## 4 Conclusions  
The results of this study suggest that portable Raman spectrometers, both handheld and modular, equipped with an excitation source at 785 nm possess satisfactory Raman spectra of colon tissues and reference biopolymer compounds. The spectra measured using Ahura FirstDefender and i-Raman Plus have intense and well-resolved bands. Important spectral parameters, such as the ratio of the principal signals to the noise level or the half-width of these signals, were determined and found to be suitable for all instruments tested. For these devices, the prominent intense Raman bands of colon tissue biochemical markers occurred at the correct wavenumber positions comparable to previously published values and the values obtained using the laboratory instrument. The DXR SmartRaman spectrometer detected even small changes in the signal intensity or position for adenomatous polyp and adenocarcinoma samples, which could be critical for early diagnosis. In contrast, for the handheld device and, to a lesser extent, the modular one, the band overlap did not permit the detection of some of these spectral features.  
Laboratory and portable Raman instruments were used successfully to discriminate and classify normal, benign, and malignant colon tissues using appropriate multivariate statistical methods. Despite its less pronounced spectral characteristics, the handheld Raman spectrometer can be used in early diagnosis of colorectal carcinoma, comparable to the modular and laboratory instruments. In addition, its ease of use, small size, and rapid measurement of biological samples make it an attractive tool for medical practice.  
**Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app14020791/s1](https://www.mdpi.com/article/10.3390/app14020791/s1)]([https://www.mdpi.com/article/10.3390/app14020791/s1](https://www.mdpi.com/article/10.3390/app14020791/s1)), Figure S1: Peak decomposition of the Raman spectra of calf thymus DNA obtained with laboratory, modular, and handheld instruments. Table S1. Raman band assignments for the reference compounds. Table S2. Contribution of biological macromolecules in the Raman spectra of normal colon tissue.  
**Author Contributions:** Conceptualization, A.S. and L.P.; methodology, A.S. and J.P.; software, A.S.; validation, A.S., D.J. and M.V.; formal analysis, A.S., Z.K., D.J. and M.V.; investigation, A.S. and J.P.; resources, M.V. and J.P.; data curation, A.S.; writing--original draft preparation, A.S.; writing--review and editing, A.S.; visualization, A.S. and D.J.; supervision, A.S.; project administration, L.P.; funding acquisition, L.P. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Ministry of Health of the Czech Republic; grant number NU20-09-00229.  
**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Ethics Committee of the First Faculty of Medicine and the General University Hospital in Prague (Project NU20-09-00229, 18 June 2020).  
**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.  
**Data Availability Statement:** Data are contained within the article.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.