), 1×109 (5.6±0.1 log10 cfu/g) and 10×109 (6.4±0.1 log10 cfu/g) (P<0.0001). No significant changes in phyla were observed, but sequence reads binned to multiple operational taxonomic units matching closest to Ruminococci increased during probiotic supplementation. B. subtilis R0179 survives passage through the human GI tract and is well tolerated by healthy adults at intakes from 0.1 to 10×109 cfu/day. The trial has been registered at www.clinicaltrials.gov under NCT01802151.

Unstable flow structures in the Blasius boundary layer

Finite amplitude coherent structures with a reflection symmetry in the spanwise direction of a parallel boundary layer flow are reported together with a preliminary analysis of their stability. The search for the solutions is based on the self-sustaining process originally described by Waleffe (Phys. Fluids 9, 883 (1997)). This requires adding a body force to the Navier-Stokes equations; to locate a relevant nonlinear solution it is necessary to perform a continuation in the nonlinear regime and parameter space in order to render the body force of vanishing amplitude. Some states computed display a spanwise spacing between streaks of the same length scale as turbulence flow structures observed in experiments (S.K. Robinson, Ann. Rev. Fluid Mech. 23, 601 (1991)), and are found to be situated within the buffer layer. The exact coherent structures are unstable to small amplitude perturbations and thus may be part of a set of unstable nonlinear states of possible use to describe the turbulent transition. The nonlinear solutions survive down to a displacement thickness Reynolds number Re * = 496 , displaying a 4-vortex structure and an amplitude of the streamwise root-mean-square velocity of 6% scaled with the free-stream velocity. At this Re* the exact coherent structure bifurcates supercritically and this is the point where the laminar Blasius flow starts to cohabit the phase space with alternative simple exact solutions of the Navier-Stokes equations.

Clinical outcome of autologous chondrocyte implantation is correlated with infrared spectroscopic imaging-derived parameters

OBJECTIVE

To investigate whether Fourier transform infrared imaging spectroscopy (FT-IRIS), a modality based on molecular vibrations, is a viable alternative to histology and immunohistochemistry (IHC) for assessment of tissue quality and patient clinical outcome.

METHODS

Osteochondral biopsies were obtained from patients (9-65 months post-surgery) who underwent an autologous chondrocyte implantation (ACI) procedure to repair a cartilage defect (N = 14). The repair tissue was evaluated histologically by OsScore grading, for the presence of types I and II collagen by IHC, and for proteoglycan (PG) distribution and collagen quality parameters by FT-IRIS. Patient clinical outcome was assessed by the Lysholm score.

RESULTS

Improvement in Lysholm score occurred in 79% of patients. IHC staining showed the presence of types I and II collagen in all samples, with a greater amount of collagen type II in the deep zone. The amount and location of immunostaining for type II collagen correlated to the FT-IRIS-derived parameters of relative PG content and collagen helical integrity. In addition, the improvement in Lysholm score post-ACI correlated positively with the OsScore, type II collagen (IHC score) and FT-IRIS-determined parameters. Regression models for the relation between improvement in Lysholm score and either OsScore, IHC area score or the FT-IRIS parameters all reached significance (p < 0.01). However, the FT-IRIS model was not significantly improved with inclusion of the OsScore and IHC score parameters.

CONCLUSION

Demonstration of the correlation between FT-IRIS-derived molecular parameters of cartilage repair tissue and patient clinical outcome lays the groundwork for translation of this methodology to the clinical environment to aid in the management of cartilage disorders and their treatment.

A linear parametric approach for analysis of mouse respiratory impedance

Assessment of the lung mechanics is crucial in lung function studies. Commonly lung mechanics is achieved through measurement of the input impedance of the lung where the experimental data is ideal for the application of system identification techniques. This study proposes a new approach for investigating the severity of lung conditions and also evaluating the treatment progression. The proposed method is established based on linear parametric identification of lung input impedance in mice and is applied to normal and asthmatic models (including acute, tolerant and chronic asthma) as well as a pharmacological intervention model. Experimental findings confirm the effectiveness of the analysis technique applied here. We discuss the potential application of this method to analyses of human lung mechanics.

IL-2 and IL-4 stimulate MEK1 expression and contribute to T cell resistance against suppression by TGF-beta and IL-10 in asthma

The T cell-driven airway inflammation in chronic asthma is uninhibited and sustained. We examined the resistance of T cells from asthmatic patients against suppression by TGF-β, IL-10 and glucocorticoids and explored its signaling mechanism. CD4(+)CD25(-) T cells from allergic asthmatic subjects demonstrated increased TCR-stimulated proliferation as compared with healthy and chronic obstructive pulmonary disease controls. This proliferation was resistant to inhibition by TGF-β, IL-10, and dexamethasone and to anergy induction. CD4 T cells from asthmatic patients, but not chronic obstructive pulmonary disease, allergic rhinitis, and healthy subjects, showed increased expression of MEK1, heightened phosphorylation of ERK1/2, and increased levels of c-Fos. IL-2 and IL-4 stimulated the expression of MEK1 and c-Fos and induced T cell resistance. The inhibition of MEK1 reversed, whereas induced expression of c-Fos and JunB promoted T cell resistance against TGF-β- and IL-10-mediated suppression. We have uncovered an IL-2- and IL-4-driven MEK1 induction mechanism that results in heightened ERK1/2 activation in asthmatic T cells and make them resistant to certain inhibitory mechanisms.

Effect of strontium ions substitution on gene delivery related properties of calcium phosphate nanoparticles

Gene therapy has been considered a strategy for delivery of therapeutic nucleic acids to a specific site. Calcium phosphates are one gene delivery vector group of interest. However, low transfection efficiency has limited the use of calcium phosphate in gene delivery applications. Present work aims at studying the fabrication of strontium substituted calcium phosphate nanoparticles with improved gene delivery related properties. Strontium substituted calcium phosphate was prepared using a simple sol gel method. X-ray diffraction analysis, Fourier transform infrared spectroscopy, transmission electron microscopy, specific surface area analysis, zeta potential measurement and ion release evaluation were used to characterize the samples. This characterization showed strontium and carbonate co-substituted calcium phosphate which resulted in nano size particles with low crystallinity, high specific surface area, positive surface charge, and a high dissolution rate. These improved properties could increase the DNA concentration on the vector as well as the endosomal escape of the complex that leads to higher transfection efficiency of this novel gene delivery vector.

Mg2+ substituted calcium phosphate nano particles synthesis for non viral gene delivery application

Gene therapy provides a unique approach to medicine as it can be adapted towards the treatment of both inherited and acquired diseases. Recently, calcium phosphate vectors as a new generation of the non viral gene delivery nano carriers have been studied because of their biocompatibility and DNA condensation and gene transfer ability. Substituting cations, like magnesium, affects physical and chemical properties of calcium phosphate nano particles. In this study, Mg(2+) substituted calcium phosphate nano particles have been prepared using the simple sol gel method. X-ray diffraction analysis, Fourier transform infra red spectroscopy, transmission electron microscopy, specific surface area analysis, zeta potential measurement and ion release evaluation were used for characterization of the samples. It was concluded that presence of Mg ions decrease particle size and crystallinity of the samples and increase positive surface charge as well as beta tricalcium phosphate fraction in chemical composition of calcium phosphate. These properties result in increasing the DNA condensation ability, specific surface area and dissolution rate of the samples which make them suitable particles for gene delivery application.