Raman spectroscopy and multivariate analysis for the rapid discrimination between native-like and non-native states in freeze-dried protein formulations

Use of Raman spectroscopy and PCA for quality evaluation and out-of-specification identification in biopharmaceutical products

Over the past three decades, there was a remarkable growth in the approval of antibody-based biopharmaceutical products. These molecules are notably susceptible to the stresses occurring during drug manufacturing, often leading to structural alterations. A key concern is thus the ability to detect and comprehend these alterations caused by processes, such as aggregation, fragmentation, oxidation levels, as well as the change in protein concentration throughout the process steps, potentially resulting in out-of-spec products. In the present study, Raman spectroscopy, coupled with Principal Component Analysis (PCA), has proven to be an excellent tool for characterizing protein-based products. Notably, it offers the advantages of being minimally invasive, rapid and relatively insensitive to water. Therefore, it was successfully employed to discriminate between various stresses impacting a monoclonal antibody (mAb). The molecule used in this study is a fully human IgG1 fusion protein. Thermal stress was induced by incubating the samples at 50 °C for one month, while oxidative stress was induced by introducing hydrogen peroxide. Additionally, dilutions were performed to explore a broader range of protein concentrations. Specific key bands were identified in the Raman spectra, which facilitated the PCA classification and allowed for their association with distinct changes in the secondary and tertiary structures of the protein. Notably, it was observed that signals corresponding to amino acids exhibited a decrease in intensity with increasing levels of thermal stress, while other alterations were noted in the amide bands. It was shown that changes in the range 2800-3000 cm-1 pertains to the dilution process, while specific peaks of C-H stretching were essential for the discrimination between the oxidative-stressed samples and the thermal and diluted counterparts. Furthermore, the model calibrated on the mAb demonstrated remarkable performance when used to evaluate a different product, e.g. a hormone.

Evaluation and Screening of Biopharmaceuticals using Multi-Angle Dynamic Light Scattering

Biopharmaceuticals are large, complex and labile therapeutic molecules prone to instability due to various factors during manufacturing. To ensure their safety, quality and efficacy, a wide range of critical quality attributes (CQAs) such as product concentration, aggregation, particle size, purity and turbidity have to be met. Size exclusion chromatography (SEC) is the gold standard to measure protein aggregation and degradation. However, other techniques such as dynamic light scattering (DLS) are employed in tandem to measure the particle size distribution (PSD) and polydispersity of biopharmaceutical formulations. In this study, the application of multi-angle dynamic light scattering (MADLS) was evaluated for the determination of particle size, particle concentration and aggregation in 3 different protein modalities, namely bovine serum albumin (BSA) and two biopharmaceuticals including a monoclonal antibody (mAb) and an enzyme. The obtained calibration curve (R² > 0.95) for the particle number concentration of the 3 proteins and the observed correlation between MADLS and SEC (R² = 0.9938) for the analysis of aggregation in the enzyme can be employed as a 3-in-1 approach to assessing particle size, concentration and aggregation for the screening and development of products while also reducing the number of samples and experiments required for analysis prior to other orthogonal tests.

Evaluation of a Raman Chemometric Method for Detecting Protein Structural Conformational Changes in Solution

Raman scattering shows promise as a powerful routine tool, to determine both secondary and the smaller tertiary structural changes that precede aggregation in both solutions and solids. A method was developed utilizing principal component analysis (PCA) of Raman spectra for detection of small, but meaningful, pH induced changes in tertiary protein structure linked to aggregate formation using α-lactalbumin solutions as a model. The sample preparation and spectral parameters, were optimized for a bulk Raman probe. Analysis of large regions (600-1850 cm^-1) yielded principal component (PC) scores useful for semi-quantitative comparison of protein conformation between formulations. PC loadings corresponded to specific structural peaks known to change with solution pH. PCA of circular dichroism (CD) spectra of dilute solutions yielded similar results. Sucrose is a common formulation excipient with a Raman spectrum that overlaps many protein peaks. With sucrose in the protein solution, the ability of PCA to discern protein structural changes from the Raman spectra was somewhat reduced. Analysis of a more limited spectral region (1530-1780 cm^-1) with negligible sucrose spectral contribution improved the discrimination of protein conformational states. The new Raman method accurately distinguished differences in protein structure in concentrated solutions. The long-term goal is to explore Raman characterization as a routine monitoring tool of protein stability in both solution and solid states.

Emerging PAT for Freeze-Drying Processes for Advanced Process Control

Lyophilization is a widely used drying operation, but long processing times are a major drawback. Most lyophilization processes are conducted by a recipe that is not changed or optimized after implementation. With the regulatory demanded quality by design (QbD) approach, the process can be controlled inside an optimal range, ensuring safe process conditions. Process analytical technology (PAT) is crucial because it allows real-time monitoring and is part of a control strategy. In this work, emerging PAT (manometric temperature measurement (MTM), comparative pressure measurement, heat flux sensors, and ice ruler) are used for measurements during the freeze-drying process, and their potential for implementation inside a control strategy is outlined.

Innovative Drying Technologies for Biopharmaceuticals

In the past two decades, biopharmaceuticals have been a breakthrough in improving the quality of lives of patients with various cancers, autoimmune, genetic disorders etc. With the growing demand of biopharmaceuticals, the need for reducing manufacturing costs is essential without compromising on the safety, quality, and efficacy of products. Batch Freeze-drying is the primary commercial means of manufacturing solid biopharmaceuticals. However, Freeze-drying is an economically unfriendly means of production with long production cycles, high energy consumption and heavy capital investment, resulting in high overall costs. This review compiles some potential, innovative drying technologies that have not gained popularity for manufacturing parenteral biopharmaceuticals. Some of these technologies such as Spin-freeze-drying, Spray-drying, Lynfinity® Technology etc. offer a paradigm shift towards continuous manufacturing, whereas PRINT® Technology and Microglassification^TM allow controlled dry particle characteristics. Also, some of these drying technologies can be easily scaled-up with reduced requirement for different validation processes. The inclusion of Process Analytical Technology (PAT) and offline characterization techniques in tandem can provide additional information on the Critical Process Parameters (CPPs) and Critical Quality Attributes (CQAs) during biopharmaceutical processing. These processing technologies can be envisaged to increase the manufacturing capacity for biopharmaceutical products at reduced costs.

Analytical Techniques for Structural Characterization of Proteins in Solid Pharmaceutical Forms: An Overview

Therapeutic proteins as biopharmaceuticals have emerged as a very important class of drugs for the treatment of many diseases. However, they are less stable compared to conventional pharmaceuticals. Their long-term stability in solid forms, which is critical for product performance, depends heavily on the retention of the native protein structure during the lyophilization (freeze-drying) process and, thereafter, in the solid state. Indeed, the biological function of proteins is directly related to the tertiary and secondary structure. Besides physical stability and biological activity, conformational stability (three-dimensional structure) is another important aspect when dealing with protein pharmaceuticals. Moreover, denaturation as loss of higher order structure is often a precursor to aggregation or chemical instability. Careful study of the physical and chemical properties of proteins in the dried state is therefore critical during biopharmaceutical drug development to deliver a final drug product with built-in quality that is safe, high-quality, efficient, and affordable for patients. This review provides an overview of common analytical techniques suitable for characterizing pharmaceutical protein powders, providing structural, and conformational information, as well as insights into dynamics. Such information can be very useful in formulation development, where selecting the best formulation for the drug can be quite a challenge.

Raman Spectroscopy Methods to Characterize the Mechanical Response of Soft Biomaterials

Raman spectroscopy has been used extensively to characterize the influence of mechanical deformation on microstructure changes in biomaterials. While traditional piezo-spectroscopy has been successful in assessing internal stresses of hard biomaterials by tracking prominent peak shifts, peak shifts due to applied loads are near or below the resolution limit of the spectrometer for soft biomaterials with moduli in the kilo- to mega-Pascal range. In this Review, in addition to peak shifts, other spectral features (e.g., polarized intensity and intensity ratio) that provide quantitative assessments of microstructural orientation and secondary structure in soft biomaterials and their strain dependence are discussed. We provide specific examples for each method and classify sensitive Raman characteristic bands common across natural (e.g., soft tissue) and synthetic (e.g., polymeric scaffolds) soft biomaterials upon mechanical deformation. This Review can provide guidance for researchers aiming to analyze micromechanics of soft tissues and engineered tissue constructs by Raman spectroscopy.

Monitor Ionizing Radiation-Induced Cellular Responses with Raman Spectroscopy, Non-Negative Matrix Factorization, and Non-Negative Least Squares

Radiation therapy (RT) is one of the most commonly prescribed cancer treatments. New tools that can accurately monitor and evaluate individual patient responses would be a major advantage and lend to the implementation of personalized treatment plans. In this study, Raman spectroscopy (RS) was applied to examine radiation-induced cellular responses in H460, MCF7, and LNCaP cancer cell lines across different dose levels and times post-irradiation. Previous Raman data analysis was conducted using principal component analysis (PCA), which showed the ability to extract biological information of glycogen. In the current studies, the use of non-negative matrix factorization (NMF) allowed for the discovery of multiplexed biological information, specifically uncovering glycogen-like and lipid-like component bases. The corresponding scores of glycogen and previously unidentified lipids revealed the content variations of these two chemicals in the cellular data. The NMF decomposed glycogen and lipid-like bases were able to separate the cancer cell lines into radiosensitive and radioresistant groups. A further lipid phenotype investigation was also attempted by applying non-negative least squares (NNLS) to the lipid-like bases decomposed individually from three cell lines. Qualitative differences found in lipid weights for each lipid-like basis suggest the lipid phenotype differences in the three tested cancer cell lines. Collectively, this study demonstrates that the application of NMF and NNLS on RS data analysis to monitor ionizing radiation-induced cellular responses can yield multiplexed biological information on bio-response to RT not revealed by conventional chemometric approaches.

A novel drug–drug coamorphous system without molecular interactions: improve the physicochemical properties of tadalafil and repaglinide

Tadalafil and repaglinide, categorized as BCS class II drugs, have low oral bioavailabilities due to their poorly aqueous solubilities and dissolutions. The aim of this study was to enhance the dissolution of tadalafil and repaglinide by co-amorphization technology and evaluate the storage and compression stability of such coamorphous system. Based on Flory–Huggins interaction parameter (χ ≤ 0) and Hansen solubility parameter (δ_t ≤ 7 MPa^0.5) calculations, tadalafil and repaglinide was predicted to be well miscible with each other. Coamorphous tadalafil–repaglinide (molar ratio, 1 : 1) was prepared by solvent-evaporation method and characterized with respect to its thermal properties, possible molecular interactions. A single T_g (73.1 °C) observed in DSC and disappearance of crystallinity in PXRD indicated the formation of coamorphous system. Principal component analysis of FTIR in combination with Raman spectroscopy and Ss ¹³C NMR suggested the absence of intermolecular interactions in coamorphous tadalafil–repaglinide. In comparison to pure crystalline forms and their physical mixtures, both drugs in coamorphous system exhibited significant increases in intrinsic dissolution rate (1.5–3-fold) and could maintain supersaturated level for at least 4 hours in non-sink dissolution. In addition, the coamorphous tadalafil–repaglinide showed improved stability compared to the pure amorphous forms under long-term stability and accelerated storage conditions as well as under high compressing pressure. In conclusion, this study showed that co-amorphization technique is a promising approach for improving the dissolution rate of poorly water-soluble drugs and for stabilizing amorphous drugs.

The coamorphous tadalafil–repaglinide (molar ratio, 1 : 1) prepared by solvent-evaporation method significantly improve the physicochemical properties of tadalafil and repaglinide.

Raman spectroscopy in pharmaceutical research and industry

In the fast-developing fields of pharmaceutical research and industry, the implementation of Raman spectroscopy and related technologies has been very well received due to the combination of chemical selectivity and the option for non-invasive analysis of samples. This chapter explores established and potential applications of Raman spectroscopy, confocal Raman microscopy and related techniques from the early stages of drug development research up to the implementation of these techniques in process analytical technology (PAT) concepts for large-scale production in the pharmaceutical industry. Within this chapter, the implementation of Raman spectroscopy in the process of selection and optimisation of active pharmaceutical ingredients (APIs) and investigation of the interaction with excipients is described. Going beyond the scope of early drug development, the reader is introduced to the use of Raman techniques for the characterization of complex drug delivery systems, highlighting the technical requirements and describing the analysis of qualitative and quantitative composition as well as spatial component distribution within these pharmaceutical systems. Further, the reader is introduced to the application of Raman techniques for performance testing of drug delivery systems addressing drug release kinetics and interactions with biological systems ranging from single cells up to complex tissues. In the last part of this chapter, the advantages and recent developments of integrating Raman technologies into PAT processes for solid drug delivery systems and biologically derived pharmaceutics are discussed, demonstrating the impact of the technique on current quality control standards in industrial production and providing good prospects for future developments in the field of quality control at the terminal part of the supply chain and various other fields like individualized medicine.

On the way from the active drug molecule (API) in the research laboratory to the marketed medicine in the pharmacy, therapeutic efficacy of the active molecule and safety of the final medicine for the patient are of utmost importance. For each step, strict regulatory requirements apply which demand for suitable analytical techniques to acquire robust data to understand and control design, manufacturing and industrial large-scale production of medicines. In this context, Raman spectroscopy has come to the fore due to the combination of chemical selectivity and the option for non-invasive analysis of samples. Following the technical advancements in Raman equipment and analysis software, Raman spectroscopy and microscopy proofed to be valuable methods with versatile applications in pharmaceutical research and industry, starting from the analysis of single drug molecules as well as complex multi-component formulations up to automatized quality control during industrial production.

Structural Characterization of the Intrinsically Disordered Protein p53 Using Raman Spectroscopy

The intrinsically disordered protein p53 has attracted a strong interest for its important role in genome safeguarding and potential therapeutic applications. However, its disordered character makes difficult a full characterization of p53 structural architecture. A deep knowledge of p53 structural motifs could significantly help the understanding of its functional properties, in connection with its complex binding network. We have applied Raman spectroscopy to investigate the structural composition and the conformational heterogeneity of both full-length p53 and its DNA binding domain (DBD), in different solvent environments. In particular, a careful analysis of the Amide I Raman band, which is highly sensitive to protein secondary structure elements such as α-helices, β-sheets and random coils, has revealed the presence of extended random coils in p53 and predominant β-sheet regions in its DBD. In addition, this analysis has allowed us to explore the ensemble of interchanging conformations in both p53 and its DBD, highlighting a higher conformational heterogeneity in p53 than in its DBD. Furthermore, by applying a principal components analysis, we have identified the principal spectral markers in both p53 and DBD samples. The combination of the two approaches could be insightful for the study of intrinsically disordered proteins, by offering increased versatility and wide application as a label-free, real-time and non-invasive detection method.

In-line monitoring of compaction properties on a rotary tablet press during tablet manufacturing of hot-melt extruded amorphous solid dispersions

As the number of applications for polymers in pharmaceutical development is increasing, there is need for fundamental understanding on how such compounds behave during tableting. This research is focussed on the tableting behaviour of amorphous polymers, their solid dispersions and the impact of hot-melt extrusion on the compaction properties of these materials. Soluplus, Kollidon VA 64 and Eudragit EPO were selected as amorphous polymers since these are widely studied carriers for solid dispersions, while Celecoxib was chosen as BCS class II model drug. Neat polymers and physical mixtures (up to 35% drug load) were processed by hot-melt extrusion (HME), milled and sieved to obtain powders with comparable particle sizes as the neat polymer. A novel approach was used for in-line analysis of the compaction properties on a rotary tablet press (Modul P, GEA) using complementary sensors and software (CDAAS, GEA). By combining 'in-die' and 'out-of-die' techniques, it was possible to investigate in a comprehensive way the impact of HME on the tableting behaviour of amorphous polymers and their formulations. The formation of stable glassy solutions altered the formulations towards more fragmentary behaviour under compression which was beneficial for the tabletability. Principal component analysis (PCA) was applied to summarize the behaviour during compaction of the formulations, enabling the selection of Soluplus and Kollidon VA 64 as the most favourable polymers for compaction of glassy solutions.

Recent developments in the Raman and infrared investigations of amorphous pharmaceuticals and protein formulations: A review

The success rate for drug discovery and the development of innovative therapeutic strategies are intimately related to the physical properties of the solid-state condensed matter, which have direct influence on the bioavailability of Active Pharmaceutical Ingredients. In order to transform a new molecule in efficient drug, the material is brought into an amorphous state using various manufacturing processes including freeze drying, spray drying, hot melt extrusion and loading in different delivery devices. The infrared and Raman spectroscopic analyses used for exploring disordered and amorphous states, for the monitoring of the drug physical stability in drug delivery systems are described in this review.

Renal Graft Fibrosis and Inflammation Quantification by an Automated Fourier-Transform Infrared Imaging Technique

Renal interstitial fibrosis and interstitial active inflammation are the main histologic features of renal allograft biopsy specimens. Fibrosis is currently assessed by semiquantitative subjective analysis, and color image analysis has been developed to improve the reliability and repeatability of this evaluation. However, these techniques fail to distinguish fibrosis from constitutive collagen or active inflammation. We developed an automatic, reproducible Fourier-transform infrared (FTIR) imaging-based technique for simultaneous quantification of fibrosis and inflammation in renal allograft biopsy specimens. We generated and validated a classification model using 49 renal biopsy specimens and subsequently tested the robustness of this classification algorithm on 166 renal grafts. Finally, we explored the clinical relevance of fibrosis quantification using FTIR imaging by comparing results with renal function at 3 months after transplantation (M3) and the variation of renal function between M3 and M12. We showed excellent robustness for fibrosis and inflammation classification, with >90% of renal biopsy specimens adequately classified by FTIR imaging. Finally, fibrosis quantification by FTIR imaging correlated with renal function at M3, and the variation in fibrosis between M3 and M12 correlated well with the variation in renal function over the same period. This study shows that FTIR-based analysis of renal graft biopsy specimens is a reproducible and reliable label-free technique for quantifying fibrosis and active inflammation. This technique seems to be more relevant than digital image analysis and promising for both research studies and routine clinical practice.

Dispersive and FT-Raman spectroscopic methods in food analysis

Raman spectroscopy is a powerful technique for molecular analysis of food samples.